Determination of polychlorinated dibenzo‐p‐dioxins, dibenzofurans, and biphenyls by gas chromatography/mass spectrometry in the negative chemical ionization mode with different reagent gases

I. Introduction 374 II. Approaches to Selective and Sensitive GC/MS Determination of PCDD, PCDF, and PCB 374 A. Most Prevalent Ionization Modes in GC/MS 374 B. Sensitive Detection: Negative Chemical Ionization with Different Reagent Gases 375 1. Determination of Polychlorinated Dibenzo‐p‐dioxins (PCDDs) and Dibenzofurans (PCDFs) with Different Reagent Gases 376 a. CH4 as reagent gas 376 b. O2 as reagent gas 377 c. O2 as reagent gas [atmospheric pressure chemical ionization (APCI)] 378 d. CH4/O2 as reagent gas 379 e. CH4/N2O as reagent gas 380 f. i‐C4H10/CH2Cl2/O2 as reagent gas 380 g. Ar/CH4, CH4, i‐C4H10 as reagent gases 381 h. H2 as reagent gas 381 i. Ar, Xe, SF6, H2, and He as reagent gases 381 2. Determination of Polychlorinated Biphenyls (PCBs) with Different Reagent Gases 382 a. CH4 and CH4/O2 as reagent gases 382 b. O2 as reagent gas [atmospheric pressure chemical ionization (APCI)] 382 c. CH4 and NH3 as reagent gases 383 d. CH4/O2, Ar/O2, CH4/H2O, and CH4 as reagent gases 383 III. Conclusion and Actual Problems 383 References 385 Reagent gases that are used in mass spectrometry in the NCI mode for the determination of polychlorinated dibenzo‐p‐dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) are discussed. Ion‐molecule reactions and respective characteristic ions that form while using reagent gases (CH4, O2, i‐C4H10, NH3, H2, He, Ar, Xe, SF6) or gas mixtures (CH4/O2, Ar/CH4, CH4/H2O, Ar/O2, i‐C4H10/CH2Cl2/O2) are reviewed. It is shown that only CH4, O2, CH4/O2, and CH4/N2O are widely used and well studied, even though—in the case of these reagent gases—there are contradictions between the publications of various authors. Such reagent gases as NH3 and He are not well studied, but further investigations of their use for the determination of organochlorine pollutants could be of interest. The possibilities of more sensitive and selective determination of PCDDs, PCDFs, and PCBs are discussed.