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Abstract: A gas chromatographic method was established to determine the content of methyl n-nonanone in Jingjiang Ganmao Dripping Pills. Method: Use steam distillation to prepare the test solution, nitrogen as carrier gas, detector temperature of 280 ℃, column temperature as programmed temperature increase, and inlet temperature as 240 ℃.
The main ingredients in the prescription of Jingjiang cold drop pills are houttuynia cordata, schizonepeta and other medicinal materials. In order to improve their bioavailability and achieve quick release, they are prepared as drop pills. On the basis of completing the inspection of the best process of dropping pills, the content determination was further improved. Volatile oil is the main medicinal component of Houttuynia cordata, which contains decanoylacetaldehyde, methyl n-nonanone, lauraldehyde and other components, and methyl n-nonanone is the main component in volatile oil. Determination of methyl n-nonanone in Ganmao dripping pills.
1 Instruments and reagents
Japan Shimadzu GC-14C gas chromatograph; JA5103N electronic precision balance (Shanghai Minqiao Precision Scientific Instrument Co., Ltd.); n-undecane, purchased from the American Sigma company, batch number: LB43172; the reagents used are chromatographically pure and analytically pure .
2 Chromatographic conditions
Shimadzu GC-14C gas chromatograph, equipped with a hydrogen flame ion detector, the column is a DB-1 quartz capillary column (30m × 0.25mm × 0.25μm), the inlet temperature is 240 ℃, the detector temperature is 280 ℃, starting from The initial temperature was 80 ℃, and the temperature was constant for 2min, and then the temperature was raised to 220 ℃ with 15 ℃ / min program, and then to 270 ℃ with 30 ℃ / min program, and the injection volume was 1μL.
3 Methods and results
3.1 Preparation of solution
3.1.1 Preparation of sample solution 8g sample, place the sample in a 500mL round bottom flask, add 200mL of water, connect the volatile oil extractor; add water from the upper end of the extractor to fill the scale part, and overflow into the flask, then add it precisely 2mL of ethyl acetate, connected to the reflux condenser tube, heated to reflux for 4h, let cool, take the ethyl acetate layer, place in a 10mL volumetric flask, dilute to the mark with ethyl acetate, then draw 0.8mL, and place in a 5mL volumetric flask, Dilute to the mark with ethyl acetate, that is.
3.1.2 Preparation of reference substance solution Precisely weigh the appropriate amount of methyl n-nonanone reference substance, add ethyl acetate to prepare a solution containing 3.8145mg per 1mL, that is, get.
3.1.3 Preparation of internal standard solution Precisely weigh an appropriate amount of n-undecane, and add ethyl acetate to prepare a solution containing 0.234mg per 1mL, that is, obtained.
3.2 Investigation of the linear relationship The precision of 0.01, 0.03, 0.05, 0.10, 0.15 mL of the reference solution was accurately measured, placed in a 5 mL volumetric flask, added with 2 mL of internal standard solution, diluted with ethyl acetate to the mark, and shaken; each sample was measured by 1 μL , With the ratio of the peak area of ​​the reference substance to the peak area of ​​the internal standard (AR / AS) as the ordinate, the concentration of the reference substance (CR) as the abscissa, draw a standard curve, the regression equation is: Y = 8.729X-0.0072, r = 0.9996 , Indicating that methyl n-nonanone showed a good linear relationship in the range of 0.024468 ～ 0.12234mg / mL.
3.3 Blank test Take 8g of the negative sample lacking Houttuynia cordata essential oil, prepare a negative sample solution according to the method under "3.1.1", and determine according to the law. Results There was no impurity peak at the retention time of methyl n-nonanone (7.648 min), indicating that other components in the sample did not interfere with the determination and the method was specific.
3.4 Precision test Take 1 μL of the same reference solution and repeat the injection 5 times. The RSD of the peak area of ​​methyl n-nonanone is 1.5%, indicating that the instrument is of good precision.
3.5 Repeatability test Take 3 samples of the same batch number, 8g each, prepare the test solution according to the method under "3.1.1", and determine the content of methyl n-nonanone according to the method under "3.8", the result is RSD 1.2% . It shows that the content determination repeatability is good.
3.6 Stability test of the solution Under this test condition, the test solution was taken at room temperature and protected from light for 0, 2, 4, 6, 8, 12, and 24 hours, and then measured according to the method. The RSD calculated according to the peak area was 2.8%. It indicates that the test solution is stable for at least 24h.
3.7 Recovery rate test: Take 8g of samples, 3 parts in total, add 200mL of water to a round bottom flask, respectively add 4.8936mg of methyl n-nonanone reference substance, and extract the solution according to the method under "3.1.1" and determine it. Calculate the recovery rate according to the formula R% = (AB) / C × 100% (A: the total amount measured after adding the reference substance, B: the amount of the tested component contained in the sample, C: the amount of the added reference substance), and the average recovery rate 99.22%, RSD is 2.5%, indicating that this method is feasible.
3.8 Determination of samples Prepare the reference solution and the test solution according to the method under "3.2.1". Accurately measure 1μL of each of these two solutions and inject it into the gas chromatograph. Record the chromatogram and determine the peak area. The peak area is calculated and the results are shown in Table 1.
4 Discussion
Because methyl n-nonanone is a volatile component, steam distillation is used for extraction, and an appropriate amount of ethyl acetate is added dropwise to the water layer of the volatile oil analyzer to complete the extraction of volatile oil. Be careful when separating the ethyl acetate layer. Do not bring water into it. If there is water, dehydrate it with anhydrous sodium sulfate and then measure.
Houttuynia cordata has the highest content of houttuynia cordata, and is one of the main active ingredients of houttuynia cordata, but the steam-distilled houttuynia cordata volatile oil does not have a fishy smell and does not contain houttuynia, which may be because of fishy Oxalin is chemically unstable and easily decomposed. Under heating conditions, it can be converted to methyl n-nonanone by oxidation and decarboxylation. Methyl n-nonanone has antiviral, anti-allergic and antibacterial activities, so in the end, methyl n-nonanone was selected as the quantitative index component. The internal standard method is a method that combines the advantages of the peak area normalization method and the external standard method. It is analyzed according to the analysis method of the peak area normalization method after adding the internal standard, which avoids the consistency of the injection. The accidental error caused by sex and sample discrimination effects, therefore, its analytical precision is relatively high, which is an ideal quantitative analysis method for gas chromatography.
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