1. We recently ran standard and sample in Semi-Quantitative mode by ICP-MS, but the results were not what we expected. see the below picture.
For Li, expected results: concentration of STD2.0 should double the concentration of STD1.0 because we diluted 2 ml of stock standard into STD2.0, while only 1.0 ml of stock was diluted in STD1.0
However, ICP-MS obtained the results without big difference between them.
2. in data processing, we set STD1.0 as SQStd, one of the blank as SQBlk, and one of pre-run which had internal standard as SQISTD.
The standard solution concentration was set as the following: Li 25ng/mL, Cr 110ng/mL, As 1.5 ng/mL and 150 ng/mL. Internal standard as auto add (Sc, Ge, In, Te and Bi)
3. What we found counts for each element were changed after the data processing.
Originally, for Li, counts of STD2.0 is almost double STD 1.0.see below picture
However, the counts for Li were totally changed and became not proportional.
for Li counts for STD2.0 is 4429.3; counts for STD1.0 is 3428.98 , blank is 142.86
4. my questions are
why did the counts become non-proportional after standard correction? the response of counts/concentration should be the same for the same element.
do we usually use a tuning solution ( concentration is 10ppb) as a standard solution for semi-quantitative? since mass hunter wrote this statement?
Can we use other elements as standdard? how do we choose a concentration of standard and how to choose elements of standard for semi-quantitative analysis?