Determination of low concentrations of benzene in urine using multi-dimensional gas chromatography

A method for the determination of benzene in urine of occupationally or env ironmentally exposed persons was developed. The method was based on dynamic headspace, preconcentration on a solid sorbent, followed by thermal desorp tion and gas chromatographic determination. To achieve sufficient selectivi ty, we used multi-dimensional gas chromatography in combination with the in expensive and robust flame ionisation detector. The limit of detection was 7 ng 1(-1) and the limit of quantification was 23 ng 1(-1). The linearity w as good (correlation coefficient 0.999) in the range examined (20-4000 ng 1 (-1)) and the repeatability was 9%. The average recovery at low concentrati ons (20-400 ng 1(-1)) was 86%. Analysis of a certified reference material o f benzene in water, traceable to NIST, did not differ significantly from th e certified value. Samples, frozen (-20 degreesC) in glass bottles sealed w ith Teflon-silicon septa, were stable for 1 year and refrigerated samples ( 4 degreesC) for at least 1 week. Loss of benzene during the collection and transfer of urine was investigated and found to be acceptable. The method i s a cost effective and robust alternative to GC-MS and permits reliable qua ntification of occupational exposure and, in most cases, also of urine conc entrations that can be expected from environmental exposure.