Evaluation of internal standard predictions across instrumental platforms in inductively coupled plasma mass spectrometry

In a previous paper from this laboratory, 51 different elements were ratioed to each other under a variety of altered matrix and instrumental conditions. The objective was to isolate element pairs that made good internal standards for each other. The data were collected and evaluated using a nebulizer and an inductively coupled plasma time-of-flight mass spectrometer. Although results suggested that many optimal internal standards were correctly predicted, it was not clear whether these predicted internal standard pairs would remain good choices for this instrument over an extended time period and whether changing instrumental platforms would alter the internal standard selections. This article considers the choice of previously selected good'' internal standards for several elements using the same GBC ICP(TOF)MS after several optimizations, a torch change and nebulizer replacement. It also considers the use of the previously determined good'' internal standards for an Agilent ICP(quadrupole)MS with a different nebulizer system, torch, mass analyzer, etc. Interestingly, it was found that the internal standards predicted in the initial study continued to perform well on both platforms considered in the present study. In fact, overall errors were smaller in the second set of TOF data and on the quadrupole than those in the first set of TOF data. Mass and ionization potential trends were also similar to those from the previous study. Although there remains to be an equation allowing a priori selection of the ideal internal standard, the current results suggest that the prediction program developed in the previous study is effective over time and instrumental platforms.