Abstract:

Fluoroacetic acid is a highly polar poison used for rodent control. When ingested by the human body, it seriously damages nerve cells and heart tissues and even causes death by cardiac arrest or respiratory failure. Common detection methods for fluoroacetic acid include gas chromatography-mass spectrometry and liquid chromatography-mass spectrometry, both of which require complex pretreatment methods, such as derivatization. In this study, a method to determine fluoroacetic acid in human blood and urine based on accelerated solvent extraction-ion chromatography-mass spectrometry (ASE-IC-MS) was established. Two pretreatment methods, namely, acetonitrile precipitation and accelerated solvent extraction, were compared. Furthermore, the effects of different extraction conditions, such as the extraction time, extraction temperature, and number of cycles, were investigated. The most suitable chromatographic separation conditions, such as the chromatographic column, column temperature, and elution procedure, were determined, and the MS conditions, such as the collision energy (CE) and declustering potential (DP) of the ion pairs of the target compound, were investigated. Based on the experimental results, the optimal pretreatment methods and detection conditions were obtained, and reliable data were collected. Deionized water was used as the extraction solvent, and blood and urine samples were processed by accelerated solvent extractor. The supernatant was sequentially collected via centrifugal ultrafiltration and 0.22 μm membrane filtration, diluted 50 times, and then injected into the chromatographic column for detection. An Ion Pac AS20 IC column was used for isocratic elution with 15.0 mmol/L KOH solution as the eluent. The effluent was passed through a suppressor and into a triple quadrupole mass spectrometer, which was used to perform MS/MS (ESI^-) in multiple reaction monitoring (MRM) mode. The quantitative ion was m/z 77.0>57.0 when the CE and DP were -15.0 eV and -20.0 V, respectively. An external standard method was used for quantitative analysis. The results showed a good linear relationship for fluoroacetic acid in the range of 0.5-500.0 μg/L (r>0.999), with limits of detection (LOD) and quantification (LOQ) of 0.14 and 0.47 μg/L, respectively. The recoveries of fluoroacetic acid in blood and urine were 93.4%-95.8% and 96.2%-98.4%, respectively. The intra-day RSDs for blood and urine were 0.8%-1.6% and 0.2%-1.0%, respectively, while the inter-day RSDs were 2.3%-3.8% and 3.9%-6.9%, respectively. Further investigation revealed that the matrix effects of this method in blood and urine, at -7.4% and -3.0%, respectively, were fairly weak. The established method was successfully applied to detect fluoroacetic acid in human blood and urine obtained from a poisoning case, and the results obtained provided crucial clues that led to swift case resolution. The efficiency of the method was significantly higher than that of conventional detection methods. In conclusion, the developed method has high sensitivity and good repeatability and is suitable for the rapid detection of fluoroacetic acid in human blood and urine. Moreover, because this method does not require derivatization, it is simple and efficient.

Key words: accelerated solvent extraction (ASE), centrifugal ultrafiltration, ion chromatography-tandem mass spectrometry (IC-MS/MS), fluoroacetic acid, blood, urine