Ultrafiltration for baclofen measurement in blood using liquid chromatography-tandem mass spectrometry.

The accurate measurement of baclofen concentrations in blood is essential for diagnosing baclofen-related fatalities, which have increased in recent years. This study presents a simple, rapid, and highly sensitive method for the quantitative analysis of baclofen in whole blood and serum using liquid chromatography-tandem mass spectrometry following ultrafiltration. This method is based on multiple reaction monitoring in positive-ion mode and has high sensitivity with a lower limit of quantification of 0.2 ng/mL. The precision and accuracy of this method satisfy the basic requirements for quantitative analysis (intra- and inter-day assays yielded relative standard deviation of ≤9.0%; the matrix effect ranged from 99.7%-105.4%). Using our method, baclofen concentrations of 442-493 ng/mL in blood samples and 62 mg/mL in urine were detected in cases of prolonged baclofen poisoning. No differences were observed between baclofen concentrations in whole blood and serum.