MALDI-TOF mass spectrometric determination of four pyrrolidino cathinones in human blood

Abstract

A rapid and sensitive detection method using matrix-assisted laser desorption ionization (MALDI)–time-of-flight (TOF)–mass spectrometry (MS) was developed for the analysis of four pyrrolidino cathinones: α-pyrrolidinopropiophenone (PPP), 4′-methyl-α-pyrrolidinopropiophenone (MPPP), α-pyrrolidinobutiophenone (PBP), and α-pyrrolidinovalerophenone (PVP). In this method, α-cyano-4-hydroxycinnamic acid was used as the matrix to assist ionization of the cathinones. Each MALDI–TOF–MS spectrum of the cathinones showed not only protonated molecular ion [M + H]⁺ but also several fragment ions having comparable intensities to that of [M + H]⁺. Hence, MPPP and PBP could be clearly discriminated by the mass spectra alone, although these compounds have almost the same mass numbers in their protonated molecular ions. The quantification of MPPP, PBP, or PVP was performed using PPP as internal standard, and that of PPP was performed using PBP as internal standard. The limit of detection was 1 ng/ml, and the quantification range was 2–200 ng/ml for the four cathinones using 20 μl of blood. In a fatal poisoning case in which PVP was abused, the PVP levels in whole blood samples obtained from the right heart, left heart, and femoral vein were 0.597, 0.635, and 0.580 μg/ml, respectively. We recommend the MALDI–TOF–MS method without any chromatography for both identification and quantification of the pyrrolidino cathinones in various matrices in forensic toxicological analysis, because of the simplicity, rapidness, and reliability of the method.