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Calibration of ion spray mass spectra using cluster ions
Author(s) -
Anacleto J. F.,
Pleasance S.,
Boyd R. K.
Publication year - 1992
Publication title -
organic mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 0030-493X
DOI - 10.1002/oms.1210270603
Subject(s) - chemistry , analytical chemistry (journal) , mass spectrum , mass spectrometry , ion , calibration , alkali metal , calibration curve , ion source , propionitrile , acetonitrile , chromatography , detection limit , statistics , mathematics , organic chemistry
Mass calibration for ion spray mass spectrometry can be achieved by using cluster ions formed by flow injection of solutions of alkali metal salts in aqueous acetonitrile into the liquid flowing to the ion spray needle. Source contamination is thereby reduced to a minimum. For quadrupole mass analyzers, sodium iodide provides an ideal compromise between undesirable spectral complexity and spacings between calibrant mass peaks sufficiently close that interpolation errors are negligible. When much closer spacings are required, protonated water clusters provide an excellent calibration up to about m / z 1000. If higher mass ranges are required with a large number of calibrant peaks, a solution of mixed alkali metal iodides does provide the expected spectra but intensities are poor at higher m / z values. For liquid chromatography with on‐line mass spectrometry (LC/MS) the mass calibration may be checked without changing the mobile phase by post‐column flow injection of a cesium carbonate solution, since the carbonate anion is wholly displaced by the anion of the mobile phase acid modifier, resulting in no mixed clusters. The metal salt calibrants have the additional advantage of being useful over a wide range of tuning parameters in the atmospheric pressure ionization source, covering those appropriate to both relative molecular mass determinations of large proteins and to LC/MS of small analyte species.