Rapid Microdetermination of Hydroxyproline in Biomedical Samples by Flow Injection Analysis Using Cysteine as an Antioxidant

A new practical method for the rapid microdetermination of hydroxyproline (Hyp) in biomedical samples, such as tissue and urine, in the presence of a definite amount of cysteine as antioxidant was established by means of the modified KISO method using flow injection analysis. This method uses no organic solvent and requires only 9min for each sample, which can be injected every 3min (about 5h is sufficient for 100 samples). A good linear relationship (r=0.99996) was obtained between the concentration of Hyp (0-80μg/ml) and the absorbance (0-0.514). In biomedical samples (hydrolyzates of rat stomach tissue), the recoveries (94.8-103.7%) and the reproducibility (the mean of RSD; 0.484% for ten kinds of rat tissues) were satisfactory. The correlation between values from this method and from the conventional KISO method was shown to be good enough (r=0.966) for hydrolyzate samples (n=95), when a proper amount of cysteine solution was added to both the sample and standard solutions and the concentration of the oxidant was optimized to Hyp contents.