Quality control methods for

Kieselguhr H 
Description. A fine, greyish white powder with an average particle size of 
between 10 and 40 µm. (The grey colour becomes more pronounced when the 
powder is triturated with water.) 
pH. Shake 1 g with 10 ml of carbon-dioxide-free water R for 5 minutes. Measure 
the pH potentiometrically (The international pharmacopoeia, Vol. 1, page 96); pH is 
between 6.4 and 8.0. 
Preparation. Suspend 30 g in 60 ml of sodium acetate (1.6 g/l) TS shaking 
vigorously for 30 seconds. Carefully coat cleaned plates with a layer 0.25 mm 
thick using a spreading device. Allow the coated plates to dry in air. 
Separating power. Apply separately to the adsorbent layer 5 µl of 0.10 mg/ml 
solutions containing respectively lactose R, sucrose R, glucose R, 
D
-fructose. R 
and 
D
-galactose R in pyridine R. Develop the plate using a mixture of 65 
volumes of ethyl acetate R, 23 volumes of 2-propanol R and 12 volumes of water. 
After removing the plate from the chromatographic chamber, dry it in an oven 

---

Quality control methods for medicinal plant materials 
at 105-110°C and allow to cool. Spray the plate with about 10 ml of anisaldehyde 
TS and heat to 100-105°C for 5-10 minutes. The chromatogram shows five clearly 
separated spots without tailing. 
Silica gel G 
Description. A fine, white, homogeneous powder with an average particle size of 
between 10 and 44 µm containing about 130g of calcium sulfate, hemihydrate 
per kg. 
Content of calcium sulfate. Place about 0.25 g, accurately weighed, in a flask with a 
ground-glass stopper, add 3 ml of hydrochloric acid (~70g/l) TS and 100 ml of 
water and shake vigorously for 30 minutes. Filter through a sintered-glass filter 
and wash the residue. Using the combined filtrate and washings, carry out the 
assay for calcium by complexometry (The international pharmacopoeia, Vol. 1, page 
128). Each ml of disodium edetate (0.05 mol/l) VS is equivalent to 7.26 mg of 
CaSO
4
,1/2H
2
O (MW 145.1). 
pH. Shake 1 g with 10 ml of carbon-dioxide-free water R for 5 minutes. Measure 
the pH potentiometrically (The international pharmacopoeia, Vol. 1, page 96); pH is 
about 7. 
Preparation. Suspend 30g in 60 ml of water, shaking vigorously for 30 seconds. 
Carefully coat the cleaned plates with a layer 0.25 mm thick using a spreading 
device. Allow the coated plates to dry in air. 
Separating power. Apply separately to the adsorbent layer 10 µl of 0.10 mg/ml 
solutions containing respectively indophenol blue R, sudan red G R and 
dimethyl yellow R in toluene R. Develop the plate with the same solvent over a 
distance of 10 cm. The chromatogram shows three clearly separated spots, the 
spot of indophenol blue near the points of application, that of dimethyl yellow 
in the middle of the chromatogram, and that of sudan red G between the two.