Application of headspace solid phase dynamic extraction gas chromatography/mass spectrometry (HS-SPDE-GC/MS) for biomonitoring of n-heptane and its metabolites in blood

Solid phase dynamic extraction (SPDE) is an innovative sample preparation and enrichment technique in connection with gas chromatography (GC). Using SPDE, we developed a method for simultaneous determination of n-heptane and its mono-oxygenated metabolites heptane-4-one, 3-one, 2-one, 4-ol, 3-ol, 2-ol, and 1-ol in blood. After adjustment of various extraction and desorption parameters, method validation resulted in limits of detection (LOD) between 0.006 (heptane-4-one) and 0.021 mg/L (heptane-1-ol). Intra-assay coefficients of variation ranged between 4.8% and 20.8% while relative recovery ranged between 100% and 117% (spiked concentration 0.128 mg/L, n = 8). The method was applied to blood samples, which have been collected from 20 volunteers after controlled inhalative exposure to 167, 333, and 500 ppm n-heptane. After 3 h of exposure, n-heptane and heptane-2-one were detectable in all samples in concentrations ranging up to 2.903 and 0.495 mg/L, while the concentrations of the remaining analytes were closer to the respective LOD or even below. A significant linear relationship with ambient exposure (R2 = 0.701, p < 0.001, n = 55) was found for n-heptane in blood, which could be helpful for evaluation of biological exposure limits in future. Due to its high abundance in blood, 2-heptanone could be an interesting candidate as a biomarker also in alternative matrices such as urine or saliva.

► Determination of n-heptane and mono-oxygenated metabolites in blood. ► Development, validation and application of a biomonitoring method using dynamic headspace extraction for analyte enrichment. ► Controlled inhalation exposure of volunteers to n-heptane followed by blood sampling. ► Linear correlation of external and internal exposure using n-heptane in blood as biomarker. ► Heptan-2-one main metabolite in blood and interesting candidate as a biomarker in alternative matrices such as urine or saliva.