EXPERIENCES WITH A FREQUENCY-DOUBLED ARGON ION LASER FOR FLUORESCENCEDETECTION IN OPEN-TUBULAR LIQUID-CHROMATOGRAPHY

The possibilities of the 257-nm emission from a frequency-doubled argo n ion laser as a radiation source for fluorescence detection in open t ubular liquid chromatography (OTLC) using 5-mu m-i.d. coated fused sil ica capillaries were investigated. The stability of the UV laser radia tion was surprisingly good; shortterm fluctuations were smaller than 0 .02%. The natural fluorescence of polynuclear aromatic hydrocarbons, c atecholamines, aromatic amino acids, and dipeptides after excitation w ith deep UV light was used. Depending on the photostability of a compo und, the detection sensitivity could be impaired by high excitation in tensities. The detection limits (S/N = 2) for 9-methylanthracene and 9 -phenylanthracene were 8.4 x 10(-19) and 3.7 x 10(-19) mol, correspond ing to concentrations of 21 and 9 nmol/L, respectively. Noradrenaline and adrenaline could be detected at the low-femtomole level after sepa ration on an ion-exchange column. The linear range of detection was at least four orders of magnitude for both 9-methylanthracene and trypto phan in reversed-phase and ion-exchange OTLC, respectively. (C) 1997 J ohn Wiley & Sons, Inc.