Abstract: Nimodipine is a commonly used calcium antagonist, which has a high selectivity for cardiovascular and cerebrovascular effects, and is widely used in clinical treatment of various angina pectoris, hypertension and other cardiovascular and cerebrovascular diseases [1]. The author uses gas chromatography to determine the content of nimodipine and its tablets.

Objective To determine the content of nimodipine and its tablets. Methods Gas chromatography was used to determine the content of nimodipine and its tablets. Results The average RSD of the intra-day difference was 0.86%, n = 15, and the average RSD of the inter-day difference was 1.84%, n = 15. Linear range: 10 ~ 100μg / ml, standard curve: Y = 0.0605ρ 2.03 × 10-3r = 0.9994, detection limit: 1μg / ml. The average recovery rate was 98.6%, RSD was 1.32%, n = 15. Conclusion This method is accurate, convenient and reliable. The measurement results are satisfactory, which can be used as a method for determining the content of nimodipine and its tablets.

1 Instruments and reagents

1.1 Instrument Shimadzu GC10A gas chromatograph, SE30-packed column, hydrogen flame ionization detector, CR6A data processor.

1.2 The test drug Nimodipine is provided by Tianfang Pharmaceutical Group. After multiple recrystallizations, it is used as a reference substance, and the content of normalized analysis by chromatography is more than 99%; Nimodipine tablets (10mg / tablet) were purchased from Shandong Xinhua Pharmaceutical Plant; water is redistilled water.

2 Experimental methods and results

2.1 Chromatographic conditions SE30 packed column, hydrogen flame ionization detector, inlet temperature 250 ℃, detector temperature 250 ℃, column initial temperature 180 ℃, after maintaining for 5min, rise to 220 ℃ at a rate of 10 ℃ / min, Maintain 25min; measuring range 102, attenuation 23, paper speed 1mm / min, gas flow rate: N250ml / min, H250ml / min, air 500ml / min, injection 2μl.

2.2 Experimental standard control solution. Take about 100 mg of nimodipine reference substance, accurately weigh it, place it in a 100 ml brown measuring flask, dissolve it with methanol, dilute to the mark, mix well, and get. Accurately measure 1.0, 2.0, 4.0, 6.0, 8.0, and 10.0 ml of the reference solution, place in a 100 ml brown measuring bottle, dilute with methanol to the mark, and mix well. Accurately take 2μL into the chromatograph, record the chromatogram, linearly regress the mass concentration (ρ) with the peak area (Y) of nimodipine, and obtain the linear equation: Y = 0.0605ρ 2.03 × 10-3, r = 0.9994. The test results show that nimodipine has a good linear relationship with the peak area in the range of 10 ~ 100μg / ml [2]. The test also proved that the minimum detection limit of nimodipine is 1.0 μg / ml.

2.3 Determination of recovery rate Precisely weigh 3 parts of the fine powder of nimodipine tablets (about 2 tablets), divide it into a 100ml brown measuring bottle, add about 10, 15, 20 mg of nimodipine reference substance accurately, add methanol to dissolve, Dilute to the mark and mix; after filtering, take 10.0ml of the continuous filtrate in a precise amount, place it in a 100ml brown measuring flask, add methanol to the mark and mix. According to the method under the sample measurement, the average recovery rate was 98.6% and the RSD was 1.32%.

2.4 Precision test Precisely measure 2μl of the reference substance solution (60μg / ml) and repeat the injection 10 times. The peak area RSD of nimodipine is 1.2%.

For 2.5-day and inter-day precision tests, 2 μl of 40, 60, and 80 μg / ml standard control solutions were stored in shading and low-temperature storage for intra-day and inter-day difference tests. The corresponding intra-day difference RDS was 0.86%, n = 15, The inter-day difference RSD was 1.84%, n = 15.

2.6 Determination of sample Take about 20mg of nimodipine API, accurately weigh it, put it in a 100ml brown measuring bottle, add methanol to dissolve and dilute to the mark, mix well; take 10ml precisely, put it in a 50ml brown measuring bottle, dilute with methanol to Scale and mix well. Take 10 nimodipine tablets, precisely weigh them, calculate the average tablet weight, grind them finely, accurately weigh the appropriate amount of fine powder (approximately equivalent to 20 mg of nimodipine), put them in a 100ml brown measuring bottle, dissolve and dilute to the mark , Mix well; filter, take 10ml of the continuous filtrate in a precise amount, put it in a 50ml brown measuring bottle, dilute with methanol to the mark, and mix well. Precisely take 2μl of the above solution for injection, record the chromatogram, and calculate the nimodipine content by the peak area according to the external standard method. The contents of the three batches of APIs were 99.1%, 99.2%, and 98.9%, and the RSDs were 1.25%, 1.42%, and 1.37%, respectively. The content of the three batches of tablets was 98.2%, 97.9% and 97.4% of the labeled amount, respectively, and the RSD was 1.47%, 1.32% and 1.48%, respectively.

3 Discussion

Under the premise of unchanged humidity and temperature, after light exposure, the impurity peak of nimodipine increases, the area of ​​the impurity peak increases, and the content of the main component decreases. It shows that the photodecomposition products of nimodipine increase with the increase of light time. After accelerated test and long-term stability test, there was no decrease in the main component of nimodipine or increase in impurities. This result also indicates that nimodipine is unstable to light. But long-term storage at room temperature, without decomposition, can be stored for a long time in the dark [3]. Since nimodipine is extremely unstable to light, care should be taken to avoid light during the entire test. This method was used to determine the content of nimodipine in the stability test under various conditions. Nimodipine is extremely unstable to light and relatively stable to humidity and temperature. After exposure to light, the rate of decrease in the content of the drug substance was significantly higher than that of the tablet, because the inner layer of the tablet was exposed to less light. Tests have shown that this method is accurate, convenient, and reliable, and the results of the determination are satisfactory. It can be used as a method for determining the content of nimodipine and its tablets.

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