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

Abstract

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.

A Reference Method for the Analysis of Aldosterone in Blood by High-Performance Liquid Chromatography–Atmospheric Pressure Chemical Ionization–Tandem Mass Spectrometry

“…The absolute mass detection limit of the assay is 12 pg. Imprecision was determined at four concentrations across the linear range (15,20,150, and 450 pg/mL) with total coefficients of variation of 18.5, 8.8, 10.6, and 9.5%, respectively ( Table 1). The accuracy and absolute recoveries of aldosterone and IS from human serum are shown in Table 1.…”

“…Samples of õ2 mL were diluted (10,20,50, 100, 300, and 500 pg/ CT) was used throughout the investigation. Prior to mL) was assayed daily with control samples (15,20, use all glassware was treated with a 5% solution of 150, and 450 pg/mL) and pooled patient sera. The imdichlorodimethylsilane in toluene to prevent adsorp-precision of the assay was determined by the method tion of the aldosterone onto the glass.…”