- No concentration is calculated for some unknowns. The peak codes shown are Q54 and Q56, which indicate a problem with the x value of the internal standard. However, the x values for the internal standards are set correctly to 1 and work for all the other samples.
- UNIFI 1.8 (workstation and network)
A change related to the use of internal standards was introduced in 1.8 and is detailed in US1#181031. When using an internal standard, the IS level must be specified for all injections or for none of the injections.
FIX or WORKAROUND
Remove all concentration values for the internal standard from the Default amounts table in the analysis method; update and reprocess.
The software then makes the assumption that the internal standard level is 1 for all injections and gives a calculated concentration as expected. In this case, there will be no information regarding the deviation of the IS from the expected concentration.
Add a new level specifically for the IS.
Add a new level to the Default amounts table and populate only the IS component:
Then add this level to all samples that you want to quantify with IS (in this case, using the sample editor):
Update and reprocess. This will give calculated concentration values and show the deviation of the IS from the expected values: