Liquid chromatography-mass spectrometry mobile phase

Liquid chromatography-mass spectrometry mobile-phase additives or modifiers are utilized to enhance ion abundance, to suppress sodium adducts, and to improve chromatographic peak shape. Common acidic additives used for positive ionization include formic acid (pH =... 

Apffel, A., Fischer, S., Goldberg, G., Goodley, P.C., Kuhlmann, F.E. (1995). Enhanced sensitivity for peptide mapping with electrospray liquid chromatography—mass spectrometry in the presence of signal suppression due to trifluoroacetic acid-containing mobile phases. J. Chromatogr. A 712, 177-190. 

When the mobile phase is a gas, the technique is called gas chromatography-mass spectrometry (GC-MS). In this case, the mixture is in the gas phase as it moves through the column, and the individual separated mixture components emerge in the gas phase and mix with the gaseous mobile phase, which is usually helium. When the mobile phase is a liquid, or a mixture of liquids, the technique is called liquid chromatography-mass spectrometry (LC-MS). In this case, the mixture is in the liquid phase as it moves through the column and individual separated mixture components emerge dissolved in this liquid phase. 

Homocarnosine is a dipeptide of GABA and L-histidine. After deproteinizing the sample with ethanol, the mixtures are centrifuged. The clear supernatant is evaporated to dryness and derivatized with butanol. The sample is evaporated to dryness and redissolved in the mobile phase. The homocarnosine-butyl derivatives (Fig. 2.3.4) are quantified using liquid chromatography mass spectrometry/mass spectrometry (LC-MS/MS) operating in the positive mode. With multiple reaction monitoring (MRM), the transitions of m/z 297.0 to m/z 212.0 for homocarnosine and m/z 299.0 to m/z 212.0 for 2H2-L-homocarnosine are quantified. 

To establish a sensitive and specific liquid chromatography-mass spectrometry (time-of-flight) [LC-MS (TOF)] method for the determination of donepezil in human plasma after an oral administration of 5 mg donepezil hydrochloride tablet [29]. Alkalized plasma was extracted with isopropa-nol-n-hexane (3 97) and loratadine was used as internal standard (IS). Solutes were separated on a Cis column with a mobile phase of metha-nokacetate buffer (pH 4.0) (80 20). Detection was performed on a TOF mass spectrometry equipped with an electrospray ionization interface and operated in positive-ionization mode. Donepezil quantitation was realized by computing the peak area ratio (donepezil-loratadine) (donepezil m/z 380 [M + H]+ and loratadine m/z 383[M + H]+) and comparing them with calibration curve (r = 0.9998). The linear calibration curve was obtained in the concentration range of 0.1-15 jUg/1. The detection limit of donepezil was 0.1 /zg/1. The average recovery was more than 90%. The intra- and inter-run precision was measured to be below 15% of RSD... 

Xia YQ, Jemal M (2009) Phospholipids in liquid chromatography/mass spectrometry bio-analysis comparison of three tandem mass spectrometric techniques for monitoring plasma phospholipids, the effect of mobile phase composition on phospholipids elution and the association of phospholipids with matrix effects. Rapid Commun Mass Spectrom 23 2125-2138... 

Liquid chromatography mass spectrometry (LC-MS) is now routinely used in analytical laboratories. Traditional IPRs are non-volatile salts that are not compatible with MS techniques because they play a major role in source pollution that is responsible for reduced signals. Moreover the final number of charged ions that reach the detector is impaired by ion-pair formation actually IPRs added to the mobile phase to improve analytes retention exert a profound effect on analyte ionization. Chromatographers who perform IPC-MS must optimize the eluent composition based on both chromatographic separation and compatibility with online detection requirements. 

WH Schaefer, F Dixon Jr. Effect of high-performance liquid chromatography mobile phase components on sensitivity in negative atmospheric pressure chemical ionization liquid chromatography-mass spectrometry. J Am Soc Mass Spectrom 7 1059—1069,1996. 

It has become painfully obvious that most of the excellent approaches and techniques that have been developed for use in liquid chromatography are not applicable to liquid chromatography/mass spectrometry (LC/MS) with atmospheric pressure ionization. Chapter 5 described the reagents and the range of mobile-phase compositions that are compatible with electrospray and atmospheric pressure chemical ionization (APCI), and these are limited to volatile components that do not cause significant ion suppression. Certain problems that are not significant with standard LC separations become difficult to deal with because of the limitations placed on the mobile phase by atmospheric pressure ionization (API) LC/MS. 

Schaefer, W.H. Dixon, F. Jr. Effect of High-Performance Liquid Chromatography Mobile Phase Components on Sensitivity in Negative Atmospheric Pressure Chemical Ionization Liquid Chromatography-Mass Spectrometry, J. Am. Soc. Mass Spectrom. 7, 1059-1069 (1996). 

See also Capillary Electrophoresis Overview. Chir-optical Analysis. Liquid Chromatography Column Technology Mobile Phase Selection Reversed Phase Instrumentation Amino Acids. Mass Spectrometry Peptides and Proteins. Nuclear Magnetic Resonance Spectroscopy Techniques Nuclear Overhauser Effect. Proteins Traditional Methods of Sequence Determination Foods. 

Figure 9.4 High-pressure liquid chromatography separation of 50 pg of a natural phosphatidylcholine mixture from egg yolk. The reconstructed ion chromatograms of diglyceride ions were selected from data acquired by full mass scanning from 120 amu to 820 amu. The relative intensity is shown based on the peak height. Column 3 pm Ultrasphere-ODS (4.6 mm x 7.5 cm). Mobile phase MeOH/hexane/0.1 m NH4OAC (71 5 7), 1 mlmin . Reprinted with permission from Kim, H. Y. and Salem, N. Jr, Phospholipid molecular species analysis by thermospray liquid chromatography/mass spectrometry. Anal. Chem., 58 (1), 9-14, 1986.

Bajic, S. et al.. Analysis of erythromycin by liquid chromatography/mass spectrometry using involatile mobile phases with a novel atmospheric pressure ionization source. Rapid Commun. Mass Spectrom., 14,156, 2000. 

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