Molecularly imprinted polymer stir bar sorption extraction and electrospray ionizationtandem mass spectrometry for determination of 2-aminothiazoline-4-carboxylic acid as a marker for cyanide exposure in forensic urine analysis

Abstract

In forensic casework, a stable and quantifiable marker is desirable for the determination of cyanide poisoning in biological fluids. 2-Aminothiazoline-4-carboxylic acid (ATCA) is a chemically stable urinary metabolite of cyanide that has been considered to be a reliable biological marker for cyanide exposure. However, endogenous ATCA is always present in low quantity originating from either dietary intake of cyanide or from normal metabolism of amino acids. A selective and sensitive analytical method is needed to determine the endogenous level of ATCA in order to identify cyanide poisoning. The objective of this research was to prepare molecularly imprinted polymers (MIPs) on the surface of a silica stir bar for molecularly imprinted stir bar sorption extraction (MISBSE). Under optimal extraction conditions, the MISBSE could selectively preconcentrate ATCA from urine samples. The binding capacity of one MISBSE stir bar for ATCA was determined to be 35 ± 3 ng (n = 3). Combining MISBSE with electrospray ionization tandem mass spectrometry (ESI/MS/MS), ATCA was detected without derivatization at the 400 ng/mL concentration level. This new strategy of MISBSE-ESI/MS/MS enhanced the selectivity and sensitivity for the detection of ACTA in urine samples.