lmh wrote:
if you are using qualifier ions
Ah, so using qualifiers is optional? Since I've never seen this done myself, I'm trying to piecemeal different sources to get the whole picture. With your input included I'm getting this:
Quantifier ions are used to.. well, be included in the peak area and hence to calculate the concentration of our analyte. We can use 1 quantifier (BPM) and thus lower the risk of incorporating wrong signal. But if we're confident enough that there are no other substances with such masses - we can include more ions to make peak area measurements more precise. Typically you'd use only a few ions which give the strongest signal?
Qualifier ions should be used if there's a risk to find a peak which isn't actually our analyte of interest. I assume this is the case when:
1. The mixture content is unknown
2. Or when there are simply lots of analytes, especially those with large masses and multiple-charge species are expected.
3. Or we simply want to be extra careful
When deciding if it's the right peak we have 3 options:
1. Set min peak area (our LoD) in case we don't use qualifiers.
2. Look for presence of qualifier ions. If some of them give very low (or 0) signal - ignore this peak.
3. Or set even more strict criteria: enter (or calculate) expected isotopic pattern to look for. E.g. if we look for
Cl we should expect 2 signals: 35m/z and 37m/z and their ratio must be around 66:33. If these ions are present but the ratio is 90:10 - ignore the peak.
Is this close to reality?