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 ( λ ex / λ em = 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.