I am examining haloacetic acids (HAAs), and my extraction method has me analyzing 9 methylated HAAs (methyl chloroacetate, methyl dichloroacetate, methyl trichloroacetate, methyl bromoacetate, methyl dibromoacetate, methyl tribromoacetate, methyl bromochloroacetate, bromodichloroacetic acid methyl ester, and chlorodibromoacetic acid methyl ester) on an Agilent 8860 GC-uECD.
I have run into an issue with the calibration curve. I have been advised to only use a calibration curve that results in an r^2 value of 0.995 or higher, but I am having a hard time achieving that. I recently ordered a methylated standard and diluted it to my calibration levels of 2, 5, 20, 50, 100, and 200 ppb. Even in this standard, which leaves far less room for human error than the extracted standards, only one of the 9 calibration curves resolves. Some of the compounds are not even detected in all of the calibration standards. Does anyone have any advice on how to troubleshoot a calibration curve?
Thank you so much!
Dear Melanie,
You may be having a problem with the GC column.
Sometimes, if the column is already damaged, the analytes that enter the column do not come out (at least all of it), so only a small part of what should be detected is detected. This usually occurs when part of the column filling (silica) is already beginning to be detected, although you can see this if your instrument is a GC-MS.
Best,
Fran
Melanie Vines Have a look: https://www.chromforum.org/viewtopic.php?t=18412
Hello,
You have to clean the column, give conditioning and then try again.
What about your first injection of calibration level (5 ppb) and rest levels. Is there any single calibration level matching same area or showing irregular area. Check with your compounds and their suitability with stationary phase.
All the best
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