Guidelines for capillary extraction–capillary gas chromatography: preparation of extractors and analysis of aromatic compounds in water

The benzene, toluene, ethylbenzene and xylenes system (BTEX) in clean water is studied to verify the performance of capillary extraction as an extraction-preconcentration technique well hyphenated with GC. The approach uses pieces of coated capillaries usually 5−30 cm long, trimmed from customary high-resolution GC columns but carrying glass press-fits at their ends. The preparation of these ‘capillary extractors’ is explained, and their performance is discussed providing guidelines for use. Injection by capillary extraction is such that (i) band broadening in time is null, and (ii) band broadening in space cannot be higher than the extractor length. Speed, cleanliness and operative simplicity of the capillary extraction approach are remarkable, pros and cons are complementary to those of solid phase microextraction (SPME) or stir bar sorptive extraction (SBSE). Capillary extraction–capillary GC analysis of aqueous BTEX samples, in a clean water matrix, allows low part-per-billion detection limits, and does not require heated injectors or cryofocusing devices.