Quality control methods for

Dichloromethane R. Methylene chloride, CH
2
Cl
2
.
Description. A clear colourless, mobile liquid. 
Miscibility. Freely miscible with ethanol (∼750g/l) TS and ether R.
Boiling range. Not less than 95% distils between 39 and 41°C. 
Residue on evaporation. After evaporation on a water-bath and drying at 105°C, 
leaves not more than 0.5 mg/ml. 
A suitable commercially available reagent. 
Dimethyl sulfoxide R. C
2
H
6
OS. 
Description. A colourless liquid; odourless or with a slight unpleasant odour. 
Mass density (ρ
20
). 1.10kg/l. 
A suitable commercially available reagent. 
Dimethyl yellow R. C.I. 11020; 4-dimethylaminoazobenzene; C
14
H
15
N
3
.
Caution. Dimethyl yellow R is carcinogenic. 
Description. Produces a red colour in moderately acidic alcoholic solutions and 
yellow colour in weakly acidic and alkaline solutions. 
Homogeneity. Carry out the method for thin-layer chromatography, using silica 
gel G as the coating substance and dichloromethane R as the mobile phase. 
Apply 10 µl of a 0.1 mg/ml solution in dichloromethane R. After removing the 
plate from the chromatographic chamber allow it to dry in air. Only one spot 
appears on the chromatogram. 

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Quality control methods for medicinal plant materials 
A suitable commercially available reagent. 
Dioxan R. 1,4-Dioxane, C
4
H
8
O
2
, 
Caution. It is dangerous to determine the boiling range or the residue on 
evaporation before ensuring that the reagent complies with the test for 
peroxides, described below. 
Description. A clear, colourless liquid. 
Miscibility. Miscible with water, ethanol (∼750g/l) TS and ether R.
Boiling range. Not less than 95% distils between 101 and 105°C.
Melting temperature. Solidifies when cooled in ice and does not completely remelt 
at temperatures below 10°C. 
Residue on evaporation. Evaporate on a water-bath and dry to than constant 
weight at 105°C; leaves a residue of not more than 0.1 mg/ml. 
Mass density (ρ
20
). About 1.031 kg/l. 
Water. Determined by the Karl Fischer method, not more than 5.0 mg/ml. 
Peroxides. Add 5 ml to a mixture of 1 g of potassium iodide R dissolved in 10ml 
of water, 5 ml of hydrochloric acid (∼70 g/l) TS, and 2 ml of starch TS, and mix; 
not more than a faint blue or brown colour is produced. 
A suitable commercially available reagent.