Multiple reaction-monitoring mode

Kim et al. [48] developed a rapid, sensitive, and selective LC-ESI-MS/ MS method for fhe deferminafion of lornoxicam in human plasma. Lornoxicam and isoxicam (infernal standard) were extracted from human phasma wifh efhyl acefafe at acidic pH and analyzed on a Sunfire Cis column with the mobile phase of methanol-ammonium formate (10 mM, pH 3) (70 30). The analyte was detected using a mass spectrometer, equipped with electrospray ion source. The instrument was set in the multiple-reaction-monitoring mode. The standard curve was linear (r = 9998) over the concentration range of 0.5-500 ng/ml. The coefficient of variation and relative error for the intra- and inter-assay at four QC level were 0.7% fo -4.2% and —4.5% to 5%, respectively. The recoveries of... 

QQQ Pharmaceuticals and metabolites Multiple reaction monitoring mode for high sensitivity and specificity Only targeted analysis... 

Kovarik P, Grivet C, Bourgogne E, Hopfgartner G. Method development aspects for the quantitation of pharmaceutical compounds in human plasma with a matrix-assisted laser desorption/ionization source in the multiple reaction monitoring mode. Rapid Commun Mass Spectrom 2007 21(6) 911—919. 

LC coupled with detection by mass spectrometry (MS) offers the potential for excellent sensitivity and specificity. Sample preparations suitable for niacin analysis by LC-UV and other methods should also be suitable for LC-MS. However, chromatographic methods developed for LC-UV or LC-fluorescence methods would in most cases have to be modified due to issues such as ion suppression and problems created by non-volatile species in commonly used mobile phases. Niacin has a relatively low molecular mass (123 Da), and thus in selected ion recording (SIR) mode, there may still be significant interference problems. With instruments that allow a multiple reaction monitoring mode (MRM), however, interference problems can potentially be avoided even without optimized chromatography or sample clean-up. 

An LC-MS-MS method with AP-CI to determine the concentration of 25-hydroxyvitamin D (25-OH-D(2)/-D(3)) in human plasma. A deuterated standard is used and the tandem spectrometer is in the multiple-reaction-monitoring mode. Intra- and interassay variations 2-6% recoveries 104-99%. Potential applications are the evaluation of the vitamin D status in postmenopausal women and elderly subjects, the diagnosis of vitamin D insufficiency/deficiency, as well as for the treatment and prevention of osteoporosis. 

Mass spectrometers with single or triple quadrupole are most commonly used in the determination of polyphenolic compounds where electrospray ionization (ESI) is used as an interface. UHPLC-MS and UHPLC-MS/MS, which work in a selected ion mode (SIM) and multiple reaction monitoring mode (MRM), respectively, offer high sensitivity, selectivity, and high throughput for the determination of polyphenols and their metabolites in biological fluids. 

Electrospray MS. Analysis of methanol solutions in the positive ion mode gives molecular ions of distearyldimethylammonium chloride. Strong ions are seen for the Cj / Cis, Cis/Ci6, and Cifi/Cig homologs, as well as some minor components (15,120). It must be noted that the response factors differ sharply for similar compounds. For example, the response factor for hexadecyltrimethylammonium bromide is only 45% of that for dode-cyltrimethylammonium bromide (117). The same observations on calibration with deuter-ated analogs and fragments for MS-MS analysis made above for FAB also apply to electrospray (117). Electrospray MS was demonstrated for detection of benzalkonium chloride on human skin, using a triple quadrupole instmment in multiple reaction monitoring mode (121). 

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