A simple reversed-phase HPLC method was developed for the analysis of potential impurities and degradants in lactose. Evaporative light scattering (ELS) detection was used with a customized sample preparation procedure to enhance sensitivity. This enables quantitation down to 0.05%, while maintaining trouble-free ELS performance. The method separates lactose from structurally similar carbohydrates and also separates the constituent monohydrates, D-glucose and D-galactose. A polymeric amino phase column was chosen instead of the more commonly used silica based column because it enhances chromatographic specificity and demonstrates greater longevity due to better bonded phase stability. Potential impurities and degradants in lactose were quantitated using a second order polynomial calibration curve generated from D-glucose standard solutions. The HPLC method was fully validated with respect to specificity, limit of detection and quantitation, precision, accuracy, and robustness. In addition, the appropriateness of using a quadratic calibration curve for quantitation was demonstrated.
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