I'm trying to follow a method of plasma sample processing I have found in a paper so that the samples may been analysed by LC-MS/MS. In the paper, it states that standards and dried plasma samples were dissolved in "75 mM ammonium citrate and 12.5 mM ascorbic acid (pH 6 buffer)", but it does not state the ratio of each solution used. I can't seem to find any other literature that uses such a mixture of solutions for this purpose. Does anyone know whether there is a standard ratio I'm supposed to use?
Many thanks in advance,
Susy
Hi Susannah,
Aren't you just supposed to reconstitute in a solution containing both 75 mM citrate and 12.5 mM ascorbic acid (pH 6)?
Citrate buffer should be avoided for LC-MS analysis. Why you would need citrate buffer in the sample prep? Whats your analyte of interest?
Eef Dirksen Navid J. Ayon Thanks both for your answers.
Eef Dirksen yes, that's what I was wondering as well, but I haven't come across any literature using both together as a buffer so couldn't help but wonder whether there was a specific amount of each supposed to be used. I'm going to give that a go and see if it works, but thought I'd check to see whether there was something glaringly obvious I was missing!
Navid J. Ayon what is the reason citrate buffer should be avoided? I'm interested in melatonin and its precursor.
Thanks! :)
Susannah, citrate buffer is on the non volatile side and can deposit on MS source and block capillaries and HPLC tubing. Use ammonium formate or acetate instead.
- Badges
- Science method