Determination of volatile organic compounds in biological fluids and tissues using solid phase microextraction and gas chromatography: Styrene and toluene

Purpose. Epidemiological and animal research investigations have shown that toluene and styrene are toxic compounds that lead to impairment of the nervous system. Liquid-liquid phase, head-space and solid phase micro extraction methods are generally used to quantitate toluene and styrene in biological samples. Though these methods are sufficiently robust and apt for quantitative analysis, most of them are not sensitive enough for applications involving extremely small sample volumes. Here we report a method for quantitative analysis of low concentrations of styrene and toluene in biological samples using head space solid phase micro extraction (HS-SPME) and gas chromatography (GC) equipped with a flame ionization detector (FID). A wide linear range of detection, high sensitivity, good reproducibility and accuracy makes this method appropriate for quantitative determination of styrene and toluene levels in biological fluids and tissues, particularly when limited sample volume is available for analysis.; Methods. The method was developed by optimizing the operating parameters that affect the HS-SPME-GC process during adsorption and desorption. Five operating parameters were evaluated in the following order: desorption time, depth of the fiber in the GC injection port during desorption, adsorption time, adsorption temperature and sample volume. During optimization, one parameter was varied at a time while keeping the other parameters constant. Once a parameter was optimized, its optimized condition was used in the evaluation of the remaining parameters and during method validation. Method validation includes studies on linearity, accuracy, precision, detection limits, recovery, interference and stability.; Results. During method development five operating parameters were evaluated and optimized in the following order: Desorption time (30 seconds), depth of the fiber in the GC injection port during desorption (3.7 cm), adsorption time (4 mins) and adsorption temperature (room temperature). The optimized method had a wide range of linearity (0.05-50 ng/muL), high precision (less than 5%), good accuracy (less than 10%) and low detection limits (0.13 ng/10 muL and 0.08 ng/10 muL for styrene and toluene respectively) For biological sample matrices of lipid content less than 10%, relative recovery was approximately 100%. Since recovery of styrene decreases significantly when the lipid composition of the matrix is greater than 10% this method cannot be used to determine styrene concentrations in fatty tissues like the brain and adipose tissue without taking lipid content into consideration for estimating recoveries.; Conclusion. This HS-SPME-GC method can easily be applied to estimate styrene and toluene concentrations in body fluids such as blood, urine, cerebrospinal fluid, perilymph and bile as well as tissues of low lipid content like cochlea. The method is specifically designed for pharmacology and toxicology studies where extremely small volumes of sample are available for analysis. The analytical technique can be used to further study the pharmacokinetics of styrene and toluene in animal and human models. It can also be used to assess levels in tissues in order to study the mechanism of toxicity of styrene and toluene in animal models. This method has been successfully used by our research group to study---(1) Distribution of styrene in cochlea; (2) Kinetics of styrene in blood as a function of time; and (3) Kinetics of styrene in blood as a function of concentration.