[Comparison of standard methods for determination of pseudocumene in urine using gas chromatography with the...

The biological indicators that have been proposed for monitoring occupational exposure are: concentration of the solvent or metabolized compounds in alveolar or expired air samples, in venous or arterial capillary blood samples and in urine samples. Recently, many researches have reported significant relationships between the time-weighted average exposure and the urinary concentrations for various solvents. The aim of our study was to compare two methods in which urinary concentrations of pseudocumene were determined by gas chromatography using headspace technique. The standard method was based on determining concentration of organic solvents in 100 mm3 or 1 cm3 samples of urine. The incubation conditions were as follows: equilibration temperature and time: 70 degrees C, 30 min., respectively. 1 cm3 of gas phase was sampled with a gas-tight syringe and injected into a gas chromatograph. The new method using Headspace Sampler was based on determining concentrations of solvents in 10 cm3 samples of urine. The operating conditions were: equilibration time 30 min.; equlibration temperature 80 degrees C; pressurization time 0.1 min.; loop fill time 0.1 min.; loop equilibration 0.1 min.; loop equilibration time 0.05 min.; inject time 1 min.; loop temperature 150 degrees C, transfer line temperature 150 degrees C. HP 7694 Headspace Sampler minimizes sample degradation with a chemically inert pathway extending from the sample loop to the column head. The analytical parameters of both methods (linearity, precision, reproducibility, stability and sensitivity) are fully compatible with the principles of biological monitoring. Application of the headspace autosampler eliminated interference from the biological matrix and made it possible to achieve very low detection limit.