Determination of polychlorinated dibenzo‐p‐dioxins, dibenzofurans, and biphenyls by gas chromatography/mass spectrometry in the negative chemical ionization mode with different reagent gases
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Abstract 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. CH 4 as reagent gas 376 b. O 2 as reagent gas 377 c. O 2 as reagent gas [atmospheric pressure chemical ionization (APCI)] 378 d. CH 4 /O 2 as reagent gas 379 e. CH 4 /N 2 O as reagent gas 380 f. i‐C 4 H 10 /CH 2 Cl 2 /O 2 as reagent gas 380 g. Ar/CH 4 , CH 4 , i‐C 4 H 10 as reagent gases 381 h. H 2 as reagent gas 381 i. Ar, Xe, SF 6 , H 2 , and He as reagent gases 381 2. Determination of Polychlorinated Biphenyls (PCBs) with Different Reagent Gases 382 a. CH 4 and CH 4 /O 2 as reagent gases 382 b. O 2 as reagent gas [atmospheric pressure chemical ionization (APCI)] 382 c. CH 4 and NH 3 as reagent gases 383 d. CH 4 /O 2 , Ar/O 2 , CH 4 /H 2 O, and CH 4 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 (CH 4 , O 2 , i‐C 4 H 10 , NH 3 , H 2 , He, Ar, Xe, SF 6 ) or gas mixtures (CH 4 /O 2 , Ar/CH 4 , CH 4 /H 2 O, Ar/O 2 , i‐C 4 H 10 /CH 2 Cl 2 /O 2 ) are reviewed. It is shown that only CH 4 , O 2 , CH 4 /O 2 , and CH 4 /N 2 O 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 NH 3 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. © 2003 Wiley Periodicals, Inc., Mass Spec Rev 21:373–387, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/mas.10037Keywords:
Atmospheric-pressure chemical ionization
Abstract 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. CH 4 as reagent gas 376 b. O 2 as reagent gas 377 c. O 2 as reagent gas [atmospheric pressure chemical ionization (APCI)] 378 d. CH 4 /O 2 as reagent gas 379 e. CH 4 /N 2 O as reagent gas 380 f. i‐C 4 H 10 /CH 2 Cl 2 /O 2 as reagent gas 380 g. Ar/CH 4 , CH 4 , i‐C 4 H 10 as reagent gases 381 h. H 2 as reagent gas 381 i. Ar, Xe, SF 6 , H 2 , and He as reagent gases 381 2. Determination of Polychlorinated Biphenyls (PCBs) with Different Reagent Gases 382 a. CH 4 and CH 4 /O 2 as reagent gases 382 b. O 2 as reagent gas [atmospheric pressure chemical ionization (APCI)] 382 c. CH 4 and NH 3 as reagent gases 383 d. CH 4 /O 2 , Ar/O 2 , CH 4 /H 2 O, and CH 4 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 (CH 4 , O 2 , i‐C 4 H 10 , NH 3 , H 2 , He, Ar, Xe, SF 6 ) or gas mixtures (CH 4 /O 2 , Ar/CH 4 , CH 4 /H 2 O, Ar/O 2 , i‐C 4 H 10 /CH 2 Cl 2 /O 2 ) are reviewed. It is shown that only CH 4 , O 2 , CH 4 /O 2 , and CH 4 /N 2 O 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 NH 3 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. © 2003 Wiley Periodicals, Inc., Mass Spec Rev 21:373–387, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/mas.10037
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An atmospheric pressure photoionization (APPI) source and an atmospheric pressure chemical ionization (APCI) source were compared for the selective detection of microbial respiratory ubiquinone and menaquinone isoprenologues using tandem mass spectrometry. Ionization source- and compound mass-dependent parameters were optimized individually for both sources, using the available quinone standards. Detection levels for the two ion sources were determined with ubiquinone-6 (UQ6) and menaquinone-4 (MK4, vitamin K2) standards using flow injection analysis and selected reaction monitoring (SRM). With APPI the calculated lower limit of detection (LLOD) was 1.7 fmol microl(-1) for UQ6 and 2.2 fmol microl(-1) for MK4 at a signal-to-noise ratio of 3. These LLODs were at least three times lower than with APCI. The selectivity of detection afforded by SRM detection reduced complex mixture analysis to 3 min per sample by eliminating the need for chromatographic separations. The detection method was successfully applied to quinone quantification in a variety of environmental samples and cell cultures. Adequate amounts of respiratory quinones can be extracted and quantified from samples containing as low as 2 x 10(7) cells.
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Abstract A method is described for the enrichment of very long chain fatty acids (VLCFAs) from total fatty acids of heterotrophically cultivated green freshwater alga Chlorella kessleri and their identification as picolinyl esters by means of liquid chromatography‐mass spectrometry with atmospheric pressure chemical ionization (LC‐MS with APCI). The method is based on the use of preparative reversed phase HPLC of hundred‐milligram amounts and their subsequent identification by microbore APCI LC‐MS. A combination of these two techniques was used to identify unusual VLCFAs up to C 47 , both saturated and monounsaturated, with two positional isomers (ω‐9 and ω‐26).
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High-performance liquid chromatography with atmospheric pressure chemical ionization mass spectrometry (APCI-MS) in the negative-ion mode has been succesfully used for qualitative and quantitative determination of fifteen phenolic compounds found in olive mill wastewater. APCI gives information about both the molecular weight of these molecules and about their structure, showing consistent collision-induced dissociation pathways, which have been elucidated to give detailed information about the structure of the fragments. Quantitative analysis, using p-bromophenol as an internal standard, was carried out using calibration graphs for injections in the 0.01–1000 ng range, working both in scanning and selected-ion monitoring data aquisition modes, resulting in correlation coefficients higher than 0.98 for all compounds.
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A total of 15 standard compounds with structures similar to those normally found in crude oils were analyzed using an ultrahigh-resolution and high-accuracy Fourier transform ion cyclotron resonance (7.2 T LTQ FT Ultra, Thermo Fisher, Bremen, Germany) mass spectrometer. Four different ionization techniques were used: electrospray ionization (ESI), atmospheric pressure chemical ionization (APCI), atmospheric pressure photoionization (APPI), and a novel technique that couples APCI and APPI, herein termed atmospheric pressure photo- and chemical ionization (APPCI). Relationships between chemical structures and ionization efficiencies were established for these techniques, which operate via different ionization mechanisms. The unsaturation level and position of the double bond were shown to be key factors on ionization efficiency for all ionization techniques. Comparisons between molecules with similar backbones but with different heteroatoms were also made. For the whole mixture, APPI showed the highest sensitivity for the positive ion mode and ESI showed the highest sensitivity for the negative ion mode. APPCI was found to be the most comprehensive ionization technique, whereas as expected, ESI preferentially ionized the most polar compounds. APPCI produced, however, more than one ionic species per molecule, a disadvantage in terms of data complexity. Such "splitting" was observed for APPI and APCI. Ions with the same molecular formula formed from different molecules were also detected by APPCI, producing composite abundances that would mislead chemical and geochemical conclusions based on petroleomic approaches. We suggest that, although less comprehensive, ESI is overall the most suitable ionization technique for petroleomic studies.
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A method was developed for the determination of two phenylurea herbicides and their degradation products using liquid chromatography–atmospheric pressure chemical ionization (APCI)-mass spectrometry without any additives in the mobile phase. The APCI detection sensitivity of these compounds was maximized when the vaporizer temperature was set at 250 °C and a positive-ion detection mode was chosen. Under these conditions, the detection limits (S/N = 3) of these compounds in total-ion and selected-ion monitoring were 2.5–3.0 and 0.12–0.26 ng, respectively. In a biodegradability test on diuron, small quantities of degradation products could be determined by the proposed method.
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