Chromatography Forum

I am only familiar with IR, so this might not lead anywhere: Do you look at a band or the whole spectrum? If you look at a band only and this is quantitatively OK after LC, you may have missed the "dirt" which inflated your LC outcome. If you have a whole spec quantitatively the same than I would look at what Uwe suggested more closely.

We've checked for calculation errors. Our current theories are: the metering pump isn't picking up the amount it's supposed to, something is all of a sudden in our samples boosting peaks. Some vials we analyzed have been sent out for analysis. We're awaiting these results. They should tell us which one it is.

Thanks

I had this exact same problem in my last lab. Good thing you caught it early with a little logic check. Here's what I would do: Run a 10 injections of your standard as a sample.

If all injections are the same wrong amount it is a calculation/ settings issue. If the amounts are signifigantly different for each injection then you have an instrument issue.

- Check the dilution factor column in the software, it works as a multiplier on the amounts reported.
- Make sure the injection volume set for the standards is the same as for samples.
- Check the amounts entered in the Amounts Tab match the documents they are shipped with.
- If you make the standards in house make sure they were prepared at the correct dilution level.

Good Luck,
Let us know how it goes.

Well, our results from the other plant were in the 13% range for EtOH. Ours were 21% and 29%. We did have an instrument problem. All day yesterday and today it has behaved.

I'd still like to know what exactly happened. Was there a clog in the measuring pump that takes up sample? Was the sensor in the measuring pump not registering correctly?

Thanks for eveyone's help. Hopefully whatever it was has worked its way out.