Post-Extraction Losses of Volatile Aromatic Hydrocarbons During Capillary Extraction–HRGC Analysis: A Quantitative Assessment (original) (raw)

Benzene, toluene, ethylbenzene and o-, m-, and p-xylenes (BTEX), were extracted from aqueous samples by capillary extraction (CEx), a manual form of in-tube microextraction inherently compatible with capillary GC, and analyzed by HRGC analysis in order to quantify the post-extraction losses of these volatile organic compounds. Accuracy of the VOC determination by CEx-HRGC is dependent on these losses. The used active extraction devices were fused silica open-tubular capillaries of 0.25 mm i.d., with lengths in the range of 3-15 cm, coated with a 0.25 lm film of PTE-5 (5% phenyl methylpolysiloxane) stationary phase. The losses decreased remarkably when the extractor lengths were increased. In particular, the losses were modest or negligible for capillary extractors of usual length, though the losses increased with rising solute volatility and 'lag time' (the length of time required to connect in-line the laden capillary extractors with the HRGC column). BTEX losses between 2% (benzene) and 0.5% (o-xylene) resulted from CEx conducted under very usual conditions, independently from sample concentration. The short-term precision of the CE-HRGC experiments, expressed as relative standard deviation, was 0.8-4.9% (n = 5).