Determination of benzene in urine and breath for monitoring of benzene exposure

Abstract: The aim of this work was to develop and validate methods for determination of unmetabolized benzene in breath and urine. The methods were intended for the bio monitoring of benzene to assess both occupational and environmental exposure.A method was developed for the determination of benzene in end-exhaled air. The sampling device consisted of a modified peak expiratory flow meter into which the subjects expired. A 100 ml sample was drawn through an adsorbent tube, filled with Tenax TA. The adsorbent was thermally desorbed and the analysis was made by gas chromatography (GC) and flame ionization detection (FID). The limit of detection (LOD), with a sample volume of 100 ml, was 0.5 µg/m3. The repeatability varied from 2.6% in the laboratory to 13% in the field. Storage of samples at room temperature for 1 week showed no significant decrease.Two methods for the determination of benzene in urine were developed, both based on sample preparation by dynamic headspace and preconcentration of the analyte on a solid adsorbent. The adsorbent was subsequently thermally desorbed. To achieve sufficient selectivity, we used GC and mass selective (MS) detection in one method and multi-dimensional separation and FID in the other. The selectivity was good in both methods and the performance was comparable. LOD for the MS-method was 6.5 ng/L, and for the multi-dimensional method 7.0 ng/L. Linearity was good in the concentration range examined (20-4000 ng/L). Repeatability was <9%. Recovery in the sample preparation step was 83-85%. Losses during the collection were also studied. Samples could be stored frozen in glass bottles for 1 year.A robust sample preparation method for the extraction of benzene in urine was developed. It was based on extraction through a flat, porous membrane to a gaseous acceptor and pre-concentration on a solid adsorbent. The analysis was made by thermal desorption and GC-MS. The extraction efficiency was close to quantitative (95%) at room temperature. Extraction at 50ºC did not increase recovery. Memory effects were small. Linearity was good in the concentration range examined (20-4000 ng/L). The repeatability at 50 ng/L and 400 ng/L was 1.5% and 1.2%, respectively. The LOD was 12 ng/L. In contrast to dynamic headspace, the method is easily automated.Unmetabolised benzene in breath or urine is a specific biological marker for benzene exposure. The collection of breath and urine is simple, non-invasive and acceptable for the subjects. The limit of detection of the methods permit quantifications of benzene in breath and urine in occupationally exposed subjects, and in the majority of the general population.