Electrospray ionization monitoring

Tian, Q. et al., Screening for anthocyanins using high-performance liquid chromatography coupled to electrospray ionization tandem mass spectrometry with precursor-ion analysis, product-ion analysis, common-neutral-loss analysis, and selected reaction monitoring, J. Chromatogr. A, 1091, 72, 2005. 

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. 

Positive-ion single reaction monitoring Finnigan MAT API I ESI (electrospray ionization) 4.5 kV... 

Konermann, L. Douglas, D. J. Acid-induced unfolding of cytochrome c at different methanol concentrations Electrospray ionization mass spectrometry specifically monitors changes in the tertiary structure. Biochemistry 1997, 36, 12296-12302. 

L. Konermann and D. J. Douglas. Unfolding of Proteins Monitored by Electrospray Ionization Mass Spectrometry A Comparison of Positive and Negative Ion Modes. J. Am. Soc. Mass Spectrom., 9(1998) 1248-1254. 

Electrospray ionization Sample introduction Reaction monitoring... 

Gutteck U, Rentsch KM. 2003. Therapeutic drug monitoring of 13 antidepressant and five neuroleptic drugs in serum with liquid chromatography-electrospray ionization mass spectrometry. Clin Lab Med 41 1571. 

ESI-MS has been used for the quantification of a number of substrates and products of enzymatic reactions [56,57]. Hsieh et al. report the use of ion spray mass spectrometry (a technical variation of electrospray ionization) coupled to HPLC for the kinetic analysis of enzymatic reactions in real time [58]. The hydrolysis of dinucleotides with bovine pancreatic ribonuclease A and the hydrolysis of lactose with 3-galactosidase were monitored and the resulting data were used for the estimation of and v x of these reactions. Another field of application of electrospray mass spectrometry is the screening of combinatorial libraries for potent inhibitors [31,59]. 

Following extractive deproteinization of the plasma, the amino acids (and their stable-isotope-labeled internal standards) are separated by HPLC and introduced into the mass spectrometer. Electrospray ionization results in the formation of electrically charged molecules, which are separated on the basis of their mass/charge (m/z) ratio in the first quadrupole. Following fragmentation in the collision cell, the characteristic fragment for each amino acid is selected in the second quadrupole. This process is named multiple reaction monitoring. 

Cristoni S, Cuccato D, Sciannamblo M, Bernardi LR, Biunno I, Gerthoux P, Russo G, Weber G, Mora S (2004) Analysis of 21 deoxycortisol, a marker of congenital adrenal hyperplasia, in blood by atmospheric pressure chemical ionization and electrospray ionization using multiple reaction monitoring. Rapid Commun Mass Spectrom 18 77-82... 

Marwah A, Marwah P, Lardy H (2001) Liquid chromatography-electrospray ionization mass spectrometric analysis of corticosterone in rat plasma using selected ion monitoring. J Chro-matogr 757 333-342... 

The metabolites of interest in urine are separated using reverse-phase HPLC combined with electrospray ionization (ESI)-MS/MS, and detection is performed using multiple-reaction monitoring. Stable-isotope-labeled reference compounds are used as internal standards. 

Dalmazio, I., Santos, L.S., Lopes, R.P., Eberlin, M.N. and Augusti, R. (2005) Advanced oxidation of caffeine in water on-line and real-time monitoring by electrospray ionization mass spectrometry. Environ. Sci. Technol.,... 

K. R. and Mabury, S.A. (2004) The aquatic persistence of eight pharmaceuticals in outdoor microcosms monitored by HPLC-UV and LC-MS-MS using electrospray ionization. Environ Toxicol Chem, 23, 1431-1440. 

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). 

Figure F2.4.1 Liquid chromatography/mass spectrometry (LC/MS) analysis of isomeric carotenes in a hexane extract from 0.5 ml human serum. Positive ion electrospray ionization MS was used on a quadrupole mass spectrometer with selected ion monitoring to record the molecular ions of lycopene, p-carotene, and a-carotene at m/z (mass-to-charge ratio) 536. A C30 HPLC column was used for separation with a gradient from methanol to methyl-ferf-butyl ether. The a -trans isomer of lycopene was detected at a retention time of 38.1 min and various c/ s isomers of lycopene eluted between 27 and 39 min. The all-frans isomers of a-carotene and P-carotene were detected at 17.3 and 19.3 min, respectively.

Higher sensitivity and selectivity for HPLC analyses can be achieved by detection with MS, which has gained extreme attention due to ease of use through electrospray ionization [Barnes et al., 1998 Franke et ah, 2002 Twaddle et al., 2002]. For food isoflavone analyses we favor PDA monitoring... 

Detector LC-MS operated in electrospray ionization SIM monitoring SR25990C m/z 308.00 Repaglinide m/z 453.55 Mobile phase ACN water formic acid = 60 40 0.1... 

CCA and clopidogrel Column Cig-ether HPLC analytical column at 50 °C Detector LC-MS/MS operated in electrospray ionization (ESI) interface at positive ion mode MRM monitoring Clopidogrel m/z 322.0663 -> 212.0478 CCA m/z 308.0506 -> 198.0322 Mobile phase Gradient from 10% to 100% of ACN 0.1% formic acid Human plasma... 

---