Quality control methods for

Silica gel, HF
254
, silanized 
Description. A fine, white, homogeneous powder which, after shaking with 
water, floats on the surface because of its water-repellent properties. It contains 
about 150 g of a fluorescent indicator per kg with an optimal intensity at 254 nm. 
Preparation. Suspend 30 g with 60 ml of a mixture of 2 volumes of water and 1 
volume of methanol R shaking vigorously for 2 minutes. Carefully coat the 
cleaned plates with a layer 0.25 mm thick using a spreading device. Allow the 
coated plates to dry in air, then dry for 30 minutes in an oven at 100-105°C. 
Separating power. Prepare a mixture containing 0.1 g of each of methyl laurate R, 
methyl myristate R, methyl palmitate R and methyl stearate R. Then add 40 ml 
of a 0.3g/ml decanted solution of potassium hydroxide R in ethanol (~710g/l) 
TS and heat under reflux on a water-bath for 1 hour. Cool, add 100 ml of water, 
acidify with hydrochloric acid (~70g/l) TS and extract with three 1-ml volumes 
of chloroform R. Dry the combined chloroform extracts over anhydrous sodium 
sulfate R, filter and evaporate to dryness. Dissolve the residue in 50 ml of chloro-
form R. Apply separately to the adsorbent layer, three 10 µl portions of this 
solution and develop the chromatogram in a mixture of 65 volumes of dioxan R, 
25 volumes of water and 10 volumes of glacial acetic acid R. After removing the 
plate from the chromatographic chamber, heat it in an oven at 120°C for 30 
minutes. Allow to cool, spray with a solution containing 35 mg of 
phosphomolybdic acid R per ml of 2-propanol R and heat at 50°C until the spots 
become visible. Expose the plate to ammonia vapour until the adsorbent turns 
white. The chromatogram shows four clearly separated spots. 
Fluorescence. Prepare a 1.0 mg/ml solution of benzoic acid R in a mixture of 9 
volumes of 2-propanol R and 1 volume of formic acid (~1080g/l) TS. Apply to 
the adsorbent layer at 10 points of application, increasing the quantities of the 

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Quality control methods for medicinal plant materials 
solution from 1 µl to 10 µl. Develop the chromatogram using a mixture of 9 
volumes of 2-propanol R and 1 volume of formic acid (~1080g/l) TS. Allow the 
solvents to evaporate and examine the chromatogram in ultraviolet light at 254 
nm. The benzoic acid appears as dark spots on a fluorescent background in the 
upper third of the chromatogram for amounts of 2 µg and more. 

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Quality control methods for medicinal plant materials