2-(5-Benzoacridine)ethyl-p-toluenesulfonate as sensitive reagent for the determination of bile acids by HPLC with fluorescence detection and online atmospheric chemical ionization-mass spectrometric identification

Abstract

2-(5-Benzoacridine)ethyl-p-toluenesulfonate (BAETS), a dual-sensitive probe, was reacted with bile acids in the presence of K(2)CO(3) catalyst in dimethyl sulfoxide (DMSO) solvent to give BAETS-bile acid derivatives. Derivatives exhibited intense fluorescence (FL) with an excitation maximum at lambda(ex) 270 nm and an emission maximum at lambda(em) 510 nm. MS analysis using APCI-MS indicated that derivatives had excellent APCI-MS ionizability with percentage ionization delta values changing from 0 to 88.83% in aqueous acetonitrile and from 0 to 89.15% in aqueous methanol. The collision induced dissociation spectra of m/z [M + H](+) contained specific fragment ions at m/z [M + H-H(2)O](+), [M + H-2H(2)O](+), [M + H-3H(2)O](+), 347.3, and 290.1. Repeatability was good for LC separation of BAETS-bile acid derivatives with aqueous acetonitrile as mobile phase. The relative standard deviations (RSDs) of retention time and peak area at 6.6 nmol mL(-1) levels with fluorescence detection (FL) were from 0.045 to 0.072% and from 2.16 to 2.73%, respectively. Excellent linear responses were observed, with regression coefficients >0.9995. The FL detection limits (S/N = 3) were in the range of 18.0-36.1 fmol. The online APCI-MS detection limits are in the range of 500-790 fmol (at a signal-to-noise ratio of 3).