Troubleshooting standard response issues

ampules

  1. Is the problem with standards or only with samples? If the low response is only with extracted samples, the problem is elsewhere in your method. Please see the blog post Now you see it, now you don’t-Troubleshooting method recovery problems.
  2. When was the standard ampule opened? If not fresh, open a new one. As mentioned in the blog post Extending the expiration date on a reference standard, the expiration date no longer applies once the container is opened.
  3. What were the storage conditions for the standard? As discussed in the blog post Handling your analytical reference standards, temperature and light exposure can make a world of difference. Be sure to check your certificate of analysis for proper storage conditions and precautions.
  4. If the standard is a mix of analytes, are all of them low or high? If you made a dilution, check your math and measurement techniques for dilutions that were made. Repeat them and verify. Make sure the initial volume used for dilution from the vial is made correctly, as discussed in the blog post Chemical reference standards; don’t just snap and pour.
  5. If you have any ampules from other lot numbers or vendors, prepare parallel dilutions and compare. Particularly if you have previously done this analysis and are not getting what you expect, obtain another standard and prepare it exactly in the same way and on the same day, alongside the one you are having trouble with. A stability issue can only be confirmed if you have data that shows that you are able to get acceptable results with another lot number or standard from another vendor.
  6. If you usually analyze this standard in combination with other standards, prepare your test dilutions without adding any other standards to the mix. Because the analytes can interact and affect each others’ stability, this is critical to isolate the issue. If you get to this point and have confirmed an issue with one product and not the other, contact the vendor. If this is a Restek product, contact us in Tech Services for assistance in resolving the issue.
  7. If your test dilutions demonstrate a problem with all of the lots or sources tested, then there is probably something unique to your analytical system that is causing a low response. If you would like assistance with troubleshooting on your HPLC or GC, feel free to contact our Tech Services group for help. We will need to see your operating conditions and settings, as well as chromatograms, so please be prepared to send a copy of those by email.

I hope this has been helpful. Thank you for reading.

 

 

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3 Responses to “Troubleshooting standard response issues”

  1. Andre says:

    Hi,

    Thanks for sharing the great helpful article on resolving response issues and i hope it will help me in troubleshooting the
    response issues. Keep updating.

    Andre
    Industrial Component Manufacturers

  2. Alex Banuelos says:

    Hello,

    So for some our Analyets are showing up with peaks and showing the calculated amount of that Internal Standard, but a few we don’t see any peaks. As the data displays it as not found. I’ve changed the Mobile phases and columns and that seems to not help show peaks for those same few. I’ve changed the windows to find the peaks and see where they’re located which i think i found and we still don’t get any data for those few analytes for Late Eluters. The Analytes we arn’t able to see are Carisoprodol, Propoxyphene, Desipramine. Fentanyl & Meprobamate for Early Eulters aren’t showing as well. If we can receive any help, it would be much helpful!

    Alex Banuelos

    Ameridrug Laboratories

  3. Hello Alex,

    Have you ran a standard column test mix to check the performance of your LC and column? If this is a new method, we can work offline to help you work out the parameters.

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