Densitometric TLC Research Articles

Densitometric determination of betamethasone dipropionate and salicylic acid in lotions, and validation of the method

A simple and rapid densitometric method has been developed for determination of betamethasone dipropionate and salicylic acid in lotions. The samples were diluted with 96% ethanol and spotted on precoated silica gel TLC plates which were then eluted with ethanol (96%)-toluene-chloroform-glacial acetic acid, 6.0 + 20 + 14 + 0.5 ( v/v ). Quantitative evaluation was performed by measuring the absorbance reflectance of the betamethasone dipropionate and salicylic acid spots at λ = 250 and 310 nm, respectively. This densitometric TLC method is selective, precise, and accurate and can be used for routine analysis of lotions in pharmaceutical industry quality-control laboratories.

Densitometric and videodensitometric TLC determination of timolol and betaxolol in ophthalmic solutions

A new, accurate, rapid TLC method has been established for determination of timolol maleate (Timohexal 0.1%, Timoptic 0.25%) and betaxolol hydrochloride (Betoptic 0.5%) in ophthalmic solutions. The selectivity of the separation of these drugs has been investigated by TLC on silica gel 60F 254 , silanized C 8 silica gel, and aluminum oxide 60 F 254 plates with ascending and horizontal development. Suitable conditions for separation were use of silica gel with ethyl acetate-methanol-25% aqueous ammonia, 80 + 18 + 2 ( v/v ), as mobile phase. The substances were visualized by UV irradiation at λ = 254 nm or by spraying with suitable reagents. Detection and quantification of timolol maleate and betaxolol hydrochloride were performed densitometrically at λ = 300 nm and λ = 218 nm, respectively, and videodensitometrically at λ = 254 nm. Results from quantitative analysis were statistically assessed by use of the calibration procedure, a calibration equation, the correlation coefficient ( R 2 ), and relative stan...

Determination of fluoxetine and paroxetine in pharmaceutical formulations by densitometric and videodensitometric TLC

Two new, simple, rapid, and accurate thin-layer chromatographic methods have been developed for determination of fluoxetine in capsules and paroxetine in tablets. The drugs were chromatographed on silica gel 60 F 254 plates in horizontal chambers with benzene-acetone-ethanol-25% aqueous ammonia, 9 + 7 + 2 + 1 ( v/v ) as mobile phase. Densitometric detection was performed at λ = 218 nm and 293 nm for fluoxetine and paroxetine, respectively; video-densitometric detection was performed at λ = 254 nm for both drugs. The range of linearity was 2–10 μg per spot for fluoxetine and 0.5–8 μg per spot for paroxetine. The relative standard deviation for determination of these antidepressants in pharmaceuticals was less than 4.3% for densitometry and less than 4.9% for video-densitometry. Recovery of fluoxetine from capsules was 105.1% by use of densitometry and 104.3% by use of videodensitometry; recovery of paroxetine from tablets was 99.15% and 98.2%, respectively.

TLC Densitometric Determination of Mometasone Furoate in Topical Preparations: Validation

A simple and rapid densitometric method has been developed for determination of mometasone furoate in the topical pharmaceutical preparations. After extraction of the analyte with 96% ethanol, the extracts were spotted on pre‐coated silica gel plates, which were then developed with a mixture of dichloromethane‐diethyl ether (3:1). Quantitative evaluation was performed by measuring the absorbance reflectance of the analyte spots at 260 nm. The densitometric method is selective, precise, and accurate and can be used for routine analysis of the topical preparations in pharmaceutical industry quality control laboratories.

Densitometric determination of impurities in pharmaceuticals. Part VIII. Simultaneous determination of fluoxetine and (1RS)-3-methylamino-1-phenylpropan-1-ol,N-methyl-3-phenylpropan-1-amine, and C-1 as drug impurities

A densitometric TLC method has been developed for identification and quantification of fluoxetine and its impurities — (1 RS )-3-methylamino-1-phenylpropan-1-ol, N -methyl-3-phenylpropan-1-amine, and C-1, the last of which has not previously been analyzed. The compounds were separated on silica gel 60 F 254 HPTLC plates, with chloroform-methanol-25% ammonia, 45 + 4.5 + 0.5 ( v/v ), as mobile phase. UV and visible densitometric scanning were performed at λ = 260 and 530 nm, respectively, after visualization of the chromatograms with ninhydrin solution. The method enables good separation of the constituents ( R F = 0.20, 0.41, 0.52, and 0.67) with sufficiently high detection limit and recovery for the individual constituents.

Microbiological and densitometric TLC analyses for peptides in liposomes.

Quantitative determination of Leucinostatins and/or of similar peptides, such as Peptaibols, is sometimes quite difficult to perform especially when they are entrapped in vectors, i.e. liposomes, whose components display UV absorbances that may obscure those of the active principle. Therefore, in these cases, it is useful to find alternative ways, especially when high pressure liquid chromatography (HPLC) is difficult to perform or needs long procedure times. In the present paper, the use of microbiological and densitometric methods for quantitative analysis of Leucinostatin A (Leu-A) are described and the results compared with those from HPLC analyses. The use of microbiological and densitometric assays, furnished results comparable with those obtained by HPLC. Of the two methods used, the microbiological procedure appeared to be less accurate and precise.

Adaptation of the Nelson-Somogyi reducing-sugar assay to a microassay using microtiter plates

The Nelson-Somogyi assay for reducing sugars was adapted to microtiter plates. The primary advantages of this modified assay are (i) smaller sample and reagent volumes, (ii) elimination of boiling and filtration steps, (iii) automated measurement with a dual-wavelength scanning TLC densitometer, (iv) increased range and reproducibility, and (v) automated colorimetric readings by reflectance rather than absorbance.

Determination of chenodeoxycholic acid on 3-cyanopropyltrichlorosilane-treated high-performance thin-layer chromatographic plates

Chenodeoxycholic acid in commerical drugs was analyzed by high-performance, thin-layer chromatography (HPTLC) using a cyanoalkyl chemically-bonded stationary phase, prepared by treating pre-coated silica with 3-cyanopropyltrichlorosilane (3CPTS). The 3CPTS-treated plates were used to evaluate commerical chenodeoxycholic acid in drug capsules. After development with methanol on the 3CPTS-treated plate, the chenodeoxycholic acid spot in the chromatogram was measured with a TLC densitometer equipped with a dual-wave length TLC scanner at λ=370nm. By this method, the fluorescence intensity of chenodeoxycholic acid was measured within 2.6% error over the range 30–240ng and the limit of detection was 30ng.

Quantification of Niacin and Niacinamide in Vitamin Preparations by Densitometric Thin Layer Chromatography

Abstract A densitometric TLC method was developed for the determination of the B-3 vitamins niacin and niacinamide in commercial vitamin preparations. The method involves removal of excipients by ethanol precipitation, separation of the vitamins by high performance TLC on phosphor-containing silica gel layers, and in situ scanning of sample and standard zones. The per cent recoveries for niacinamide in vitamin products were 96 to 104% and for niacinamide added to products 99 and 102%. Recoveries of added niacin were 99 to 102%, but recoveries of niacin in products ranged from 0 to 74% of the label values. Additional ingredients did not interfere with the determination.

Determination of Allantoin in Drug Preparations by Quantitative High Performance TLC

Abstract A densitometric TLC method was developed for the quantification of allantoin in creams and suppositories used to treat vaginal infections. Allantoin was extracted with water at elevated temperature, diluted to a known volume, and separated by HP silica gel TLC. Allantoin was detected by spraying with p-dimethylamine-benzaldehyde reagent. The absorption of standards and samples was compared by in situ scanning. Recoveries of allantoin from authentic samples ranged from 96–102%, except for one sample that assayed high. The accuracy of the method was demonstrated by standard addition analysis of this sample.

Determination of Sulfanilamide and Sulfisoxazole in Drug Preparations by Quantitative High Performance TLC

Abstract A densitometric TLC method was developed for quantification of sulfanilamide and sulfisoxazole in creams, supppositories, and tablets. The sulfas were extracted into acidic ethanol, diluted to an appropriate volume, and separated by silica gel HPTLC. The fluorescence quenching of the sulfa zones in samples and standards was compared by in situ scanning. Recoveries of the drugs from authentic samples ranged from 96–105%. Recoveries from products with old expiration dates were low. Identity of the sulfa drugs in products was confirmed by application of fluorescamine and Bratton-Marshall detection reagents.

散剤中ヒドロコルチゾンの簡易試験

A thin-layer chromatographic method for the determination of hydrocortisone in powdered preparations after the treatment of hydrocortisone with sulfuric acid is described. After developing with chloroform/methanol (85: 15 v/v), silica gel plates were dried, sprayed with sulfuric acid solution, and heated. Hydrocortisone spot on the chromatogram was measured with a TLC densitometer equipped with a dual-wave length TLC scanner at λEx 380nm, AEM 550nm.

Determination of Aminacrine Hydro-Chloride in Drug Preparations by TLC with Fluorescence Densitometry

Abstract A densitometric TLC method was developed for quantification of aminacrine hydrochloride in creams, jellies, and suppositories. Aminacrine was extracted into acidic ethanol, diluted to a known volume, and separated by high performance silica gel TLC. The fluorescence of aminacrine zones in samples and standards was compared by in situ scanning. Recoveries of aminacrine from authentic samples ranged from 95.4 to 103.4%.

Fluorescence–TLC Densitometric Determination of Diazepam and Other 1,4-Benzodiazepines in Serum

A sensitive fluorescence-TLC densitometric procedure was developed for the specific determination of diazepam (I) and its two metabolites, desmethyldiazepam (II) and oxazepam (III), in serum. After extraction from serum with benzene, the compounds were separated by TLC and converted with a sulfuric acid spray to greenish-yellow fluorescence spots with Rf values of 0.72, 0.43, and 0.17, respectively. Quantitation of the TLC plate was accomplished by scanning with a densitometer at 380nm. The sensitivities of the assay were 18 (I), 6 (II), and 5 (III) ng/ml of serum. This procedure also was applicable to other 1,4-benzodiazepines in biological fluids.

Quantitative determination of griseofulvin and griseofulvin-4'-alcohol in plasma by fluorimetry on thin layer chromatograms.

Abstract A method for quantitatively determining griseofulvin and griseofulvin-4′-alcohol in plasma was developed employing measurement of fluorescence directly on thin layer chromatograms. Chromatograms of plasma extracts were mechanically scanned with a modified Photovolt TLC Densitometer. The areas under the peaks produced by the scan were found to be linear with the amount of fluorescent material on the spots within a useful range. The errors incurred in the assay were 3.2 for the determination of griseofulvin and 4.7 for griseofulvin-4′-alcohol. The results of the TLC fluorimetric assay and the spectrophotofluorometric assay on plasma samples following oral doses of griseofulvin to rabbtis were in good agreement.