Sensitivity drop of nicotinic acid/nicotinamide - LC-MS
Posted: Thu Feb 19, 2015 1:43 pm
I am using LC-MS-ESI-TOF (LCT Premier, Waters). Over the last 5 years nicotinic acid - m/z+1 124 (and also nicotinamide m/z+1 - 123) intensity has dropped 200 times (from 2000 to 10) and it is not possible to measure it any more. The intensities of other analytes, e.g. thiamine (m/z 265), pantothenic acid m/z+1 220) have remained the same. All the LC-MS conditions (columns, eluents etc) have also remained the same during the years.