Serum CoQ10 Quantification Protocol

Blood samples were drawn from a vein at the baseline (just before meal ingestion), and 1.5, 3, and 5 h after the start of the meal, and serum was obtained by centrifugation after clot formation. Quantitative analysis of serum CoQ₁₀ concentration was measured by Kaneka Techno Research Co., Ltd., using liquid chromatography with tandem mass spectrometry (LC/MS/MS) [43 , 44 (link)]. In brief, 0.7 mL of the isopropanol was added to 0.1 mL of serum, mixed, and stored at −80°C until just before the analysis. After centrifugation, the supernatant was filtered through a membrane filter. Then, 200 μL aliquots were mixed with 200 μL of methanol and 50 µL of oxidized CoQ₉ (50 ng/mL in 2-propanol) as an internal standard and used as the sample for LC/MS/MS, which was performed using an AB Sciex Triple Quad 5500 LC-MS/MS system and a reversed-phase octadecyl-silica column (AB Sciex, Framingham, MA, USA). The intra- and interday coefficients of variation for CoQ₁₀ were less than 2 and 10%, respectively.