Sensitive and selective analysis of coenzyme Q10 in human serum by negative APCI LC-MS

Abstract

Two new sensitive and selective LC-MS methods have been developed for the quantification of the total coenzyme Q₁₀ concentration in human blood serum. The sensitivity of the methods is based on the very efficient formation of the radical anions of CoQ₁₀ [M⁻˙] by negative atmospheric pressure ionisation, APCI(−). The mass detection of the [M⁻˙] ions, m/z = 862.6, was performed either in selective ion monitoring (SIM) or in MS² mode (m/z = 862.6 → m/z = 847.6) using an LCQ-deca ion-trap mass spectrometer. Two standard serum samples with medium (0.73 µg ml⁻¹) and high (1.96 µg ml⁻¹) total CoQ₁₀ concentrations were analysed by LC-APCI(−)-SIM and LC-APCI(−)-MS² and the results compared with a HPLC literature procedure with electrochemical detection (ECD). Both the LC-MS methods were shown to be more selective and with comparable or better sensitivity than the HPLC-ECD method. The LC-MS-SIM and LC-MS² chromatograms of the medium concentration sample showed CoQ₁₀ signal to noise ratios of 25 and 625, respectively. In addition, a simple and fast serum pre-treatment procedure was developed, in which the serum CoQ₁₀H₂ content was quantitatively oxidised quantitatively to CoQ₁₀ in less than 15 min by 1,4-benzoquinone.