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Reversed‐phase ion‐pair chromatography‐diode array detection of the bispyridinium compound MB327: plasma analysis of a potential novel antidote for the treatment of organophosphorus poisoning
Author(s) -
John Harald,
Mikler John,
Worek Franz,
Thiermann Horst
Publication year - 2016
Publication title -
drug testing and analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.065
H-Index - 54
eISSN - 1942-7611
pISSN - 1942-7603
DOI - 10.1002/dta.1821
Subject(s) - chemistry , chromatography , detection limit , analytical chemistry (journal)
In the case of poisoning by organophosphorus nerve agents or pesticides, there is still a lack of pharmacological treatment of the cholinergic crisis selectively targeting the nicotinic acetylcholine receptor. Recently, the compound MB327 was identified as a potential novel lead structure to close this gap, thus demanding a quantitative assay for initial pharmacokinetic (PK) studies. MB327 is a salt consisting of the dicationic bispyridinium compound (BPC) 1,1´‐(propane‐1,3‐diyl)bis(4‐tert‐butylpyridinium) and two iodide counter ions. Due to the permanent positive charge of the BPC, an isocratic reversed‐phase ion‐pair chromatographic separation (RPIPC) was developed using heptanesulfonic acid as ion‐pairing reagent and 45% v / v methanol as organic modifier (1 mL/min). Selective UV‐detection (230 nm) was done by a diode array detector (DAD) for reliable, rugged, precise (RSD < 7%) and accurate (96–104%) quantitative analysis of 50 μL swine plasma (linear range 1–1000 µg BPC/mL plasma, lower limit of quantification 2 µg/mL). During method validation, diverse parameters essential for the chromatographic process were investigated to generate van´t Hoff, van Deemter and width plots allowing calculation of thermodynamic data like the distribution constant K (5.7 ± 0.3), change in enthalpy, ΔH 0 : −23.66 kJ/mol, and entropy, ΔS 0 : −65 J/(mol*K). In addition, RPIPC‐DAD analysis enabled calculation of molar absorptivities of the BPC, ε 230 : 17 400 ± 1100 L/(mol*cm), and iodide, ε 230 : 9900 ± 400 L/(mol*cm), which determination was hampered by interference with each other in conventional cuvette UV‐spectrophotometric measurements. Finally, the RPIPC‐DAD procedure was applied to samples from an in vivo study of swine. Copyright © 2015 John Wiley & Sons, Ltd.