A substantial number of pesticides are still very difficult to analyse in water at the 0.10 µg/L level, the maximum allowable concentration for the quality of water intended for human consumption set by the European Union. Among them are the widely used polar non-selective glyphosate herbicide and its major degradation product AMPA.Several chromatographic methods have been developed for the analysis of glyphosate and AMPA. Methods involving liquid chromatography seem to give better results since glyphosate and AMPA are very polar compounds. The nature of chromatographic phase depends on the detection mode selected. For instance, ionic phases are combined with conductimetric detection [1], mass spectrometry detection [2,3], UV or fluorescence after post-column derivatization with OPA [4], ninhydrin [5,6,7] or Al 3+ -morin reagent [8]. With a precolumn derivatization with 9-fluorenylmethylchloroformate (FMOC-Cl) for instance, reversed phase column may be used before fluorescence or UV detection.A pre-concentration of sample is necessary to reach the limit of quantification of 0.10 µg/L. Without any pre-concentration, the best performances were obtained by LC-MS analysis with a limit of detection (L. The aim of this study was to reach a limit of quantification lower than 0.10 µg/L without any pre-concentration or purification of samples before analysis. The work was oriented along two ways:1. Improvement of a published method involving LCFluorescence analysis after pre-column FMOC derivatization for direct determination of glyphosate and AMPA in water samples at the 0.10 µg/L level that is suitable for monitoring purposes (part I). This choice is explained below.2. Development of a new method based on derivatization of glyphosate and AMPA with fluorogenic reagents. The first results of this work are presented in part II with 4-chloro-7-nitrobenzofurazan reagent.Among the methods described in literature for the analysis of glyphosate and AMPA in water by liquid chromatography, the way of pre-column derivatization along with fluorescence detection was selected because its easy use. Few coupling reagents have been tested: dansyl chloride [10], ptoluenesulfonyl chloride [11,12] Abstract. An analytical method has been developed for the determination of glyphosate herbicide and its metabolite aminomethylphosphonic acid (AMPA) in natural waters to a level of 0.10 µg/L with a good linearity in the range 0.10-2.00 µg/L and coefficients of variation under 20 % for each spiked level. The procedure involves a precolumn derivatization step with 9-fluorenylmethylchloroformate (FMOC-Cl) yielding highly fluorescent derivatives of the analytes which then can be determined by HPLC with fluorescence detection. The method is used for analysis of natural (surface and ground) and treated waters. Matrice effects have been pointed out, particularly the effects of hard ionic content and the effects of chlorine residues into treated waters.
Abstract. A GC method is described for the simultaneous determination of triazines and phenylureas in aqueous samples by large volume injection with a Programmable Temperature Vaporisator injector (PTV) and ion trap detection (ITD). The analytical column (DB 5MS, 30 m, 0.25 mm, 0.25 µm) is connected to a pre-column (DB 5MS, 5 m, 0.25 mm, 0.25 µm) via a cross piece valve (MCS) to prevent residual solvant vapour from polluting the analytical column. The 8 pesticides (4 triazines and 4 ureas) are determined by this method, the linearity is improved using 2 Fisher test. The detection and the quantification limits are also determined for each compounds and are less than 0.10 µg/L which is the limit fixed by the ECC reglementation on drinking water.
IntroductionIn the first part of this study [1], a method for the determination of glyphosate (i.e., N-(phosphonomethyl)glycine) and AMPA (i.e., (aminomethyl)phosphonic acid) in water was developed, using the well-known fluorogenic reagent FMOC (i.e., 9-fluorenylmethyl chloroformate).The ability of FMOC to react in water with both compounds to give fluorogenic products permitted to use the very sensitive fluorimetric detector to reach the 0.1 µg/L level of quantification. But one of the main problems when using such detector is the presence in certain matrix of impurities. To avoid this, we can make supplementation or modify the analytical conditions.In the second part of the study, we attempted to develop a confirmation method and focus our efforts on amino function derivatization with fluorogenic reagents. Among them [2,3,4], the non fluorescent 4-chloro-7-nitrobenzofurazan [4] (i.e., NBD-Cl) was tested. This reaction has already been proposed by Cochrane et al. [5] for the derivatization of primary and secondary amino group for amino acids. NBDCl, introduced in 1968, reacts with primary and secondary amines to produce fluorescent derivatives; it also reacts with hydroxyl and thiol groups but its higher reactivity toward amino groups is effective for selective derivatization. Furthermore these adducts absorb and emit at shorter wavelengths and are less fluorescent than amine derivatives.NBD-Cl is extensively used as derivatization reagent for chromatographic analysis of amino acids and other low molecular weight amines. Unlike o-phthalaldehyde and fluorescamine, it reacts with secondary amines and it is therefore able of derivatization with secondary amino acids [2,3,4]. The aromatic nucleophilic substitution of glyphosate with NBD-Cl is presented in figure 1.The aim of this second part was to evaluate the ability of NBD-Cl to react in water with the non selective herbicide glyphosate and its degradation product AMPA at traces level. An optimisation of derivatization and separation conditions have been made. In the conclusion, we have compared both methods in terms of specificity and sensitivity. Experimental part ChemicalsGlyphosate and AMPA in water (10 ng/µL) were supplied from Dr Ehrenstorfer (Germany). NBD-Cl (4-chloro-7-nitrobenzofurazan 99 %) and glyphosate (N-(phosphonomethyl)-glycine 97 %) powders were purchased from Fluka (France). Acetonitrile (ACN), ethanol and diethyl ether, HPLC grade, were purchased from Carlo Erba (France). Abstract. An analytical method was developed for the determination of glyphosate and AMPA in water. This method involves derivatization in situ with NBD-Cl reagent at 60°C. The quantification is performed using liquid chromatography with fluorescence detection after a separation on an amino column. The limit of quantification was estimated at 1 µg/L level for glyphosate and at 0.1 µg/L level for AMPA.
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