A standard addition method to quantify histamine by reductive amination and hydrophilic interaction liquid...

Histamine is an organic nitrogenous compound that acts as a neurotransmitter in the uterus, spinal cord, and brain and is involved in local immune responses. In this study, we developed a fast and simple derivatization method based on reductive amination that can be used to quantify histamine by hydrophilic interaction liquid chromatography coupled with tandem mass spectrometry. Histamine isotope analogs were synthesized via reductive amination. Histamine was modified with H₂-formaldehyde to form N-dimethylated histamine to act as a standard or with D₂-formaldehyde to form N-dimethylated histamine-d₄ to act as an internal standard. Using this method, we achieved a limit of detection of 3.6 ng/mL, a limit of quantification of 7.9 ng/mL, and a linear calibration curve with a coefficient of determination (R²) of 0.9987. Furthermore, the intra-day relative standard deviations ranged from 0.9% to 3.7% and the inter-day relative standard deviations ranged from 2.0% to 17.6%. After derivatization, N-dimethylated histamine showed 382.5% signal enhancement compared to unmodified histamine in mass spectrometry detection. To demonstrate the applicability of this method for biological samples, we utilized standard addition method to quantify histamine in fetal bovine serum and achieved a recovery of 86.7%.