Recent Advancements in Method Development and Exposure Assessment for 45 Blood VOCs Analyzed by Headspace SPME GC-MS

Abstract

For over three decades our laboratory has been developing and improving methods for quantifying toxic volatile organic compounds (VOCs) in blood in support of numerous national and regional studies, including nine National Health and Nutrition Examination Survey (NHANES) cycles. Absorption of VOCs most commonly occurs through inhalation, as 100% of blood circulates to the lungs for exchange with alveolar gas. The high blood:gas partition ratios of most VOCs favor preconcentration in the blood, but blood VOC equilibration with tissues and organs is what influences VOC elimination half-life. As such, VOC analysis in blood is best-suited for compounds that are stable in the body by offering a direct measure of VOC burden experienced by tissues and organs.The current analysis method uses headspace solid-phase microextraction (HS-SPME) and gas chromatography-mass spectrometry (GC-MS). Important to the success of this method is the use of isotopically labeled analogs specific to every compound to compensate for competition effects in the headspace and SPME fiber, as well as adsorption and volatilization losses. The combination of these techniques has enabled us to simultaneously quantify a broad array of VOCs (boiling points from 32 to 204 °C) in the low parts-per-trillion (ng/L) range from a 3-mL blood sample.This presentation will include an overview of the blood VOC method and describe recent improvements to achieve accuracy and precision of < 15% for nonpolar compounds (e.g., alkanes) and within 5% for most of the other VOCs. We will also describe noteworthy blood VOC trends in the United States and reveal new analytes that are to be included in future studies and NHANES cycles. In addition to individual VOC trends, we will describe recent work comparing relative VOC levels among participants using artificial neural networks as a means to objectively distinguish exposure between different VOC sources within a large population.