DETERMINATION OF AMINO-ACIDS BY CAPILLARY ZONE ELECTROPHORESIS BASED ON SEMICONDUCTOR-LASER FLUORESCENCE DETECTION

Chlorophyll is fluorescent in the deep-red region and is determined by semiconductor laser fluorometry after its separation with capillary zone electrophoresis. The separation efficiency is several hundred thousand in the theoretical plate. Methylene blue is used as a chromophore in indirect fluorometry. The detection limit achieved is 1-pmol levels. A new labeling reagent is synthesized, which consists of a thiazine chromophore for fluorescence detection and a succinimidyl ester for combination with an amino acid. The labeled amino acids are clearly resolved by capillary zone electrophoresis, the detection limit being 10-pmol levels. Amino acids are further labeled with a visible dye such as fluoresceinisothiocyanate (FITC) or 7-(diethylamino)coumarin-3-carboxylic acid succinimidyl ester (DCCS), and are detected with visible semiconductor laser fluorometry using second harmonic emission (415 nm) of the near-infrared semiconductor laser. The detection limit achieved is approximately 100-amol levels.