Alain Laplanche

Ultra-pressure liquid chromatography–electrospray tandem mass spectrometry for multiresidue determination of pesticides in water

A multiresidue analysis method has been developed for the determination of pesticides in water by ultra-performance liquid chromatography (UPLC) combined with tandem mass spectrometry (MS/MS). The selected pesticides represent a broad range of polarity and volatility [benzoylcyclohexanedione (mesotrione and sulcotrione); chloroacetamide (acetochlor, alachlor, dimethenamide, and metolachlor); phenoxyacetic acid (2,4-D and MCPA); phenoxypropionic (dichloprop and mecoprop); phenylurea (chlortoluron, diuron, isoproturon, linuron, and metoxuron); sulfonylurea (foramsulfuron, iodosulfuron, and nicolsulfuron); triazine (atrazine, cyanazine, desethylatrazine (DEA), desisopropylatrazine (DIA), simazine, and terbutylazine)]. The analytes were extracted using solid-phase extraction (SPE). The separation was carried out on an acquity UPLC BEH C18 column (1.7 microm, 50 mm x 1 mm ID) using a gradient elution profile and mobile phase consisting of 0.1% formic acid in water and acetonitrile. The pesticides were detected with a tandem mass spectrometer after being ionised positively or negatively (depending on the molecule) using an electrospray ionisation (ESI) source. To achieve the suitable extraction conditions for sample preparation, several parameters affecting the efficiency of SPE such as the nature of the sorbent and the eluent, extractant volume and pH were studied. The best recovery was obtained by the extraction with an Oasis HLB cartridge and 3 mL of a solution of acetonitrile/dichloromethane (1:1, v/v) at pH 2. The average recoveries of the pesticides in different samples ranged from 82 to 109%. The weight least squares (WLS) linear regression was used to calculate the limits of detection and quantification (LOD and LOQ) because the dispersion was heteroskedastic. All the pesticides could be correctly quantified at a concentration level of 50 ng L(-1) and most of them could be detected at a concentration inferior or equal to 8 ng L(-1). Efficiency and robustness of this method were evaluated by the analysis of several samples of real natural water.

Static headspace analysis of aliphatic amines in aqueous samples

Static headspace preconcentration was developed for the gas chromatographic analysis of aliphatic amines in aqueous samples. A liquid–gas ratio of 1, an incubation temperature of 80°C (15 min), a pH of 13.7 and a mixture of salts (NaCl and K2SO4) at saturation concentration gave a maximal headspace amine concentration. C1–C4 volatile aliphatic amines were separated on a specific PoraPLOT Amines capillary column. The detection limit was 0.2 μg/l for secondary and tertiary amines using a nitrogen–phosphorus detector. Primary amines were detected at higher concentrations (from 10 μg/l to 3000 μg/l). This polar capillary column required the systematic addition of ammonia to the sample (0.05 M concentration) in order to obtain a good repeatability (RSD=0.6–6.4%). This technique has been applied successfully for the monitoring of amine concentration at sub-μg/m3 level in a compost treatment plant using absorption sampling in a hydrochloric acid solution.

Standard addition method for the determination of pharmaceutical residues in drinking water by SPE–LC–MS/MS

The study of the occurrence and fate of pharmaceutical compounds in drinking or waste water processes has become very popular in recent years. Liquid chromatography with tandem mass spectrometry is a powerful analytical tool often used to determine pharmaceutical residues at trace level in water. However, many steps may disrupt the analytical procedure and bias the results. A list of 27 environmentally relevant molecules, including various therapeutic classes and (cardiovascular, veterinary and human antibiotics, neuroleptics, non-steroidal anti-inflammatory drugs, hormones and other miscellaneous pharmaceutical compounds), was selected. In this work, a method was developed using ultra performance liquid chromatography coupled to tandem mass spectrometry (UPLC–MS/MS) and solid-phase extraction to determine the concentration of the 27 targeted pharmaceutical compounds at the nanogram per litre level. The matrix effect was evaluated from water sampled at different treatment stages. Conventional methods with external calibration and internal standard correction were compared with the standard addition method (SAM). An accurate determination of pharmaceutical compounds in drinking water was obtained by the SAM associated with UPLC–MS/MS. The developed method was used to evaluate the occurrence and fate of pharmaceutical compounds in some drinking water treatment plants in the west of France.

Analysis and occurrence of odorous disinfection by-products from chlorination of amino acids in three different drinking water treatment plants and corresponding distribution networks.

Previous studies have established that odorous and stable chloraldimines are formed during amino acid chlorination in drinking water treatment. In order to identify at low level (10(-8) M) the presence of these odorous disinfection by-products in drinking water matrixes an analytical method was developed by using head space apparatus (HS) combined with a sorbent trap system linked to a GC with a mass spectrometer detector (HS/Trap/GC/MS). The analyses were carried out in three different drinking water supplies from the Paris area, during the four seasons. Free amino acids were monitored at the inlet of the plant. The odorous disinfection by-products were analyzed at the outlet of each drinking water treatment plant and the different distribution networks were connected to the corresponding plant. The results confirmed that the odorous chloraldimines are produced during chlorination of free amino acids in three different matrixes in different seasons throughout the year (N-chloroisobutaldimine; N-chloromethyl-2-butaldimine; N-chloromethyl-3-butaldimine (6-10 nM). The analytical method (HS/Trap/GC/MS) used to monitor odorous disinfection by-products appeared to be adapted for the detection of these by-products at nM level.

Kinetics of oxidation of odorous sulfur compounds in aqueous alkaline solution with H2O2.

Sulfur species oxidation is a crucial issue in wastewater treatment. The production of sulfur compounds like H2S, CH3SH, C2H5SH, disulfides and dimethyle sulfide generates odorous nuisances for the neighborhood. The oxidation of these species by H2O2 in alkaline solution has been investigated. The results showed that thiols CH3SH and C2H5SH react with H2O2 only in their dissociated form RS- with rate constants respectively k = 8.81 ± 0.48 M−1.s−1 and 8.37 ± 0.63 M−1.s−1. Mercaptans oxidation produces 100 % of dimethyldisulfide or diethyldisulfide. The oxidation of disulfides shows a difference of reactivity between H2O2 and HO2- towards sulfur species. Increasing the pH accelerates significantly the reactions in the case of CH3SSCH3. The oxidation rate can be described as: r = k[RSSR][H2O2][RSSR][H2O2] + k[RSSR][HO2-] [RSSR][HO2-] with k[RSSR][H2O2] = 1.2×10−4 ± 0.2×10−4 M−1.s−1 and k[RSSR][HO2-] = 3.4×10−4 ± 0.6×10−4 M−1.s−1 for CH3SSCH3. Dimethyl sulfide presents a reactivity different from disulfides. The oxidation rate can also be described as: r = k[CH3SCH3][H2O2][CH3SCH3][H2O2] + k[CH3SCH3][HO-] [CH3SCH3][HO2-], however, oxidation rate decreases with pH increase. k[CH3SCH3][H2O2] = 12.8×10−3 ± 0.96×10−3 M−1.s−1 and k[CH3SCH3][HO2-] = 4×10−3 ± 0.3×10−3 M−1.s−1.

Modelisation de l'evolution du parathion dans le milieu naturel sur un pilote de laboratoire

The evolution of parathion in a river, and its degradation by the principal natural factors (hydrolysis, photochemical oxidation, biological transformations and retention by sludge and sediments) has been studied on a laboratory pilot plant. The experimental period was 55 days. On the first 34 days, the plant was fed with a solution containing 13 mg l−1 of the pesticide, and during the following 21 days, the effluent was continuously recycled. In the condition in which our experiences were conducted, the main phenomena were biological degradation of the pesticide into non poisonous amino-parathion and its adsorption on the sediments. The quantity of the parathion reduced is proportionated to the quantity of the ATP found in the activated sludge tank. This biological method being the more important, the shock effect of the parathion on a bacterial population was studied by varying the organo-phosphorous concentration (5-10-15 mg l−1) and the quantity of volatile suspended solid (1-2-3 mg l−1). The microorganisms were not affected by the poison and a reduction to aminoparathion was obtained. The quantitative results may be expressed by the following equation − d(parathion)dt=K(ATP) (parathion). On the other hand a very large dose of parathion (1 mg l−1) destroyed the living organism. The presence of anionic or cationic surfactant plays no part in the toxicity of the parathion (15 mg l−1) on the biomass but the degradation of the organo-phosphorous pesticide is totally inhibited.

Comparative Study of Odors Removal in a Wastewater Treatment Plant by Wet Scrubbing and Oxidation by Chlorine or Ozone

Publisher Summary This chapter presents a comparative study of odor removal in a wastewater treatment plant by wet scrubbing and oxidation by chlorine or ozone. The models issued from this work provide a computerized tool capable of scaling a chemical washing deodorization plant, predicting the pollutants remaining in the treated air, and the reagents required to permanently ensure an absence of olfactory pollution. Urban wastewater treatment plants are frequently a source of olfactory nuisances caused by a multitude of compounds. The main pollutants are sulfur, nitrogen molecules and organic compounds such as aldehydes, ketones and volatile fatty acids. They are frequently present in the effluent as it enters the plant. Current deodorization techniques involve trapping or destroying the malodorous molecules. The techniques used include— masking, thermic oxidation with or without a catalyst, adsorption, biological oxidation, and wet scrubbing with or without a chemical reaction. The oxidizing agents used in the wastewater treatment stations are chlorine or ozone with the objective of destroying the absorbed molecules and, in certain cases, improving performance by accelerating mass transfer from the gaseous to the liquid phase.

Adsorption of Volatile Organic Compounds (VOC) mixtures onto activated carbon. Experimental study and simulation of multicomponent adsorption

In the present study, a simple mathematical model has been developed to simulate multicomponent fixed bed adsorption. The Linear Driving Force model is used to describe the intraparticle mass transfer. The competitive effect is accounted for through the multicomponent adsorption isotherm. This multicomponent equilibrium is described by the Ideal Adsorbed Solution Theory (IAST). To apply this theory, pure component adsorption isotherm data are represented by the Freundlich equation on a piecewise basis. For the prediction, operating conditions (flow rates, bed depths, input concentrations) and some characteristics of activated carbon must be known. It is also necessary to have pure component isotherm data. To demonstrate the applicability of the model, fixed bed experiments were carried out using a ternary mixture, containing methylethylketone, ethylene chloride, methylene chloride. A good agreement between calculations and experiments was obtained.

Contribution of the Differential Pulse Polarography (DPP) to the Analysis of Nitrated and Nitrosated Micropollutants in Waters

Taking into consideration the high toxicity of the nitrated and nitrosated products (e.g. nitrosamines, nitrophenols...), their analysis have to be made very carefully.

Co-current and counter-current spraying of odour-neutralizing products.

A lab‐scale pilot plant was developed in order to measure the efficiency of some odour‐neutralizing products for the removal of odorous compounds. Experiments were carried out on gas and liquid flows in two configurations: co‐current and counter‐current, which differ in the values of the drop diameter and the contact time, leading to different behaviours between highly water‐soluble compounds like ammonia and other compounds like sulphurous compounds. Mass transfer was shown to be modified by the presence of neutralizing products as a result of their pH and surface tension. Few chemical reactions, except for acidic or basic ones, could be highlighted. Olfactometric analyses were carried out and showed that, because of possible confusion between odours caused by the neutralizing product and odours caused by the by‐products, it was difficult to conclude that an obvious relation existed between physico‐chemical and olfactometric efficiencies.