Quality control methods for

Combustion of the organic matter 
Combustion of the organic matter in oxygen is the preparatory step for the 
determination of chlorine and phosphorus. The pesticide is extracted from the 
sample and purified, if necessary. The extract is concentrated, evaporated to 
dryness, transferred to a sample holder, and burned in a suitable conical flask 
flushed with oxygen. The gases produced during combustion are then absorbed 
in a suitable solution. The absorbed chlorine is determined as chloride and the 
absorbed phosphorus as orthophosphate, both colorimetrically. 
Apparatus 
The combustion is carried out in a 1-litre conical flask made of borosilicate glass, 
into the stopper of which is fused one end of a piece of platinum wire about 1 
mm in diameter. To the free end of the wire is attached a piece of platinum 
gauze measuring about 1.5 x 2 cm to provide a means of holding the sample 
clear of the absorbing liquid during combustion. 
Sample holder for chlorine-containing residues. For a small quantity of solid 
material, use a sample holder made from a piece of halide-free filter-paper about 
5 cm long and 3 cm wide; for a small volume of liquid, preferably use a sample 

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Quality control methods for medicinal plant materials 
holder in the form of a cone made from cellulose acetate film. Prepare the cone 
as follows: wearing cloth gloves and using a suitable cardboard template cut the 
film in a circle of 4 cm radius. 
Manually pin the two edges together to form a cone. Seal the joined edges using 
heat to form a seam about 5 mm wide. Immerse the seam in acetone R to about 
one half of its width for 10 seconds. Remove and dry it immediately in a stream 
of hot air. Using forceps, wash the cone by dipping in a 1-litre beaker containing 
warm sodium hydroxide (~240 g/l) TS for 10 seconds at a temperature of about 
60°C. Rinse the cone thoroughly with water and allow to drain dry on a piece of 
aluminium foil. Place each cone in a clean funnel (diameter 65 mm). 
Sample holder for phosphorus-containing residues. Use a piece of halide-free filter-
paper about 4 cm square as the sample holder. 
Combustion of chlorine-containing residues 
Transfer an aliquot of the extract as prepared above onto the sample holder 
which is placed in a funnel using a solvent that will not dissolve the sample 
holder. Allow the solvent to evaporate. Wearing rubber gloves, remove the 
sample holder and its dry contents from the funnel, and fold it over and up to 
form a small packet, about 1 cm
2
in area, and secure it in the centre of the 
platinum gauze. Insert a narrow strip of filter-paper, about 1 x 3 cm, as a fuse 
into the top of the holder, between the folds of the packet. Add 30 ml of water to 
the combustion flask. Moisten the neck of the flask with water. Fill the flask 
thoroughly with oxygen by means of a tube with its end just above the liquid. 
Ignite the free end of the paper strip and immediately insert the stopper. Hold 
the stopper firmly in place. When vigorous burning has begun, tilt the flask to 
prevent incompletely burned material from falling into the liquid. Immediately 
after combustion is completed, shake the flask vigorously for 10 minutes to 
dissolve the combustion products. Place a small quantity of water around the 
rim of the flask, and carefully withdraw the stopper. Rinse the stopper, platinum 
wire, platinum gauze and sides of the flask with water. Transfer the liquid and 
liquids used for rinsing to a 50-ml volumetric flask and dilute to volume with 
water. 
Combustion of phosphorus-containing residues 
Dip the sample holder made from filter-paper into methanolic sodium 
hydroxide TS, then suspend it in a current of heated air. Immediately transfer 
about 0.2 ml of an aliquot of the extract as prepared above to the sample holder 
with the aid of 0.2-ml portions of chloroform R using a micropipette. Allow the 
solvent to evaporate from the paper, fold it to form a small packet about 1 cm
2
in 
area and place it in the centre of the platinum gauze. Insert a strip of filter-paper, 
about 1 x 3 cm, as a fuse into the top of the holder, between the folds of the 
packet. Add 10 ml of sulfuric acid (~37 g/l) TS to the combustion flask and 
continue with the combustion as described above. Transfer the solution and the 
liquid used for rinsing to a 25-ml volumetric flask and dilute to volume with 
water. 

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Quality control methods for medicinal plant materials