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

•A novel method to evaluate matrix effects for analyses containing derivatization.•Reduced signal can be due to signal suppression and/or derivatization reaction yield.•For DEEMM derivatives matrix reduces reaction yield but enhances ESI/MS signal.•Onion matrix had major impact on the TAHS derivatization reaction yield.

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.A method for matrix effect evaluation was developed. It was also confirmed that matrix effects can be reduced by dilution.