TLC-Densitometry for Determination of Omeprazole in Simple and Combined Pharmaceutical Preparations.

TLC combined with densitometry was used and chromatographic conditions developed to separate omeprazole and diclofenac sodium from their potential impurities. The development of the TLC-densitometry method is based on the elaboration of new chromatographic conditions allowing for the simultaneous determination of omeprazole and diclofenac sodium in a pharmaceutical preparation. Identification and quantification of omeprazole in simple and combined (with diclofenac) pharmaceutical preparations was performed on silica gel 60F254 using one mobile phase: chloroform-methanol-ammonia (36:4:0.60, v/v). Diclofenac sodium was determined in the presence of omeprazole after 2D separation on silica gel using two mobile phases of the first phase of chloroform-methanol-ammonia (36:4:0.60, v/v) and the second mobile phase cyclohexane-chloroform-methanol-glacial acetic acid (6:3:0.5:0.5 v/v). The developed method is simple, economical, specific, precise, accurate, sensitive, and robust, with a good range of linearity for the quantification of omeprazole and diclofenac sodium. TLC in combination with densitometry can be used as an effective analytical tool for quality control and quantitative determination of omeprazole in simple and combined pharmaceutical preparations containing diclofenac sodium. TLC in combination with densitometry can be recommended for the analysis of omeprazole and diclofenac sodium in the absence of HPLC or spectrophotometer in the laboratory or to confirm results obtained with other analytical techniques.

Use of TLC-Densitometric Method for Determination of Valproic Acid in Capsules.

Determination of valproic acid in the drug was carried out on the aluminum silica gel 60F254 plates and using acetone-water-chloroform-ethanol-ammonia at a volume ratio of 30:1:8:5:11 as the mobile phase, respectively. Two methods of detection of valproic acid were used. The first was a 2% aqueous CuSO4×5H2O solution, and the second was a 2',7'-dichlorofluorescein-aluminum chloride-iron (III) chloride system. The applied TLC-densitometric method is selective, linear, accurate, precise, and robust, regardless of the visualizing reagent used for the determination of valproic acid in Convulex capsules. It has low limits of detection (LOD) and limits of quantification (LOQ), which are equal to 5.8 µg/spot and 17.4 µg/spot using a 2% aqueous CuSO4×5H2O solution as visualizing agent and also 0.32 µg/spot and 0.97 µg/spot using a 2',7'-dichlorofluorescein-aluminum chloride-iron (III) chloride system as visualizing reagent, respectively. The described analytical method can additionally be used to study the identity of valproic acid in a pharmaceutical preparation. The linearity range was found to be 20.00-80.00 µg/spot and 1.00-2.00 µg/spot for valproic acid detected on chromatographic plates using a 2% aqueous CuSO4×5H2O solution and the 2',7'-dichlorofluorescein-aluminum chloride-iron (III) chloride system, respectively. A coefficient of variation that was less than 3% confirms the satisfactory accuracy and precision of the proposed method. The results of the assay of valproic acid equal 96.2% and 97.0% in relation to the label claim that valproic acid fulfill pharmacopoeial requirements. The developed TLC-densitometric method can be suitable for the routine analysis of valproic acid in pharmaceutical formulations. The proposed TLC-densitometry may be an alternative method to the modern high-performance liquid chromatography and square wave voltammetry in the control of above-mentioned substances, and it can be applied when other analytical techniques is not affordable in the laboratory.

A cost-effective and sensitive TLC-densitometric identification of meloxicam.

The influence of different chromatographic conditions and the process of spot visualization on determining the limit of detection as well as quantification (LOD and LOQ) of meloxicam by TLC-densitometric technique was estimated. Of all chromatographic conditions tested, the lowest limiting values, thus the best sensitivity, in the NP-TLC system was achieved on silica gel 60F254 and neutral aluminum oxide plates developed with the mobile phase consisting of ethyl acetate/toluene/n-butylamine (2:2:1, V/V/V). In the case of the RP-TLC method, a mixture of methanol/water (8:2, V/V) enabled densitometric detection of meloxicam at the lowest concentration level on RP-8F254 and RP-18F254 plates. Additionally, the smallest LOD value of meloxicam ensured crystalline violet and gentian violet as visualization agents on silica gel 60F254 and neutral aluminum oxide 150F254 plates, resp. Comparison of the densitometrically obtained spectra of meloxicam drug and its standard after the use of appropriate visualization agents could be a good and cheap alternative tool for the identification of meloxicam as an active pharmaceutical ingredient.

Comparison of the Utility of RP-TLC Technique and Different Computational Methods to Assess the Lipophilicity of Selected Antiparasitic, Antihypertensive, and Anti-inflammatory Drugs.

The aim of this study was to assess the lipophilicity of selected antiparasitic, antihypertensive and non-steroidal anti-inflammatory drugs (NSAIDs) by means of reversed phase-thin layer chromatography (RP-TLC) as well by using Soczewinski-Wachtmeister's and J. Oscik's equations. The lipophilicity parameters of all examined compounds obtained under various chromatographic systems (i.e., methanol-water and acetone-water, respectively) and those determined on the basis of Soczewinski-Wachtmeister's and Oscik's equations (i.e., RMWS and RMWO) were compared with the theoretical ones (e.g., AlogPs, AClogP, milogP, AlogP, MlogP, XlogP2, XlogP3) and the experimental value of the partition coefficient (logPexp). It was found that the RMWS parameter may be a good alternative tool in describing the lipophilic nature of biologically active compounds with a high and low lipophilicity (i.e., antihypertensive and antiparasitic drugs). Meanwhile, the RMWO was more suitable for compounds with a medium lipophilicity (i.e., non-steroidal anti-inflammatory drugs). The chromatographic parameter 0(a) can be helpful for the prediction of partition coefficients, i.e., AClogP, XlogP3, as well as logPexp of examined compounds.

Application of Thin-Layer Chromatography in Combination with Densitometry for the Determination of Diclofenac in Enteric Coated Tablets.

Diclofenac belongs to the drug class non-steroidal anti-inflammatory drugs widely used in Europe as well as all over the world. Thus, it is important to conduct research on its quality control of available pharmaceutical preparations like for example enteric coated tablets. Among various analytical techniques, thin-layer chromatography (TLC) is ideal for this task due to their short time analysis, ease of operation and low cost. Hence, the aim of this study was to develop the optimal conditions of analysis and quantitative determination of diclofenac sodium in enteric tablets by using TLC in combination with densitometry. Of all chromatographic systems tested, the best is the one which consists of silica gel 60F254 and cyclohexane: chloroform:methanol:glacial acetic acid (6:3:0.5:0.5 v/v) as the mobile phase, which allows the successful separation of examined diclofenac sodium as active component and the largest number (twelve) of its degradation products as potential impurities of its pharmaceutical products. This indicates that the newly developed method is more effective than previously reported assays by Starek and Krzek. Linearity range was found to be 4.00-18.00 µg/spot for diclofenac sodium. The results of the assay of enteric tablet formulations equals 98.8% of diclofenac sodium in relation to label claim is in a good agreement with pharmaceutical requirements.

A Simple and Cost-Effective TLC-Densitometric Method for the Quantitative Determination of Acetylsalicylic Acid and Ascorbic Acid in Combined Effervescent Tablets.

A new, simple, and cost-effective TLC-densitometric method has been established for the simultaneous quantitative determination of acetylsalicylic acid and ascorbic acid in combined effervescent tablets. Separation was performed on aluminum silica gel 60F254 plates using chloroform-ethanol-glacial acid at a volume ratio of 5:4:0.03 as the mobile phase. UV densitometry was performed in absorbance mode at 200 nm and 268 nm for acetylsalicylic acid and ascorbic acid, respectively. The presented method was validated as per ICH guidelines by specificity, linearity, accuracy, precision, limit of detection, limit of quantification, and robustness. Method validations indicate a good sensitivity with a low value of LOD and LOQ of both examined active substances. The linearity range was found to be 1.50⁻9.00 µg/spot and 1.50⁻13.50 µg/spot for acetylsalicylic and ascorbic acid, respectively. A coefficient of variation that was less than 3% confirms the satisfactory accuracy and precision of the proposed method. The results of the assay of combined tablet formulation equal 97.1% and 101.6% in relation to the label claim that acetylsalicylic acid and ascorbic acid fulfill pharmacopoeial requirements. The developed TLC-densitometric method can be suitable for the routine simultaneous analysis of acetylsalicylic acid and ascorbic acid in combined pharmaceutical formulations. The proposed TLC-densitometry may be an alternative method to the modern high-performance liquid chromatography in the quality control of above-mentioned substances, and it can be applied when HPLC or GC is not affordable in the laboratory.