Infusion mass spectrometry liquid chromatography

Very low flow electrospray is called nanoelectrospray [26] where the samples are infused into the mass spectrometer at the nanoliter flow rate range. The infusion of a few microliters will result in a stable signal for more then 30 min, using pulled capillaries or chip-based emitters [27]. With infusion, signal averaging allows to improve the limit of detection in tandem mass spectrometry. Nanoelectrospray is particularly important in combination with nanoflow liquid chromatography or chip-based infusion for the analysis of peptides and proteins. 

Hopfgartner, G. The combination of liquid chromatography/tandem mass spectrometry and chip-based infusion for improved screening and characterization of drug metabolites. Rapid Commun. Mass Spectrom. 2005, 19, 618-626. 

In lipidomics, MS can be used either by direct infusion, that is, by the so-called shotgun MS, or in combination with chromatographic separation, typically LC and sometimes also with GC. Both approaches have their own advantages and limitations. Most targeted lipid analyses are performed with liquid chromatography coupled to mass spectrometry (LC-MS), while the use of gas chromatography-mass spectrometry (GC-MS) is utilized only for the analysis of fatty acids and some steroids. In addition, surface analysis by MS has been applied in lipid analysis of intact tissues. 

The molecular mass of protein and peptide samples was determined by electrospray ionization mass spectrometry using a Perkin-Elmer Sciex API 100 mass spectrometer. The sample was introduced either by infusion or by on-line liquid chromatography/mass spectrometry (LC/MS) using a splitter. The data were obtained by scanning from 450 to 2000 Da with a scan time of 5 s and a step size of 0.25 Da with 1.0 ms dwell time per mass step. The molecular mass of the sample was obtained using the software provided by the instrument manufacturer. 

Plat, J., Brzezinka, H., Lutjohann, D., Mensink, R.P. and von Bergmann, K. Oxidized plant sterols in human serum and lipid infusions as measured by combined gas-liquid chromatography-mass spectrometry. J. LipidRes. 42, 2030-2038 (2001). 

Shou, W.Z., Naidong, W. (2003) Post-column infusion study of the dosing vehicle effect in the liquid chromatography/tandem mass spectrometric analysis of discovery pharmacokinetic samples. Rapid Communications in Mass Spectrometry, 17,589-597. 

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