Transfer of TLC screening methods designed for use in developing countries to quantitative HPTLC-densitometry methods for diazepam and amodiaquine tablets

Abstract

Summary. Transfer of two rapid thin-layer chromatography (TLC) screening methods used to detect markedly substandard and fake pharmaceutical products to quantitative high-performance TLC (HPTLC)-densitometry methods is demonstrated using a model procedure that was published earlier. These TLC methods for diazepam and amodiaquine are contained in a Compendium of methods by Kenyon and Layloff and a Minilab method manual from Global Pharma Health Fund E.V., respectively, for use in countries with limited resources. Merck HPTLC Premium Purity silica gel 60 F 254 glass plates, automated standard and sample solution application with a CAMAG Linomat 4, and automated densitometry with a CAMAG Scanner 3 were used for detection, identification, and quantification. Sample peak identity and purity validation were carried out by spectral comparison checks available in the winCATS software. Accuracy was estimated by the standard addition approach with overspotting standard and sample solutions. HPTLC gives better efficiency, selectivity, and resolution than TLC, and the new methods overcome the deficiencies in technology related to manual application and visual zone comparison that do not allow the Compendium and Minilab TLC procedures to support regulatory compliance actions. These new methods can be fully validated according to the International Conference on Harmonization guidelines or by interlaboratory studies if required by their applications.

Development of Quantitative HPTLC-Densitometry Methods Following a Model Approach for Transfer of TLC Screening Methods for Pharmaceutical Products of Metformin HCL, Potassium Clavulanate, Caffeine, Fluoxetine HCL, and Gabapentin

“…General preparation procedures were carried out as described earlier [1][2][3] unless otherwise specified. All standards and ground (by mortar and pestle) tablets or capsule contents were dissolved with the aid of 10 min each of magnetic stirring and sonication before syringe filtration to remove undissolved excipients prior to further dilution or direct application.…”

“…Detailed HPTLC-densitometry methods and instruments were described earlier [1][2][3][6][7][8][9][10][11][12]. Silica gel 60 F 254 Premium Purity HPTLC glass plates (20 x10 cm; EMD Millipore Corp., Billerica, MA, a division of Merck KGaA, Darmstadt, Germany; Part No.…”

“…The Scanner 3 winCATS software automatically created calibration curves (linear or 2 nd order polynomial) based on scan areas versus standard weights applied, interpolated weights of drugs in bracketed samples based on scan areas, and tested peak purity and identity of the sample based on spectral comparison. Accuracy of the developed methods was validated by using standard addition with a 70-130% calibration curve as described earlier [3]. …”

“…A model process was previously described [1][2][3] for transfer of qualitative/semiquantitative thin-layer chromatography (TLC) screening methods for pharmaceutical products with quality defects contained in the Global Pharma Health Fund E.V. (GPHF) Minilab manual [4] or U.S. Food and Drug Administration Compendium of Unofficial Methods for Rapid Screening of Pharmaceuticals by Thin Layer Chromatography [5] to quantitative highperformance TLC (HPTLC)-densitometry methods.…”

“…(GPHF) Minilab manual [4] or U.S. Food and Drug Administration Compendium of Unofficial Methods for Rapid Screening of Pharmaceuticals by Thin Layer Chromatography [5] to quantitative highperformance TLC (HPTLC)-densitometry methods. The model process was applied earlier to formulations containing acetylsalicylic acid, acetaminophen, ibuprofen, and chlorpheniramine maleate [1]; mebendazole, diphenhydramine HCl, amodiaquine, and artesunate [2]; amodiaqine and diazepam [3]; lumefantrine + artemether [6]; albendazole, amodiaquine + artesunate [7]; pyrazinamide + ethambutol + isoniazid + rifampicin [8]; quinine sulfate, mefloquine, and dihydroartemisinin + piperaquine phosphate [9]; azithromycin, imipramine HCl, and sulfadoxine + pyrimethamine [10]; clarithromycin, azithromycin, and amodiaquine + artesunate [11]; and cefixime, cefuroxime axetil, cephalexin hydrate, ciprofloxacin HCl, levofloxacin, and metronidazole [12].…”