Karl-Fisher method for determination of water content in Huoxuezhitong capsules

Moisture determination is one of the necessary items for Huoxuezhitong capsules. The toluene method commonly used at present is often affected by factors such as the operator's observation level and distillation time control. It is difficult to ensure accuracy. In this paper, Karl Fischer titration is used to determine the blood circulation It is more convenient, accurate and safe to relieve the pain of Jiao Niang.

1 Instruments and reagents

1.1 Instrument

One millionth electronic balance (Mettler-Toledo dual range); card moisture analyzer; GC-6820 gas chromatograph micro sampler.

1.2 Test drug

Huoxue Zhitong capsules (commercially available); Karl Fischer reagent (without pyridine); anhydrous methanol, anhydrous ethanol, and toluene are all analytically pure; water is purified water.

2 Methods and results

2.1 Kaskov method

Dissolve time orthogonal test take Huoxuezhitong capsules, pour out the contents and grind and mix well, take 15 parts, each about 50mg [5] [6], accurately weighed, into the titration cup, stir 1, 3, 5. Orthogonal comparison of 7, 7 and 15 minutes. It is concluded that after stirring for 5 minutes, the water is almost completely dissolved [7].

2.2 Comparison of three moisture determination methods

2.2.1 Kjeldahl method

Take Huoxuezhitong capsules, pour out the stirring time min Moisture 16.08, 6.20, 5.8138.32, 8.25, 8.3558.41, 8.43, 8.3978.43, 8.39, 8.38158.41, 8.43, 8.37 average number of Karl Fischer method (%) Toluene method (%) average gas phase method (%) average 18.418.598.4028.438.48.588.68.388.438.398.618.40 No. sample water content (mg) added amount (mg) total amount (mg) recovery rate (%) average (%) RSD (%) 14.2059.21100.224.2259.2099.634.211014.23100.244.191014.23100.4100.10.354.211519.1999.964.201519.22100.1 Schedule 3 Recovery rate Schedule 2 Determination method comparison test Schedule 1 Dissolution time orthogonal test drug Check the contents and grind and mix well, take 3 parts, each about 50mg, weigh accurately, into the titration cup, stir for 5min, titrate.

2.2.2 Toluene method

Take Huoxuezhitong capsules, pour out the contents, grind and mix well, then take 3 parts, each about 12g, accurately weighed and measured by toluene method.

2.2.3 Gas chromatography

Take Huoxue Zhitong Capsules, pour out the contents and grind and mix well, then take 3 parts, each about 2.5g, weigh accurately, place in a 25ml measuring bottle, and dilute to the mark with absolute ethanol. Another about 0.2g of purified water was weighed accurately, placed in a 25ml measuring flask, and made up to the mark with absolute ethanol. According to Appendix â…¨ of the 2005 edition of the Chinese Pharmacopoeia. And compare the three methods, the results are shown in Table 2.

2.3 Sample recovery test

Precisely weigh about 50 mg of the content of Huoxuezhitong capsules with known water content and about 5, 10, and 15 mg of purified water (2 times each), place them in a titration cup, and measure according to the sample measurement method.

3 Discussion

When Karl-Fischer's method is used to measure Huoxuezhitong capsules, stirring for 5 minutes can fully dissolve the water in the sample in anhydrous methanol. Due to the complex composition of Chinese patent medicines, the dissolution time of different varieties needs to be explored [10]. The toluene method has a higher water content than the gas phase method and the Karl Fischer method, and the toluene method contains other components [11]. The Kaskov method has the advantages of safety, simplicity, accuracy, good reproducibility, and small sampling volume. This method is suitable for rapid determination of moisture in fixed drugs.

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