Selective reaction of homocysteine with o-phthalaldehyde under flow conditions in highly alkaline medium: fluorimetric determination using zone fluidics.

In the present study we report the reaction between homocysteine and o-phthalaldehyde under flow conditions. Homocysteine reacts on-line with the derivatization reagent in a strong alkaline medium and in the absence of nucleophilic reagents to yield a fluorescent derivative (λex /λem = 370/480 nm). The reaction variables were investigated using the concept of zone fluidics. Selectivity factors against other compounds were calculated at 10-fold excess. The findings formed the basis of an automated proposed method that was found to be linear in the range 0.1-1.5 μmol L-1 , with a limit of detection of 20 nmol L-1 and relative standard deviation < 0.5% (within-day) and 3.2% (between-day). The method proved to be rapid, offering a practical sampling rate of 24 h-1 and accurate following application to an artificial urine matrix with minimum dilution.