As the percentage of the organic phase changes, the retention time of NBD-F remains relatively stable, while the retention times of the derivatization products changes. The pH of the mobile phase affects the separation of the NBD-F and the derivatization products. NBD-F is a fluorescent derivatization reagent that is originally developed for amino acid analysis, and recently applied to the analysis of other amino acid derivatives such as N-methyl-D-aspartic acid and glutathione. The use of NBD-F appears to have several advantages in that the derivatization procedure is simple and its derivatives are highly stable.