Urinary benzene determination by SPME/GC–MS: A study of variables by fractional factorial design and response surface methodology

The urinary excretion of the unmetabolized benzene seems to be a very good index for biomonitoring benzene in occupationally exposed people. The use of solid phase microextraction (SPME) offers important advantages for its determination. Several variables can influence the benzene extraction process. Experimental design methodology was used to estimate the influence of the different variables and to evaluate the simultaneous effect of the more significant variables on the benzene extraction. The results showed that sample temperature, sample volume and their interaction were the more significant factors. A model was found that relates the amount of benzene extracted with the studied variables. The more adequate working conditions were: extraction temperature 15 °C, incubation time 1 min, extraction time 1 min and 2.5 ml of sample volume. The results indicate that this method is capable of providing sensitive and accurate results for the biomonitoring of benzene in urine.