Simple and sensitive determination of malondialdehyde in human urine and saliva using UHPLC-MS/MS after derivatization with 3,4-diaminobenzophenone.

Malondialdehyde has been used as a biomarker for lipid peroxidation in biological samples. An ultra-high performance liquid chromatography with tandem mass spectrometry method was developed to determine the levels of malondialdehyde in human urine and saliva samples. To select the optimum derivatization reagent from four diamino compounds, the reactivity and sensitivity of their derivatives were compared, and 3,4-diaminobenzophenone was selected. The optimum reaction conditions for malondialdehyde with 3,4-diaminobenzophenone were as follows: a reagent dosage of 50 mg/L, pH of 4, and reaction for 30 min at 50°C. The formed derivative product was analyzed using ultra-high performance liquid chromatography with tandem mass spectrometry without additional extraction or concentration steps. In the optimal conditions, the method was used to determine malondialdehyde concentration in human urine and saliva samples. The limits of quantification for malondialdehyde in biological samples were over a concentration range of 0.1-0.3 μg/L. Additionally, the calibration curve showed a linearity greater than r2  = 0.997. The method was used to analyze 14 human urine and saliva samples from healthy volunteers. Malondialdehyde was detected in the concentration range of 1.7-33.6 μg/g creatinine in all human urine samples and 0.1-1.3 μg/L in all human saliva samples.