Chemical Stability and Compatibility - Standards and analyses of Li, Mn, Ni, and Co

I'd like to get an opinion on the multi-element blend that I've been using for analysis to get an idea of the compatibility and stability, and see if you have any suggestions. Our current standards contain: 0.25, 0.5, 1, and 4 ppm of Al, Ag, B, Cu, P, Sn, Ti, Zn, and Zr 5, 10, 15, and 20 ppm of Co 2.5, 5, 10, and 20 ppm of Li 5, 10, 20, and 30 ppm of Mn and Ni 10% HNO3 Li is always somewhat problematic to analyze for, as are Cu and Ag (which has a very inaccurate calibration curve no matter the precision used when making standards). We may also want to consider adding S and Fe to the standards in the future. Most of our samples primarily consist of Li, Mn, Ni, and Co. For these, a sample is 150mg of material digested in 5mL aqua regia and allowed to evaporate ~80-90%, then diluted to 50mL, 10ppm Sc IS. 1mL of this solution is diluted to 50mL again, in 10% HNO3, 10ppm Sc IS. The former is used to analyze for the trace elements and the latter for the bulk elements. We are not concerned with the error from the slightly elevated Sc in the more dilute sample, as we are mainly interested in the ratio of those elements rather than the absolute values. Some of our samples are mostly Li with the primary elements of interest being Ni, Mn, and Co (Li is not of interest in these analyses). These are ~20mg of almost pure Li metal dissolved in 5 mL H2O, then neutralized and brought to 10mL, 10% HNO3, 10ppm Sc IS. Do you have any thoughts or suggestions regarding this type of analysis?