Fluorometric Determination of Quinolinic Acid Using the Catalytic Activity of Horseradish Peroxidase

The conversion of quinolinic acid (QA) into a fluorescent compound by the catalytic activity of horseradish peroxidase (HRP) was investigated in the presence of hydrogen peroxide without exposure to light. Nonfluorescent quinolinic acid was converted into a fluorescent compound with maximum excitation and emission wavelengths at 328 and 377 nm, respectively. This fluorescent derivatization reaction with HRP in the presence of hydrogen peroxide was adopted for the determination of trace amounts of QA. The calibration curve obtained was linear from 0.1 to 5.0 nmol of QA in a 1.0 ml sample solution. The detection limit was 0.04 nmol/ml. The relative standard deviation at 3.0 nmol of QA was 3.58% (n=8). This method was applied to the determination of QA spiked in control serum I and II. The recovery rates of QA were greater than 98%, and satisfactory results were obtained for both control serum I and II.