Analysis of α- and β-amanitin in Human Plasma at Subnanogram per Milliliter Levels by Reversed Phase Ultra-High Performance Liquid Chromatography Coupled to Orbitrap Mass Spectrometry

Amatoxins are known to be one of the main causes of serious to fatal mushroom intoxication. Thorough treatment, analytical confirmation, or exclusion of amatoxin intake is crucial in the case of any suspected mushroom poisoning. Urine is often the preferred matrix due to its higher concentrations compared to other body fluids. If urine is not available, analysis of human blood plasma is a valuable alternative for assessing the severity of intoxications. The aim of this study was to develop and validate a liquid chromatography (LC)-high resolution tandem mass spectrometry (HRMS/MS) method for confirmation and quantitation of alpha- and beta-amanitin in human plasma at subnanogram per milliliter levels. Plasma samples of humans after suspected intake of amatoxin-containing mushrooms should be analyzed and amounts of toxins compared with already published data as well as with matched urine samples. Sample preparation consisted of protein precipitation, aqueous liquid-liquid extraction, and solid-phase extraction. Full chromatographical separation of analytes was achieved using reversed-phase chromatography. Orbitrap-based MS allowed for sufficiently sensitive identification and quantification. Validation was successfully carried out, including analytical selectivity, carry-over, matrix effects, accuracy, precision, and dilution integrity. Limits of identification were 20 pg/mL and calibration ranged from 20 pg/mL to 2000 pg/mL. The method was applied to analyze nine human plasma samples that were submitted along with urine samples tested positive for amatoxins. alpha-Amanitin could be identified in each plasma sample at a range from 37-2890 pg/mL, and beta-amanitin was found in seven plasma samples ranging from <20-7520 pg/mL. A LC-HRMS/MS method for the quantitation of amatoxins in human blood plasma at subnanogram per milliliter levels was developed, validated, and used for the analysis of plasma samples. The method provides a valuable alternative to urine analysis, allowing thorough patient treatment but also further study the toxicokinetics of amatoxins.