Development of a method for dioxin analysis of small serum samples with reduced risk of volatilization

To analyze the dioxin content of samples, including dibenzo-p-dioxins/dibenzofurans, and coplanar polychlorinated biphenyls (Co-PCBs), a large volume is usually necessary. This is difficult, however, when analyzing clinical samples, such as serum and tissue. We therefore sought to increase the sensitivity of high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) in analyzing dioxins by injecting most of the extract from a small clinical sample. The concentration of each congener was estimated by injecting extracts of 5-g samples into a gas chromatography capillary precolumn (AT column) and by assaying extracts of 25-g samples by conventional splitless methods. We found that the limit of detection with the AT column was lower than that obtained by the splitless technique. In the AT column technique, 100 microL of the 110-microL final solution, equivalent to 4.5 g of the original sample, was injected into HRGC/HRMS. In contrast, 2 microL of the 20-microL final solution, equivalent to 2.5 g of original sample, was assayed using the splitless method. Moreover, when 25 fg of ultratrace dioxin was added to 100 microL of HRGC/HRMS sample and injected into the AT column, the peak area was almost the same as that obtained with 2 microL of HRGC/HRMS sample injected using the splitless method. Although assaying 10-20 microL of sample by the splitless method presents difficulties due to sample volatility, this problem can be reduced by using volumes larger than 100 microL. We tested this application by quantifying the parts-per-trillion levels, on a lipid weight basis, of each congener in a serum sample of 5 g using the AT column HRGC/HRMS method. We found this application to be successful and practical for mass screening of dioxin exposure in clinical samples.