Strong anion-exchange discs

One special application of SEE involves its joint use with subcritical water to extract Dacthal and its acid metabolites from soil the herbicide is converted to monoacid and diacid derivatives that are more readily soluble in water than the parent compound. Thus, following extraction of Dacthal with supercritical CO, at 400 bar at 150°C for 15 min, its monoacid and diacid metabolites were extracted from soil in 10 min, using subcritical water conditions (viz. 200 bar and 50°C). The metabolites were trapped in situ on a strong anion-exchange disc placed over the exit frit in the extraction cell and subsequently combined with Dacthal by placing the disc into the GC autosampler vial containing the SEE extract to allow their simultaneous elution from the disc and deriva-tization to their ethyl esters. Only a single sample was analysed also, because the disc-catalysed alkylation reaction did not transesterify Dacthal, its speciation was maintained [180]. 

Recently, Hawthorne et al. coupled the ASE technique to solid-phase extraction using sorption discs that were placed in the extraction chamber together with the sample in order to simultaneously concentrate and extract polar compounds such as acid herbicides and their esters from soils, using strong anion-exchange (SAX) discs [99]. They also used this combined methodology to develop a convenient method of shipping extracts from field sites to the analytical laboratory [100]. In the former application, the esters of the... 

Extraction discs placed directly over the exit frit of the extraction cell have been used for the preconcentration of highly water-soluble acidic compounds from soil [39]. A strong anion-exchange (SAX) sorption disc facilitated not only preconcentration but also derivatization of the analytes. 

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