Micellar liquid chromatographic determination of metformin hydrochloride using fluorimetric detection after pre-column derivatization: application to pharmacokinetic parameters in immediate and sustained release formulations.

An accurate and selective method using micellar liquid chromatography was developed to determine metformin hydrochloride both in its pharmaceutical dosage forms and human plasma. Separation was conducted using a Zorbax SB-Phenyl (250 × 4.6 mm id) stainless steel column at ambient temperature after pre-column derivatization with 9,10-phenanthraquinone. A mobile phase composed of 0.1 M sodium dodecyl sulfate, 10% 1-propanol and triethylamine (0.3%) in 0.02 M phosphoric acid, adjusted to pH 2.5, was used at a flow rate of 1 ml/min with fluorimetric detection at 450 nm after excitation at 306 nm. The proposed method showed high sensitivity with limit of quantification of 0.35 μg/ml and limit of detection of 0.23 μg/ml, being linear from 0.5 to 3.0 μg/ml. Being highly sensitive, the method could be applied to spiked human plasma, and also to follow the pharmacokinetic parameters of the studied drug in healthy volunteers after administration of both its immediate and sustained release tablet formulations. Such procedures were carried out without any extraction steps, which improves the accuracy and precision of the proposed method when applied to human plasma. Detailed validation procedures were also carried out giving results in accordance with the comparison method. The proposed method has also the advantage of being environmentally safe, where the use of organic solvents is highly limited in comparison with other traditional chromatographic separation methods that depend mainly on a high proportion of organic modifiers. This concept, in turn, emphasizes the application of green chemistry in the analysis of pharmaceutical products. The simplicity, relatively low cost and short analysis time of the suggested method makes it a candidate for routine quality control work.