Reliability of biological monitoring methods for Volatile Organic Compounds exposure assessment

Exposure assessment may be performed by ambient air monitoring and by biological monitoring (BM) of body fluids. The main analytical technique in BM, for the analysis of Volatile Organic Compounds (VOCs) in blood and urine, is the static head-space technique followed by capillary gas chromatography with different detectors. The actual measurement uncertainties are, at best, 15 to 30%, depending on the actual concentration. Among the numerous uncertainty sources, calibration standards are one of the most important. IUPAC highly recommended the development of new reliable and standardized procedure to prepare matrix calibration standards. In this work the reliability of static head-space gas chromatography measurement for biological monitoring is discussed. Measurement theory is overviewed, current procedures for preparation of matrix calibration standards are metrologically analyzed, solutions to improve accuracy of calibration standards and analytical reproducibility are presented. Calculated accuracy for actual preparations of matrix calibration standards is resulted lower than 5%, VOC-spiking to vapor phase and a careful design of component vial volumes and temperature can improve method reliability.