-
- Posts: 11
- Joined: Mon Mar 01, 2021 2:23 pm
- Location: Latvia
Making EI analyses of mixtures of solvents on ITS40 ( it still works ) I do not see molecular peaks - usually present +1 or sometimes -1 from molecular wt. For example, in EI MS of Acetone, Ethyl and Butyl Acetates must be 58, 88 and 116 peaks respecivelly, but in fact 59, 89 and 117 are observed. Sample load variations leads to change in relative intensity of peaks, but general picture remails all the same. It makes difficulties with identification for more complicated compounds.
0.25mm ID column, 99.9995 helium as a carrier, two stage vacuum pump EVP DRV16 ( 16 cub.m. per h ), ionisation current 25uA, 1280V multiplier voltage, all samples tested contains 0.1 - 2 % of water. FC-43 calibration shows lower intensity of 414 and 502 peaks then expected ( 2 - 3 % of 69 ).
Any idea about the reason ? Thanks for your help !