Electro-generated Chemiluminescent Determination of Methotrexate in Pharmaceutical Preparations by Tris (2,2-bipyridine)ruthenium(II) Using Flow Injection

Mohammad A. Abdalla, Ibrahim Z. Al-Zamil, Saad A. Al-Tamrah, Telal S. Omar

A novel electro-generated chemiluminescence method for the determination of methotrexate (2,4-diamino-N¹⁰-methyl pteroyl glutamic acid) in pharmaceutical formulations is proposed. The method was based on the chemiluminescence (CL) emission intensity produced as a result of the electrochemical oxidation of the  into the active  form, which then reacts with the methotrexate and produces light. Reaction variables were thoroughly investigated. The optimum conditions were incorporated in the procedure. Linear calibration curve were obtained for signal in mV versus concentration in mol L¹ in the range 0-21×10⁷ M with percentage relative standard deviation of less than 2% (n = 6) and correlation coefficient of r = 0.99986. The method described here proved to be very convenient and easy to use for the assay of methotrexate in drug formulations. This method was tested by the determination of methotrexate in different drugs containing known concentration.