SODIUM TRIFLUOROACETATE AS A TUNE CALIBRATION COMPOUND FOR POSITIVE-ION AND NEGATIVE-ION ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY IN THE MASS RANGE OF 100-4000 DA/

We have identified aqueous:acetonitrile solutions of alkali-metal trif luoroacetate compounds as tune/calibration standards for both positive - and negative-ion electrospray ionization mass spectrometry (ESI/MS). Each alkali-metal trifluoroacetate solution in water and acetonitrile (50:50, v/v) yields evenly spaced, singly charged peaks in the mass r ange of 100-3500 Da. Intense peaks are formed either by infusing the s olution using a syringe pump, by infusing the solution into a stream o f liquids [such as a high-performance liquid chromatography (HPLC) mob ile phase] flowing to the electrospray needle, or by injecting the sal t-containing solution into an HPLC mobile phase containing trifluoroac etic acid. The advantages of these compounds include: (i) generation o f singly charged ions in both positive and negative ionization modes i n the mass range of approximately 100-3500 Da, (ii) formation of evenl y spaced peaks with similar intensity across the entire mass range, (i ii) the most abundant isotope in each mass cluster is the lowest mass peak (monoisotopic mass), which is free from variation in natural isot ope distribution, (iv) commercial availability, (v) they easily dissol ve in common liquid chromatography solvents, and (vi) lack of any long -lasting memory effects or background problems. (C) 1998 American Soci ety for Mass Spectrometry.