No abstract

We describe here a new method for the analysis of alkanes ( n-hexane, n-heptane, n-octane, n-nonane, n-decane, n-undecane, and n-dodecane) in blood using headspace solid-phase microextraction gas chromatography/mass spectrometry. This method is used to measure picogram per milliliter levels of n-alkanes in blood that may result from nonoccupational exposure to alkanes and other volatile nonpolar compounds from common sources such as petroleum-based fuel. This alkane signature is useful in distinguishing typical fuel biomarkers (e.g., benzene and toluene) from other confounding exposure sources such as cigarette smoke. Development of this method required special attention to sample handling as alkanes are not highly soluble in aqueous matrixes and exist as ubiquitous compounds found in many laboratory materials and the environment. In particular, significant n-hexane contamination ( approximately 0.4 ng/mL) occurred from collecting blood samples in vacutainers. This residue was removed by boiling the vacutainer stoppers in methanol followed by vacuum baking. For all the alkanes, the calculated accuracy demonstrated for the water-based standards ranged from 3.3% to 17% as deduced from the difference of the lowest and middle standards from the curve fit. Quality control data among runs over a 10 month period were found to vary from 14% to -29%, with a few exceptions. The resulting quantification limits for n-hexane through n-decane ranged from 0.069 to 0.132 ng/mL. In the analysis of 1200 blood samples from people with no known occupational exposure, median blood levels for all n-alkanes were below these quantification limits. n-Hexane levels above the method detection limit were, however, found in 1.3% of the samples.

Biomonitoring, or the measurement of environmental chemicals in human tissues and fluids, is used to supplement-and in some cases replace-more traditional exposure assessments which measure chemicals in environmental media. Volatile organic compounds (VOCs) in physiological fluids are biomarkers of exposure that present numerous challenges for sample collection and analysis. To date, a thorough evaluation of methods for collection and analysis of breast milk samples for volatiles has not been conducted. In this paper, we describe the development and validation of methods for collecting, storing, and analyzing 36 volatile organic compounds (VOCs) in breast milk to assess VOC exposure of lactating women and nursing infants. Volatile analyte loss was minimized by collecting and storing samples in containers with small headspace volume resulting in recovery >or=70% for all 10 VOCs detected in most breast milk samples. Potential contamination by chloroform, benzene, toluene, ethylbenzene, xylenes, and methyl-tert-butyl ether was minimized by using specially treated sample collection materials. Method detection limits in the low parts per trillion range were achieved by using solid-phase microextraction headspace sampling, gas chromatography, and selective ion monitoring mass spectrometry. We used this method to analyze 3 mL aliquots of breast milk collected from 12 women and found that 10 of the 36 VOCs were detectable in most samples (median values follow): m/p-xylene, 0.539 ng mL(-1); toluene, 0.464 ng mL(-1); 1,4-dichlorobenzene, 0.170 ng mL(-1); tetrachloroethylene, 0.165 ng mL(-1); o-xylene, 0.159 ng mL(-1); ethylbenzene, 0.0149 ng mL(-1); styrene, 0.129 ng mL(-1); benzene, 0.080 ng mL(-1); chloroform, 0.030 ng mL(-1); and methyl-tert-butyl ether, 0.016 ng mL(-1).