The development and validation of an analytical method for determination of vitamin K is of paramount importance considering the growing worldwide concern with questions regarding the quality of life, nutrition, health and environment and the importance of this micronutrient in health. It is developed a method based on capillary micellar electrokinetic chromatography (MEKC) for the determination of vitamin K1 and K3. The optimal condition for analysis by MEKC were obtained by means of experimental and instrumental univariate study (borate buffer 3.1 gL(-1), pH equal 8.5; CTAB 18.2 gL(-1), 20 per cent acetonitrile v/v 25 celsius degrees, 30 kV, T equal 15 s). A study with a longer optical path-length capillary cell was performed to improve the detection limit (LOD) and the limit of quantification (LOQ) of the method. Analytical curves of both vitamins presented linear and homoscedastic behavior, with r values near 0.99. The values of LOD and LOQ for vitamin K1 and vitamin K3 were on the order of 10(-5) g.L(-1) and 10(-4) g.L(-1), respectively. The precision of the method was between 2 and 7 per cent for the peak area. Recoveries for vitamin K1 were 101 more or less 2 per cent and 103 more or less 2 per cent for samples of vitamin supplement and green tea, respectively. For vitamin K3, recovery obtained was 99 more or less 3 per cent for the sample tea. Comparative tests performed among the proposed method by MEKC and the reference method based on HPLC showed good accuracy (tcalculated less than ttabulated). The measurement uncertainty associated with the method developed showed values between 2 and 30 per cent, and the relevant sources were those associated with the analytical curve and the preparation of solutions. The developed analytical method can contribute to achieve sensitive and reliable measurements of different forms of vitamin K.