Negative chemical ionization derivatives

Electron capture negative chemical ionization (ECNI) with methane as reagent gas was used to analyze 17 halogenated diphenylethene, -ethane and -ethanol derivatives such as DDE (150), DDD (151), DDT (152) and dicofol (153)335. Both the ethylenic double bond... 

Mateo-Vivaracho, L., Cacho, J. and Ferreira, V. (2007) Quantitative determination of wine polyfunctional mercaptans at nanogram per litre by gas chromatography-negative chemical ionization mass spectrometric analysis of their pentafluorobenzyl derivatives,... 

Schuyl, P. J. W., de Joode, T., Duchateau, G. S. M. J. E. et al (1994) Negative chemical ionization and collisionally activated decomposition mass spectra of 0-2,3,4,5,6-pentafluor-obenzyloxime derivatives of prostaglandins. Biol Mass Spectrom., 23, 47-50. 

GC is a separation technique which is based on partition principles between the stationary liquid phase and the mobile gas phase. The derivatization of substances such as auxins and auxin conjugates is needed to increase their volatility and to improve the chromatographic characteristics of the analyte. It is also used to enhance the detector response, then the sensitivity of the assay. The selection of the derivative for MS depends on the method of ionization. A derivative with favorable El characteristics could be useless for measurements by negative chemical ionization (NCI). Semi-quantitative data were obtained from lAA derivatives mass spectra and their respective merits to GC behaviour and MS ionization are compared in Table 1. 

Kozar, M., and Fox, A. (2002), Analysis of a stable halogenated derivative of muramic acid by gas chromatography-negative ion chemical ionization tandem mass spectrometry, J. Chromatogr., 946, 229-238. 

Coupling of liquid chromatography with mass spectrometry provides unequivocal online spectrometric identification of tetracycline antibiotics in animal-derived foods. Typical applications of mass spectrometry in confirming tetracycline residues in edible animal products describe coupling of liquid chromatography with mass spectrometry via particle-beam (280), electrospray (292), or atmospheric pressure chemical ionization (307), using negative-ion detection interfaces. 

The N1C1-MS (negative ion chemical ionization-mass spectrometry) of the pentafluoro-benzoate derivative of 42 has been identical to the corresponding derivative of [4,4-D2]HPB. The levels of HPB released from hemoglobin of NNK-treated rats, determined using [3,3-D2]- and [4,4-D2]-HPB standards, were the same40. 

On column benzylation of phenols was carried out with 3,5-bis(trifluoromethyl)benzyl-dimethylphenylammonium fluoride (54). Fluorinated benzyl derivatives allow very sensitive detection of phenols at ppt levels, by GC-MS in the negative ion chemical ionization mode. Derivatizing with pentafluorobenzyl bromide (C6F5CH2Br) was proposed for GC-MS detection of airborne carboxylic acids and phenols" . 

The stoichiometry of the proton in Eqs. (10.7) and (10.8) (denoted by j) is a collective term that represents three possible configurations for the M Hy cit +- - (6Z ) complex. The value of j is 1 when Hc iP occurs in the complex, as in MHcif (6Z ). In this instance, a single carboxyl and the hydroxyl are protonated on the citrate molecule. Such complexes are significant only when solution pH values are less than 4. More commonly, j is zero or negative, the latter representing either the occurrence of H iciP in the complex (all citrate moieties ionized) [as in MH icit (ag)], or the occurrence of H ciP and a metal hydrolysis product in the complex [as in MOH(H icit)2 (ag)]. Chemical models derived from potentiometric acid-base titration studies cannot distinguish between the two potential proton sources (citrate hydroxyl or metal-bound water), as titrations... 

Kolliker, S., M. Oehme, and C. Dye. 1998. Structure elucidation of 2,4-dinitrophenyl-hydrazone derivatives of carbonyl compounds in ambient air by HPLC/MS and multiple MS/MS using atmospheric chemical ionization in the negative mode. Anal. Chem. 70 1979-1985. 

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