Amatoxins (α- and β-Amanitin) and phallotoxin (Phalloidin) analyses in urines using high-resolution accurate mass LC-MS technology.

Abstract

Mycotoxin intoxications can result from the consumption of amatoxins like α- and β-amanitin or of phallotoxin, present in several toxic mushrooms like Amanita phalloides. To identify and quantify amatoxins and phallotoidin in biological matrixes, we developed a method using liquid chromatography coupled with an ultra-high-resolution and accurate mass instrument (liquid chromatography-high-resolution-mass spectrometry, LC-HR-MS), Q Exactive™ (Thermo Fisher). The method includes a simple solid-phase extraction of urine samples spiked with flurazepam as internal standard (IS), using Bond Elut Agilent Certify cartridges (C18, 200 mg, 3 mL). LC separation was performed on a C18 Accucore column (100 × 2.1 mm, 2.6 µm) using a gradient of 10 mM ammonium acetate buffer containing 0.1% (v/v) formic acid and of acetonitrile with 0.1% (v/v) formic acid. Separation of analytes was obtained in 7 min, with respective retention times for α-amanitin, β-amanitin, phalloidin and IS of 1.9, 1.7, 3.5 and 3.8 min, respectively. Quantitation on the LC-HR-MS system was performed by extracting the exact mass value of each protonated species using a 5-p.p.m. mass window, which was 919.3614, 920.3455, 789.3257 and 388.1586 for α-amanitin, β-amanitin, phalloidin and IS, respectively. Calibration curves were obtained by spiking drug-free urine at 1-100 ng/mL. Mean correlation coefficients, r(2), were above 0.99 for each amatoxins and phalloidin. According to currently accepted validation procedures, the method was tested for selectivity, calibration, accuracy, matrix effect, precision and recovery. Authentic urine samples from 43 patients suffering from a suspected intoxication with mushrooms were analyzed by LC-HR-MS, and the results were compared with ELISA competitive immunoassay. The LC-HR-MS presented large benefits over immunoassay of being specific, faster and more sensitive, making it suitable for daily emergency toxicological analysis.