Coenzyme Q10 quantification in muscle, fibroblasts and cerebrospinal fluid by liquid chromatography/tandem mass spectrometry using a novel deuterated internal standard

RATIONALE Neurological dysfunction is common in primary coenzyme Q10 (2,3-dimethoxy, 5-methyl, 6-polyisoprene parabenzoquinone; CoQ10; ubiquinone) deficiencies, the most readily treatable subgroup of mitochondrial disorders. Therapeutic benefit from CoQ10 supplementation has also been noted in other neurodegenerative diseases. CoQ10 can be measured by high-performance liquid chromatography (HPLC) in plasma, muscle or leucocytes; however, there is no reliable method to quantify CoQ10 in cerebrospinal fluid (CSF). Additionally, many methods use CoQ9, an endogenous ubiquinone in humans, as an internal standard. METHODS Deuterated CoQ10 (d6-CoQ10) was synthesised by a novel, simple, method. Total CoQ10 was measured by liquid chromatography/tandem mass spectrometry (LC/MS/MS) using d6-CoQ10 as internal standard and 5mM methylamine as an ion-pairing reagent. Chromatography was performed using a Hypsersil GOLD C4 column (150x3mm, 3 mu m). RESULTS CoQ10 levels were linear over a concentration range of 0200 nM (R2=0.9995). The lower limit of detection was 2 nM. The inter-assay coefficient of variation (CV) was 3.6% (10 nM) and 4.3% (20 nM), and intra-assay CV 3.4% (10 nM) and 3.6% (20 nM). Reference ranges were established for CoQ10 in CSF (5.78.7 nM; n=17), fibroblasts (57.0121.6 pmol/mg; n = 50) and muscle (187.3430.1 pmol/mg; n=15). CONCLUSIONS Use of d6-CoQ10 internal standard has enabled the development of a sensitive LC/MS/MS method to accurately determine total CoQ10 levels. Clinical applications of CSF CoQ10 determination include identification of patients with cerebral CoQ10 deficiency, and monitoring CSF CoQ10 levels following supplementation. Copyright (c) 2013 John Wiley & Sons, Ltd.