Tocopherols and tocotrienols are chemical compounds insusceptible to the ionization process under atmospheric pressure conditions. Therefore, the selection of the optimal ion source settings for their quantification requires special attention. The aim of this study was to analyse the influence of the APCI source parameters on the response of tocochromanols and two related compounds.
Standard solutions of target compounds were injected on the HPLC-APCI-MS/MS system separately and analysed in 30 randomly selected ion source settings. The obtained responses were modelled by multivariate linear regression with least absolute shrinkage and selection operator. The developed models were used for choosing best APCI conditions.
Multivariate linear models were built for eight tocochromanols, trolox and BHT. The APCI settings derived from the models did not increase the peak areas obtained for T and T3 during ionization process. Ionization conditions based on models for trolox and BHT improved analytical responses for 12-36% and 4-32%, respectively. The application of the ion source settings optimal for trolox and BHT to tocochromanols did not result in better analytical responses.
The ionization pattern of tocochromanols in APCI source is problematic and should be further investigated. Modelling methodology for response improvement presented in this study can be applied in similar studies.