Enhancement of fluorescence intensity of dansyl amino acids on silica gel plate using cycloheptaamylose.

Abstract

Cycloheptaamylose (C7A) was found to greatly enhance and stabilize the fluorescence intensity of dansyl (DNS) amino acids on silicagel layer and this finding was applied to the detection and determination of these compounds on thin-layer chromatogram. Procedure : After the development of DNS-amino acids, the thin-layer plate is sprayed with 10 ml of 1.8% C7A, dried over phosphorus pentoxide and the spots are detected under a mercury lamp or determined using a scanning fluorometer. Above 10 fold increase in the fluorescence was observed. The fluorescence was stable for 90 min under exposure to air in the diffused light and for 24 hr over phosphorus pentoxide under reduced pressure. Limits of detection for 24 DNS-amino acids were in the range of 0.1 to 0.5 pmole/spot. Standard curves for DNS-amino acids were linear in the ranges of 5 to 30 pmole. Samples from 1 to 5 pmole could also be determined semiquantitatively.