Matrix influence on derivatization and ionization processes during selenoamino acid liquid chromatography electrospray ionization mass spectrometric analysis

Considering the importance of derivatization in LC/ESI/MS analysis, the objective of this work was to develop a method for evaluation of matrix effect that would discriminate between matrix effect due to the derivatization reaction yield and from the ESI. Four derivatization reagents (TAHS, DEEMM, DNS, FMOC-Cl) were studied with respect to matrix effects using two selenoamino acids and onion matrix as model system. A novel method for assessing matrix effects of LC/ESI/MS analyses involving derivatization is proposed, named herein post-derivatization spiking, that allows evaluating effect of matrix on ESI ionization without derivatization reaction yield contribution. The proposed post-derivatization spiking method allowed to demonstrate that the reason of reduced analytical signal can be signal suppression in ESI (as in case of DNS derivatives with matrix effects 38–99%), alteration of derivatization reaction yield (TAHS, matrix effects 92–113%, but reaction yields 20–50%) or both (FMOC-Cl, matrix effects 28–88% and reaction yields 50–70%). In case of DEEMM derivatives, matrix reduces reaction yield but enhances ESI/MS signal. od for matrix effect evaluation was developed. It was also confirmed that matrix effects can be reduced by dilution.