Analysis of leukotrienes by liquid chromatography/electrochemistry after conversion to dinitrobenzoate derivatives

A sensitive liquid chromatography method has been developed using electrochemistry for the determination of leukotrienes in biological fluids. Biological specimens are treated with 3,5-dinitrobenzoyl chloride in acetonitrile which undergoes rapid reaction with hydroxyl groups of non-peptidic leukotrienes in the presence of pyridine and with amino groups of peptidic leukotrienes in the presence of potassium tetraborate buffer. The resulting dinitrobenzoate derivatives of leukotrienes are highly electroactive, suitable for reduction or oxidation at moderate potentials by an electrochemical detector. In reductive mode at -0.7 V or oxidative mode at +1.15 V potentials, the lower limits of detection for leukotriene derivatives were approximately 8 +/- 3 pg and 70 +/- 16 pg respectively, with a signal-to-noise ratio of 5 to 1. This method was applied to the detection of leukotrienes in plasma, nasal and bronchial fluids of patients with asthma.