Iron carboxylate oxygen-centered-triangle complexes detected during electrospray use of organic acid modifiers with a comment on the finnigan TSQ-700 electrospray inlet system.
Use of infusion methods rather than high-performance liquid chromatography allowed us to confirm the observation that solutions of propionic acid-isopropanol restore sensitivity lost due to trifluoroacetic acid in electrospray mass spectra of basic substances, particularly peptides. In this work, when propionic acid-isopropanol was used, we detected an abundant ion with m/z 622 that shifted to m/z 538 when we substituted acetic acid-methanol for the propionic acid-isopropanol. Via accurate mass measurement and tandem mass spectrometry the origin of the ion was identified as the complex Fe3O(O2CR)6(L)0-3, where L is one of several ligands from solvent or water. The grounding arrangement of the Finnigan TSQ-700 electrospray source produces electrolytic currents that may accentuate the abundance of this complex and specifically produces observable gas bubbles that adversely affect the spray stability.
Section on Analytical Biochemistry, Laboratory of Clinical Science, National Institute of Mental Health, Bethesda, Maryland, USA.
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Ijames
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Dutky
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Fales