DETERNINATION OF FETAL BILE ACIDS IN HUMAN NEONATES BY GAS CHROMATOGRAPHY-NEGATIVE ION CHEMICAL IONIZATION MASS SPECTROMETRY

Abstract

A highly sensitive and specific quantitative assay of the fetal bile acids in neonatal biological fluids has been developed by capillary gas chromatography-mass spectrometry (GC-MS) using selected ion monitoring with negative ion chemical ionization (NICI), 1β-, 2β-, 4β- and 6α-Hydroxylated bile acids were synthesized as authentic samples for the analysis of fetal bile acids. Calibration curves for these bile acids are useful over the range of 5-500pg and the detection limit was 1fg (SN=5) in the NICI mode using isobutane as a reagent gas. Recoveries of the bile acids and thier conjugates from the bile acid free serum ranged from 90 to 107% of the added amounts of thier standard samples. The analysis of bile acids in neonatal biological fluids was carried out by the developed method. The fetal bile acids, CA-1β-ol (I): 0.12μg/ml, 2.0% of the total bile acids, CDCA-1β-ol (II): 0.04μg/ml, 0.7%, CA-6α-ol (III): 0.06μg/ml, 0.9%, HCA (IV): 0.27μg/ml, 4.4%, CA-2β-ol (V): 0.06μg/ml, 0.9% and CA-4β-ol (VI): 0.18μg/ml, 2.9% were found in the serum from neonates, and also determinded in the urine from neonates (I: 1.56μg/ml, 45.0%, II: 0.11μg/ml, 3.2%, III: 0.28μg/ml, 8.1%, IV: 0.07μg/ml, 1.9%, V: 0.33μg/ml, 9.2%). It is discussed on the significance of hydroxylation at C-1β, C-2β, C-4β and C-6α position of bile acids and their urinary elimination in fetal and neonatal periods.