An Assay to Quantify Methylphenidate and Atomoxetine in Pharmaceutical Preparations by Micellar Liquid Chromatography

We developed a practical and economic method based on micellar liquid chromatography for the quantification of atomoxetine and methylphenidate, two central nervous system stimulants used to treat attention deficit hyperactivity disorder, in solid dosage forms. Samples were solved in mobile phase and directly injected, after filtration. Both drugs were resolved from matrix compounds using a carbon-18 column and a mobile phase consisting in a solution of 0.10 mol/L sodium dodecyl sulfate-6% 1-pentanol, phosphate-buffered to pH 7, running at 1 mL/min under isocratic mode. Detection was by absorbance at 210 nm. The effect of the surfactant and the organic modifier on the elution strength of the mobile phase was established for theoretical purposes and to expedite the optimization step, using a chemometric approach. The procedure was successfully validated by the guidelines of the International Council of Harmonization in terms of selectivity, linearity (determination coefficient > 0.995), calibration range (1-10 mg/L), trueness (99.6%-102.8%), precision (< 2.8%), and robustness, and it was applied to measure the amount of drugs in commercial presentations. The method exhibited adequate analytical performances, used a low amount of harmful and pollutant reagents, required available laboratory material, and displayed an adequate sample throughput; thus, it was useful for routine analysis.