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

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.