Ion Chromatography in Combination with ESI Ion Trap MS for the Analysis of Diphacinone in Animal Livers

Abstract

Analysis of diphacinone is often performed on C18 column by reserved phase liquid chromatographic methods coupled with ultraviolet detection or by ion-pair chromatography coupled with mass spectrometry. In this work, a sensitive and selective method using eluent generator reagent free ion chromatography coupled with electrospray ionization ion trap mass spectrometric detection for the quantification of diphacinone in animal livers has been developed. Samples were extracted with 10% (v/v) methanol in acetonitrile after spiking with warfarin (internal standard, IS) and cleaned by solid-phase extraction. The analytes were separated on an IonPac AS11 analytical column (250 mm × 4.0 mm) using 30.0 mmol L−1 KOH (achieved by a KOH eluent generator) containing 10% (v/v) methanol as organic modifier at a flow rate of 1.0 mL min−1. Detection was performed by negative electrospray ionization and ion trap tandem mass spectrometry in multiple reaction monitoring mode with a transition of m/z 339 → 167 for diphacinone, and 307 → 161 for IS, respectively. The calibration curve was linear (r 2 = 0.993) in the concentration range of 1.0–200.0 ng mL−1 with a lower limit of quantification of 0.3 ng g−1 in animal livers. Intra- and inter-day relative standard deviations (RSDs) were less than 8.7 and 12.5%, respectively. Recoveries of diphacinone ranged from 81.2 to 89.5%. It was confirmed that this method could be used in clinical diagnosis or forensic toxicology.