High-performance liquid chromatography of lactose with evaporative light scattering detection, applied to determine fine particle dose of carrier in dry powder inhalation products

A method for quantification of the fine particle dose of lactose is described, using a hydrophilic interaction chromatography (HILIC) method and evaporative light scattering detection. The HILIC method used an aminopropyl column and a mobile phase consisting of acetonitril/water (80/20, v/v) for isocratic elution. Sensitive chromatography was obtained using a low concentration of water in the extraction solvent. The detection limit (RSD < 10%) at an injection volume of 10 μL is 10 μg/mL. Linearity was obtained in the range of 10–80 μg/mL (R2 > 0.99). A relative standard deviation (RSD) of 0.5% (N = 6) demonstrated good precision of the optimized method.