Derivative spectrophotometry allows quantitative determination of essential oils in dispersible powders of spray-dried nanocapsules

This study aimed to develop and validate an analytical methodology based on derivative spectrophotometry to determine the true concentration of ginger (ZEO) and rosemary (REO) essential oils in nanocapsule redispersible powder formulations. Second-order derivative spectrophotometry made it possible to nullify the interference of nanocapsule components at 240 and 245 nm wavelengths for ZEO and REO, respectively. The validated method was linear in the range 0.01-0.04 mg mL−1 for ZEO and 0.6-0.96 mg mL−1 for REO. It is also accurate with RSD of 1.82 and 1.44 for ZEO and REO respectively, and shows recovery rates close to 100% in both essential oils when assessing accuracy. The methodology used allowed the determination of the essential oils in the presence of the formulation components, simply and quickly, showing to be an option to be used for quantification of OEs in these nanometric systems.