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Accurate, simple, and selective spectrophotometric and spectrodensitometric methods were developed and adopted to quantify velpatasvir (VPS) and sofosbuvir (SFV) concurrently in their pure forms and tablets. The spectrophotometric technique was based on the first derivative of ratio spectra (1DD) technique and developed to determine VPS and SFV simultaneously in table formulation. However, the spectrodensitometric technique was based on thin-layer chromatography (TLC) and densitometry and developed to determine VPS and SFV simultaneously in tablet dosage form. Chromatographic separation was performed using chloroform:methanol 9.5:0.5 (%, v/v) as the mobile phase on glass-coated TLC plates. Detection was achieved using a 265-nm deuterium lamp in absorbance mode. Both analytical methods were validated according to the International Conference on Harmonization (ICH)-Q2B guidelines. The linearity in the range of concentration ranges of 1–50 μg/mL and 5–80 μg/mL were obtained for VPS and SFV, respectively, using 1DD spectrometric method. However, the linearity in the range of 5–50 and 10–70 μg/band for VPS and SFV, respectively, were recorded using TLC–densitometric method. Accuracy was recorded ˃100% for VPS and SFV using both methods. This is the first TLC–densitometry method that can separate and quantify the studied mixture of the drugs. The proposed analytical methods were found to be accurate, precise, selective, robust and sensitive for simultaneous analysis of VPS and SFV in tablet dosage forms. [ABSTRACT FROM AUTHOR]

The article investigates the possibility of using thin-layer chromatography and spectrodensitometer analysis of TLC-chromatograms to determine impurities in ciprofloxacin tablets. HPTLC silica gel 60F254 chromatographic plates and the mobile phase dichloromethane:methanol:ammonia:acetonitrile (30:40:20:10) were used to obtain chromatograms that enabled quantitative determination of ciprofloxacin ethylenediamine analogue in the tablet dosage form. The results of testing were consistent with the data obtained by a validated method. The proposed method makes it possible to determine an identified impurity if the data obtained from tests do not comply with the specification.

In this study, thin-layer chromatography with densitometry and gas chromatography-mass spectrometry (GC-MS) were used to evaluate the chemical stability of hexyl nicotinate. Normal-phase thin-layer chromatography (NP-TLC) analysis was performed on silica gel 60 F254 plates with acetone--n-hexane in volume composition of 30:70 (v/v) as the mobile phase. The investigation of the chemical stability of hexyl nicotinate was performed in aqua-ethanolic solutions stored in ordinary and quartz flasks heated at 40°C and exposed to ultraviolet (UV) radiation (λ = 254 nm). Hexyl nicotinate was stable in aqua-ethanolic solution stored in ordinary flasks heated to 40°C and exposed to UV radiation (λ = 254 nm). Based on GC-MS analysis, the preliminary identification of the decomposition products of hexyl nicotinate in aqua-ethanolic solution, which was exposed to UV radiation (λ = 254 nm) in a quartz flask for 200 h, was achieved. Thermogravimetric analysis showed the complete disappearance of hexyl nicotinate at a temperature of 392.2°C. [ABSTRACT FROM AUTHOR]

Four accurate and sensitive methods were developed and validated for determination of naphazoline hydrochloride (NAP) and chlorpheniramine maleate (CLO) in the presence of naphazoline hydrochloride alkaline degradation product (NAP Deg). The first method is a spectrophotometric one , where NAP was determined by the fourth derivative (D4) spectrophotometric method by measuring the peak amplitude at 302 nm, while CLO was determined by the second derivative of the ratio spectra (DD2) spectrophotometric method at 276.4 nm. The second method is a chemometric-assisted spectrophotometric method in which partial least squares (PLS-1) and partial component regression (PCR) were used for the determination of NAP, CLO and NAP Deg using the information contained in their absorption spectra of ternary mixture. The third method is a TLC-densitometric one where NAP, CLO and NAP Deg were separated using HPTLC silica gel F254 plates using ethyl acetate:methanol:ammonia: (8:2:0.5, by volume) as the developing system followed by densitometric measurement at 245 nm. The fourth method is HPLC method where NAP, CLO and NAP Deg were separated using ODS C18 column and a mobile phase consisting of 0.1 M KH2PO4 (pH = 7):methanol (55:45 v/v) delivered at 1.5 mL min−1 followed by UV detection at 265 nm. The proposed methods have been successfully applied to the analysis of NAP and CLO in pharmaceutical formulations without interference from the dosage form additives and the results were statistically compared with a reported method.

Two sensitive and selective methods were developed and validated for simultaneous determination of pramocaine HCl and hydrocortisone acetate in pharmaceutical dosage form. The first method is a spectrodensitometric method where pramocaine HCl and hydrocortisone acetate were separated using toluene:methanol:chloroform: 10% NH3[(5:3:6:0.1, by volume) as the developing system followed by densitometric measurement at 290 nm] and 250 nm for pramocaine HCl and Hydrocortisone acetate, respectively. The second method is a high performance liquid chromatographic method for separation and determination of both drugs using reversed phase C18column and mobile phase consisting of distilled water:acetonitrile:triethylamine (530:470:0.1, by volume); pH was adjusted to 3 by o-phosphoric acid. The proposed methods were successfully applied for the analysis of pramocaine HCl and hydrocortisone acetate in laboratory prepared mixtures and in pharmaceutical dosage form and the results obtained were assessed by applying the standard addition technique. Statistical comparison between the results obtained by applying the proposed methods and official method for the cited drugs was done and no significant difference was found at p = 0.05. [ABSTRACT FROM AUTHOR]

Adsorption thin layer chromatography (NP-TLC) with densitometry has been established for the identification and the quantification of acetylsalicylic acid, caffeine, and ethoxybenzamide in combined tablets. UV densitometry was performed in absorbance mode at 200 nm, 275 nm, and 300 nm for acetylsalicylic acid, caffeine, and o-ethoxybenzamide, respectively. The presented method was validated by specificity, range, linearity, accuracy, precision, detection limit, quantitative limit, and robustness. It could be said that the NP-TLC-densitometric method is suitable for the routine analysis of acetylsalicylic acid, caffeine, and ethoxybenzamide in combined tablets in quantity control laboratories. [ABSTRACT FROM AUTHOR]

Abstract: Four accurate and sensitive methods were developed and validated for determination of naphazoline hydrochloride (NAP) and chlorpheniramine maleate (CLO) in the presence of naphazoline hydrochloride alkaline degradation product (NAP Deg). The first method is a spectrophotometric one , where NAP was determined by the fourth derivative (D4) spectrophotometric method by measuring the peak amplitude at 302nm, while CLO was determined by the second derivative of the ratio spectra (DD2) spectrophotometric method at 276.4nm. The second method is a chemometric-assisted spectrophotometric method in which partial least squares (PLS-1) and partial component regression (PCR) were used for the determination of NAP, CLO and NAP Deg using the information contained in their absorption spectra of ternary mixture. The third method is a TLC-densitometric one where NAP, CLO and NAP Deg were separated using HPTLC silica gel F254 plates using ethyl acetate:methanol:ammonia: (8:2:0.5, by volume) as the developing system followed by densitometric measurement at 245nm. The fourth method is HPLC method where NAP, CLO and NAP Deg were separated using ODS C18 column and a mobile phase consisting of 0.1M KH2PO4 (pH=7):methanol (55:45 v/v) delivered at 1.5mLmin−1 followed by UV detection at 265nm. The proposed methods have been successfully applied to the analysis of NAP and CLO in pharmaceutical formulations without interference from the dosage form additives and the results were statistically compared with a reported method. [Copyright &y& Elsevier]

Adsorption thin layer chromatography (NP-TLC) with densitometry has been established for the identification and the quantification of acetylsalicylic acid in tablets. UV densitometry was performed in absorbance mode at 200 nm. The presented method was validated by specificity, range, linearity, accuracy, precision, detection limit, quantitative limit, and robustness. The TLC-densitometric method was also compared with a pharmacopeial UV-spectrophotometric method for the assay of acetylsalicylic acid, and the results confirmed statistically that the NP-TLC-densitometric method can be used as a substitute method. It could be said that the NP-TLC-densitometric method is suitable for the routine analysis of acetylsalicylic acid in quantity control laboratories. [ABSTRACT FROM AUTHOR]

NP-TLC and RP-TLC techniques with the densitometry were compared to the determination of tocopherol acetate in oral fluid Vitaminum E. It was stated, that tocopherol acetate was better separated from tocopherol using NP-TLC technique than RP-TLC technique. Therefore, NP-TLC with densitometry has been used for the identification and the quantitative determination of tocopherol acetate in pharmaceutical preparation. The NP-TLC method with densitometry was validated. The accuracy of the method was evaluated by measurement of recovery. According to the results of the experiments performed using the NP-TLC-densitometric method, it was determined that the procedure used in this study is reliable with specificity, accuracy, precision, and robustness. It could be said that the NP-TLC-densitometric method is suitable for the routine analysis of tocopherol acetate in quality control laboratories. [ABSTRACT FROM PUBLISHER]

Adsorption thin layer chromatography with densitometry has been established for the identification and the quantification of naproxen in tablets. UV densitometry was performed in absorbance mode at 230 nm. The presented method was validated by specificity, range, linearity, accuracy, precision, detection limit, quantitative limit, and robustness. The TLC-densitometric method was also compared with a pharmacopeial UV-spectrophotometric method for the assay of naproxen, and the results confirmed statistically that the TLC-densitometric method can be used as a substitute method. [ABSTRACT FROM AUTHOR]

A simple, rapid, and effective method for TLC separation of two EU-authorized UV filters octyl methoxycinnamate (OMC) and diethylamino hydroxybenzoyl hexyl benzoate (DHHB) on silica gel 60 is proposed. Separation conditions were optimized and cyclohexane-diethyl ether-acetone 15:1:2 (v/v) was used as mobile phase. Quantification of both filters on the same chromatographic plates was achieved by densitometric scanning in absorption-reflectance mode at 300 and 360 nm, respectively. The method enabled separation of other UV-absorbing ingredients commonly found in cosmetic sunscreen preparations, for example parabens or ethylhexyltriazone (ET). Good quality, linear calibration plots were generated over the range 200-2000 ng per spot both for OMC and DHHB. The method was validated. [ABSTRACT FROM AUTHOR]

Adsorption thin layer chromatography with densitometry has been established for the identification and the quantification of hydrocortisone in tablets. UV densitometry was performed in absorbance mode at 250 nm. The presented method was validated by specificity, range, linearity, accuracy, precision, detection limit, quantitative limit, and robustness. The TLC-densitometric method was also compared with a pharmacopeil UV-spectrophotometric method for the assay of hydrocortisone, and the results confirmed statistically that the TLC-densitometric method can be used as a substitute method. [ABSTRACT FROM AUTHOR]

TLC separation of the UV filters avobenzone (AVO) and octocrylene (OCR) on RP-18 and silica gel 60 as stationary phases, with numerous mobile phases, revealed that these compounds have similar retention properties under almost all the chromatographic conditions investigated. Analysis of avobenzone in the presence of octocrylene may be achieved on silica gel 60 with cyclohexane-diethyl ether 1:1 (v/v) as mobile phase, at the selective wavelength 380 nm, at which octocrylene does not absorb (Method A). Analysis of octocrylene in the presence of avobenzone by the same method was, however, impossible because of insufficient chromatographic separation of AVO and OCR and overlap of the absorption ranges of AVO and OCR (with OCR peaks being obscured by those of AVO). An alternative separation strategy was proposed that proved successful for OCR in the presence of AVO. This involved chromatography on silica gel 60 with cyclohexane-piperidine 15:1 (v/v) as mobile phase (Method B). When these chromatographic conditions were used, retention of avobenzone changed substantially and OCR peaks became clearly visible. Spectrodensitometric scanning for OCR was then performed at 300 nm. Both methods were validated, and gave calibration plots of good linearity. [ABSTRACT FROM AUTHOR]

NP-TLC and RP-TLC techniques with densitometry have been established for the identification and the quantification of ibuprofen in selected pharmaceutical preparations, namely: Nurofen, Ibuprom, and Ibum. Analyses were performed on silica gel 60 F254 plates using n-hexane-ethyl acetate-acetic acid, 15:5:0.7, v/v (NP-TLC) and on RP18 F254s plates using methanol-water, 9:1, v/v (RP-TLC). UV densitometry was performed at 200 and 224 nm for NP-TLC and RP-TLC analysis, respectively. NP-TLC and RP-TLC techniques with the densitometry and the spectrodensitometry applied to the investigation and the determination of ibuprofen in pharmaceutical preparations are selective, precise, and accurate. The techniques also realize the criterion of the linearity in the required range of ibuprofen concentrations. [ABSTRACT FROM AUTHOR]

A particularly rapid HPTLC method has been established for chromatographic separation and quantification of p-aminobenzoic acid (PABA) in complex dietary supplement tablets. After chromatography, PABA was determined by spectrodensitometry at 270 nm. PABA spots were then visualized by a novel staining procedure involving the Bratton-Marshall coupling reaction after spraying with 8-hydroxyquinoline in situ on the chromatographic plates. After visualization, spectrodensitometric analysis was repeated at 500 nm. Linearity, intermediate precision, sensitivity, accuracy, and precision were compared for both methods. Results from tablet analysis were verified with the modified Bratton-Marshall spectrophotometric procedure. [ABSTRACT FROM AUTHOR]

Vitamin K1 (phylloquinone) was investigated with the use of reversed phase thin layer chromatography (RP-TLC) on RP8F254s, and RP18F254s (E. Merck) plates, using methanol as a mobile phase. It was stated that a larger amount of the bands on a chromatogram were obtained on RP8F254s plates than on RP18F254s plates. Six densitometric bands on RP8F254s plates were observed, where vitamin K1 had RF = 0.45 and λmax = 254 nm; however, the impurities had the RF values equal to 0.27, 0.54, 0.59, 0.62, and 0.75, respectively. It was stated that RP-TLC with densitometry and spectrodensitometry is a good method for the analysis of the qualitative composition of vitamin K1. [ABSTRACT FROM AUTHOR]

Thin layer chromatography with densitometry and spectrodensitometry was used to evaluate the stability of methyl nicotinate. Normal phase thin layer chromatography analysis was performed on silica gel 60 F254 with an acetone +n-hexane mobile phase. The investigations of chemical stability of methyl nicotinate were performed on silica gel 60 F254 at a temperature of 120°C, in an ethanolic solution stored at 8°C, as well as in aqueous and ethanolic solutions stored in ordinary- and quartz-flasks heated at 40°C and exposed to UV radiation (λ = 254 nm). Methyl nicotinate was only stable in aqueous and ethanolic solutions stored in ordinary flasks at 40°C and exposed to UV radiation (λ = 254 nm). [ABSTRACT FROM AUTHOR]

Abstract: Four sensitive, selective and precise stability-indicating methods for the determination of Clopidogrel Bisulfate (CLP) in presence of its alkaline degradate and in pharmaceutical formulations were developed and validated. Method A is a second derivative (D2) spectrophotometric one, which allows the determination of CLP in presence of its alkaline degradate at 219.6, 270.6, 274.2 and 278.4nm (corresponding to zero-crossing of the degradate) over a concentration range of 4–37μgmL−1 with mean percentage recoveries 99.81±0.893, 99.72±0.668, 99.88±0.526 and 100.46±0.646, respectively. CLP can be determined in the presence of up to 65% of its degradate. D2 method was used to study the kinetic of CLP alkaline degradation that was found to follow a first-order reaction. The t 1/2 was 6.42h while K (reaction rate constant) was 0.1080mol/h. Method B is the first derivative of the ratio spectra (DD1) spectrophotometric method, by measuring the peak amplitude at 217.6 and 229.4nm using acetonitrile and CLP can be determined in the presence of up to 70% of its degradate. The linearity range was 5–38μgmL−1 with mean percentage recoveries 99.88±0.909 and 99.70±0.952, respectively. Method C based on the determination of CLP by the bivariate calibration depending on simple mathematic algorithm which provides simplicity and rapidity. The method depends on quantitative evaluation of the absorbance at 210 and 225nm over a concentration range 5–38μgmL−1 with mean percentage recovery 99.27±1.115. CLP can be determined in the presence of up to 70% of its degradate. Method D is a TLC-densitometric one, where CLP was separated from its degradate on silica gel plates using hexane:methanol:ethyl acetate (8.7:1:0.3, v/v/v) as a developing system. This method depends on quantitative densitometric evaluation of thin layer chromatogram of CLP at 248nm over a concentration range of 0.6–3μg/band with mean percentage recovery 99.97±1.161. CLP can be determined in the presence of up to 90% of its alkaline degradate. The selectivity of the proposed methods was checked using laboratory prepared mixtures. The proposed methods have been successfully applied to the analysis of CLP in pharmaceutical dosage forms without interference from other dosage form additives and the results were statistically compared with the official method. [Copyright &y& Elsevier]

Phloroglucinol (P), niclosamide (N), salicylanilide (S) and thymol (T) were chromatographed on silica gel TLC plates with n-hexane-acetone in different volume proportions as mobile phases. Comparison and characterization of chromatographic spots of examined compounds on the basis of resolution (RS), separation factor (α), constant of the pair separation (RαF), and ΔRF values were discussed. The RS parameter, serving to evaluate the substance separation, was determined by visual and densitometric methods. It was proven that the RS parameter determined by the visual method for two adjacent substances is always larger than that determined by the densitometric method. It was stated that the densitometric method is correct, objective, and assures standard conditions for the parameter RS determination. [ABSTRACT FROM AUTHOR]

The spectrodensitograms of α-tocopherol acetate, α-tocopherol, cholecalciferol, estradiol, testosterone, and hydrocortisone on different chromatographic sorbents (silica gel 60, silica gel 60F254, mixture of silica gel 60 and kieselguhr F254, neutral aluminium oxide 60F254, neutral aluminium oxide 150F254, and RP18W) were compared. The resultant spectrodensitograms of the studied compounds indicate that applied sorbents have an influence on the wavelength of the obtained fundamental absorption band (λmax) and the additional absorption bands, as well as on their intensity values [AU]. This fact indicates the need for standaridization of the spectrodensitometric investigations regarding the applied chromatographic conditions. [ABSTRACT FROM AUTHOR]

A binary mixture of terbinafine hydrochloride and triamcinolone acetonide was determined by three different methods. The first one concerned with determination of both drugs using first derivative (D1) spectrophotometric technique at 297 and 274 nm over concentration ranges of 5–30 and 4–24 μg ml−1, with mean percentage accuracies 99.90±0.67 and 100.25±0.49, respectively. The second method depends on ratio-spectra 1st derivative (RSD1) spectrophotometry at 298 and 248 nm over the same concentration ranges with mean percentage accuracies 100.22±0.51 and 99.93±0.56, respectively. The spectrodensitometric analysis provides a rapid and precise method for the separation and quantitation of both terbinafine hydrochloride and triamcinolone acetonide. The method depends on the quantitative densitometric evaluation of thin layer chromatogram of terbinafine hydrochloride and triamcinolone acetonide at 283 and 238 nm over concentration ranges of 5–25 and 2.5–22.5 μg spot−1, with mean percentage accuracies 100.66±0.51 and 100.27±0.73, respectively. The suggested procedures were checked using laboratory prepared mixtures and were successfully applied for the analysis of their pharmaceutical preparations. The three methods retained their accuracy and precision when applying the standard addition technique. The results obtained by applying the proposed methods were statistically analysed and compared with those obtained by a reported method. [Copyright &y& Elsevier]

Three methods were developed for the determination of aceclofenac in the presence o fits degradation product, diclofenac. In the first method, third-derivative spectrophotometry (D[sub 3]) is used. The D[sub 3] absorbance is measured at 283 nm where its hydrolytic degradation product diclofenac does not interfere. The suggested method shows a linear relationship in the range of 4-24 µg mL[sup -1] with mean percentage accuracy of 100.05±0.88. This method determines the intact drug in the presence of up to 70% degradation product with mean percentage recovery of 100.42±0.94. The second method depends on ratio-spectra first-derivative (RSD[sub 1]) spectrophotometry at 252 nm for aceclofenac and at 248 nm for determination of degradation product over concentration ranges of 4-32 µg mL[sup -1] for both aceclofenac and diclofenac with mean percentage accuracy of 99.81±0.84 and 100.19±0.72 for pure drugs and 100.17±0.94 and 99.73±0.74 for laboratoryprepared mixtures, respectively. The third method depends on the quantitative evaluation of thin-layer chromatography of aceclofenac using chloroform:methanol: ammonia (48:11.5:0.5 v/v/v) as a mobile phase. Chromatograms were scanned at 274 and 283nm for aceclofenac and diclofenac, respectively. The method determined aceclofenac and diclofenac in concentration ranges of 2-10 and 1-9 µg spot[sup -1] with mean percentage accuracy of 100.20±1.03 and 100.14±0.98 for pure drugs and 99.77±0.74 and 100.07±0.78 for laboratory-prepared mixtures, respectively. This method retains its accuracy in the presence of up to 80% degradation product for the studied drug. The suggested procedures were checked using laboratory,prepared mixtures and were succesfully applied for the analysis of their pharmaceutical preparation. The validity of the proposed methods was further assessed by applying a standard addition technique. The obtained results agreed... [ABSTRACT FROM AUTHOR]

Two selective, sensitive and reproducible methods for the determination of carbimazole are described. The spectrophotometric determination of carbimazole was achieved through its reaction with a known excess of potassium bromate in bromide solution, then residual reagent was treated with sodium fluorescein in buffered medium at pH 5.5, where equivalent eosin is produced, which absorbed maximally at 517 nm. Stoichiometric study of the reaction showed that, carbimazole reacts with potassium bromate in the ratio of 1:1. The spectrophotometric method is linear over a range of 30–110 μg%. The spectrodensitometric analysis provides a rapid and precise method for the separation and quantitation of carbimazole. The method depends on the quantitative densitometric evaluation of thin layer chromatogram of carbimazole at 291 nm. It determines the drug in concentration range of 5–22.5 μg per spot. The two methods retained their accuracy and precision when applying the standard addition technique. The results obtained by applying the proposed methods were statistically analysed and compared with those obtained by the official B.P. method. [ABSTRACT FROM AUTHOR]