4.5.6. Selection of the Analytical Wavelength for Oleanolic Acid

As mentioned earlier, there were problems with the detection of oleanolic acid in the extracts and we had to decide to choose a characteristic wavelength for this compound. Therefore, in the next stage of our experiment, to enhance both the measurement accuracy and detection limit, we applied 0.1 mm of the densitometer slit. The oleanolic acid zone on the chromatographic plate was scanned in the range of 300–680 nm of the light spectrum. The range wavelength of 500–620 nm was promising. Figure 12 shows the selection of the analytical wavelength for oleanolic acid—560 nm. This wavelength was chosen for further investigations.

Determination of the analytical wavelength for oleanolic acid. Stationary phase silica gel 60 HPTLC plates, mobile phase n-hexane:dichloromethane:methanol:water (4:5:0.6:0.1 v/v). Densitometric detection at 560 nm after derivatization with anise aldehyde.