Approaches to the Determination of Limit of Detection in 2,3,7,8-TCDD Analyses

Procedures based on signal-to-noise ratio are most commonly used in determining limit of detection for the analysis of 2,3,7,8-tetrachlorinated dibenzo-p-dioxin (2,3,7,8-TCDD). The surrogate standard is 1,2,3,4-TCDD, while the internal standard is C₁₂ 1,2,3,4-TCDD. Both are added to the sample prior to processing. The calibration curve for isotope dilution gas chromatography/mass spectrometry analysis of 2,3,7,8-TCDD is obtained by plotting ratios of the gas chromatography (GC) peak areas vs ratios of the weights, the ratios corresponding to those of the unlabeled 2,3,7,8-TCDD and internal standard. The chapter deals with data obtained using low-resolution mass spectrometry (LRMS). Lower detection limits may be achieved by the use of high-resolution mass spectrometry (HRMS) or tandem mass spectrometry (MS). Isotope dilution MS is a type of internal standard calibration and analysis, in which the internal standard is an isotopically labeled analog of the analyte.