This invention relates to a process for the quantitative determination of the total chlorine in a matrix, possibly expressed as polychlorinated biphenyls (PCBs) equivalent, in particular in insulating liquids, oils in general, soils or metal components of apparatuses, foods, products for agriculture, in compliance with Best Available Techniques (BAT) and Best Environmental Practices (BEP) guidelines for Smart Field Test (SFT).

The PCBs can be absent (< 2 mg kg ^"1 ) in fresh insulating liquids and in oils in general, whereas - for what oils in operation used in equipment are concerned - the concentration must be below the limits prescribed by laws and local regulations (ex. <50 mg kg ^"1 according to Directive 96/59/EC, etc.). The inventory of the oils and the equipment containing or contaminated by PCBs, as well as their life cycle management (LCM) and the periodic monitoring with the decontamination and/or disposal of such oils and equipment is a fundamental requisite to prevent unreasonable risks for workers, public health and the environment, in compliance with the normative set of reference (Convention of Stockholm for persistent organic pollutants - POPs - of 22/5/2001 ; norms CENELEC CLC/TR 50503:2010; IEC 602960; IEC 60422; etc.).

The determination of the PCBs in a matrix requires a complex, expensive and extended process, starting with a representative sampling with a throw away kit, the shipment of the sample to an accredited laboratory operating according to specific methodologies (ex. IEC 61619, EN 12766) equipped with expensive apparatuses (ex. Gas chromatographs with ECD sensors) and specialised operators.

The well known cases of contamination by PCBs of the food chain (sausages, hams, poultry, pork meat etc. - cases occurred in Belgium in 1999 and in Ireland etc.) and the scandals deriving from the unlawful recycling of used vegetable oils, contaminated by PCBs during the recycling phases (transportation, stocking and use as an ingredient for livestock farming) dictated new requisites for quality control and traceability during all the operational phases. Also, a wide case history exists of sites contaminated by PCBs as a result of preceding spills from equipment or accidental cases with explosions and fires and/or unlawful disposals. The identification and the reporting of these sites require a fast and effective preliminary evaluation of the concentration of PCBs in the various matrices involved, finalised toward the definition in a rapid, effective and economical way, of a map of the contamination of the site (perimeter, depth and level of contamination for the single matrices) thus planning the type and priority of corrective actions, as well as monitoring the activities for the decontamination, recovery and disposal of the various matrices involved (soil, porous concrete, metal parts) in accordance with current norms and local regulations.

The most effective, least expensive solution, not requiring considerable investments in equipment and specialised personnel, is the use of simple and rapid Field Screening Tests to quantify the concentration of total chlorine expressed as PCBs equivalent, which are scientifically validated, in accordance with what indicated by the same norms mentioned above.

Currently,, the market offers products providing the determination of total chlorine, exploiting colorimetric, electro-chemical and enzymatic methods, for example:

- kit Dexsil® (USA) designated as Clor-N-oil, i. e. field tests for the screening of PCBs in insulating oils;

-kit Dexsil® (USA) designated as Clor-N-soil, i. e, field tests for the screening of PCBs in soil;

- the apparatus by Dexsil® designated as L2000DX PCB/Chloride ANALYZER System for the quantitative determination of chlorine in insulating oils, and

- the PCBs immunoassay kit by Hach for the measurement of PCBs in soil.

The kits currently available on the market for the determination of total chlorine expressed as PCBs equivalent in oils and soil present some critical factors.

Critical factor I The kit Clor-N-Oil is a colorimetric method having the main limitation of being unable to quantify the concentration of total chlorine in the oil, but only the compliance with a prefixed threshold value (ex. 500, 50 o 20 mg kg ^"1 ).

Critical factor II

The kit Clor-N-Oil, L 2000 uses highly toxic substances such as, for example, nickel nitrate and mercury nitrate.

Critical factor III

The kit Clor-N-Oil requires a substantial amount of oil (at least 10 ml) thus determining a corresponding amount of waste to be disposed of.

Critical factor IV

The Dexsil® L2000 is able to provide a quantification of the total chlorine with the cost of the use of a much more expensive dedicated instrument (with respect to the Clor-N-Oil) equipped with a selective electrode for chloride iones, capable of solving the limitations linked to the kit Clor-N-Oil.

Critical factor V

In the Dexsil® kits, the sodium and the naphthalene required to convert the organic chlorine into chloride is placed in two separate vials.

Critical factor VI

The kit for immunoassay by Hach, based upon enzymatic reactions, is of a purely semiquantitative nature and it can be applied to solids only and not to oils.

F.L. Benton et al.: "Quantitative Volumetric Analysis of Carbon-Bonded Halogen with Sodium Naphthalene", Analytical Chemistry, vol. 20, no. 3, 1 March 1948, pages 269-270 XP55015068 describes an analysis method of an halogen linked to atoms of carbon (thus excluding the inorganic chlorine) based exclusively on the use of sodium naphthalene in ethereal solution of which the dispersion characteristics are not indicated. The sample containing the halogen to be analysed is weighted in a glass bulb and is placed in a separating "funnel" - i.e. a container unsuitable for field use and absolutely not comparable with a "vial" - where the sodium naphthalene solution is added, forming sodium halide. The latter is separated by adding just water three times. The watery layers are then titred potentiometrically.

Scott Hinman: "Determination of Soluble Chloride: the Volhard Titration", 9 September 2009, XP55015103 describes the Volhard method for the determination of chlorine, expressly specifying that the colloidal particles that are formed when the silver iones are added to solutions of chloride are too small to be removed by filtration.

Thus the object of this invention is to provide a process capable of overcoming the criticalities described above.

This scope is achieved thanks to a process having the characteristics described in one or more of the claims to follow.

The process of the invention presents the advantages or requiring lesser investments, as well as using not much toxic substances and a reduced amount of sample, for the quantitative determination, in particular by colorimetric and/or electro-chemical way, of the total content of chlorine - i.e. PCBs screening - in an organic liquid matrix, which could be possibly derived from a solid matrix to be analysed (soils or surfaces - wipe test).

Within this description, "total chlorine" is intended as the concentration of organic and inorganic chlorine present in the matrix sampled and measured as total chlorides.

As "PCB equivalent" is intended the concentration of PCBs as equivalent mixture of PCBs expressed as typical Aroclor 1260 obtained by the conversion of the total chlorides through known conversion coefficients, capable of ensuring zero "false negatives" and to accept the "false positives" caused by the possible presence of other chlorinated compounds not classifiable as PCBs.

As "PCB Screening" is intended the evaluation of the total chlorine correlated to the potential mixtures of PCBs, present in the matrixes, with a result exceeding the prescribed limits, such to require a subsequent and specific quantitative determination of the PCBs, according to the above mentioned methodologies (IEC 61619, EN 12766 etc.).

As "false negatives" are intended the results indicating the absence of PCBs even when these are present in a concentration exceeding the limit of quantification of the method.

As " false positives" are intended the results indicating the presence of PCBs even when these are absent or are present in a concentration lower than the limit of quantification of the method. Such positive value can be attributed to the existence of other halogenated substances not classifiable as PCBs, with a result exceeding the prescribed limits such to require a subsequent and specific quantitative determination of the PCBs, in accordance with the above mentioned methodologies (IEC 61619, EN 12766 etc.).

As "representative sampling of liquids or solids" is intended the sampling of one or more determined amounts of liquid or solid matrix (oil or soil, for example, and in compliance with the laws and technical norms of the sector) in such a manner that the value of the concentration of PCBs determined is applicable to the entire matrix as a whole.

As "wipe test sampling" is intended the transfer, through controlled rubbing, of the PCBs from surfaces on which it has been deposited onto appropriate throw away tissues soaked with solvents (hexane, acetone or mixtures) from which it is easily extractable and quantifiable as mg of PCBs for a normalised surface (ex. 100 cm ).

As "micro dispenser" is intended a mechanical/electronic apparatus for the precise dosing of discrete and variable aliquots of titration solution. The matrices on which the process of the invention can be done are, for example, insulating oils with mineral or synthetic base, lubricating oils, hydraulic oils, vegetable oils, natural or synthetic esters and solutions obtained from metal parts, soil and solid surfaces in general.

The quantitative determination of the total concentration of chlorine and the PCBs screening occurs preferably by colorimetric and/or potentiometric way. In particular, the process of the invention is based essentially upon a series of simple operational phase of conversion of the organic chlorine into inorganic chlorine through the reaction between 5 ml of oil (50% less with respect to the 10 ml of Clor-N-Oil, critical factor III) and a pre- dosed micro dispersion of sodium biphenyl or sodium naphthalene in a glycol or a derivative of it (normally dimethoxy ethyl ether also designated as diglyme), kept in an inert atmosphere in a sealed gastight disposable vial, in order to ensure for a long time the surprising performances in terms of limits of quantification, repeatability and reproducibility of the invention. The possibility of keeping the sodium biphenyl or naphthalene in inert atmosphere in a sealed disposable vial proved the simplification of the analytical methodology with respect to the kit Dexsil® (criticality V) since it reduces the number of parts and analytical operations. At the end of the reaction the chlorides obtained are extracted by a watery solution containing non-toxic potassium nitrate (and not mercury or nickel nitrate, cf. Critical factor II) and sulphuric or nitric acid, added to the vial after opening it. Then, the extraction solution is filtered through a 0.45 μηι nylon or teflon filter into a first container containing a pre-dosed volume of watery solution with a known concentration of silver nitrate. The products of the reaction are filtered through an additional 0.45 μηι teflon or nylon filter, into a second container for the quantification of the chlorine by a colorimetric way through titration with a 0.1 M solution of potassium thiocyanate added by a micro doser, with the presence of ferric sulphate. As an alternative, so that the sensibility of the quantification is increased, the latter can be done by electrochemical way, by a selective electrode for silver iones. In case of a colorimetric quantitative determination, at the moment the equivalent point is reached, the solution under examination turns from colourless into orange. In practice, the chlorides of such solution are caused to precipitate with an excess of silver nitrate and the residual silver iones are quantified by one of the above mentioned methods. In case a solid matrix is examined, ex. soil, the relevant chlorinated compounds must be pre-emptively extracted by washing with a known amount of a solvent, such as for example, hexane, heptane, trimethyl pentane, acetone, ethyle ether. So, a liquid matrix is obtained, which is subject to the same process describe above.

In case a surface must be analysed, the so called wipe test, i.e. a mechanical-chemical removal of chlorinated organic compounds by using a disposable tissue soaked with hydrocarbon solvent (ex. hexane, acetone and mixtures) is used. These components are then extracted from the tissue by the addition of an hydrocarbon solvent, as for example, heptane or trimethyl pentane, obtaining a liquid matrix, which is subject to the same process described above.

As already indicated, the sodium biphenyl or naphthalene complex is specifically prepared in an appropriate sealed vial in which an oxygen and carbon dioxide-free atmosphere is ensured.

Thanks to the process of the invention, the total chlorine can be determined with high levels of repeatability a reproducibility both in the field and in laboratory, involving non- specialised personnel and without using expensive and bulky dedicated equipment, such as gas chromatographs with ECD probes (as required by complex authorisations for the presence radioactive isotope Ni 63). Thanks to this, it is possible, in particular, to measure values of total chlorine and PCBs screening between 2 through 1000 mg kg ^"1 (and beyond with an appropriate dilution) in the oils.

The process of the invention proved to be surprisingly as the simplest, economical and fast response under all the application scenarios, solving the critical factors described above, for the determination of total chlorine and PCBs screening in compliance with the guidelines of Best Available Techniques (BAT) and Best Environmental Practices (BEP) for Smart Field Test (SFT).

The following examples, provided without a limitative title, further illustrate the application of the process of the invention also with the help of the enclosed drawing tables, in which:

figure 1 is a graph showing the comparison between the results obtained on exhausted mineral insulating oils applying the colorimetric technique of this invention and the gas chromatography ECD in accordance with norm IEC 61619 and EN 12766 (with error bars),

figure 2 is an example of the calibration curve usable in the method for the colorimetric determination of the invention with the concentration of the PCBs indicated as a function of the micro litres of titration solution added (potassium thiocyanate 0.05 or 0.1 M) in the typical case of an exhausted mineral oil, and

figure 3 is an example of calibration curve usable with the potentiometric determination method of the invention with concentration of PCBs Aroclor 1260 indicated as a function of the concentration of the residual silver iones, in the case of a typical exhausted mineral oil.

Example 1

In a disposable sealed vial in argon atmosphere filled with 1 ml of Na biphenyl at 20% w/w, 5 ml of oil to be analysed is poured (colour ASTM: 4, TAN: 0,706 mg OH/g sam le; cone. PCBs: 257 mg kg ^" ' - analysis GC-ECD). The vial is sealed and vigorously shaken for about 30 seconds; the vial is reopen and 10 ml of acid extracting solution containing potassium nitrate is added, it is resealed and vigorously shaken for 2 minutes. The separation into two phases is awaited for about 10 minutes, than transfers the whole into a 20 ml disposable syringe without the piston, to the end of which a 0.45 μπι filter is placed. The watery phase is in this manner separated from the oily phase and directly transferred in a first disposable dark glass container containing a prearranged amount of solution of AgN0 ₃ 0,1 M (500 μΐ). The suspension turns considerably cloudy; the first container is lightly shaken for a few seconds and the content is transferred into a 10 ml syringe without the piston to the low end of which a 0.45 μιη filter is placed. In this manner the suspension is filtered and transferred into a second 20 ml container filled with a 100 μΐ solution of indicator Fe ₂ (S0 ₄ )3; the solution turns pale-yellow. Using a micro doser, a solution of KSCN 0.1 M is added with doses of 10 μΐ at a time; gradually, a white precipitated is formed. After adding 220 μΐ, the suspension turns orange. Through the coefficient of conversion obtained from the calibration line of the method (cf. Fig.2) it was calculated that such value corresponds to a concentration of 252 mg kg ^"1 of PCBs equivalent Aroclor 1260.

Example 2

In a disposable sealed vial in argon atmosphere filled with 1 ml of Na biphenyl at 20% w/w, 5 ml of oil to be analysed is poured (colour ASTM: 1.5, TAN: 0.075 rng _K oiVg sample; cone. PCBs: 27 mg kg ^"1 - analysis GC-ECD). The vial is sealed and vigorously shaken for about 30 seconds; the vial is reopen and 10 ml of acid extracting solution containing potassium nitrate is added, it is resealed and vigorously shaken for 2 minutes. The separation into two phases is awaited for about 10 minutes, than transfers the whole into a 20 ml disposable syringe without the piston, to the end of which a 0.45 μηι filter is placed. The watery phase is in this manner separated from the oily phase and directly transferred into a first disposable dark glass container containing a prearranged amount of solution of AgNC"3 0,1 M (500 μΐ). The suspension turns imperceptibly cloudy; the first container is lightly shaken for a few seconds and the content is transferred into a 10 ml syringe without the piston to the low end of which a 0.45 μηι filter is placed. In this manner the suspension is filtered and transferred into a second 20 ml container filled with a 100 μΐ solution of indicator Fe ₂ (S0 ₄ )3; the solution turns a very pale-yellow. Using a micro doser, a solution of KSCN 0.1 M is added with doses of 10 μΐ at a time; gradually, a white precipitated is formed. After adding 420 μΐ, the suspension turns orange. Through the coefficient of conversion obtained from the calibration line of the method (cf. Fig.2) it was calculated that such value corresponds to a concentration of 34 mg kg ^"1 of PCBs equivalent Aroclor 1260.

Example 3

In a disposable sealed vial in argon atmosphere filled with 1 ml of Na biphenyl at 20% w/w, 5 ml of oil to be analysed is poured (colour ASTM: 4, TAN: 0.706 mg OH/g sample; cone. PCBs: 257 mg kg ^"1 - analysis GC-ECD). The vial is sealed and vigorously shaken for about 30 seconds; the vial is reopen and 10 ml of acid extracting solution containing potassium nitrate is added, it is resealed and vigorously shaken for 2 minutes. The separation into two phases is awaited for about 10 minutes, than transfers the whole into a 20 ml disposable syringe without the piston, to the end of which a 0.45 μιη filter is placed. The watery phase is in this manner separated from the oily phase and directly transferred into a first disposable dark glass container containing a prearranged amount of solution of AgN0 ₃ 0,1 M (500 μΐ). The suspension turns considerably cloudy; the first container is lightly shaken for a few seconds. The residual concentration of silver iones is determined using a selective electrode of silver iones. The concentration of chloride iones is determined by the coefficient of conversion obtained from the calibration curves of the method (cf. Fig.3). In this case a value of 284 kg ^"1 of PCBs equivalent Aroclor 1260 was obtained.

Example 4

In a disposable sealed vial in argon atmosphere filled with 1 ml of Na biphenyl at 20% w/w, 5 ml of oil to be analysed is poured (colour ASTM: 1, cone. PCBs: 9.8 mg kg ^"1 - analysis GC-ECD). The vial is sealed and vigorously shaken for about 30 seconds; the vial is reopen and 10 ml of acid extracting solution containing potassium nitrate is added, it is resealed and vigorously shaken for 2 minutes. The separation into two phases is awaited for about 10 minutes, than transfers the whole into a 20 ml disposable syringe without the piston, to the end of which a 0.45 μιτι filter is placed. The watery phase is in this manner separated from the oily phase and directly transferred into a first disposable dark glass container containing a prearranged amount of solution of AgN0 ₃ 0,1 M (500 μΐ). The suspension turns considerably cloudy; the first container is lightly shaken for a few seconds. The residual concentration of silver iones is determined using a selective electrode of silver iones. The concentration of chloride iones is determined by the coefficient of conversion obtained from the calibration curves of the method (cf. Fig.3). In this case a value of 10.2 kg ^"1 of PCBs equivalent Aroclor 1260 was obtained.

Example 5

In a 250 ml glass flask, 10 g of dry soil contaminated by PCBs at 420 mg kg ^" ' is placed, 50 ml of hexane are added and the whole is placed in an ultrasound bath for one hour. A filtration over paper is done and the solution (solution A) is collected for the subsequent quantification of the PCBs.

In a disposable sealed vial in argon atmosphere filled with 1 ml of Na biphenyl at 20% w/w, 5 ml of solution A to be analysed is poured. The vial is sealed and vigorously shaken for about 30 seconds; the vial is reopen and 10 ml of acid extracting solution containing potassium nitrate is added, it is resealed and vigorously shaken for 2 minutes. One waits about 10 minutes for the separation into two phases than transfers the whole into a 20 ml disposable syringe without the piston, to the end of which a 0.45 μηι filter is placed. The watery phase is in this manner separated from the oily phase and directly transferred into a first disposable dark glass container containing a prearranged amount of solution of AgN0 ₃ 0,1 M (500 μΐ). The suspension turns considerably cloudy; the first container is lightly shaken for a few seconds. The residual concentration of silver iones is determined using a selective electrode of silver iones. The concentration of chloride iones is determined by the coefficient of conversion obtained by using the calibration curves of the method (cf. Fig.3). In this case a value of 142 mg kg ^"1 of PCBs equivalent on the solution A was obtained that referred to the soil, corresponding to 468 mg kg ^"1 of PCBs equivalent Aroclor 1260, with a good approximation with the real concentration.

Naturally, without prejudice to the principle of the invention, the details for carrying it out and the forms of implementation can widely change with respect to what described herein purely for an exemplifying title, without for this reason going out the claims area.