AUTOMATED DERIVATIZATION FOR ONLINE SOLID-PHASE EXTRACTION GAS-CHROMATOGRAPHY - PHENOLIC-COMPOUNDS

An automated system for derivatization was coupled on-line with solid- phase extraction-gas-chromatography (SPE-GC). The system was optimized for the determination of phenol and chlorinated phenols in aqueous sa mples. The test analytes were acetylated with acetic anhydride; proper buffering of the sample was a critical factor. Nest, the phenol aceta tes were enriched on a SPE cartridge and transferred to a GC; two appr oaches were studied. In the first approach, the derivatives were enric hed on disposable C18 cartridges (ASPEC type) and desorbed with methyl acetate. An aliquot of the final eluate was injected on-line into the GC by means of a loop-type interface. In the second approach, trace e nrichment was pel formed on a 10 x 2 mm i.d. LC-type precolumn packed with polystyrenedivinylbenzene copolymer (PLRP-S). This precolumn was dried with a nitrogen purge and the phenol acetates were desorbed with ethyl acetate which was injected on-line into the retention gap of th e GC under partially concurrent solvent evaporation (PCSE) conditions. The derivatization-SPE-GC system which was based on the loop-type int el face has the advantage of simplicity and easy operation, the main d rawback is the impossibility to determine phenol acetates which elute prior to trichlorophenol acetates. With the derivatization-SPE-GC appr oach using PCSE-based desorption, even the most volatile analyte of th e test series, phenol acetate, can be determined successfully. The ent ire procedure, including the derivatization step, was fully automated and integrated in one set-up. The analytes were detected with a flame ionization detector (FID). The precision data for the integrated on-li ne derivatization-SP-FID system were fully satisfactory, with RSD valu es of 1-12% at the 1 mu g/1 level. When a sample volume of 2.2 mi was analyzed, the detection limits for the chlorinated phenol acetates Her e in the 0.1-0.3 mu g/1 range.