NDMA split peak
Posted: Wed Feb 07, 2018 3:00 pm
Hello,
I'm using a GC 6890 and a MS 5973 to analyze n-nitrosodimethylamine. Everything was going well until we fell 2 PT's. We have a higher concentration than expected. When I looked back at the chromatograph, I noticed that for the PT's sample only I have a small peak besides/overlapping my internal standard peak. I don't find the same problem in my standards nor my spiked sample. If I integrate the two peaks, I have the right concentration of NDMA. Even when I check the surface area, the difference is not a lot compared to the spiked sample so I had no clue if I had to integrate the two peaks or not. (Ex. spike ISTD 77936, Sample ISTD 1 peak = 71073 2 peaks= 87894..) What can cause my internal standard peak to separate only for the PT samples? I checked last year PT chromatographs and there's no separation. Thank you, Marie
I'm using a GC 6890 and a MS 5973 to analyze n-nitrosodimethylamine. Everything was going well until we fell 2 PT's. We have a higher concentration than expected. When I looked back at the chromatograph, I noticed that for the PT's sample only I have a small peak besides/overlapping my internal standard peak. I don't find the same problem in my standards nor my spiked sample. If I integrate the two peaks, I have the right concentration of NDMA. Even when I check the surface area, the difference is not a lot compared to the spiked sample so I had no clue if I had to integrate the two peaks or not. (Ex. spike ISTD 77936, Sample ISTD 1 peak = 71073 2 peaks= 87894..) What can cause my internal standard peak to separate only for the PT samples? I checked last year PT chromatographs and there's no separation. Thank you, Marie