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Capillary electrophoresis/mass spectrometry determination of inorganic ions using an ion spray‐sheath flow interface
Author(s) -
Huggins Thomas G.,
Henion Jack D.
Publication year - 1993
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.1150140181
Subject(s) - chemistry , analytical chemistry (journal) , oxalate , mass spectrometry , ion , aqueous solution , capillary electrophoresis , chromatography , inorganic chemistry , organic chemistry
The determination of inorganic cations and anions by capillary electrophoresis/mass spectrometry (CE/MS) is reported using an ion spray‐sheath flow interface coupling. A twelve‐component synthetic mixture of cations which included the positive ions of K, Ba, Ca, Mn, Cd, Co, Pb, Cr, Ni, Zn, Ag, and Cu was loaded into the capillary column at levels ranging from 30 to 300 pg, separated by CE, and detected by indirect UV and in the full‐scan ( m / z 35–450) positive ion CE/MS mode using an aqueous buffer containing 30 m M creatinine and 8 m M α‐hydroxyisobutyric acid, pH 4.8. Creatinine forms adducts with the cations which are observed in the gas phase and requires rather high (120 electron volts) declustering energy to dissociate. This produces a reduction in charge state to form the free, singly charged, inorganic cations which are observed in the mass spectra. CE/MS analysis of an aqueous acidic extract of used aircraft engine oil revealed high levels of lead as well as lower levels of chromium and nickel. CE‐indirect UV analysis of a synthetic mixture containing 300 pg each of 11 inorganic ions, which included the anions of Br, Cl, NO 2 , NO 3 , S 2 O 3 , N 3 , SCN, SO 4 , SeO 4 , oxalate, and MoO 4 , is shown. The running buffer which affected this separation contained 5 m M ammonium dichromate, 10 m M ammonium acetate, and 20 m M diethylenetriamine at pH 9.3. Although indirect UV detection revealed good separation of these anions, CE/MS analysis of this mixture was complicated by interfering ion current signals from the cluster ions formed by the interaction between the additives and the analytes. Thus only three of these singly charged anions, e.g. Br, SCN, and HSeO 4 , could be satisfactorily detected in this mixture by CE/MS.