Electrospray ionization mass spectrometry multiple reaction monitoring

Norris, A.J., Whitelegge, J.P., Faull, K.F., Toyokuni, T. (2001) Kinetic Characterization of Enzyme Inhibitors Using Electrospray-ionization Mass Spectrometry Coupled with Multiple Reaction Monitoring. Anal. Chem. 73 6024-6029. 

The method for chloroacetanilide soil metabolites in water determines concentrations of ethanesulfonic acid (ESA) and oxanilic acid (OXA) metabolites of alachlor, acetochlor, and metolachlor in surface water and groundwater samples by direct aqueous injection LC/MS/MS. After injection, compounds are separated by reversed-phase HPLC and introduced into the mass spectrometer with a TurboIonSpray atmospheric pressure ionization (API) interface. Using direct aqueous injection without prior SPE and/or concentration minimizes losses and greatly simplifies the analytical procedure. Standard addition experiments can be used to check for matrix effects. With multiple-reaction monitoring in the negative electrospray ionization mode, LC/MS/MS provides superior specificity and sensitivity compared with conventional liquid chromatography/mass spectrometry (LC/MS) or liquid chromatography/ultraviolet detection (LC/UV), and the need for a confirmatory method is eliminated. In summary,... 

LC/MS/MS. LC/MS/MS is used for separation and quantitation of the metabolites. Using multiple reaction monitoring (MRM) in the negative ion electrospray ionization (ESI) mode, LC/MS/MS gives superior specificity and sensitivity to conventional liquid chromatography/mass spectrometry (LC/MS) techniques. The improved specificity eliminates interferences typically found in LC/MS or liquid chro-matography/ultraviolet (LC/UV) analyses. Data acquisition is accomplished with a data system that provides complete instmment control of the mass spectrometer. 

Coupling of liquid chromatography with mass spectrometry can provide unequivocal on-line spectrometric identification of anthelminthic residues in animal-derived foods. Typical applications of such techniques include the confirmation of moxidectin residues in cattle fat by liquid chromatography-thermospray mass spectrometry (352), and the confirmation of eprinomectin residues in bovine liver tissue by liquid chromatography, electrospray ionization, and multiple reaction monitoring in the MS-MS mode with positive ion detection (370). 

For abbreviation of analyte names see Sect. Abbreviations . ACN acetonitrile, APCI atmospheric pressure chemical ionization, dial, microdialysis samples, ESI electrospray ionization, FA formic acid, iso isocratic, IT ion trap, lin range linear range, MeOH methanol, MRM multiple reaction monitoring, MS full scan mass spectrometry, n.s. not specified, OAc acetate, QqQ triple quadrupole mass spectrometer, SIM selected ion monitoring, Solv HPLC solvent, SQ single quadrupole mass spectrometer, T temperature Ratios given as v/v... 

Fig. 5 Statistical evaluation of LC-MS-based methods for tropane alkaloids referred in this chapter. (a) Relative frequency of ionization methods. +APCI positive atmospheric pressure chemical ionization, +ESI positive electrospray ionization, FAB fast atom bombardment, +TSP positive thermospray, (b) Relative frequency of scan modes used. MS full scan MS, MS/MS tandem mass spectrometry (product ion scan), MRM multiple reaction monitoring, SIM selected ion monitoring, (c) Relative frequency of mass analysers used. EBQtQ2 double focusing sector field mass spectrometer, IT ion trap, QqQ triple quadrupole, SQ single quadrupole. Considered publications were found by PubMed data-based search and references cited in these articles...

Table 19.1 Ions monitored for determination of niacin by isotope dilution mass spectrometry using positive electrospray ionization. Both natural and labelled nicotinic acid are protonated in positive ion electrospray ionization, giving quasi-molecular ions at mass-to-charge ratios (m/z) of 124 and 128, respectively, which can be monitored directly in selected ion recording (SIR) experiments and selected as the parent ions in multiple reaction monitoring (MRM) experiments. In MRM experiments protonated nicotinic acid can be induced to produce daughter ions at several other m/z values, but the given transitions are the ones with the highest signal intensity.

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