VOLATILE, NONPURGEABLE, WATER-SOLUBLE CO

An azeotrope is a liquid mixture of two or more substances which behaves like a single substance, in that it boils at a constant temperature and the vapors released have a constant composition. Azeotropic distillation is a technique which uses the ability of selected organic compounds to form binary azeotropes with water to facilitate the separation of the compounds from a complex matrix. 2.2 Macrodistillation technique: One liter of the sample is buffered to pH 7, spiked with the surrogate spiking solution, and brought to boiling in a 2 L distillation flask. The polar, volatile organic compounds (VOCs) distill into the distillate chamber for 1 hour, and are retained there (Figure 1). The condensate overflows back into the pot and contacts the rising steam. The VOCs are stripped by the steam and are recycled back into the distillate chamber. Analytes are detected and quantitated by either direct aqueous injection GC/MS or GC/FID. 2.3 Microdistillation technique: An aliquot (normally 5 g or 40 mL) of sample is azeotropically distilled, and the first 100 µL to 300 µL of distillate are collected. The water soluble volatile organic compounds are concentrated into the distillate using a microdistillation system. Most semi- and nonvolatile interferences remain in the boiling flask. Use of an internal standard is recommended to improve method precision. Concentration factors are typically one and two orders of magnitude for soil and water matrices, respectively. The distillation takes five to six minutes. Analytes are detected and quantitated by either direct aqueous injection GC/MS or GC/FID.