Chromatography Forum

I have analysed coffee sample by HPLC method, this same sample was analysed by another laboratory using LCMS/MS method and results was about half lower (Ochratoxin A: 2,3 ug/kg vs. 1,3ug/kg). Does anybody of You know, why results can differ so much? Is it fault of sample preparation, matrix, or...?

THX in advance for Your replays.

hello,
i think sample preparation is likely to be the guilty (solvent, filtration, extraction)....you use an external standard method i suppose, so different responses in different instruments should give the same result...however i don't know which exatly you are dealing with (chromatogram eg) so my hypothesis is not so strong.

bye

I am considering sampling method can be guilty too. what I mean is what sample send to another laboratory wasn't taken by skilled man and can be not representative. but another way... is it possible to be so much differences in content of OTA?

HI,
are the different risults that you found supported by only one test or more?Did you try to make a sort of homogeneity test (sampling at various heights and/or containers eg)?As regard the stability of ota I could be wrong but i think it is quiet stable in normal conditions.

this seems to be the area of natural products. If so, the components can be effected by season, location, species, climate, weather, age, storage time and condition, etc; the process mentioned by Vicente and last but not least, the accuracy of your method( such as the method accuracy permit 50% difference when tested on standard reference). hope this help you,

I wonder is it possible so much differences just becouse of sampling method. both subsamples was taken from this same part of coffee.

would you mind letting us know how big your peaks? Thanks