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How to identify benzoin

Aug. 23, 2019

Benzoin is a very important medicinal material. Mainly divided into Thai benzoin and Sumatra benzoin. In this cultural article, you will be introduced to the identification of benzoin, loss on drying, determination of content and so on.


(1) Take about 0.25g of benzoin, put it in a dry test tube, and slowly heat it, that is, a pungent aroma occurs, and a sublimate of most prismatic crystals is produced.

(2) Take about 0.1g of benzoin, add 5ml of ethanol, grind, filter, and add 0.5ml of 5% ferric chloride ethanol solution to the filtrate, which will be bright green and then turn yellow-green.

Loss on drying

Take the benzoin coarse powder, place it in a sulfuric acid vacuum dryer, dry to constant weight, and lose weight by 2.0%. The total ash should not exceed 0.50%. The insoluble matter in the alcohol is accurately weighed 2.5 g of the fine powder of the product, placed in a Soxhlet extractor, and leached with ethanol until all the alcohol-soluble substances are leached, and the residue is dried at 100 ° C to a constant weight, and is calculated in the test sample. Insoluble matter in ethanol shall not exceed 2.0%.

Content determination

Take about 1.5g of benzoin powder, accurately weigh it, place it in a conical flask, add 25ml of potassium hydroxide titration solution (0.5mol/L) made of ethanol, heat and reflux for 1.5 hours, remove the ethanol on the water bath, and heat the residue to 50ml of water. Disperse evenly, let cool, add 150ml of water and 50ml of magnesium sulfate solution (1→20), stir well, let stand for 10 minutes, then filter by air, wash the filter residue with water 20ml, combine the washing liquid and filtrate, add hydrochloric acid to make acid After that, it was transferred to a separatory funnel, and extracted four times with 50 ml of ethyl ether (50 ml, 40 ml, 30 ml, 30 ml), and the mixture was combined with diethyl ether solution, and extracted with a sodium hydrogen carbonate solution (1→20). (20ml, 20ml, 10ml, 10ml, 10ml), each time the separated water is washed with the same ether 20ml, combined with water, add hydrochloric acid to make acid, and then use ether to shake and extract 4 times (30ml, 20 ml, 10 ml, 10 ml), combined with ether solution, placed in a fixed weight flask, placed, until most of the ether was evaporated, the flask was rotated, the residue was evenly dispersed on the inner wall of the flask, and dried in a sulfuric acid dehydration dryer to a constant Heavy, precise weighing, calculate the amount (%) contained in the test sample, and then The amount (%) contained in the dried product of the alcohol-soluble extract is determined by the moisture content of the test article and the insoluble matter in the ethanol, that is, the total balsamic acid content. The benzoin containing total balsamic acid is not less than 30.0% based on the dry product of the alcohol-soluble extract.

The above is about the identification of benzoin and the determination of its content. If you have any need for benzoin, please contact us!

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