Determination of galactose in human blood by high‐performance liquid chromatography: Comparison with an enzymatic method and application to the pharmacokinetic study of galactose in patients with liver dysfunction

Galactose, the C‐4 epimer of glucose, is an agent of choice for the quantitation of liver function. A simple, precise, and accurate high‐performance liquid chromatographic (HPLC) assay with refractive index detection was developed for the determination of galactose in human whole blood. The method consists of organic solvent‐heavy metal deproteinization procedures and reversed‐phase chromatography on a cation‐exchange column in the calcium form. Calibration graphs were linear over the concentration range 100–2500 μg/mL, with correlation coefficients >0.999. The within‐day coefficient of variation (CV) ranged from 2.08 to 8.94%, and the between‐day CV ranged from 1.61 to 10.9%. The limit of quantitation was 100 μg/mL in whole blood. However, the limit of detection was 75 μg/mL based on a signal‐to‐noise ratio of ⩾3. Eight structurally related sugars and polyols were investigated to check for potential interferences using the analytical condition of the assay. The possible metabolites of galactose present in the body were also checked to determine the specificity of this assay. The proposed HPLC assay was compared with an enzymatic assay and an excellent correlation was observed (HPLC = 1.0299Enz. – 12.907, r = 0.952, p < 0.001). This HPLC method has been successfully applied to the pharmacokinetic study of galactose in six patients with liver dysfunction. Following the intravenous administration of a dose of 0.5 g/kg body weight, galactose pharmacokinetics followed a nonlinear two‐compartment model with Michaelis–Menten elimination from the central compartment. The maximum elimination rate and the Michaelis–Menten constant of galactose in these patients were 44.0 ± 14.9 μg/mL/min and 478 ± 250 μg/mL, respectively. The distribution parameters K₁₂ and K₂₁ were 0.0749 ± 0.0365 and 0.147 ± 0.081 min⁻¹, respectively. The volume of the central compartment was 0.204 ± 0.045 L/kg body weight.