Determination of Imipenem and Cilastatin in Medicinal Products by Micellar Electrokinetic Chromatography

Background: Imipenem, first member of the carbapenem class of β-lactams, is an antibiotic produced by Streptomyces cattleya. It is an N-formimidoyl derivative of thienamycin, co-administered with cilastatin, a specific and highly active dehydropeptidase I (DHP-I) inhibitor. Imipenem plays a key role in the treatment of infections not readily treated with other antibiotics, because of its high resistance to the β-lactamase enzymes produced by drug-resistant Gram-negative bacteria. Methods: The elaborated method of micellar electrokinetic chromatography (MEKC) followed by UV absorption detection at 210 nm was used to separate imipenem and cilastatin from its related substances. The best results were obtained with borate buffer (25 mM) pH 9.2 and sodium dodecyl sulphate (75 mM). Uncoated capillary (60/50cm; 75μm I.D.) with normal polarity and voltage values of 25 kV, were used throughout the investigation. The optimised method of imipenem and cilastatin determination was validated in terms of linearity, accuracy and precision, and provides a detection limit of 0.4 μg/mL and 0.2 μg/mL at S/N=3 for imipenem and cilastatin, respectively. Results: The repeatability of the method, expressed by relative standard deviations (RSD) in the migration times, reached 0.60% and 0.78% for imipenem and cilastatin, respectively, whereas for the corrected peak areas RSD were 1.14% and 1.02%, accordingly. Satisfactory separation of analyzed compounds was achieved within 7 minutes of electrophoresis. Conclusion: A comparison of newly proposed MEKC with existing HPLC method was performed and demonstrated an improvement in analysis time, an increase in theoretical plate number and a lower amount of both sample and background electrolyte (BGE) required.