GC-MS Analysis of Deuterium Enrichment of Retinol in Serum and Estimation of Vitamin A Total Body Stores.

This method describes the determination of deuterium enrichment of retinol in serum and the estimation of vitamin A stores in the body. The process involves extracting retinol from 0.4 mL of serum using 0.5 mL of 0.85% saline solution, 100 µL of internal standard solution, and 5 mL of chloroform-methanol (2:1 v/v) solution. After centrifugation and removal of the lower chloroform layer, the mixture is dried under nitrogen and resuspended in 0.1 mL of ethanol, and the retinol fraction is separated from other constituents using an HPLC system equipped with a PE C18 column. The retinol fraction can be collected manually or with a fraction collector. Subsequently, the retinol fraction is dried under nitrogen and derivatized with O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) containing 10% trimethylchlorosilane. Finally, labeled and non-labeled retinol isotopes are quantified using a GC-MS system equipped with a 19091z-431 HP-1 methyl siloxane capillary column, employing electron capture negative chemical ionization with helium as the carrier gas and methane as the ionization agent. The ratio of labeled to non-labeled retinol is then used in the Olson, Green, or mass balance equations to estimate vitamin A stores.