Rationale: N,N-Dimethyldodecylamine is produced from lauryl alcohol and dimethylamine. C12-C16 alkyldimethylamines are used as intermediates for the manufacture of amineoxides and quaternary amino compounds. In the present study a gas chromatography-mass spectrometry (GC/MS) method for the determination of C12-C16 alkyldimethylamines in blood was developed and validated. The reason for this study was the detection of the above compounds in the postmortem blood sample of a fatal suicide case.
Methods: Analysis of amines was performed using a gas chromatograph (Agilent Technologies 7890A) with an MS 5975C inrXL, EI/CI MSD with triple-axis detector in selected ion monitoring mode, after liquid-liquid extraction. Four different organic solvents (butyl acetate, ethyl acetate, n-hexane and n-heptane) were used for the optimization of the extraction procedure, resulting in ethyl acetate being the solvent of choice for the extraction procedure. A QuEChERS step was applied (20 mg of MgSO4 , 5 mg of NaCl) to 1 mL of blood and pH was adjusted at 12 (K2 CO3 buffer solution). After the addition of the extraction solvent, samples were vortexed, centrifuged and directly injected into the GC/MS system.
Results: In validation, the method was found to be selective and sensitive (limit of detection from 0.3 to 0.5 ng/mL, limit of quantitation from 10.0 to 20.0 ng/mL), whilst validation included recovery, stability, accuracy and precision (relative standard deviation). Validation results were found satisfactory: intra- and interday precision ranged from 0.4% to 2% and from 0.6% to 1.9% respectively, while intra- and interday accuracy ranged from 87% to 109% and from 86% to112.8%. C12-C16 alkyldimethylamines were detected in blood samples at a concentration of 8.39 μg/mL (C12), 3.01 μg/mL (C14) and 0.42 μg/mL (C16).
Conclusions: A rapid, sensitive and reliable method was developed for the determination of C12-C16 alkyldimethylamines in postmortem blood, after optimization of the sample preparation procedure, and finally successfully applied to a real postmortem blood sample from a fatal case involving these compounds.
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