Tandem-in-time mass spectrometry method for the sub-parts-per-trillion determination of 2,3,7,8-chlorine-substituted dibenro-p-dioxins and -furans inhigh-fat foods

Limits of quantitation (LOQs) for a quadrupole ion storage tandem-in-time m ass spectrometry (QISTMS) method were evaluated through replicate analysis of unfortified peanut oil, shortening, lamb at, and butter for all 2,3,7,8- chlorine-substituted polychlorodibenzo-p-dioxins (PCDDs) and polychlorodibe nzofurans (PCDFs), Ten congeners were measurable in butter (0.27-2.5 pg/g) and nine congeners were measurable in lamb fat (0.09-2.6 pg/g) with good pr ecision. LOQs for high-fat foods were estimated by triplicate analysis of p eanut oil fortified at two levels. Accurate! and reproducible results were achieved at 0.5 pg/g for most PGDD/Fs (1.0 pg/g for heptachlorodibenzo-p-di oxin and heptachlorodibenzofuran and 2.0 pg/g for octachlorodibenzofuran) a nd at 0.2 pg/g for 2,3,7,8-tetrachlorodibenzofuran (TCDF) and 2,3,7,8-tetra chlorodibenzo-p-dioxin (TCDD), QISTMS distinguished between catfish and chi cken eggs with elevated TCDD levels from background samples collected from the most regions of the continental United States. QISTMS determined the ex tent of TCDD contamination in butter, lamb fat, and cottonseed oil collecte d from rural villages in Kazakhstan. Replicate analysis of catfish and chic ken eggs by the QISTMS method produced comparable results to high-resolutio n mass spectrometry (HRMS). Lower limits of detection will be needed if QIS TMS is to fully complement HRMS in the measurement of TCDD levels in food.