Sensitive determination of dissolved tryptophan in freshwater by alkaline hydrolysis and HPLC

A sensitive method involving alkaline hydrolysis and HPLC analysis has been developed to detect nanomolar levels of tryptophan dissolved in freshwater . The procedure includes 1) alkaline hydrolysis with nitrogen atmosphere in Teflon-lined Pyrex tubes with 4.2 M sodium hydroxide at 110 degreesC for 1 6 h, in which ascorbic acid was used as an antioxidant; 2) a determination step, in which tryptophan was separated efficiently from other amino acids by HPLC and measured by fluorescence. The mean recovery for tryptophan stan dard was 91.4% with an RSD of 3.3%. Using this method, dissolved tryptophan concentrations ranged from 10.91 to 41.83 nM in water samples from Lake Bi wa, Japan.