Development of Gas Chromatographic Method with Electron Capture Detector for Determination of Some PCDDs inWheat and Rice Grain Matrix

This study develops a gas chromatographic method coupled to micro-electron capture detector to determine four basic polychlorinated dibenzo- p -dioxins (PCDDs) congeners: 1, 1,2,3,7,8-pentachlorodibenzo- p -dioxin; 2, 2,3,7,8-tetrachlorodibenzo- p -dioxin; 3, 1,2,3,6,7,8-hexachloro-dibenzo- p -dioxin; and 4, 1,2,3,4,6,7,8-heptachlorodibenzo- p -dioxin  in wheat and rice. The PCDDs were extracted using 1:1 acetone: n -hexane mixture followed by cleaning with acidic aluminium oxide in polypropylene mini columns and eluted with dichloromethane. In quantitative determinations, the limit of detection for congener 1 of PCDDs was 0.4 ng mL -1 while for other congeners (2–4) it was found to be 1.0 ng mL -1 . The congener 1 was checked at spiking levels of 0.02, 0.05 and 0.1 ng g -1 , and its recovery was 85.96–120.74% and 95.32–116.88% from wheat and rice, respectively. Wheat and rice were also spiked by congers 2–4 at spiking levels of 0.05, 0.1 and 0.5 ng g -1 ; the recovery ranges from wheat were 87.70–115.54%, 85.64–117.88% and 88.40–119.32% for congener 2, 3 and 4, respectively, while from rice the recovery was 77.67–115.68%, 83.18–119.68% and 79.76–131.15% for congener 2, 3 and 4, respectively. The limit of quantification was determined as 0.1 ng g -1 for congener 1 and 0.5 ng g -1 for other three PCDDs (2–4). The intra-day and inter-day RSDs of peak areas ( n = 3) for four congeners (2 ng mL -1 ) were ranged at 2.5–8.1% and 3.1–10.6%, respectively. This study provides a simple and cost-effective gas chromatographic-electron capture detector method to study some basic PCDDs in wheat and rice grains first time in Pakistan with fair precision and accuracy when expensive high resolution gas chromatographic-mass spectrometry method is not accessible.