Determination of Anthraquinone Content in Lac Dye Through Combined Spectrophotometry and HPCE

This study is aim to establish the method for determination of anthraquinone content in lac dye with the combined spectrophotometry and HPCE, With the 0.5%Mg(Ac)2-CH3OH solution as the colour-developing agent, the carminic acid concentration within the concentration of 5∼50 μg/mL presents a good linear relationship with the absorbance under the wavelength of 540 nm (R=0.9994). Through the test, the results showed that the total anthraquinone content in lac dye was 82.13%, average recovery rate 97.80%, RSD 1.31%. Under 291 nm detection wavelength and 25 °C column temperature, with pH8.035 60mmol/LNa2HPO4-Na2B4O7 • 10H2O mixed buffer as background electrolyte and 60 cm × 75 μm uncoated capillary column as separation lanes, separation voltage 20 kV, pressure 0.5psi × 10 s for sample injection, the relative contents of five components laccaic acids A, B, C, D, E were measured by peak area normalization method; combined with the spectrophotometry, the contents of five anthraquinone components - laccaic acids A, B, C, D, E were determined, respectively 40.42%, 17.66%, 2.54%, 1.51%, 20.00%.