Quality control methods for

Kieselguhr G 
Description. A fine, greyish white powder with an average particle size of 
between 10 and 40 µm containing about 150g of calcium sulfate, hemihydrate 
per kg. (The grey colour becomes more pronounced when the powder is 
triturated with water.) 
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 (~70 g/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 CaS0
4
, 1/2H
2
0 (M
r 
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 should be between 7 and 8. 
Preparation. Suspend 30g in 60ml of sodium acetate (1.6g/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 
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.