Development of an automated system for the analysis of inorganic chloramines in swimming pools via multi-syringe chromatography and photometric detection with ABTS

International audienceInorganic chloramines are disinfection by-products resulting from the unwanted reaction between chlorine used as disinfectant in swimming pools and nitrogenous compounds brought by bathers. This parameter (total chloramines or combined chlorine) is currently measured on site by a colorimetric method that does not allow to measure only inorganic chloramines. In this paper, a multi-syringe chromatography system combined with a post column derivatization is applied for the first time for the specific detection of the three individual inorganic chloramines (monochloramine, dichloramine and trichloramine). These latter ones are separated using a low-pressure monolithic C18 column, and separately detected after a post-column reaction with the chromogenic reagent ABTS (2,2'-azino-bis-(3-ethyl-benzothiazoline)-6-sulfonic acid-diammonium salt). Development of two ABTS reagents provides discrimination of chlorine and monochloramine that are not separated on the column. Optimization of the experimental conditions enables determination of inorganic chloramines with very good detection limits (around 10 µg eq.Cl2 L-1) without interferences from other chlorinated compounds such as organic chloramines or free available chlorine. The validation of the whole procedure has been successfully applied to real swimming pools samples

Development of a fluorescence-based microplate method for the determination of volatile fatty acids in anaerobically digested and sewage sludges

International audienceThis paper presents a simple, accurate and multi-sample method for the determination of volatile fatty acids (VFAs) thanks to a 96-well microplate technique. A procedure using an activating reagent of the carboxylic function (water-soluble carbodiimide EDC) and a fluorescent amino labeling reagent (N-(1-naphthyl)ethylenediamine, EDAN) allows the formation of an isoindole derivative that needs to be separated from initial fluorescent amine for efficient VFAs determination. Isolation of these fluorescent VFA-derivatives was carried out by use of the fluorescent quenching of EDAN with o-phthaldialdehyde (OPA). Quenching was most efficient at pH around 7 and by heating at 40 degrees C within the microplate reader. This optimized procedure has been applied to various carboxylic acids and other organic compounds, demonstrating that VFA exhibit the highest fluorescence responses with homogeneous results for the main ones (acetic, propionic and butyric acid, all mass concentration expressed as acetic acid equivalents). This protocol was calibrated against acetic acid and determination of VFA was thus possible in the range 3.9-2000 mg L-1 (acetic acid equivalents). Subsequent application to real samples (sewage sludges or anaerobically digested samples) and comparison to gas chromatography analyses gave accurate results, proving the great potential of our high-throughput microplate-based technique for the analysis of VFA. (C) 2011 Elsevier B.V. All rights reserved

Development of a simple, low-cost and rapid thin-layer chromatography method for the determination of individual volatile fatty acids

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A highly-sensitive microplate fluorimetric method for the high-throughput determination of nitrate ion in aqueous compost extracts

International audience9 In this paper, a new spectrofluorimetric method for the determination of nitrate in aqueous 10 compost extracts is presented. The microplate procedure is based on the reduction of nitrate 11 to ammonium by means of Zn powder under acidic conditions and the following derivatization 12 of ammonium with o-phtaladehyde (OPA) and N-acetylcysteine (NAC) to give a fluorescent 13 derivative. Optimization work allowed performing the reduction in 30 min on a small sample 14 volume (150 µL) and using a little quantity of metal (20 mg). The use of strong acids is also 15 avoided. Excellent limit of detection was achieved (1.3 µM = 0.08 mg.L-1 NO3-) along with good 16 precision levels (4.2 and 14.3 % for 50 and 5 µM, respectively) and a satisfactory linear 17 dynamic range (4-100 µM). A good agreement between data coming from our method and 18 from ion-exchange chromatography was found on real compost samples, indicating a good 19 level of accuracy. 20 21 2

Occurrence and fate of selected surfactants in seawater at the outfall of the Marseille urban sewerage system

International audienceThis paper describes an investigation of linear alkylbenzene sulfonates (LAS) and nonylphenol ethoxylates (NPEO) and their metabolites in the vicinity of the Marseille sewage outfall (wastewater treatment plant with a capacity of 1.860 million inhabitant equivalents, Northwestern Mediterranean, southeast of France). This analytical survey describes their occurrence in the subsurface and sea surface layers and investigates their possible fates in this marine environment. The results indicated the presence of LAS in both layers and up to 3 km from the discharge point, whereas the concentration of sulfophenyl carboxylic acids, which are the main metabolites of LAS, was only significant near the sewer outfall and in the surface layer. The NPEO were present only in minor quantities, especially near the discharge point, and no other selected metabolites were detected. The fate of the surfactants in question was then assessed by two types of experiments according to their potential means of degradation under natural conditions. Biodegradation assays were conducted according to a protocol defined by the United States Environmental Protection Agency (''Biodegradability in sea water, 835.3160''), with variations in the substrate input frequencies. Photodegradation experiments were carried out in a solar simulator reactor. These results demonstrated the low photodegradability and rapid primary biodegradation of LAS (with half-life times between 10.3 and 11.5 days) in the coastal area under study, although some LAS metabolites were more recalcitrant to biodegradation in this specific environment, which was also validated by linear alkylbenzene analysis in the two selected sediment stations