Cyril Masselot

RES

Keywords: Mediation and mediatization of the social action, community systems, digital edition

ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

"You who are an expert in communication, of whom you do think of our site?" How many times the professionals of the communication, the researchers as the communications managers, see each other shouted out so, summoned to express an opinion "of expert" on an object of communication most of the time not contextualized? What reveals this request, otherwise a justification hastily, which asks for an answer generally established on a judgment aesthetic and not on the scientific consideration of a communicational procedure bringing in on an equal footing the stakes in meaning, in relation and in usage?

The social request of this type of intervention creates a certain awareness maybe influenced by the fashion of "all communicational" [START_REF] Breton | Internet. La communication contre la parole ?[END_REF], being translated by a pressure of the social actors (of the professional ground) as students, who can also note in scientific articles, to make operational notions developed in ICS (Information adn Communication Sciences), with the aim of improving mainly the project management. The communication is then lived as useful tool, organized by technical acts which a fine « connoisseur » could build of craftiness in the style of a well oiled mechanics.

The social actors involved in observatories of territorial intelligence (cf. corpus, but also Girardot on 2004, [START_REF] Bertacchini | Entre information & processus de communication : l'intelligence territoriale[END_REF][START_REF] Dumas | Intelligence, Territoire, Décentralisation, ou la Région à la française[END_REF] effectively fast subscribed to the necessity of producing quantified and qualified information, in a first concern of directing their actions according to the needs of the populations. Quickly appeared the question to put in relation this constructed information and the other actors, the close relations or distant (Girardot on 2004[START_REF] Masselot | Systèmes d'information territoriaux et politiques sociales : quand l'observation territoriale s'empare du net[END_REF]. The method of used territorial intelligence (ib.) then imagined to convene reflections which ICS lead for a long time, of the informative process in the communicationnel process, without forgetting the manners allowing the realization of the sense.

This study is fed by a report builds at the same time of territorial experiments (cf. corpus and webographie), of classes dispensed in University of Letters (License's and Master's degree, Digital Edition option), and from the scientific production (colloquiums, reviews and publications of various sciences). "The operational integration of the knowledge as the essential requirement of the power" (communication call of the 16th congress of the SFSIC, on 2008) engender a transformation which it is advisable to accompany and whose ICS can grow rich: do we have to undergo it without bringing to it of the reflection? A second report, arisen from attempts of scientific answers to the evoked social request, accompany the first one: that of a sometimes stiff subdivision between the various fields of research, while the expertise appeals to numerous notions of ICS and other disciplines, according to this famous interdisciplinarity in questioning (cf. the acts of the XVth congress SFSIC, Bordeaux in May, 2006). We shall thus question here the relations between ICS and social action under the angle of the Territorial Intelligence, by envisaging diverse modellings or experimented mediations, by stigmatizing the current limits, and by observing a case of formation where these questions gave place to specific educations.

Corpus

Actions of research:

The accompaniment of more than about twenty territorial observatories on an around ten years gave place to so many experiments, at the same time of a new method of intervention based on the observation, and new practices were linked to the structuralization of the information and to the use of the produced knowledge.

-Analysis of the portal of the city of Besançon and Grand Besançon (http://www.besancon.fr/) The direction of the communications office of the city of Besançon (Doubs) asked us in 2007 to evaluate the portal citizen set up in 2004, with the following objectives: « business » intelligence, analysis ergonomic, informative analysis, communicational and semiotic, statistical analysis, and users analysis. Beyond the obtained results, this study is interesting for our subject in two directions: -It demonstrates that the territorial public communication, from now on convinced of the utility of the evaluation of its actions, also agrees to be analyzed by means of scientific notions which have most of the time difficulty in being leading on the territorial area, as the appeal to isotopies and horizons of expectation, for example; -It allowed of acter an effective articulation between several disciplines in the same objective, certainly operational thus reducing, but where they played in complementarity and not in competition: it was

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possible to convene together notions appropriate for ICS and for sciences of the Language, as well as for ergonomics, for cognitive psychology, techniques of survey… It is thus these points which will feed our reflections afterward.

-Conception of the information system of follow-up of the users of the Adapei of Besançon This structures so appears: "Association of the parents and the friends of persons mental defectives, work to assure the defence and the promotion of the children, the teenagers and the adults, to facilitate their self-realisation". This association is being equipped with a specific information system of follow-up and with accompaniment of their beneficiaries; it asked us to draft the specifications, which was finalized and put handed in June, 2005, then to accompany its concrete realization: follow-up of the structuralization of the data in information (informative process), conception and realization of the procedures of communication internal as external, evaluates on the quantitative and qualitative treatments. It is about a socio-technical device which we call "territorial intelligence community system" (TICS) and who applies in practice the theories and the methodologies worked by the territorial intelligence.

-TICS applied to Accem (Gorrion) An experiment of the same type is led at the moment in Spain, with the association Accem, which receives, welcomes and accompanies refugees and immigrants, promoting "the insertion and the equality of the rights and the responsabilities of all the persons, whatever his/her origin, sex, race, religion or social group ". This second experiment allows to confront the conception of a TICS with the other cultural and professional realities. The questions of communication which ensue from it take advantage then of a good level of modelling by taking advantage of similar experiments.

-CaENTI: European network of the territorial intelligence, supported by an coordination action of the FP6. The main objective of this coordination action is to develop methods and tools of territorial intelligence, in the service of the observation and of the territorial intervention, by combining the works of social actors and researchers. The TICS is a first tangible result of these researches, and the partners who test them at the moment (Adapei and Accem mainly) are members of this European network. The activities which are led are there thus by definition the « compost » of the experiments which feed us here.

Educations:

The specificity of the research in action also lives in its constant articulation with the educations, favors giving the possibility of confronting the results with their capacity of transfer in a didactic frame, questioning there even the process of meta-reflection which often misses in the urgency of the project management subjected to the constraints of the social and economic policies.

-Chronologically, we conceived first of all didactic sequences established on our results of research in entitled Dess "on-line Documentary Information system" (1996)(1997)(1998)(1999); then a Professional License degree "Professions of the Exposition and Information Technologies " allowed us to widen our educational applications in the other fields, in particular patrimonial and cultural. -We then decided to develop an IUP "Methodologies and Information technologies" containing two courses, "on-line Information systems" and "Produced and Multimedia Services", on whom we were able then to approach also the social sciences, and the concept of Territorial Intelligence (Mitropoulou Eléni and Masselot Cyril, 2007a). -The reformulation of the IUP in the formations of LMD (Licence-Master-Doctorat) type allowed to add second year of Master's degree in a course "Digital Edition", which widely based on the researches led by the European network of the territorial intelligence. In Licenses and Master's degrees, we organize especially courses centred on the conception of the multimedia information systems, the multimedia writing, the informative processes and communicationnels connected to these systems, as well as the approaches « semio-com » (semiotic-communication) of the on-line services.

A Communicational and Community System

The quoted experiments showed that the temptation is big to appeal to the systematic approach, to organize it in the time of the project, according to the changeable contexts of institutions, politics and societies.

This reflection gave place to new attempts to approach rather than of instrumentalisation (Herbaux on 2007, [START_REF] Masselot | Systèmes d'information territoriaux et politiques sociales : quand l'observation territoriale s'empare du net[END_REF] including the other knowledge developed by ICS. These actions of research are in the course of deepening, and already give however some track interesting, as the communicational influence caused by drift of instrumentalisation without method and little conceptualized.

They concern mainly the Territorial Intelligence, which became one of the objects of study of ICS, the connection being mainly in the human compost of the activity, common to both approaches. The implementation of experiments of this order proves that the practices of the social actors integrate henceforth an informative approach and communicational which appeals to various notions elaborated within the field of ICS. The first capital gain of the application of the method which they notice is the construction of partnership, what corresponds to the improvement of the getting in touch and the quality of this relation. The second identified contribution is a better knowledge of the needs of the citizens, the available resources, the territorial context, and thus the definition of better procedures of decisions and applications of the territorial policies: where the sense takes back body… The method Catalyses organized in a SCIT is interested first of all in the two very precise moments of a process of communication:

• that of the production of sense, which takes place during the formalization of the data in information (required semantic redundancy…) • then during the elaboration of the communication strictly speaking, according to the initial data and the produced information.

It is thus advisable to structure these stages in a communicational aim, without omitting that the fourth dimension of the uses. The global plan of the TICS thus models a procedure of territorial observation, from the data collection to the distribution of the results (Girardot on 2006(Girardot on , 2007(Girardot on and 2008)):

Plan of a Territorial Intelligence Community System, TICS (caENTI, JJ. Girardot, 2007)

In summary, from a questionnaire, named here a guide of diagnosis and evaluation, an observatory organizes on a territory (above all human being) the first data collection, which are seized then either on-line in the software brick spotted by "Icasit" on the plan, or in the outstanding version of the software Pragma (in green). A series of data processings, a stage of formalization described below intervene then. It is unmistakable that it is not only a question of tidying up data in compartments -categories, but that the action to give a shape to this material, is in itself a carrier of sense: from the data collection, the social actor produces sense. What can seem an evidence in ICS recover from the awareness in the territorial practices of observation: the initial formation as continuous takes here all its interest, by clarifying a process of communication generalized for example.

Production of the sense

The first stage, said about production of the sense, must be conceived according to the various necessary communications:

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• intern to the team which carries the project: the treatment has to be the most complete possible, the most pushed, adducing for example multiple statistical explorations in purposes of improvement of the produced knowledge. It is here that we produce most sortings (from the first balance sheet to the qualified balance sheet, then in the balance sheet reflecting the selection of the characters, including the profiles of calculated individuals), of crossed sortings (allowing to better understand the quantitative phenomena as qualitative), of indexations of the answers, the graphs illustrating the results… This team acquires here a fine understanding of the initial data, by appropriation, as well as a first vision of the results to be communicated, what allows it a first semipublic shaping, still in the state of working documents.

• intern to the Operational Group (orange silhouette by the middle of the plan of the TICS): a selection in elements produced previously must be made to keep the most interesting to be subjected to a wider discussion. These results prepared for a collective second reading allow the participants to analyze in common the obtained statistics, without having to return many a time behind. It is this stage which really produces the territorial intelligence useful for the observatory. • extern: this stage allows the Operational Group to organize a public publication, thus a communication the addressees of which are less known and about which we know less how to control the horizons of expectation. The objective is here to establish final documents to report these quantitative results as qualitative, in the general public, and especially, in the financiers.

It is a question here of exceeding the first mission of a observatory in the classic sense of the term, which is above all to collect in a way structured by the data. The agencies which realize this type of study position generally as an external expert to the project. The obtained result is then an often consequent report, drafted by these experts, whose reading remains bitter and requires most of the time an accompaniment on behalf of these same experts to understand the contents. Concretely, the territorial descriptors chosen by these experts can not turn out relevant for the actors of ground confronted with an unstable reality, which the statistics globalized at the level of a territory of a superior scale do not light.

It is thus evident that the way of observing influence this stage of production of information. The real objective of the diagnosis is distorted here: it is really a question for the actors of knowing the needs of a population and a territory; it is a question for the experts of producing a report… The horizons of expectation [START_REF] Jauss | Pour une esthétique de la réception[END_REF][START_REF] Iser | Der Akt des Lesens[END_REF] activated by these two professional categories are not thus in phase. In this only stage of production of the information from existing facts, the method Catalyses clarified in the plan of the TICS allows to modify this approach of observation:

-Descriptors and modalities allowing to structure the facts in data, then the data in information, are collectively built by the territorial actors, accompanied (and only accompanied) by experts; -These experts adhere to the first objectives of the observation, namely the implementation of territorial actions with the aim of improving the situations of the users of the structures (institutional or not); -The collection, important moment of the structuralization, is too made by the actors, conscious of the -This collection, organized collectively, belongs to it only a process of communication at the same time with the users, and interns: the form allowing to unwind in the time this process is also a product allowing the exchange with the users (he can be informed in several meetings, according to the elaboration of the individual project and his follow-up). The respect for this approach profession generates a process of communication in the service of the decision-making support and of the territorial action. -The collection, always, is a process in tense stream, contrary to a study of photographic type, the observation being permanent by definition. The evolution of the situation of the territory is however visible by a series of statistical treatments operated at the diverse "T" moments, generally mid-term and late in the year civil for example. Daily, weekly, monthly automatic dashboards or by period are also available, to have a synthetic and global vision of certain key indicators for a given territory. The informative process described here is to be considered as an element of inescapable governance: the actors write themselves the indicators which allow them to pilot the territorial intervention, the actions to be set up, to repeat, or to be re-qualified. The experts have a role of scientific accompaniment (being experimented by definition), but also of transfer, thus formation. They are not traditionally external any more in the approach, but really involved at the diverse moments of the observation.

So, the definition of the contents of the guide of the Accem was made at the same time as that of an European guide within the caENTI. It allowed both projects of the mutual profits, feeding one of the other one on specific points: Accem brings its expertise in themes linked to the migrations intra and extra-

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European, the other participants feeding the Spanish guide of themes as the health, the handicap, the housing… Adapei elaborates the contents of its information system by beginning with what is common to all the business sectors (five), then details by sector, by establishment and by service the information useful for the follow-up of the individual routes and for the statistical treatments.

Production of the relation

The abstract analysis of any product of communication implies certain number of reflections which it is advisable to bring to a successful conclusion to produce the relation enter the created information (where a part of the sense builds itself), and the actors of the reception:

• The identification of the target public has to give a clear centring of the complexity of the act of communication in itself: a series of recommendations at once strategic and ergonomic are going to ensue from this analysis. Address peers whose thematic culture is equivalent means appealing to the shared knowledges. The TICS having an important role in the Territorial Intelligence, they also address the decision-makers (politics, financiers) and in the general public (interested or not in themes). • This first stage has for immediate consequence the consideration of the diverse stakes: operational objectives of territorial action, influence of the local politics, perennisation of the activities (thus structures), justification of the use of private and public funds… These stakes are not all influential to equal part according to the moment of the statement (connected to the temporal but also spatial, cultural, relational context etc.). To identify it the importance in these contexts is thus a determining element of the quality of the communication. • The conception and the realization of the objectives and the intentions of communication lead then to a pragmatic awareness of "what we really want to say". To put these reflections in black and white and to confront them then to the public and identified stakes allows to participate so in the elaboration of a communication plan including different stages, in the time, places, and the possible relations with the receivers. • The specificity of the approach communicationnelle of the TICS lives largely in the essential function of transfer and formation. The objectives of communication take into account in this frame of the fact which any act of communication in Territorial Intelligence contains intrinsically a part of didactic transposition, linked to the innovation of the systematic approach of the territory and its constituents.

The methods and used tools also ask for prerequisites at the risk of being unintelligible, thus provoking a hostile reaction … These analyses allow exactly to identify what it is advisable to clear up or not, and especially in the way to put in relation of the individuals with these knowledges. • We can then deepen the horizons of expectation [START_REF] Jauss | Pour une esthétique de la réception[END_REF][START_REF] Iser | Der Akt des Lesens[END_REF] possible: which will be the ones who will be activated by these actors of the reception, how they modify the angle of communicationnelle approach, which decisions set before realizing concretely objects and authorities of communication.

• The production of the relation can usefully rest on the construction of networks of meaning, isotopies, in a first communicationnel objective (the sense builds itself gradually during the consumption, by significant redundancy of units recovering from the same isotopie), and in an objective of consolidation of the human network, by demonstrating by this demolition of the meanings that the public really share the same cultural and relational contexts, because they understand the same components according to the same cognitive plans.

The production of the relation co-builds itself then between actors of the emission and the reception so bringing to light in the obtained reliance (according to the definition of Bolle de Bal 1981) the reality of a community of project, strong condition of the appropriation of the approach.

The case of the portal of the City and the conglomeration of Besançon illustrates these approaches: the structuralization of the data in information is a mastered process. On the other hand, their direction, the consideration of the conditions of reception, the elaboration of narrative plan, enonciation plan, the diverse elements contributing to the reliance were in the heart of the preoccupations of the direction of the service of communication. To analyze the existing product, the contained information, the medium and support, under the angle at the same time ICS and the Territorial Intelligence, allowed to share in internal the same speech putting clearly diverse communicationals milestones. In brief, it was necessary to establish a communicational charter which could then give place to an editorial charter.

Consommation of the two dimensions

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All the stake in the communication becomes a reality in the uses which are made, in the consumption of both dimensions of the produced sense and the created relation. The uses of the produced information recover, according to what was said higher, several fitted processes, each adding by definition a new value to the transformed object:

• From facts to data: the process of observation organized according to the method Catalyses and instrumented by the tools which compose it, is led by the actors of the Operational Group (cf. plan of the TICS), from the stage said about conception. It is thus about an internal process to this group of actors, which is also an approach of crossed formation, where actors and guides (experts, academics, experimented actors) exchange knowledge on territories and human beings. The raw material (the observable facts) consists of human beings largely, services and territorial actions, economic activities, leisure activities of all which composes the life on a given territory. It is not enough to look at a fire to produce a sense from what we see; a first informative process has to extract the most formless possible datum from it in the sense of Perriault (on 2003) by a semiological encoding (where the sign (S) consists of the union of a significant (Sa), of one indicated (In), and a referent (Ref), the whole in system: S= ((Sa U In) U Ref)) allowing from a referent to deduct from it one indicated confirms, then significant one acceptable and useful. A part of the sense of the information is already produced by this process, but we still have no information as far as the datum is still shapeless real. • From data to information: this formalization is going to be affected by the structuralization of a guide of collection (questionnaire for example) and by the practical organization of the data collection. The pragmatic necessity of obtaining indicators of decision-making support to act on territories with the citizens obliges to elaborate a consensus on the process of creation of the sense, validated by the evaluation of the produced information which prove that they are useful in the method Catalyse. We thus refer here to the first part of the plan of the TICS:

TICS : from data to informations

• From the treatment of the information to the knowledge: most of the information produced from the initial data give place to new treatments, quantitative and qualitative, in the optics to generate new knowledge. Every descriptor can give place to a quantitative statistical exploitation the result of which will be a data sheet of numbers (the frequency) with the percentages calculated on the totality of the population and on the totality of the given answers. This board can be illustrated by a graph (in bars, histogram or circular as the case may be). These results are going to give place to comments and interpretations. From the existing information, crossed sortings are going to take place (the most known of them being the population pyramid for example), codings and recodages are going to create variables of synthesis (age groups from dates of birth for example)… So much case where a new information is created from constructed information. Other exploitations also take place: qualitatively, the analysis said about the data in statistics (we should say information in fact) brings in the factorial analysis of the correspondences (AFC) and the hierarchical ascending classification (CAH): the production of the sense continues by investigating the first information. Finally, the results of these treatments are commented and interpreted, confronted with the resources and territorial contextual indicators, so many acts so creating new information. We thus refer here to the second part of the plan of the TICS:

TICS: Treatment of the information

The uses of the relationship process are more complex and require to them only a wider research, a fast panorama of which we raise here only:

• The processes of creation of the information also convene the communication, as we suggested it before, because they are operated by definition by actors and often have objectives of internal communication in the elaboration of the knowledge. • There is thus a first internal floor where the method Catalyses puts in relation of the information in diverse stages, with a restricted group of actors, those who are concretely in charge of the observation in everyday life. • Said uses of "second circle" take place then when it is a question of widening the works led on the first information produced in the interpretations of the obtained results. The first group restricted by the observatory makes a whole series of statistical tasks, examined then by the operational group: this examination is constituted by a series of acts of communication where the information is again worked, and especially interpreted. The objective is then to end in the implementation of thematic workshops, which in turn will decide on concrete projects of actions, what is illustrated in the plan of SCIT by the low part:

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• This plan breaks off when we consider that the distribution outside of the observatory really intervenes (what is represented by @, recovering the idea of the publication and the edition of the results). It is a limit of the plan, because the phases of communication and information are not ended for all that totally for the observatory Catalyse: it still remains to take into account the uses which will be made by the other categories of public, as the political decision-makers, the financiers and support (regions with a measure of autonomy, states, Europe), the social actors or still simply the general public. The data processing, as the processes of the communication, are conceived from then on as being in the service of this operational objective. Accem conceives for example its observatories also as engines, allowing to create and to animate local, national and European networks. The initial objective is thus articulated around the improvement of the accompaniment of the individual projects, by a territorial réticulée action. The phatique aspect is put here in the service of the action, of what takes place after the moment of the communication. However, a regularly won initial bet is to improve the reliance, to improve also the informative process. The experience indeed proves that the consideration by the social actors of the communication influences strongly the way of building the information, and of communicating them. A didactic approach of "to make it in action" is often more effective for an autonomous construction of the knowledges, as much for the students in initial formation as for the professionals.

Materialization of sense

The communication listens during the reception to reconstruct the sense of the observed facts, the data, the constructed information and the elaborated relations, behind the diffused results and thus consummate. The information and the communication such as established in a TICS find their utility in the understanding of the social and territorial phenomena. What leads at once that these observations have a peculiarity on most of the traditional studies: their perpetuity. This plan has no sense if it is conceived in a poor temporality, that is in a purely linear and not cyclic, synchronic and not diachronic vision. The diverse stages take all their interest from the moment the constructed results can be confronted with news data, by new information, by new gettings in touch, what also allows to estimate the led actions. In the observatory, we can say that the understanding of the informative phenomena and communicationnels gives a new sense to these actions, and that the knowledge of the territory allows to realize them.

For the operational group, as it is the case in Accem, the consumption of both dimensions allows a not unimportant distance, so organizing a new territorial approach, the identification of the actions, structuring the decision-making support and the evaluation of the actions, what will be also useful for the decisionmakers and evoked financiers.

This materialization does not escape totally the addressers, it is in any case the hypothesis which justifies the approach of evaluation begun by the communications office of the City of Besançon, which is not without convincing results: improvement ergonomic of the portal, its scenarization and the topography by the consideration of the constituents of the processes of communication, clarification of the editorial objectives and the sharing of the same language, the improvement of the statistics. The project led by Adapei let a very big place with the previous stage, at the risk of falling in the pointed réunionite, during the structuralization of the contents, in the optics guarantee the quality of this (re)materialization of the sense. It is effectively unthinkable that a bad communication between social workers can carry damage to the beneficiaries. The initial prejudice was to facilitate the maximal appropriation of the approach of observation to protect the quality from it and the relevance.

It is a stage where the communication plays the role of "relational glue" (Bougnoux on 2001) and accompaniment in the change. In the style of the theories of MacLuhan, the project is managed by a group called referents, about fifteen persons representing the diverse sectors, the establishments and the services (on approximately 350 workers). To consider them as leaders means investing them as ambassadors of the method of observation and accompaniment of the users with their close colleagues.

Conclusion

We approach here one of the possible dimensions of the relations between the territorial intelligence and ICS, on the basis of the plan of the TICS, within the framework of the method Catalyse. It would be reducing to envisage only this link as only relationship. It is rather about an example several times experimented in real conditions which lets glimpse the existing mutual contributions. From a point of view which becomes RES -Cyril MASSELOT 10/11 attached to the processes of communication, such a territorial approach is complex as far as it contains within it a multitude of facts of communication and information. It is from then on indispensable, of our point of view, that the diverse actors participants in these stages are conscious of the systematic approach of the communication, the view as the interactive process.

A specific communication plan thus is to be set up, on base of the plan of the TICS, integrating at the same time the diverse moments and the levels of communication (internal, internal widened, financiers and general public), in an aim of consumption (of usage) both dimensions informative and communicationnelle. The usage of the method and the results is indeed in the heart of the process, and is going to condition the passage from a stage to the other one: it will be a question here of estimating every authority and every object of communication to rebalance the following phases, as much from the point of view of the data processing as of their consumption.

At the same time, to observe the communication in the broad sense social actors of a territory also contributes to understand their culture, their "habits and customs". The plan displayed here must be again searched, to describe the internal routines which contain certainly their stakes and specificities. It should allow to approach still unresolved questions, in this precise frame, as the cultural and professional influence of the medium: the multimedia writing confronted with the classic reports of type which the actors contractually have to return, the relation between support and medium according to the acts of communication, which balances between the documentary, informative stakes and communicationnels and how to obtain it…


Kawther Thomas H Kauffmann
email: thomas.kauffmann@metz.supelec.fr

Ben Mabrouk

Marc D Fontana

Raman probe for the simultaneous measurement of anion concentration in mixtures of salt solutions

We propose to detect by Raman spectrometry the presence of several anions in mixtures of salt solutions and to measure simultaneously their respective concentrations. In this study we show how chemometric methods based on statistical analysis like Principal Components Analysis (PCA) and Partial Least Square Regression (PLSR) can be applied for the spectra treatment. Unlike current water probes often based on conductivity, our new Raman sensor is able to identify simultaneously and in one single measurement several anions such as NO3 -, SO4 2-, HPO4 2-or Cl -sought for the water pollution monitoring. Moreover our sensor gives rise to reliable, accurate and fast measurement (a few seconds) and can therefore be very useful for in situ water quality control applications.

INTRODUCTION

Several salts like nitrates and phosphates are frequently used in agriculture as fertilizers and are increasingly present in ground waters, basins or rivers. Moreover, other salts, and particularly chlorides, are used as de-icers during winter and can also be found in large quantities in waters. These salts in ionic form have a negative impact on the environment causing the eutrophication of lakes and the destruction of eco-systems [START_REF] Berenzen | Effects of chronic ammonium and nitrite contamination on the macroinvertebrate community in running water microcosms[END_REF]. Currently, several methods are available to detect and measure the concentration of these ions in solutions. In one hand are the electroanalytical sensors [START_REF] Bhadekar | Developments in analytical methods for detection of pesticides in environmental samples[END_REF] measuring a voltage, a current or impedance, which allow to carry out in-situ measurements but can usually measure only one ion at a time using a specific electrode (NO3 -, Cl -, ...) by comparison with a reference electrode. On the other hand, there are laboratory analysis methods like chromatography for example [START_REF] Lucy | Recent advances in ion chromatography: A perspective[END_REF] which give more accurate results but require sampling and a long recording time measurement.

Here Raman spectrometry (RS) is proposed as new probe for the simultaneous detection of several salts diluted in water and the determination of theirs concentrations [START_REF] Fontana | Raman spectroscopic sensors for inorganic salts[END_REF]. RS is a well know optical technique generally used to study the vibration of molecular bonds [START_REF] Lyon | Raman spectroscopy[END_REF]. Based on the inelastic diffusion of the light by a materials, RS provides several information about the sample which can be a solid, a liquid or a gas. Thus, the different parameters related to a specific Raman line (position, intensity, full width at half maximum) give indications about the sample [START_REF] Ph | Imagerie Raman de matériaux et dispositifs hétérogènes[END_REF][START_REF] Barbillat | Spectrométrie Raman[END_REF] like the molecular composition used to identify species (ions in solution in our case) thanks to the lines positions or the concentrations related to the peaks intensities. RS is particularly adapted for liquid analysis, allowing fast and in-situ measurements (no sampling) and gives rise to a simultaneous detection of several ions in solutions. Moreover, RS associated with chemometric methods [START_REF] Svensson | Reaction monitoring using Raman spectroscopy and chemometrics[END_REF] gives rise to an efficient probe for water monitoring.

II. MATERIAL AND METHOD

A. Raman spectrometry and salt solutions

Raman spectrometry consists in exciting a material with a laser and collecting the light diffused by it. Indeed, although the majority of the scattered light does not exchange energy with the material i.e. no change in wavelength (Rayleigh scattering), a small part of the light interacts with the sample and has therefore a different wavelength (inelastic scattering). This is the Raman scattering which highlights vibration modes of the molecules. A Raman spectrum therefore provides a fingerprint of the molecular bonds of a material and the study of its evolution or its modification provides information about the sample (bonds, concentration, temperature, mechanical stress etc.). Here Raman spectrometry is used as a probe for the detection and the measurement of salt diluted in water with all the advantages of this technique: use of contacless or immersion probe, no sample preparation, in-situ and fast measurement.

Analysis of Raman spectra of salts diluted in water shows a modification of the water spectrum by the anions present in the solution (the OH stretching band in particular) and characteristic peaks [START_REF] Ben Mabrouk | Raman study of cation effect on sulfate vibration modes in solid state and in aqueous solutions[END_REF]. Some of these ions have a specific signature in the wavenumber range around 1000 cm -1 (30 THz). For example, the line located at 981 cm -1 is specific to the sulfate anion SO4 2-and the line at 1048 cm -1 to the nitrate anion NO3 -. In addition to being indicators of the type of ions present in solution, these peaks evolve in intensity with the concentration of the species so that a calibration can be usually done for each anion [START_REF] Fontana | Raman spectroscopic sensors for inorganic salts[END_REF]. Moreover, other salts such as chlorides [START_REF] Furic | Raman spectroscopic study of sodium chloride water solutions[END_REF] do not exhibit specific lines (not active in Raman) but just slightly disturb the wide O-H stretching band of the water spectrum around 3500 cm -1 so that the determination of the concentration is still possible but more difficult in this case [START_REF] Burikov | New opportunities in the determination of inorganic compounds in water by the method of laser Raman spectroscopy[END_REF][START_REF] Kauffmann | Optical sensor of salt concentration: Uncertainty evaluation[END_REF].

B. Instrumentation

Several salted solutions (pure and mixtures) at different concentrations of nitrate, sulfate, phosphate and chloride were prepared by weight. Spectra were recorded in 5 seconds at room temperature with a RXN-1 Raman spectrometer (Kaiser Optical Systems). As shown in Fig. 1, an excitation laser line at 532 nm was used and the laser light was focused through a 10 objective at a distance above 1 cm from the liquid sample contained in a quartz cell. The Raman light is collected in backscattering configuration by the same optic, filtered to overcome the Rayleigh line and is diffracted through a grating on a CCD camera (Andor) using two lines of 1024 pixels and cooled at -40 °C. Acquisition was done by the iCRaman software (Mettler Toledo) and the spectral range starts at 100 cm -1 and ends at 4350 cm -1 within a spectral resolution of 2 cm -1 . Signal processing and chemometric analysis (PCA and PLSR) were performed according to a self-made program using the R language [START_REF] Core | R: A language and environment for statistical computing[END_REF].

C. Principal components analysis

Chemometric analysis includes all the statistical and mathematical for extracting information from a spectrum [START_REF] Wold | Chemometrics; what do we mean with it, and what do we want from it?[END_REF][START_REF] Wold | Chemometrics, present and future success[END_REF]. Generally based on the analysis of a large number of data, several methods are used to rank the spectra in order to sort the corresponding species. Others methods are used to link the spectra evolution with species concentration to establish a calibration law. Chemometric analysis is widely used in IR spectroscopy [START_REF] Muehlethaler | The application of chemometrics on Infrared and Raman spectra as a tool for the forensic analysis of paints[END_REF] and more and more in Raman studies [START_REF] Svensson | Reaction monitoring using Raman spectroscopy and chemometrics[END_REF][START_REF] Cooper | Chemometric analysis of Raman spectroscopic data for process control applications[END_REF].

Here we use the principal components analysis (PCA) in order to detect the presence of several anions in a mixture of salt solutions. The principle of a PCA is to reduce the number of spectral variables using an orthogonal transformation and turn them into uncorrelated variables called principal components (PC) ranked in order of largest possible variance. The interest of a PCA is that the number of principal components is very small (generally less than 10) compared to the large number of original variables. In this study, Raman spectra have 2048 spectral variables i.e. intensities, which are reduced by PCA to scores and loadings. Scores are the coordinates of each spectrum in the different dimensions (principal components) and loadings are the representation of these dimensions according to the wavenumbers. The distribution of these scores in the space of dimensions is used to group individuals (spectra) according to common principal components and thus to link them to a physical or chemical parameter. This "scores plot" allows highlighting similarities between spectra according principal components. It is a very useful tool to class or group spectra and therefore the related species. If individuals are uniformly distributed along one of these dimensions, it is possible to perform a regression on this component (PCR for principal components regression) in order to establish a calibration model.

D. PLS regression and evaluation

Partial Least Square Regression (PLSR) is another regression method developed by Wold in the 1960s [START_REF] Wold | Chemometrics, present and future success[END_REF] more powerful than the PCR and widely used in spectrometric application (infrared or Raman) for quantitative analysis. PLS regression works in the same way as the PCA but take into account the response values e.g. species concentrations and their variations, in the determination of the calibration model.

The efficiency of a regression can be evaluated by different methods and criteria. Here, three criteria were used: the regression coefficient R 2 , the root mean square error RMSE and the bias BIAS. The regression coefficient corresponds to the spreading predictions parallel to the ideal line. R 2 is usually given for a regression but this parameter although necessary is not sufficient. It is important to consider other several parameters as the RMSE and the bias for example in order to evaluate a regression model. Thus, the RMSE measure the differences between values predicted by the model and the observed value and has the same unit as the predicted value. The bias allows the identification of an offset on the prediction. If the bias is negative the true values are underestimated and overestimated if positive. Raman spectra of several salt solutions (deliberately shifted) showing characteristic lines of NO3 -, SO4 2-and HPO4 2-anions around 1000 cm -1 and the wide OH stretching band of the water centered at 3500 cm -1 and affected by the Cl -anion.

Figure 3.

Scores plot resulting from a PCA on several pure salt solutions of nitrates, sulfates, phosphates and chlorides.

III. RESULTS AND DISCUSSION

A. Ion identification

In this study several salt solutions of nitrates (NaNO3 and KNO3), sulfates (K2SO4 and Na2SO4), phosphates (Na2HPO4 and K2HPO4) and chlorides (NaCl, CaCl2 and KCl) were prepared and their Raman spectra were recorded under the same experimental conditions and normalized by the SNV method (Standard Normal Variate) (see Fig. 2). A PCA taking into account 5 principal components was applied on the set of spectra. Scores plot resulting of the projection of the different spectra according to the two first principal components PC1 and PC2 is given in Fig. 3.

One can see that a PCA allows classing the spectra in several clusters according to the type of anion: NO3 -, SO4 2-, HPO4 2-and Cl -. Because of the intense peak of NO3 -at this concentration compared to the lines of the other polyatomic anions (SO4 2-and HPO4 2-) PC1 mainly reflects the influence of the nitrate ion. In the same way, chlorides which do not have any specific lines but affect the O-H band more strongly than polyatomic ions is more represented by the second components PC2. Sulfates and phosphates which both give lines and affect the O-H stretching band are placed according to the two dimensions but can also be easily distinguished.

B. Prediction models

In order to built prediction models for these anions, a PLS analysis was applied on several salt solutions with different anion concentrations given in mol/l. So 32 chlorides solutions with concentrations from 0 up to 4.02 mol/l, 17 nitrates solutions from 0 up to 624 mmol/l, 18 sulfates solutions from 0 up to 704 mmol/l and 17 phosphates solutions from 0 up to 574 mmol/l were prepared and used in this work. Moreover in order to evaluate the quality of the model established for each anion, a cross validation is done using the "leave-one-out" method. Results of the PLS regression showing values of R 2 , RMSE and BIAS are given in Tab. I for each anion in calibration and validation. RMSE and BIAS are expressed in mmol/l. Curves for Cl -and NO3 -are given as example in Fig. 4.

Results show that a good prediction model can be established whatever the type of anion. Thus, PLS analysis on polyatomic anions with their specific signatures around 1000 cm -1 gives good calibration models according to R 2 > 0.99 and RMSE < 5 mmol/l in each case i.e. less than 1 % considering the full concentration range. Moreover, although chlorides just slightly affect the water spectrum, PLS method allows a good calibration model for this anion with R 2 > 0.999 and a RMSE of 12.6 mmol/l, also less than 1 %. We remind that results in validation are always worse than in calibration. Here validation results can be considered as good with high R 2 in all cases and RMSE less than 30 mmol/l i.e. 2.5 % for the phosphate anion and 1 % for the others. C. Salt mixture analysis Now that prediction models have been built for each anion, we are able to analyze salt solutions. For this, several solutions were prepared and the previous chemometric methods have been applied on their Raman spectra. Sample n°1 corresponds to pure water, samples n°2 and n°3 to pure salt solutions of chloride and nitrate respectively, and samples n°4 and n°5 are mixtures of several salts. Results of the PLS analysis is given in Tab. II.

First, the method allows a very good concentration prediction on pure solutions with an error (difference between predicted and real concentrations) less than 10 mmol/l (sample n°1, n°2 and n°3). Then, the method gives also good results on salt mixtures (sample n°4 and n°5) although prediction errors are higher, ranging from 10 to more than 150 mmol/l sometimes. The determination of phosphate content is not completely satisfactory compared to the detection of the other anions. This is likely due to a less sensitivity of phosphate in both the direct Raman signature and the O-H band, as revealed by the scores of this anion in Fig. 3. IV. CONCLUSION Raman spectrometry can be a very useful tool for water analysis. Thus this optical technique is able to quickly and simultaneously detect and measure several substances dissolved in water like nitrates, sulfates, phosphates and chlorides sought for water quality control. We have shown in this paper that chemometric analysis can differentiate anions in solutions making it easier to detect the presence of species that do not have characteristic peaks but slightly influence the spectrum of water like the chlorides. PLS regressions applied on several salt spectra give rise to good calibration models allowing predicting the concentration of each anion, even in salt mixture solutions simultaneously.

Figure 1 .

 1 Figure 1.

Figure 2 .

 2 Figure 2.

Figure 4 .

 4 Figure 4. Calibration and validation curves for Cl -, and NO3 -anions resulting from a PLS analysis.

TABLE I .

 I RESULTS OF PLS REGRESSION MADE ON NITRATES, SULFATES, PHOSPHATES AND CHLORIDES SOLUTIONS.

			Calibration			Validation
	Anion	R 2	RMSE	BIAS	R 2	RMSE	BIAS
	NO3 -	0.9982	4.3	0	0.9966	5.9	0.07
	SO4 2-	0.9983	4.0	0	0.9940	7.5	-0.1
	HPO4 2-	0.9974	4.4	0	0.9733	14.2	0.6
	Cl -	0.9998	12.6	0	0.9994	27.3	-0.9

TABLE II .

 II ANION CONCENTRATION PREDICTION OF PURE AND MIXTURES SALT SOLUTIONS.

		Concentration (mmol/l)		Prediction (mmol/l)
	Sample Cl -	NO3 -	SO4 2-HPO4 2-Cl -	NO3 -	SO4 2-HPO4 2-
	n°1	0	0	0	0	1	7	3	4
	n°2	510	0	0	0	502	1	2	5
	n°3	0	625	0	0	1	630	3	4
	n°4	510	620	430	380	543	832	479	507
	n°5	428	294	176	143	463	304	184	1


Thomas H Kauffmann

Marc D Fontana

SIMULTANEOUS QUANTIFICATION OF IONIC SOLUTIONS BY RAMAN SPECTROMETRY AND CHEMOMETRIC ANALYSIS

Keywords: Raman spectrometry, salt solutions, chemometrics, PCA, PLS regression

We report on the detection by Raman spectrometry of several pollutants dissolved in water such as nitrates, sulfates or chlorides. Unlike current water probes often based on conductivity our Raman probe measures simultaneously the concentration of each species in a few seconds only. We show how chemometrics methods based on statistical analysis like the principal components analysis and the partial least square regression can be applied for the spectra treatment.

INTRODUCTION

Raman spectrometry (RS) is a well known optical technique generally used to study the vibration of molecular bonds [1]. Based on the inelastic diffusion of the light by a material, RS provides several information about the sample which can be a solid, a liquid or a gas. RS is proposed here as new probe for the simultaneous detection of several salts diluted in water and the determination of theirs concentrations. The different parameters related to a specific Raman line (i.e. position, intensity, full width at half maximum) give information about the sample [START_REF] Ph | Imagerie Raman de matriaux et dispositifs htrognes[END_REF][START_REF] Barbillat | Spectromtrie Raman[END_REF]. Thus, the line positions related to the molecular composition are used to identify species and the peaks intensities give rise to the concentrations. RS is particularly adapted for liquid analysis, allowing fast and in-situ measurements (no sampling) and associated with chemometrics methods [START_REF] Wold | Chemometrics, present and future success[END_REF] provides an efficient probe for water monitoring.

MATERIAL AND METHODS

Raman spectrometry of salt solutions

Raman spectrometry consists in exciting a material with a laser and collecting the light diffused by it. Indeed, although the majority of the scattered light does not exchange energy with the material i.e. no change in wavelength (Rayleigh scattering), a small part of the light interacts with the sample and has therefore a different wavelength (inelastic scattering). This is the Raman scattering which evidences vibration modes of the molecules. A Raman spectrum therefore provides a fingerprint of the molecular bonds of a material and the study of its evolution or its modification provides information about the sample (bonds, concentration, temperature, mechanical stress etc.). Here Raman spectrometry is used as a probe for the detection and the measurement of salt diluted in water with all the advantages of this technique: use of contacless or immersion probe, no sample preparation, insitu and fast measurement.

Analysis of Raman spectra of salts diluted in water shows a modification of the water spectrum by the anions present in the solution (the OH stretching band in particular) and characteristic peaks [START_REF] Ben Mabrouk | Raman study of cation effect on sulfate vibration modes in solid state and in aqueous solutions[END_REF]. As shown in Fig. 1 some of these ions have a specific signature in the wavenumber range w around 1000 cm -1 (∼ 30 THz). For example, the line located at 981 cm -1 is specific to the sulfate anion SO 2- 4 and the line at 1048 cm -1 to the nitrate anion NO - 3 . In addition to being indicators of the type of ions present in solution, these peaks evolve in intensity I with the concentration of the species so that a calibration can be usually done for each anion [START_REF] Fontana | Raman spectroscopic sensors for inorganic salts, Spectroscopic Properties of Inorganic and Organometallic Compounds[END_REF][START_REF] Kauffmann | Inorganic salts diluted in water probed by Raman spectrometry: Data processing and performance evaluation[END_REF]. Moreover, other salts such as halides (chlorides for example) do not exhibit specific lines (not active in Raman) but just slightly disturb the wide OH stretching band of the water spectrum lying between 2700 and 3900 cm -1 so that the determination of the concentration is more difficult in this case [START_REF] Burikov | New opportunities in the determination of inorganic compounds in water by the method of laser Raman spectroscopy[END_REF][START_REF] Kauffmann | Optical sensor of salt concentration: Uncertainty evaluation[END_REF] especially since the OH band is also affected by the salts giving direct signatures.

( )

Fig. 1. Normalized Raman spectra (deliberately shifted) of salt solutions showing caracteristic lines of NO - 3 and SO 2- 4 anions around 1000 cm -1 and the wide OH stretching band of the water affected by the anions. Water spectrum is given in dash line for comparison.

Principal Components Analysis

Chemometric analysis includes all the statistical and mathematical methods for extracting information from a spectrum [START_REF] Wold | Chemometrics, present and future success[END_REF][START_REF] Wold | Chemometrics; what do we mean with it, and what do we want from it?[END_REF]. Generally based on the analysis of a large number of data, several methods are used to rank the spectra in order to sort the corresponding species. Others methods are used to link the spectra evolution with species concentration to establish a calibration law. Chemometric analysis is widely used in IR spectroscopy [START_REF] Muehlethaler | The application of chemometrics on Infrared and Raman spectra as a tool for the forensic analysis of paints[END_REF] and more and more in Raman studies [START_REF] Cooper | Chemometric analysis of Raman spectroscopic data for process control applications[END_REF][START_REF] Svensson | Reaction monitoring using Raman spectroscopy and chemometrics[END_REF]. Here we use the principal components analysis (PCA) which allows to highlight similarities between spectra according the principal components. PCA is used to detect the presence of several anions in salt solutions, especially halides.

The principle of a PCA is to reduce the number of spectral variables using an orthogonal transformation and turn them into uncorrelated variables called principal components (PC) ranked in order of largest possible variance. The interest of a PCA is that the number of principal components is very small (generally less than 10) compared to the large number of original variables. In this study, Raman spectra have 2048 spectral variables i.e. intensities, which are reduced by PCA to scores and loadings. Scores are the coordinates of each spectrum in the different dimensions (principal components) and loadings are the representation of these dimensions according to the wavenumbers. The distribution of these scores in the space of dimensions is used to group individuals (spectra) according to common principal components and thus to link them to a physical or chemical parameter. This "scores plot" allows highlighting similarities between spectra according principal components. It is a very useful tool to class or group spectra and therefore the related species.

Partial Least Square Regression

Partial Least Square Regression (PLSR) is a regression method developed by H. Wold in the 1960s [START_REF] Wold | Nonlinear estimation by iterative least squares procedures[END_REF] widely used in spectrometric application (IR or Raman) for quantitative analysis in industry. PLS regression works in the same way as the PCA but take into account the response values e.g. species concentrations and their variations, in the determination of the calibration model.

The efficiency of a regression within a calibration model can be evaluated by different methods and criteria. Here, as usually in many studies [START_REF] Kang | Quantitative analysis of mixed hydrofluoric and nitric acids using Raman spectroscopy with partial least squares regression[END_REF][START_REF] Estienne | Multivariate calibration with Raman spectroscopic data: a case study[END_REF], three parameters are calculated in order to estimate the power of the regression: the regression coefficient (R 2 ), the root mean square error (RMSE) and the bias (BIAS) which are detailed hereafter.

The regression coefficient corresponds to the spreading predictions parallel to the ideal line. R 2 is usually given for a regression but this parameter although necessary is not sufficient. Thus, the RMSE evaluates the differences between values ŷi predicted by the model and the observed value y i and has the same unit as the predicted value. The BIAS provides the offset on the prediction. The true values are underestimated or overestimated if the BIAS is negative or positive respectively.

These three criteria can be calculated by the following expressions:

R 2 = 1 - n � i=1 (y i -ŷi ) 2 n � i=1 (y i -ȳ) 2
(1)

RM SE = � � � � � � n � i=1 (y i -ŷi ) 2 n -1 (2)
BIAS = n � i=1 ( ŷi -y i ) n ( 3
)
where n is the number of points used for the regression and ȳi the mean of the y i values.

Experimentation

Several salted solutions of nitrate, sulfate, and halide (fluoride, chloride, bromide and iodide) at different concentrations from 10 to 100 mmol/L were prepared by weight. Spectra were recorded in 5 seconds at room temperature with a RXN-1 Raman spectrometer (Kaiser Optical Systems) which can be used for in situ measurements. An excitation laser line at 532 nm was used and the laser light was focused through a 10x objective at a distance above 1 cm from the liquid sample contained in a quartz cell. The Raman light is collected in backscattering configuration by the same optic, filtered to get rid of the Rayleigh line and is diffracted through a grating on a CCD camera (Andor) using two lines of 1024 pixels and cooled at -40 °C. Acquisition was done by the iCRaman software (Mettler Toledo) and the spectral range starts at 100 cm -1 and ends at 4350 cm -1 within a spectral resolution of 2 cm -1 . Signal processing (SNV normalization) and chemometric analysis (PCA and PLSR) were performed according to a home-made program using the R language [START_REF] Core | R: A Language and Environment for Statistical Computing, R Foundation for Statistical Computing[END_REF].

RESULTS

Ion identification

First, a PCA was applied on the set of Raman spectra consisting of nitrate, sulfate, chloride and iodide and the scores plot resulting of the projection of the different spectra according to the two first principal components PC 1 and PC 2 is given in Fig. 2. One can see that a PCA allows classing the spectra in several clusters according to the type of anion: NO - 3 , SO 2- 4 , Cl -and I -. Because of the intense peak about 1000 cm -1 nitrate and sulfate spectra can be clearly separated. Halides which do not have direct signatures but disturb the OH stretching band are grouped together. However, it is possible to differentiate chlorides and iodides into this group. For each anion, the corresponding spectra are ranked in the order of concentrations from 10 to 100 mmol/L.

( ess)

.5

Fig. 2. Scores plot resulting from a PCA on Raman spectra of nitrates, sulfates, chlorides and iodides solutions.

Ion quantification

Then, a PLS regression was applied on the set of spectra in order to build prediction models for these 4 anions. In order to evaluate the quality of the model established for each anion, a cross validation was done using the leave-oneout method. One removes the first of the n samples and performs the calibration model with the n -1 remaining samples to predict the concentration of the removed sample. This sample is then set back in the calibration set while the second one is removed for prediction. The same operation is repeated for all samples. 10 PC were used to establish the calibration for the halides (Cl -and I -) and 8 PC were used for NO - 3 and SO 2- 4 . The number of PC nPC needed for each anion in the PLSR is given by the evolution of the RMSE in validation according to the number of PC (see Fig. 3). Although the RMSE in calibration always decreases with number of PC, the RMSE in validation passes through a minimum before increasing (over-fitting phenomenon).

Results of the PLS regression showing values of the regression coefficient R 2 , the root mean square error RMSE and the bias are given in Tab.1 for each anion in calibration and validation.

Nitrate and sulfate spectra give a RMSE in validation less than 1 mmol/L (i.e. < 1%), no bias and a value of R 2 > 0.999. Halides give higher RMSE (2.5 mmol/L for I - and 6.9 mmol/L for Cl -) and lower R 2 especially for the chlorides. However, these results are very good and allows quantification of chlorides with an error less than 250 mg/L (limit of drinkability).

Halides analysis

Finally, this method was applied on a set of halides spectra which do not give specific signature in the Raman spectrum and are therefore more difficult to detect. Fig. 4 illustrate the slight influence of the halides on the OH stretching band of the water spectrum for two concentration values of 50 and 100 mmol/L. Here, only the spectral range between 2600 and 3900 cm -1 corresponding to the OH stretching band was used in the PCA calculation.

The scores plot given in Fig. 5 allows to differentiate the several halides which are ranked according the first component in the order of their mass. PLS regression was also used for the halides analysis as the first attempt to create a quantification model. 7 components were used for F -, 6 for Cl -, 5 for Br -and 4 for I -. Results of the PLS are given in Tab.2.

Although the calibration results are correct, those found in validation are not as good as previously. We found here a R 2 less than 0.9 for each anion and a RMSE between 9.2 and 22.7 mmol/L. However, although the method still needs to be improved, these first results on halides which have little influence on the water spectrum for these concentration range (10-100 mmol/L), show the possibility of quantification and are encouraging for the future.

CONCLUSIONS

Raman spectrometry can be a very useful tool for water analysis. Thus this optical technique is able to quickly and simultaneously detect and measure several substances dissolved in water like nitrates, sulfates, and halides sought for water quality control. We have shown that chemometric analysis can differentiate anions in solutions making it easier to detect the presence of species that do not have characteristic peaks but slightly influence the spectrum of water like the chlorides. PLS regressions applied on several salt spectra give rise to good calibration models allowing predicting the concentration of each anion. The quantification method needs to be improved in the case of halides analysis for low concentrations. This method will be applied for the simultaneous prediction of anion concentration in salt mixture solutions.

1 Fig. 3 .

 13 Fig. 3. Scree plot showing the optimal number of principal components to choose for each anion in the PLS regression.

Fig. 4 . 5 Fig. 5 .

 455 Fig. 4. Slight influence of halide solutions on the OH stretching band of the water spectrum for 50 and 100 mmol/L.

Table 1 .

 1 Results of PLS regression made on nitrates, sulfates, chlorides and iodides solutions. RMSE and BIAS are expressed in mmol/l.

			Calibration			Validation
	Anion	R 2	RMSE BIAS	R 2	RMSE BIAS
	NO -3	0.9999	0.2	0	0.9995	0.6	0
	SO 2-4	0.9999	0.2	0	0.9994	0.7	0
	Cl -	0.9987	1	0	0.9369	6.9	-0.3
	I -	0.9998	0.4	0	0.9925	2.5	0

Table 2 .

 2 Results of PLS regression made on fluorides, chlorides, bromides and iodides solutions. RMSE and BIAS are expressed in mmol/l.

			Calibration			Validation
	Anion	R 2	RMSE BIAS	R 2	RMSE BIAS
	F -	0.9973	1.4	0	0.7730	13.2	-0.2
	Cl -	0.9874	3.1	0	0.6369	16.9	0.7
	Br -	0.9323	7.2	0	0.3318	22.7	-0.6
	I -	0.9677	5	0	0.8869	9.2	0.1