COMPARATIVE STRATEGIES FOR CORRECTION OF INTERFERENCES IN ISOTOPE-DILUTION MASS-SPECTROMETRIC DETERMINATION OF VANADIUM

Vanadium has been determined in SRM 1573a, Tomato Leaves, by isotope d ilution mass spectrometry using thermal ionization (TIMS) and resonanc e ionization (RIMS). The capabilities of the two techniques to compens ate for interferences from chromium and titanium are compared. For the rmal ionization, corrections to the m/e 50 signal of 13-60% were made for interferences. The resulting V concentration had a relative standa rd deviation of 1.2%. Regression analysis of the data identified secon d-order corrections that resulted in a between sample precision of 0.4 6%. Resonance ionization had a demonstrated specificity of 2000:1 agai nst Cr and Ti interferences. The resulting ratio measurements were les s precise than the thermal ionization, but the vanadium ratio could be measured directly with no corrections necessary for interferences. Th e concentration (+/- 1 sigma measurement uncertainty) for V determined was 835.4 +/- 3.8 ppb by TIMS with second-order interference correcti ons, 824 +/- 10 ppb by TIMS as initially measured, and 828 +/- 15 ppb as measured by RIMS.