Response for one compound in one sample run from batch way too high - otherwise OK.
Hello,
I have a bizarre issue that has occurred once before. One of my in-house quality controls is around 280% too high ( see figure and sample ID K0900-11). The sample is injected twice during the run and both injections result in similar results. Here is what I have found out so far:
Information on run:
Matrix : Blood
Gradient run on 1,7µm 2.1x100 mm BEH C18 column
Mobile phase A: 0.1% Formic acid in MilliQ water
Mobile phase B: Acetonitrile
Injection volume: 5 µL
Does anyone have a suggestion what the issue could be? As I say, this has happened once before and seems to be very compound specific and the internal standard is not correcting for the issue.
I have a bizarre issue that has occurred once before. One of my in-house quality controls is around 280% too high ( see figure and sample ID K0900-11). The sample is injected twice during the run and both injections result in similar results. Here is what I have found out so far:
Information on run:
Matrix : Blood
Gradient run on 1,7µm 2.1x100 mm BEH C18 column
Mobile phase A: 0.1% Formic acid in MilliQ water
Mobile phase B: Acetonitrile
Injection volume: 5 µL
- Issue is not internal standard. We are using D4-Clonazepam and the IS area is similar in these samples to other samples.
- Issue is not mixing of the QC samples. As you can see, the sample is labeled K0900-11. So this is vial 11 from a batch. K0900-10 which was run in the previous week, and K0900-12 which was run in the week after are both within 20% of expected values.
- This is not due to too much sample in the vial. All other compounds in the QC sample are within 20% deviation from expected values. Only Clonazepam is so high.
- This is not the injection volume since the IS response is similar to other injections and also the IS should correct for a difference in injection.
Does anyone have a suggestion what the issue could be? As I say, this has happened once before and seems to be very compound specific and the internal standard is not correcting for the issue.
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