Serum Carotenoid Analysis by HPLC

Fasting (overnight fast > 9 h) blood samples were collected at 0, 3, and 6 months for XC serum analysis. Blood samples were collected by standard venepuncture techniques in 9 mL blood collection tubes (BD Vacutainer SST Serum Separation Tubes) containing a “Z Serum Sep Clot Activator”. Collection tubes underwent thorough mixing of the clot activator. The blood samples were left for 30 min at room temperature to clot and then centrifuged at 725 g for 10 min in a GruppeGC12 centrifuge (Desaga Sarstedt) to separate the serum from the whole blood. Following centrifugation, serum was transferred to light-resistant microtubes and stored at circa −80 °C until the time of batch analysis. Serum carotenoid analysis was performed by high performance liquid chromatography (HPLC), using a method previously described by our laboratory [31 (link)]. The calibration lines used, as well as the lower and upper limits of quantification (LLOQ and ULOQ respectively), were as in the cited work. Serum carotenoid analysis was completed in sixteen independent batches, with a maximum intra-day precision of 7.28%, measured as RSD, and an inter-day precision of 3.16% (RSD).