RU2063019C1 - Method of clophelin quantitative determination - Google Patents

Abstract

FIELD: analytical chemistry. SUBSTANCE: method of clophelin tablet determination involves preparation grinding in buffer solution at pH = 3.3 ± 0.2 in the presence of bromphenol blue. Ionic complex of clophelin with bromphenol blue is extracted with organic solvent - chloroform. Organic phase is filtered through anhydrous sodium sulfate and subjected for photometry at 410 nm. Clophelin content in tablet is calculated using data obtained for clophelin standard sample. EFFECT: high sensitivity and precision of assay. 1 dwg

Description

 The invention relates to the field of analytical chemistry, and in particular to methods for the quantitative determination of drugs, and can be used in the work of control and analytical laboratories of chemical-pharmaceutical plants and production associations "Pharmacy".

 At present, a new indicator of the quality of pharmaceutical products, dosing uniformity, is gaining importance. recommended by the State Pharmacopoeia of the USSR XI edition for dosage forms.

 The introduction of this indicator is associated with the need to control drugs of list A and B, in which the content of active substances does not exceed 0.01-0.05 g and have clinical indications for such a dosage.

 Such drugs include clonidine tablets / clonidine, catapresan, hemiton /, for which the indicator of "uniformity of dosage" has not been developed / FS 42-2100-83. Clonidine tablets 0.000075 and 0.00015 g /.

 A small therapeutic dose and high toxicity of clonidine can lead to undesirable effects in the treatment of doses lower and higher than the therapeutic. However, the right choice of the optimal dose can be ensured only if the tablets used contain constant standard amounts of the drug in separate tablets.

 A known method for determining the content of clonidine in tablets using gas-liquid chromatography / 1 /.

 The linear dependence of the concentration of the drug on the areas of the corresponding peaks is 50-200 μg / ml.

 The disadvantage of this method is the use of sufficiently complex equipment, the need for multiple extraction with an organic solvent.

 This technique is not indicated for the determination of clonidine in one tablet.

 A photometric method for the determination of clonidine with tablets / 2 / is described in the literature.

The essence of the method lies in the fact that 1N sodium hydroxide solution and sodium nitroprusside solution are added to the powder of the crushed tablets. The mixture is left for 10 minutes. Then a solution of boric acid is added and kept at 0 ^{° C.} for 15 minutes. The optical density of the colored solution is measured at a wavelength of about 570 nm.

 The disadvantage of this method is that the method is designed to analyze samples of clonidine tablets with a content of 200 to 1500 μg of the analyzed substance and cannot be used to analyze the uniformity of dosing of clonidine in tablets manufactured by the domestic industry / clonidine tablets 0.000075 and 0.00015 g / due to lack of sensitivity.

 In addition, the technique is lengthy and requires compliance with a certain temperature regime.

 The closest way to determine clonidine in tablets is the technique described in the pharmacopoeial article on clonidine tablets / 3 /.

 About 0.35 g / precise weight / powder of the crushed tablets after adding 5 ml of distilled water, 5 ml of 0.1 N sodium hydroxide solution and 10 ml of chloroform are vigorously shaken for 2 min in a separatory funnel. After delamination, the chloroform layer is filtered under vacuum through a PS-4 glass filter onto which 2 g of anhydrous sodium sulfate are preliminarily placed. Transfer the filtrate to a 25 ml volumetric flask. The extraction of 2 ml of chloroform is repeated. After delamination, the chloroform layer is filtered as described above. The chloroform solution in the volumetric flask was adjusted with 95% alcohol to the mark. In the case of olalescence, the resulting solution is additionally filtered, as described above, discarding the first 3 ml of the filtrate. In 2 conical flasks with a capacity of 20 ml are placed 10 ml of the resulting solution. 0.02 ml of a 0.1 N sodium hydroxide solution was added to the first flask, and 0.02 ml of a 0.1 N hydrochloric acid solution was added to the second flask. The optical density of the alkaline solution against the acidic solution is measured on a spectrophotometer at λ = 250 nm in a cuvette with a layer thickness of 10 mm. At the same time, the determination is carried out in the same way with 5 ml of a solution of a standard sample of clonidine (0.000090 g of clonidine is contained in 1 ml of solution).

 This method is selected for the prototype.

 This method of determining clonidine allows you to analyze the medicinal substance according to the physiologically active part of the molecule, is highly accurate.

However, the method has several disadvantages:
1. The sensitivity of the method does not allow determination of clonidine in a single dose / tablet /. The method is recommended for the analysis of the average clonidine content from a weighed sample of 20 powdered tablets.

 2. The method is long: includes multiple dilution of the analyzed and standard sample, double extraction.

 3. The method is not economical, because involves the use of expensive solvents such as ethyl alcohol.

 Solution objective: to develop a method for the quantitative determination of clonidine, which allows to evaluate the uniformity of dosage, namely, a constant standard amount of the drug in separate tablets.

 The technical result is to increase the sensitivity, accuracy and efficiency of the method.

 The technical result is achieved in that the disintegration of the tablet is carried out in a buffer solution of pH 3.3 ± 0.2 in the presence of a solution of bromphenol blue. The resulting ionic associate is extracted with chloroform, filtered through anhydrous sodium sulfate and photometric. In parallel, under the same conditions, a determination is made with a standard solution of clonidine. The content of the drug in one tablet is found by the formula.

 Distinctive features of the proposed method from the prototype.

 1. Use as a reagent a solution of bromphenol blue.

 2. Disintegration of the tablet in a buffer solution of pH 3.3 ± 0.2.

 3. Photometric measurements at a wavelength of 410 nm.

 During the study, optimal conditions for the formation of an ionic associate of clonidine with bromphenol blue were developed and a quantitative analysis of the drug in one tablet was carried out.

 It was found that clonidine interacts with bromphenol blue in a molar ratio of 1: 1. The maximum stability of the complex is observed at a 6-fold or more excess of the reagent with respect to the analyte. The optimal volume of a 0.08% bromphenol blue solution is 0.000075 g and 0.00015 g for clonidine tablets, 1.0-2.0 ml and 2.5-3.5 ml, respectively. Lower exorbitant values of the volume of the reagent lead to underestimated results due to incomplete formation of the ionic associate. Outrageous upper values are irrational, because can lead to the formation of associates of a different composition and a decrease in reproducibility of results.

 The largest and constant value of the optical density of the solution is observed in the pH range from 3.1 to 3.5. A pH value below 3.1 and above 3.5 reduces the degree of single extraction, which at a ratio of aqueous and organic phases of 1: 2 is 98.8%. The concentration of hydrogen ions was created using a citrate buffer solution, the choice of which is due to the ease of manufacture and the availability of reagents.

 Among oxygen-free organic solvents leading to the formation of practically undissociated compounds, chloroform was chosen as less toxic, more accessible and convenient to use.

 The sequence of adding reagents does not affect the light absorption of the photometric solution.

 The optimal extraction time of the ionic associate, taking into account the requirements of the USSR State Pharmacopoeia of the XIth edition, for tablettable dosage forms according to the disintegration test / not more than 15 min / and the time of clonidine extraction after tablet disintegration / not less than 4 min / is 20 min.

 The maximum optical density of the yellow-colored chloroform extract of the reaction product of clonidine with bromphenol blue is observed at 410 ± 2 nm, which is confirmed by the spectral characteristic shown in the drawing.

The apparent molar repayment rate is 1.55 x 10 ⁴ m ^-1 • l • cm ^-1 , which indicates a high sensitivity of the method. Compliance with the Bouguer-Lambert-Beer law is in the concentration range from 4 to 125 μg in 5 ml of the final volume, which is sufficient to determine the clonidine content in one tablet, taking into account the norms of permissible deviations. The sensitivity of the determination is 4 μg in 5 ml of the final volume. The relative error for the substance and model mixture of tablets is ± 1.46% and ± 1.72%, respectively
The developed method has been tested on the substance of clonidine and on the model mass of tablets. The results are presented in table 1, the developed technique is sensitive, reproducible, accurate, correct. In addition, the technique is rapid, which is especially important to reduce the analysis time by the dosage uniformity test, in which up to 30 tablets are to be analyzed from each series.

 The data for determining the uniformity of dosing of clonidine in tablets that meet the requirements of FS 42-2100-83 are presented in table 2. From table 2 it is seen that the deviation in the content of clonidine in any sample does not exceed the norms of permissible deviations.

 Example 1. The method for determination of clonidine tablets 0.000075 g.

 3 ml of citrate buffer solution pH 3.31.5 ml of a 0.08% solution of bromphenol blue, 0.5 ml of water and 5 ml of chloroform are placed in a 50 ml separatory funnel. Then, a clonidine tablet (batch 1401089) is introduced and shaken for 20 minutes. After separation of the aqueous and organic phases, the chloroform layer is filtered through a funnel with a diameter of 5 cm, in which a small layer of cotton wool and 1 g of anhydrous sodium sulfate are placed in a cuvette with a layer thickness of 3 mm. The optical density of the chloroform extract from the tablet is measured on KFK-3 at 410 nm. Comparison solution chloroform reagent extract. In parallel, under the same conditions, a determination is made with 0.5 ml of a standard clonidine solution containing 0.000150 g of the drug in 1 ml.

где A_ис оптическая плотность экстракта испытуемого раствора;
A_ст -оптическая плотность экстракта стандартного раствора;
0,000150 содержание клофелина в мл стандартного раствора, г;
V- объем стандартного раствора взятый для анализа, мл.The clonidine content / C / in grams in the analyzed sample / one tablet / is calculated by the formula

where A _{is the} optical density of the extract of the test solution;
A _{st is the} optical density of the extract of the standard solution;
0.000150 clonidine content in ml of standard solution, g;
V is the volume of the standard solution taken for analysis, ml.

Пример 2. Методика определения клофелина в таблетках 0,00015 г.The mass of the tablet is 0.0594 g, the optical density of the test solution is 0.362, the optical density of the standard solution is 0.382, clonidine was found:

Example 2. The method for determination of clonidine tablets 0.00015,

Из таблицы 3 видно, что чувствительность предлагаемого способа позволяет проводить количественное определение клофелина в одной таблетке.6 ml of citrate buffer solution pH 3.3, 3 ml of a 0.08% solution of bromphenol blue, 1 ml of water and 10 ml of chloroform are placed in a 100 ml separatory funnel. Then make a tablet of clonidine / series 790689 /. A further determination is carried out as in example 1. In parallel, under the same conditions, a determination is made with 1 ml of a standard solution of clonidine containing 0.000150 g of the drug in 1 ml. The mass of the tablet is 0.1478, the optical density of the test solution is 0.366, the optical density of the extract of the standard solution is 0.389, clonidine was found:

From table 3 it is seen that the sensitivity of the proposed method allows for the quantitative determination of clonidine in one tablet.

 Thus, the present method for the quantitative determination of clonidine in one tablet has high sensitivity, sufficient accuracy, is economical, simple to implement, and can be recommended for use in the work of control and analytical laboratories of chemical pharmaceutical plants and Pharmacy production associations in assessing the uniformity of clonidine dosage in pills. TTT1 TTT2 TTT3 TTT4

Claims (1)

 A method for the determination of clonidine, including the destruction of a tablet, dissolution in a buffer solution, extraction with an organic solvent and subsequent determination of the extraction product, characterized in that clonidine is extracted as an ionic associate with bromphenol blue at pH 3.3 ± 0.2, followed by photometry at a wavelength 410 nm.

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