Analytical equipments

Main equipment

The main equipment of the platform are listed below, with the applications for which they are used.

Equipment	Principle	Applications
δ¹⁸O and δD Analyzer	The Picarro L2130-i analyser is an essential tool for research requiring highly accurate and reliable isotopic analysis of water (δD and δ18O). It contributes to a better understanding and management of water resources, from the study of hydrological cycles to the traceability of water resources. Thanks to this advanced technology, isotopic analysis of water can be carried out with great precision and reliability, allowing to conduct innovative research and provide high-quality scientific solutions.	Isotope analysis of water Determination of water isotope ratios: H₂¹⁶O, H₂¹⁸O and HD¹⁶O molecules
C,N,S Elemental Analyser system	The elementary analyzer works on the principle of catalytic combustion and separation of the gases released during it. At the time of this combustion, the elements C, N, S are oxidized to CO₂, H₂O, NOx, SO₂ and SO₃. The NOx released during this oxidation are reduced to N2 and directly sent to the thermo-conductive detector (TCD). More >	Food - Protein determination - Verification of low N content in gluten-free products Pharmaceutical - Tracking of C content in drugs (eg aspirin, etc.) Environment - C / N ratio in soils and sulfur in volcanic discharges - Measuring stages of litter decomposition Energy - Checking the sulfur content in fuels
Isotope Ratio Mass Spectrometer - IRMS	Coupled with an elementary analyser, the Elementar Isoprime precisION determines the isotopic signatures of solid matrices (soil, sediments, plants, etc.).	Isotopic signature of solid matrices (soil, sediments, plants, etc.) - understand process such as the evolution of organic carbon in soils, or sources such as sources of nitrogen in atmospheric deposits : nitrates, ammonia, nitrogen oxides, etc - monitor food regimes within trophic networks - understand the nitrogen cycle - analyse the dynamics of pesticides
Gas Chromatography	Gas Chromatography is a technique for separating a mixture of thermostable and volatile molecules. This method is often used to check the purity of a given substance, or to separate the components of a mixture to determine the relative amounts of each compound. More >	Determination of : - volatile fatty acids (from C2 to C6) - fatty acids, in the form of methyl ester - sugars, in the form of TMS - PAHs and PCBs
High Pressure Liquid Chromatography	High Pressure Liquid Chromatography allows the separation or the purification of one or more compounds of a mixture with a view to their identification and their quantification. This technique makes it possible to carry out a large part of the analyzes made in Gas Chromatography but especially those which are impossible with these techniques such as the analysis of thermosensitive compounds or of molecular masses which are both very large and even polar. More >	• Determination of : - amino acid - water-soluble vitamins (Vit. B and Vit. C) and fat-soluble vitamins (Vit. A and Vit. E) - the GSH/GSSG ratio (oxidative stress indicator) - volatile fatty acids (from C2 to C6) - chlorophylls and xanthophylls - polyamines • Sugar dosage • Assay of cytotoxics • Identification of lipopeptides by LC-MS
Inductively Coupled Plasma spectrometry	Inductively Coupled Plasma spectrometry (ICP) is a chemical analytical method allowing the determination of almost all the elements simultaneously thanks to the high temperature of the argon plasma (> 8000°C). More >	Mineral matrices - Chemical analysis of Soils and Waters: major elements (Ca, K, Na, Mg, P, Al, Fe, Mn, S) and ETM - metallic elements in trace form (B, Cd, Cu, Pb, Zn) - Determination of S in thermal waters - Catalyst tracking Biological matrices - Detection of heavy metals (As, Cd, Hg) in plants, - Zn, Cu and Se content in bull semen - Al dosage - Eel toxicity study - Determination of Cd in cocoa beans Environment - Isotope analysis in various matrices (rock, soil, sediment, selective soil extractions, soil solution, river water, plant tissue): Si isotopes, Mg isotopes, radiogenic Sr isotopes (⁸⁷Sr/⁸⁶Sr) - Field of applications: thermal waters (anion-rich), polar rivers (low concentration, organic-rich), soil-plant systems Archeology - Tooth: radiogenic Sr isotopes (⁸⁷Sr/⁸⁶Sr)
Liquid Phase Ion Chromatography	Liquid Phase Ion Chromatography (IC) allows the identification and simultaneous quantification of various inorganic and organic ions (cations and anions). The principle of this technique is based on the differences in ion affinities for a functionalized substrate (ion exchange resin) in the presence of a carrier liquid phase (eluent). More >	Environment - Anion measurement: F^-, Cl^-, SO₄^2-, NO₂^-, NO₃^-, PO₄^3- - Measurement of cations: Ca²⁺, Na⁺, NH₄⁺, K⁺, Mg²⁺, Al⁺, Fe^2+/3+… Food - Sugar dosage - Determination of organic acids
TOC Analyser	The determination of dissolved carbon is an essential analytical prerequisite in many agronomic and environmental problems in aqueous media: detection of organic contaminants in soils, control of the decomposition of organic matter from the soil surface, etc. In these various contexts, the use of a carbon analyzer is particularly judicious when organic substances appear at low concentration levels. More >	- in the clay fraction (f <2 µm) of soils and in sediments - in solutions extracted from acid forest soils and in the liquid phase of hydromorphic soils downstream of agricultural plots - in rainwater, rivers, lysimeters in forest ecosystems - in soil and river waters in areas of permafrost thawed in the context of global warming - measurement of different forms of carbon in river water, waste water, sea water
UV-VIS Spectrometer	Spectrophotometry is a non-destructive and rapid analysis method which is widely used in the laboratory. This technique makes it possible to determine the absorbance of a chemical substance in solution, that is to say its capacity to absorb the light passing through it. UV-Visible spectrophotometry makes it possible to provide qualitative information on the nature of the bonds present within the sample (via the order of magnitude of λmax and εmax) but also to quantitatively determine the concentration of species absorbing in this spectral range (via Beer-Lambert law). More >	This technique will also make it possible to follow the kinetics of a chemical reaction.
X-Ray Diffractometer	The application of X-Ray Diffraction (DRX) relates to the identification and quantification of crystalline minerals in the soil. Among these, phyllosilicates constitute a privileged object of study given their preferential location in the fine fraction of soils and their colloidal properties: high specific surface, electrical charge, ion exchange, adsorption of metallic elements, pesticides, etc. This analysis technique makes it possible to characterize the arrangement of atoms and layers of atoms as organized within crystals. It complements other techniques and is not an exclusive tool for characterizing soil minerals. More >	- Mineralogical identification of soils (Quartz, Mica, Magnetite, Pyroxene…) - Identification of clays - Identification of cheese residues (Brushite and Giniitte)

Various specialized equipment

Chemical Oxygen Demand COD Analyzer

Chemical Oxygen Demand is carried out according to two different methods and makes it possible to determine the organic matter content of water by chemical means.

• The first technique targets homogeneous liquids where a Spectroquant kit is used.
• The second method concerns solids and will also be used if more precision is required compared to the kit.

For a kit COD, the sample is added to the tubes containing a potassium dichromate solution K₂Cr₂O₇ in the presence of concentrated sulfuric acid H₂SO₄. After heating in a thermoreactor (2h at 148°C), the absorbance of the tube (Cr₂O₇^2- is orange and the Cr³⁺ product is green) is measured in a specific spectrophotometer which provides the result in mg_DCO/L.
For a COD of solids or more precise, a conventional method is used based on the Belgian standard "NBN T 91-201 - Water analysis".
The materials which can be oxidized under the conditions of the test are oxidized in an acid medium (concentrated sulfuric acid H₂SO₄) by an excess of potassium dichromate solution K₂Cr₂O₇ in the presence of mercury sulphate which forms a complex with the chlorides (allowing them to be trapped and avoiding interference) and the catalyst, silver sulphate.
A reflux heating step is carried out for 30 minutes (15 minutes for liquids). The excess potassium dichromate is titrated with a solution of iron and ammonium sulphate (Mohr salt) in the presence of an indicator, iron orthophenanthroline (ferroin).
The oxidation is more extensive than that obtained with potassium permanganate (see NBN T91-202) although all the organic materials are not completely oxidized.
Mineral reducers (ferrous iron, sulphides, sulphites, nitrites ...) being also oxidized, can interfere.
The result is expressed in milligrams of oxygen consumed per liter (mg_DCO/L) for liquids or in grams of oxygen consumed per grams of material (g_DCO/g) for solids.

Electrical conductivity meter

Conductimetry is a dosing method based on the conductive properties of an ionic solution, called an electrolyte, which conducts electricity. This technique makes it possible to determine the concentration of the ions present but also the kinetics of a reaction or to carry out titrations.
   • The principle consists in measuring the resistance of a solution located between two electrodes; plates covered with platinum black face to face and supplied by an alternating voltage. Once the cell is immersed in the ionic solution, the voltage across its terminals is varied and the intensity of the current flowing through it is measured.
   • Depending on the concentration of ions present, the solution will have a greater or lesser conductivity. Before making a measurement, the conductivity meter must be calibrated which consists of determining the cell constant using standard solutions (usually a KCl solution).
   • Tables provide information on the conductivity of the ions and that of the standard solution as a function of the temperature which has a strong influence on the measurement.
   • The conductivity meter is based on Ohm's law: U = R*I where U represents the voltage (volts), I the intensity (amps) and R the resistance (ohms). It then gives a value of the conductance G, expressed in siemens, knowing that: G = 1/R.
   • The conductivity depends on the concentration of the ions, the nature of the ionic solution and the temperature of the solution.

Kjeldahl distillation system

The Kjeldahl method is a technique for determining the nitrogen level in a sample and has 3 phases. This does not allow the determination of nitrates and nitrites.
   • The first step is the mineralization of organic nitrogen to obtain its ammonium salt form. The acid pH allows the ammonium salt to be in its protonated form NH₄⁺. The nitrogenous organic matter degrades in the presence of a catalyst (copper sulphate and potassium sulphate) and by attack of concentrated sulfuric acid at high temperature. Carbon is eliminated in the form of carbon dioxide (CO₂), hydrogen in the form of water (H₂O) and nitrogen remains in the form of ammonium ion NH₄⁺.
   • After digestion in concentrated sulfuric acid comes the second step which is the distillation of ammonium. Adding excess sodium hydroxide alkalizes the medium, making it possible to pass from ammonium sulfate to ammonia gas. This is entrained by the distillation water steam and is condensed on contact with a condenser.
   • In the last step, the titration, the ammonia collected in a solution of boric acid H₃BO₃ (ammonia trap) forms ammonium borate which is titrated with standardized sulfuric acid in the presence of a colored indicator. This titration is said to be indirect.
The Kjeldahl method is a universal, precise and reproducible technique.

MWAE: MicroWave-Assisted Extraction - UltraWAVE

MicroWave-Assisted Extraction (UltraWAVE) is an automated single chamber reaction (SRC) technique allowing simultaneous digestion of several types of matrices (food, environmental, chemical, ect) without risk of contamination during the cycle.

• This device combines microwave heating with a high-pressure reactor that acts as a cavity and microwave vessel. Its operation is simple and completely automated with an external terminal provided with a touchscreen display.

• After weighing the samples in TFM tubes and adding the digestion acid, these are capped and loaded onto a rack which is lowered automatically into the reaction chamber. The whole is immersed in a water/acid solution allowing uniform heating and constant microwave energy. The chamber is then hermetically sealed, secured and pressurized with inert gas (40 bars). This compression prevents the samples from boiling during analysis and acts as a cover over the contents of the tubes preventing any cross contamination.

• The microwave program is launched and all the samples undergo the same digestion conditions (temperature, pressure, energy received). At the end of the cycle, cooling rapidly lowers the temperature of the samples. After decompression and evacuation of acid fumes, the rack is automatically lifted and the tubes containing the digested samples are collected and can be analyzed.

pH meter

The pH meter generally consists of two elements: an electronic box allowing the display of the numerical value of the hydrogen potential "pH" and a probe which measures this value. This glass probe contains two electrodes, one for measurement and one for reference. These electrodes are in the form of glass tubes, one contains a pH 7 buffer and the other contains a saturated solution of potassium chloride. These two electrodes can be combined (the most common today) or separate.
• The bulb of the measuring electrode is made of porous glass or a permeable glass membrane covered with silica and metal salts. There are two silver threads covered with silver chloride; one which is immersed in a pH 7 buffer in the bulb and the second is immersed in the saturated solution of potassium chloride in the reference electrode.
• When the probe is placed in a solution to be analyzed, the hydrogen ions accumulate around the bulb and replace the metal ions of the latter. This ion exchange generates an electrical flow which is captured by the silver wire. The voltage of this electrical flow is measured by comparison with the voltage generated with the reference electrode and is converted into a pH value by the pH meter. The porosity of the glass membrane decreases with its continuous use, thus the performance of the probe.
• Increasing the acidity of the solution and therefore the concentration of hydrogen ions relative to the internal solution of the electrode increases the voltage, which has the consequence of lowering the pH value. It will be the opposite in an alkaline medium because the voltage will decrease and cause the pH value to increase.
• The pH meter is calibrated before each first measurement with two buffer solutions (either pH 7 and 4 in an acid medium, or pH 7 and 10 in a basic medium). It is important to calibrate at the same temperature as that of the analysis solution otherwise there would be an impact on the accuracy of the measurements.
• This device measures a global potential or voltage which is based on the ratio between the concentration of H₃O⁺ ions and the difference in electrochemical potential which is established in the glass electrode. The reference electrode provides a stable voltage since it has a fixed concentration of potassium chloride solution. While the potential of the measuring electrode only depends on the pH of the solution to be analyzed. It is the difference in potential (voltage) generated by the ion exchange through the glass membrane of the measuring electrode and the reference electrode which is measured by the pH meter.

Soxhlet extractor

The Soxhlet extractor is a method which uses the reflux of the solvent and the siphon principle to continuously extract the solid matter with a pure solvent.
The finely ground sample is placed in a thick rod-shaped filter paper cartridge and placed in an extraction chamber. This fine grinding before extraction increases the solid-liquid contact area, which helps to shift the transfer equilibrium towards the solvent.
The solvent then continues to evaporate, while the extracted substances remain in the distillation flask and concentrate as the extraction takes place, but it is imperative that their boiling temperature is significantly higher than that of the extracting solvent.
A disadvantage of this hot method is that it can degrade heat-sensitive chemicals and you cannot work cold with this system.
Applications
• Extraction of polycyclic aromatic hydrocarbons (PAHs) from polluted soils
• Extraction of polychlorinated biphenyls (PCB) from polluted soils

SPE - Solid Phase Extraction

Solid Phase Extraction is a pretreatment technique commonly used for the extraction of analytes from complex matrices. This solid-liquid extraction method is fast and efficient, and is used to prepare a sample before assaying the analytes that make it up. Indeed, it makes it possible to extract, purify and concentrate the targeted compounds in solution or in suspension in a liquid phase by using the difference in affinity between the analyte and the interferents which will help their separation.
Solid Phase Extraction generally requires four steps.
• First, the cartridge is packaged by percolating a certain volume of solvent (or more) in order to activate the support. The cartridge must imperatively remain wet before depositing the sample.
• Second, the sample is loaded onto the cartridge and its percolation begins, allowing the separation of analytes and interferents. The targeted compounds adsorb on the cartridge.
• Third, the cartridge is washed to remove the interferents by passing a suitable eluent leaving the analytes adsorbed.
• Finally, the analytes are collected by elution with an appropriate solvent.
! Note that it is possible that the interferents adsorb on the cartridge allowing the purification of the analytes. The desorption step would therefore not be encountered in this specific case since the analytes will pass directly through the stationary phase without adsorption.
It is useful during the development of the extraction to check each washing and elution step by chromatography to avoid any loss and contamination.
A wide range of cartridges exists and the platform performs Solid Phase Extractions in normal phase, reverse phase, cation exchanger as well as the anion exchanger.

X-Ray Fluorescence (XRF) spectrometer

A portable XRF spectrometer can be used to analyse the chemical composition of a material directly on site, without destroying the sample. It is used to identify and quantify the elements present in metals, soils or industrial materials.

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