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This paper presents the development and validation of an improved method for the simultaneous analysis of synephrine and octopamine using high-performance thin-layer chromatography with densitometric detection. Separation was performed on silica gel 60F254 plates. The mobile phase is comprised of methanol, ethylacetate, methylene chloride and concentrated ammonia (2:2:1:0.05, v:v:v:v). The Rf values were 0.292 ± 0.0083 and 0.413 ± 0.0089 for synephrine and octopamine, respectively (n = 9). Ultraviolet absorbance detection at 277 nm was used for the alkaloids detection. Specificity, accuracy (recovery rates were between 96 and 99%) and precision (in both cases intra-day precision and inter-day precision were ≤ 2.0%) of the method were determined. Their amounts were calculated using the regression equations of the calibration curves which were linear in the range 0.2-1.2 µg/spot. The amounts of alkaloids in basic methanolic extracts of bitter orange peel measured by the method were 0.253 and 0.142% for synephrine and octopamine, respectively. Most of the factors evaluated in the robustness test were found to have an insignificant effect on the selected responses at 95% confidence level. The method was validated giving rise to a dependable and high-throughput procedure well suited to routine application.

Determination of Synephrine and Octopamine in Bitter Orange Peel by HPTLC with Densitometry