Determination of polychlorinated dibenzo-p-dioxin and dibenzofuran background in milk and cheese by quadrupole ion storage collision induced dissociation MS/MS

Recent developments in quadrupole ion storage scanning techniques have made possible the acquisition of mass spectrometry/mass spectrometry (MS/MS) data with high sensitivity, selectivity and reproducibility. Retail dairy products were analyzed successfully for bioincurred or background contamination by all 17 of the 2,3,7,8 substituted polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Analytes were measured by both full scan electron impact low resolution MS (EI-LRMS) and collision induced dissociation MS/MS (CID MS/MS). Results were comparable using either technique. MS/MS, however, provided higher sensitivity and selectivity on many congeners. Results for the MS/MS technique were reproducible, with little reduction in sensitivity or spectral quality during the analyses of all test samples. The MS/MS signal to noise ratio (S/N) was 10 to 100 times greater than low resolution electron impact performed with the same instrument in food matrices. Signal to noise ratios increased on most parent ions as well as for all daughter ions. Further development of this technique may provide a cost effective alternative to traditional HRMS analyses of PCDDs and PCDFs in food. (C) 1997 Elsevier Science Ltd.