Development of a Fully-automated On-line Oxidation Column-switching HPLC System for the Determination of Endogenous Melatonin in Human Clinical Samples.

A fully-automated on-line oxidation column-switching HPLC system has been developed for the determination of endogenous melatonin in human plasma and saliva. This HPLC system consists of four processes. In the first step, melatonin is fractionated using a reversed-phase C4 column (Proteonavi, 75 mm × 1.

Enantioselective micro-2D-HPLC determination of aspartic acid in the pineal glands of rodents with various melatonin contents.

Enantioselective determination of aspartic acid (Asp) in the pineal gland of rodents with various melatonin contents was performed using a highly sensitive and selective two-dimensional HPLC system. After derivatization of the amino group with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), NBD-Asp was separated using a capillary monolithic ODS column in the first dimension. The fraction of NBD-Asp was automatically collected and transferred to the second dimension, and the D- and L-Asp were separated and determined using a narrowbore enantioselective column.