Hello, I create this post because I have a problem in my laboratory regarding the dosage of organic acids by gc ms. And more particularly concerning isovalerylglycine. In recent weeks, the form di-tms has sometimes no longer been detected randomly. And at the same time, the mono-tms form is greatly increased. By re-injecting the sample, the di-tms form sometimes reappears (with a sharp drop in the mono-tms form), but not always... So I wanted to know if some of you have already observed this phenomenon? And if there was an explanation? Thank you in advance for your help