Objective: To develop a new LC/MS/MS - based method for routine measurement of total homocysteine in plasma. Material and Method: Patient samples from laboratories of Cancer Centre of J. G. Mendel were analyzed by liquid chromatography with tandem mass spectrometry. Results: Ion transitions m/z 135.9 → 89.8 for homocysteine and m/z 140 → 90 for internal standard – homocysteine-d4 were monitored in the positive multiple reaction-monitoring mode. Our newly developed LC/MS/MS method has the following characteristics: retention time of homocysteine and homocystine-d8 is 1.4 min, limit of quantitation 0.5 µmol/l and limit of detection 0.1 µmol/l. Repeatability was determined by analyzing 2 plasma samples, the variation coefficients obtained were 0.12 % at concentration of 8.3 µmol/l and 0.71 % at concentration of 18.2 µmol/l. Conclusion: The selective, specific and rapid method suitable for routine determination of total homocysteine in plasma was developed.

        Key words: homocysteine, liquid chromatography, tandem mass spectrometry.