Isomer detection on the basis of analyte adduct formation with the components of the mobile phase and tandem mass spectrometry

Abstract

To investigate and compare the detection of isomers on the basis of analyte adduct formation with the components of the mobile phase appropriate infusion experiments were performed with tandem mass spectrometry (−Q1 MS, −EPI and −MRM mode) and analyses with liquid chromatography–tandem mass spectrometry (−ESI). In experiments performed following adducts were focused: deprotonated analyte adduct with sodium acetate, deprotonated analyte dimer adduct with sodium and deprotonated analyte adduct with two molecules of sodium acetate. α-hydroxybutyrate, β-hydroxybutyrate and γ-hydroxybutyrate were used as model drugs since their effective separation and detection are a real analytical challenge when γ-hydroxybutyrate is the analyte of interest. The achieved results revealed that the drugs investigated produce similar adduct ions in the negative electrospray mode. However, β-hydroxybutyrate is not a potential interfering substance for γ-hydroxybutyrate analysis other than α-hydroxybutyrate. The interference of α-hydroxybutyrate can be minimised when analyte adduct ion fragmentation is used, since appropriate fragmentations do not produce ion fragments (m/z = 85) with efficiency required at different values of collision energy. Finally it was demonstrated that the strategy presented can be a real advantage when interfering substances with similar retention times do not produce adduct ions or produce adduct ions but with a different fragmentation pattern. Keywords: Adduct formation, Adduct fragmentation, γ-hydroxybutyrate, GHB, LC–MS/MS