1.   Reagents

Perchloric Acid (AR)

2.   Instruments

2.1 Electronic Balance

2.2 Volumetric Flask 10ml

2.3 Ultrasonic Washer

2.4 UV-VIS Spectrophotometer (53WB, Made in Shanghai)

3.   Process

3.1 Accurately weigh 15mg reference substance in the 10ml volumetric flask and dissolve it with methanol. After adding methanol to the dial, shaking up and centrifuging to employ the clear solution as reference substance solution.

3.2  Accurately weigh 30mg sample in the 10ml volumetric flask and dissolve it with methanol. After adding methanol to the dial, shaking up and centrifuging to employ the clear solution as sample solution.

3.3 Accurately suck 0.1ml sample solution in a tube with ground conical joint and a stopper. Adding newly prepared 5% Vanillin : Acetic Acid solution 0.2ml and Perchloric Acid 0.8ml, then heat 15m in 60¡æ water bath. After cooling in ice water, add 5ml Glacial acetic acid and the solution shows a blue-purple color. The same practice is repeated using the reference substance solution.

3.4 Detection

Detect the absorbance of the solutions at 590nm by the UV-VIS Spectrophotometer.

 

4.Calculation

A₁¦¶M₂

charantin%=                 ¦¶100%

                              A₂¦¶M₁

A₁: Absorbance of the sample

M₁: Amount of the sample (mg)

A₂: Absorbance of the reference substance solution

M₂: Amount of the reference substance(mg)