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Development of an automated chromatographic system for the determination of pesticide and major conversion product residues

By Ιωάννης Πατσιάς


A multiresidue analytical method for the determination of a wide range of pesticides, major conversion products and other organic micropollutants (phenols, anilines and caffeine) in water based on the on-line coupling of solid phase extraction and high performance liquid chromatography (on-line SPE/HPLC) has been developed. Analyte detection has been performed by a diode-array detector operated in tandem mode with either an electrochemical detector or a fluorescence detector placed after a two-stage post-column derivatization system. Using 100 mL sample volume the recoveries of most solutes, except for the highly polar and highly hydrophobic compounds, were better than 80_%; the recoveries of the highly polar compounds (aniline, clopyralid, picloram, hydroxysimazine, hydroxyatrazine and phenol) were lower than 80% due to their early breakthrough from the solid-phase extraction cartridges, while for the highly hydrophobic compounds the reduced recoveries were attributed to their adsorption onto the surfaces of the analytical equipment. Analyte detection limits, calculated by analyzing spiked river water samples, were better than 0.1_μg/L, which is the maximum acceptable concentration of pesticide parent compounds and phenols in drinking water according to the EU Directive 778/80. The proposed analytical method was applied to study the stability of a wide range of herbicides during sample storage for a period of three months as a function of storage temperature (refrigeration and 20_0C), sample pH (3 and 7) and acidification medium (sulfuric and ortho-phosphoric acid). Many of the compounds were found to be unstable in water, while sample storage conditions had significant effect on their stability. Among the compounds exhibiting high degree of instability were propanil, when stored under neutral conditions, diclofop-methyl, fluazifop-butyl, dinitroanilines, tralkoxydim and triasulfuron, when stored under acidic conditions, clopyralid, metamitron, metribuzin along with its conversion products and 2,4-DB, when water samples were stored at 20_0C. The stability of the above studied herbicides has been also evaluated under sorbed conditions, when water samples were processed by solid-phase extraction and the respective cartridges were stored for a period of three months under deep freeze, refrigeration or at 20_0C. Most compounds, expect for the highly polar analytes, exhibited higher stability under sorbed conditions than when being in solution of an aqueous medium. The stability of the highly polar analytes such as clopyralid, picloram, hydroxysimazine, imazapyr, metolachlor-sulfonic_acid, diketometribuzin, desaminodiketometribuzin, desaminometribuzin and metribuzin decreased significantly during storage under sorbed conditions, even though clopyralid was still more stable than when being in solution. Storage temperature and storage time had significant effect not only on herbicide stability but also on their chromatographic performance during analysis. xiii

Topics: Γεωργικά φάρμακα, Φαινόλες, Παράγωγα ανιλίνης, Καφεΐνη, Υπολείμματα, Υγρή χρωματογραφία, Εκχύλιση στερεάς φάσης, Αυτοματισμός, Pesticides, Phenols, Anilines, Caffeine, Residues, Liquid chromatorgaphy, Solid phase extraction, Automation
Publisher: Aristotle University Of Thessaloniki (AUTH)
Year: 2003
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