High-throughput quantitation of acetaldehyde and ethanol in mice using gas chromatography/mass spectrometry positive chemical ionization.

Background: Acetaldehyde, an immediate ethanol metabolite, mediates many ethanol-induced behavioral effects and is both psychoactive and toxic to animals and humans. Monitoring the kinetics of acetaldehyde using rodent models of alcohol misuse is essential for understanding and managing ethanol-associated diseases. However, quantitation of acetaldehyde in biological specimens after alcohol consumption has been challenging due to its high volatility, relatively low concentrations, and strong reactivity toward biochemical molecules. It was necessary to develop and establish an accurate and high-throughput method to quantitate acetaldehyde and ethanol.

Methods: Gas chromatography/mass spectrometry in positive chemical ionization mode coupled with a 111-vial headspace autosampler was employed to quantitate acetaldehyde and ethanol using H-acetaldehyde and H-ethanol as internal standards. A multidimensional approach was used to develop the method, including sample collection and processing, instrumental data analysis, optimization, and validation. Blood and tissues collected from genetically modified mouse models and their wild-type counterparts were studied.

Results: The method was validated and applied to quantitate acetaldehyde and ethanol in blood and tissues from multiple mouse studies on ethanol metabolism. Acetaldehyde and ethanol were well-resolved from chromatographic interferences with linear ranges of 6.25-800 μM for acetaldehyde and 1.25-160 mM for ethanol. Both regression coefficients for calibration curves were >0.999. The within- and between-run precisions for ethanol in plasma, whole blood, and serum were all <5.0%, and for acetaldehyde in plasma and serum were <9.0%, while in whole blood it was 19.2%. Sample throughput was on the order of 60 samples per 15 h daily, with a maximum of 111 per batch.

Conclusions: Despite some limitations, this validated method proved to be specific, accurate, and reproducible for high-throughput quantitation of acetaldehyde and ethanol in rodent plasma, whole blood, serum, and visceral organs.