Photometric determination of kellin in Vikalin tablets
Abstract Generated abstract
This paper addresses the analytical control of kellin content in Vikalin tablets, noting that the official photometric procedure gave insufficiently accurate and reproducible results. The authors examine optimal conditions for extracting kellin with chloroform, converting it in sulfuric acid to a yellow complex, and measuring optical density with a blue filter on a photoelectric colorimeter. They propose a refined procedure using calibration solutions and report that, under the selected conditions, kellin solutions obey the Lambert-Beer law over 0.5 to 6 mg in 25 ml at sulfuric acid concentrations of 8 to 10 N.
Full Text
PHOTOMETRIC DETERMINATION OF KELLIN IN “VIKALIN” TABLETS
Yu. L. LELCHUK, N. L. BATURINA
(Presented by the Department of Analytical Chemistry)
“Vikalin” tablets are successfully used in the treatment of certain acute gastric diseases. Their chemical composition is rather complex [1]. In the analytical control of the manufacture of these tablets, the determination of their kellin content occupies a special place. The composition, properties, and structure of kellin are described in the literature [2]. In the inter-republic technical specifications of the Ministry of Health of the USSR [1], it is recommended that kellin be determined by a photometric method; however, the working procedure proposed there has a number of substantial shortcomings. Working by this procedure, we were unable to obtain sufficiently accurate and reproducible data not only in the analysis of Vikalin, but also when working with a purified preparation of kellin itself. We studied the optimal conditions for this determination and the concentration interval of kellin over which the Lambert–Beer law is obeyed. On the basis of these data, a refined and improved working procedure was developed, fully ensuring the accuracy and sensitivity required in this case.
The method is based on extraction of kellin with chloroform, its conversion by sulfuric acid into a yellow complex (after distilling off the chloroform and dissolving the residue in a 50% solution of ethyl alcohol), and photometry of the solution on an FEK-M photoelectric colorimeter with a blue light filter.
Twice-distilled water is used; all reagents are of “chemically pure for analysis” grade; sulfuric acid is approximately a 10-normal solution; sodium hydroxide is a 5% aqueous solution; aqueous ethyl alcohol solution (1:1); chloroform purified by distillation; kellin standard.
Preparation of the Standard Kellin Solution
0.0500 g of the “kellin-standard” preparation is weighed in a plastic weighing scoop on an analytical balance and transferred through a funnel into a 25 ml volumetric flask. The remaining kellin is then washed from the scoop and funnel with an aqueous solution of ethyl alcohol (1:1), diluted to the mark, and mixed thoroughly.
The concentration of kellin in the standard solution is 2 mg/ml.
Construction of the Calibration Curve
The calibration curve is constructed for quantities of kellin from 0.5 to 6 mg in 25 ml of solution. Into 7 numbered volumetric flasks or measur…
…25-ml volumetric flasks are successively charged with the standard kellin solution: 0.25; 0.5; 1.0; 1.5; 2.0; 2.5 and 3.0 ml. To the first flask are added 4.75 ml of aqueous ethyl alcohol solution (1:1), to the second—
Table 1
Optical density of kellin solutions
| Flask No. | Added, ml: kellin solution | Added, ml: C₂H₅OH (1:1) | Added, ml: H₂SO₄, 10 N | Weight of kellin, mg | Optical density, D |
|---|---|---|---|---|---|
| 1 | 0.1 | 4.9 | 20 | 0.2 | 0.108 |
| 2 | 0.25 | 4.75 | 20 | 0.5 | 0.116 |
| 3 | 0.6 | 4.4 | 20 | 1.2 | 0.240 |
| 4 | 1.0 | 4.0 | 20 | 2.0 | 0.335 |
| 5 | 1.5 | 3.5 | 20 | 3.0 | 0.48 |
| 6 | 2.0 | 3.0 | 20 | 4.0 | 0.57 |
| 7 | 2.5 | 2.5 | 20 | 5.0 | 0.71 |
| 8 | 3.0 | 2.0 | 20 | 6.0 | 0.77 |
4.5, to the third—4, to the fourth—3.5, to the fifth—3, to the sixth—2.5 and to the seventh—2 ml. After mixing, 10-normal sulfuric acid solution is added to the mark in each flask, the contents are thoroughly mixed, allowed to stand for 10 minutes, and the optical density of all solutions is measured on an FEK-M photoelectric colorimeter in cuvettes with a 30-mm layer thickness, using a blue light filter. Distilled water serves as the comparison solution.
The experimental data obtained by us are given in Table 1 and in Fig. 1.
Fig. 1. Calibration graph for determining kellin in “Vikair” tablets
Course of analysis
For analysis, one tablet is taken and ground to a powder. For determination of kellin, 2 portions of the powder, accurately weighed on an analytical balance in plastic scoops and within the range of 0.25 g, are taken.
The weighed portions are transferred into 2 dry test tubes with well-fitted stoppers; approximately 0.5 g of anhydrous sodium sulfate is added to them and mixed. Then 5 ml of chloroform and 10 drops of a 5% sodium hydroxide solution are added, the mixture is shaken thoroughly for 3 minutes, and the chloroform extract is decanted through funnels with small filters of white ribbon into 2 other dry test tubes. The filters are previously moistened with a small portion of chloroform. Extraction of kellin from each weighed portion is repeated 2 more times with the same portions of chloroform and sodium hydroxide, and all three extracts are combined.
After this, the test tubes with the combined extracts are immersed in a water bath heated to boiling temperature, in a fume hood, until the chloroform has been completely distilled off. The resulting dry residue of Kellin is dissolved, with heating, in 5 ml of an aqueous ethyl alcohol solution (1:1), and the solutions are transferred to volumetric flasks or volumetric test tubes with a capacity of 25 ml. The residues from the test tubes are rinsed into the same flasks with small portions of 10-normal sulfuric acid. Then the same acid is added to the mark, the contents are thoroughly mixed, allowed to stand for 10 minutes, and the optical density of the solutions is measured on an FEK-M photoelectric colorimeter in cuvettes with a solution layer thickness of 30 mm, using a blue light filter. Distilled water is used as the blank solution.
From the optical density of the resulting solutions, the Kellin content in each sample is determined from the calibration graph. The Kellin content in the tablet being analyzed is calculated by the formula:
\[ x=\frac{B_2\cdot B_3}{B_1}, \]
where
\(x\) — the Kellin content in the tablet, mg,
\(B_1\) — weight of the analyzed sample of vicalin, mg,
\(B_2\) — weight of Kellin in the analyzed sample, mg,
\(B_3\) — weight of the vicalin tablet, mg.
Conclusions
The optimal conditions for the photometric determination of Kellin in “Vicalin” tablets have been studied, and on the basis of these data a refined and improved working analytical procedure has been proposed. Under the conditions of analysis, solutions of Kellin in sulfuric acid obey the Lambert–Beer law at a Kellin concentration of 0.5 to 6 mg in 25 ml of solution and an \(H_2SO_4\) concentration of \(8\text{–}10\,N\).
LITERATURE
- MRTU 42, No. 612—62. Ministry of Health of the USSR.
- State Pharmacopoeia of the USSR, p. 271. Medgiz, Moscow, 1961.