Introduction:
Amlodipine (2 - [(2-aminoethoxy) methyl] -4- (2-chlorophenyl) -1,4-dihydro-6-methyl-3,5-pyridine dicarboxylic acid 3-ethyl 5-methyl ester) is widely used in medicinal practice as an antagonist of calcium ions in angina pectoris, coronary heart disease (CHD) and hypertension. [1]
The widespread use of amlodipine in medicine, its toxic effect and the described cases of poisoning with this drug with a fatal outcome allow us to consider it a potential object of forensic chemical analysis. [2]
There are some methods of thin-layer chromatography for the qualitative determination of amlodipine, which are not systematized and scattered, this indicates the need for further development of methods for the chemical-toxicological analysis of amlodipine using spectral and chromatographic methods. [3]
The aim of the study is to determine the optimal conditions for the identification of amlodipine by thin layer chromatography.
Materials and methods:
The objects of study were a standard sample of amlodipine (Anhui Minmetals Development I/E LTD, China), tablets "Koronim" (JSC "Nobel Almaty Pharmaceutical Factory", Kazakhstan). A set of devices for TLC was used: chromatographic plates "Sorbfil PTSKh-AF-V-UF” 10x10 cm, microsyringes "MSh-10", "MSh-1" (Color); chromatographic cameras, UV chromatoscope (Lenchrome, UV cartridges 254/365); reagents and solvents of "chemically pure" and "analytical grade" categories: chloroform, hexane, acetone, ethyl acetate, butanol, ethanol 90%.
Thin-layer chromatography technique: 10 μl (100 μg) of the test solution is applied to the start line of the "Sorbfil PTSKh-AF-V-UV" 10x10 cm chromatographic plate. The plates are dried for 10 minutes in a stream of clean air, placed in a chromatographic chamber saturated with vapors of the mobile phase and chromatographed by the bottom-up method. When the front of the solvents reaches the finish line, the plate is removed from the chromatographic chamber, dried until the odors of the mobile phase are lost and viewed in UV light at a wavelength of 254 nm.
Results and discussion:
A series of experiments on the selection of conditions for effective chromatography of amlodipine in a thin layer of sorbent was carried out.
The mobile phase used for chromatography of amlodipine was selected in accordance with the eluotropic range and the recommendations of the International Association of Toxicologists for substances that exhibit basic properties, such as those commonly used - butanol, chloroform, hexane. [4] [5] (Table 1)
|
Mobile phase |
Rf value |
|
Acetone |
0.75 ±0,03 |
|
Chloroform - Ethanol – Ammonia (40:30:0.5) |
0.67 ±0,03 |
|
Chloroform - Ethanol – Ammonia (40:20:0.5) |
0.61 ±0,03 |
|
Chloroform - Ethanol – Ammonia (40:10:0.5) |
0.59 ±0,03 |
|
Butanol - Ethanol – Ammonia (30:20:0.5) |
0.3 ±0,03 |
|
Butanol - Ethanol – Ammonia (30:10:0.5) |
- |
|
Acetone - Hexane (1:2) |
- |
|
Chloroform – Ethylacetate (2:1) |
0.75 ±0,03 |
|
Butanol – acetone (2;8) |
0.83 ±0,03 |
|
Butanol - acetone (4;6) |
0.81 ±0,03 |
|
Chloroform - dioxane – propanol (3:1:1) |
- |
|
Hexane – Ethylacetate (2:1) |
0.32 ±0,03 |
|
Hexane – Ethylacetate – Ethanol (2:1:1) |
0.41 ±0,03 |
|
Hexane – Ethylacetate – Ethanol (4:2:3) |
0.51 ±0,03 |
Table 1 - Rf of amlodipine in various mobile phases
The mobility of amlodipine in conventional solvent systems has been estimated based on Rf values, which are in the range of 0.3-0.75, indicating the effectiveness of these solvent systems.
Amlodipine has an optimal Rf value within 0.51 in an experimentally selected mobile phase consisting of a mixture of hexane-ethyl acetate-ethanol (4: 2: 3). Spots at this stage are allocated compactly, without "tails".
Also, studies were carried out on the selection of reagents for the development of amlodipine on chromatographic plates, which were used as: Dragendorff's reagent, Bouchard's reagent, ninhydrin solution 0.1%, sulfuric acid. When using these chromogenic reagents, no pronounced analytical effect was revealed.
On chromatographic plates, amlodipine is well detected under UV light (254 nm), which complies with the international recommendations of the FDA and the Forensic Science Center of the Republic of Kazakhstan. The detection sensitivity of this method is 0.5 μg.
A study of the Koronim tablets containing amlodipine as an active ingredient showed that, under these chromatographic conditions, the Rf of the standard amlodipine sample and the tested tablets is the same (Fig. 1).
Conclusions:
66
A method for the determination of amlodipine by thin layer chromatography has been developed. A mixture of solvents - hexane - ethyl acetate - ethanol (4: 2: 3) "was chosen as the mobile phase", while the Rf is 0.51 ± 0.03.
Literature:
- State Pharmacopoeia of the Republic of Kazakhstan, v. 1 -Almaty: Zhibek Zholy Publishing House, 2008. - 592 p.
- Leonova MV Modern view of amlodipine and new drugs of S-amlodipine // RFK. 2011. No. 2.
- Shormanov V.K., Kvachakhia L.L., Mitrokhina A.V., Myasnyankina E.A. Features of the determination of amlodipine in biological material. Forensic-medical examination. 2019.- 62 (4). -47-54.
- A. D. Serikbaeva, E.K. Orynbasarov, S.K. Ordabaeva Development of a method for detecting clozapine by thin layer chromatography // Bulletin of KazNMU.- 2013.- №5-3.
- Mirsoatova M.A. Serikbaeva A.D., Ordabaeva S.K. Development of a chromatographic technique for detecting movalis in chemical and toxicological studies // Ontustik Kazakhstan medicine academysynyk khabarshysy. - No. 4 (84). - 2018. - T. VII. - 138-139 b.