Coupling of liquid-liquid extraction and mathematical filtration techniques for the separation and quantification of five components in semisolid dosage form with severely overlapped spectra.

Quadriderm cream was a combination of four components; Clioquinol (CLIO), Betamethasone (BETA), Tolnaftate (TOL), Gentamicin (GEN) in addition to the preservative Chlorocresol (CC). Four components CLIO, TOL, BETA, and CC were extracted in methanol and determined by mathematic filtration spectrophotometric techniques. The partially overlapped spectrum of CLIO was determined by constant value, constant multiplication, and concentration value methods then eliminated via spectrum subtraction (SS) to get the resolved ternary mixture of TOL, BETA, and CC with severely overlapping spectra. TOL was determined by derivative ratio at zero crossing point of BETA using CC as a divisor. While, BETA could be determined using TOL as a divisor at zero crossing of CC. BETA and CC were obtained using novel (DD1FS) followed by SS. By applying these novel procedures, the DD1 spectrum of each component alone was recovered where Pmax-min was directly proportional to its concentration. Liquid-liquid extraction technique was used for the semisolid dosage form where GEN was extracted with a mixture of chloroform: water (50:50, v/v); and the induced fluorescence obtained by derivatization with o-phthalaldehyde was measured at 419 nm after excitation at 359 nm. Accuracy and precision testing of the developed methods showed good results. Specificity of the methods was ensured and was successfully applied for the analysis of pharmaceutical formulation of the five components in combination. ICH guidelines were used for validation of the proposed methods. Statistical data were calculated, and the results were satisfactory revealing no significant difference regarding accuracy and precision.

Eu(III)-Sensitized Luminescence Probe for Determination of Tolnaftate in Pharmaceuticals and Biological Fluids.

A highly selective, sensitive, accurate, and reproducible luminescence procedure for determination of antifungal drug tolnaftate was developed. The introduced method was based on the formation of Europa Universalis III (Eu(III))-tolnaftate complex using sodium sulfite as a deoxygenated agent in the presence of acetate buffer (pH = 6) and micellar solution of anionic surfactant sodium dodecyl sulfate. The optimum conditions (effect of pH, buffer, surfactant, Eu(III), and sodium sulfite concentrations) for the luminescence signal were investigated and optimized. The luminescence signals were recorded at λex = 270 nm and λem = 460 nm. The method has a good linear response (0.2-130 µg/mL(-1)) between the luminescence intensity and the concentrations of the drug (r = 0.999), with a LOD 0.07 µg/mL(-1) and LOQ 0.2 µg/mL(-1). The luminescence signals of Eu (III)-tolnaftate-sodium dodecyl sulfate were found to be 200-fold more sensitive without the presence of micelle solution. The interferences of some additives, metals, amino acids, sugars, and other related pharmacological action drugs were examined and no interference was recorded. The proposed method was used for quick and simple determination of tolnaftate in its pharmaceuticals and biological fluids.

Assay of tolnaftate in human skin samples after in vitro penetration studies using high performance liquid chromatography.

Abstract: Tolnaftate, an antifungal of thiocarbamate class, is used topically in 1% formulations. Its penetration into skin layers is a prerequisite for tolnaftate action against dermatophytes. The aim of this work was to optimize and validate a simple, rapid, accurate and reproducible procedure for tolnaftate assay in human skin samples and to apply this procedure for in vitro tolnaftate penetration studies. High performance liquid chromatography (HPLC) method with UV detection was used to validate tolnaftate assay for linearity, specificity, accuracy, precision, limit of quantitation, limit of detection, drug extraction recovery and stability in skin extracts. In vitro tolnaftate penetration studies were carried out using flow-through diffusion cells, mounted with human skin. Epidermis and dermis, separated by heat-separation method, were extracted using ultrasonication in methanol. Linear range of the analytical procedure was within 0.6-100 pg/mL. The assay was specific, accurate (within-day and between-day recovery values were 98.2-104.2% and 98.7-101.4%, respectively) and precise (within-day and between-day imprecision was = 3.8%). Mean extraction recoveries of tolnaftate from epidermis and dermis were satisfactory and reaching 90%. In vitro skin penetration studies revealed that after application of 1% (w/w) tolnaftate solution in polyethylene glycol 400 for 24 hours, the mean amount of tolnaftate penetrating into the epidermis and dermis was 2.60 +/- 0.28 microg/cm2 and 0.92 +/- 0.12 microg/cm2, respectively. A validated reliable HPLC method could be recommended for biopharmaceutical evaluation of tolnaftate preparations and studies of pharmacokinetics in human skin after in vitro penetration studies.

Assay of tolnaftate and related impurities by isocratic supercritical fluid chromatography.

Tolnaftate, an antifungal drug (TF) and related impurities arising from synthesis, viz., N-methyl-m-toluidine (NMmT) and beta-naphthol-1-chlorothio carbamate (beta-NCTC) can be determined by supercritical fluid chromatography. Even though it was possible to elute TF completely with neat SCF CO2, the peaks of the impurities were found to merge. The chromatographic figures of merit of the three analytes such as retention time (tR), capacity factor (k), selectivity factor (alpha), no. of theoretical plates (N), were optimized. The three compounds can be resolved in 5 min on a Hypersil (250 x 4.0 mm) 5 mu, C18 column with supercritical carbon dioxide, modified with 1.96% methanol as the mobile phase at 9.81 MPa and at 40 degrees C. Detection was carried out at 220 nm. The data as evaluated by the linear regression least squares fit method gave linearity ranges from 0.2 to 10.0 microg/mL for TF and NMmT and 0.3 to 10.0 microg/mL for beta-NCTC with correlation coefficients > 0.99. The method was successfully employed to estimate levels of 0.01% for NMmT and 0.02% for beta-NCTC with respect to TF.

A liquid chromatographic method for the determination of tolnaftate in pharmaceutical formulations.

A simple LC method was developed and validated for the analysis of tolnaftate in various pharmaceutical formulations. This method did not require any complex sample extraction procedure. The chromatographic separation was achieved on a reversed-phase, C18 column with UV detection at 258 nm. This isocratic system was operated at ambient temperature and required 9 min of chromatographic time. The mobile phase consisted of methanol-aqueous potassium dihydrogen phosphate solution (80:20, v/v) at a flow rate of 1.5 ml min-1. Standard curves were linear over the concentration range of 1.0-51.0 micrograms ml-1. Within-day and between-day relative standard deviation values ranged from 0.7 to 2.9% and from 1.3 to 3.4%, respectively. This method was used to quantify tolnaftate in microcapsule, microsphere, cream, powder, liquid, liquid aerosol and powder aerosol formulations. This method was also used to study the stability of tolnaftate in solution during its extraction from microcapsule formulations.

Liquid chromatographic determination of tolnaftate in commercial products.

A liquid chromatographic (LC) method for the determination of the antifungal agent tolnaftate was developed. Isolation of the analyte was achieved by direct extraction or dilution with acetonitrile-water (80 + 20) followed by reverse-phase liquid chromatography using a C18 column. The mobile phase was acetonitrile-water (80 + 20) acidified with phosphoric acid. Detection was by UV absorption at a wavelength of 257 nm. The proposed procedure was applied to 20 consumer products comprising 6 formulation types, including solutions, powders, liquid and power aerosols, creams, and gels. The precision (RSD) for the products ranged from 0.23 to 1.16% (n = 5), and recoveries via fortification ranged from 98.1 to 103.0%. Six different brands of C18 columns were evaluated for use with the method. The overall simplicity and versatility of the method suggest possible adaptations to both regulatory and quality-control situations.