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A comparative study of ICH validated novel spectrophotometric techniques for resolving completely overlapping spectra of quaternary mixtures.

Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy (2015-11-01)
Nouruddin W Ali, Nada S Abdelwahab, M Abdelkawy, Aml A Emam
ABSTRACT

A pharmaceutically marketed mixture of Yohimbine, Alpha-tocopheryl acetate, Niacin, and Caffeine co-formulated as a promising therapy for erectile dysfunction. Simultaneous determination of the aforementioned pharmaceutical formulation without prior separation steps was applied using mean centering of ratio spectra and triple divisor spectrophotometric methods. Mean centering of ratio spectra method depended on using the mean centered ratio spectra in three successive steps which eliminated the derivative steps and so the signal to noise ratio was improved. The absorption spectra of the prepared solutions were measured in the wavelength range of 215-300 nm in the concentration ranges of 1-15, 3-15, 1-20, and 3-15 μg mL(-1) for Yohimbine, Alpha-tocopheryl acetate, Niacin, and Caffeine, respectively. The amplitudes of the mean centered third ratio spectra were measured at 250 nm and 268 nm for Yohimbine and Alpha-tocopheryl acetate, respectively and at peak to peak 272-273 and 262-263 nm for Niacin and Caffeine, respectively. In triple divisor method each drug in the quaternary mixture was determined by dividing the spectrum of the quaternary mixture by a standard spectrum of a mixture containing equal concentrations of the other three drugs. First derivative of these ratio spectra was obtained where determination could be achieved without any interference from the other three drugs. Amplitudes of 1-15, 3-15, 1-15, and 3-15 μg mL(-1) were used for selective determination of Yohimbine, Alpha-tocopheryl acetate, Niacin, and Caffeine, respectively. Laboratory prepared mixtures were analyzed by the developed novel methods to investigate their selectivity also, Super Act® capsules were successfully analyzed to ensure absence of interference from additives. The developed methods were validated according to the ICH guidelines. The proposed methods were statistically compared with each other and with the reported methods; using student t-test, F-test, and one way ANOVA, where no significant difference was found with respect to accuracy and precision.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
甲醇, anhydrous, 99.8%
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甲醇, ACS reagent, ≥99.8%
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氯仿, contains 100-200 ppm amylenes as stabilizer, ≥99.5%
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氯仿, anhydrous, ≥99%, contains 0.5-1.0% ethanol as stabilizer
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咖啡因, powder, ReagentPlus®
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氯仿, anhydrous, contains amylenes as stabilizer, ≥99%
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甲醇, puriss. p.a., ACS reagent, reag. ISO, reag. Ph. Eur., ≥99.8% (GC)
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氯仿, contains ethanol as stabilizer, ACS reagent, ≥99.8%
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甲醇, Laboratory Reagent, ≥99.6%
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氯仿, puriss. p.a., reag. ISO, reag. Ph. Eur., 99.0-99.4% (GC)
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咖啡因, anhydrous, 99%, FCC, FG
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咖啡因, Sigma Reference Standard, vial of 250 mg
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甲醇, ACS spectrophotometric grade, ≥99.9%
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氯仿, contains amylenes as stabilizer, ACS reagent, ≥99.8%
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甲醇, BioReagent, ≥99.93%
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甲醇, Absolute - Acetone free
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甲醇, ACS reagent, ≥99.8%
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氯仿, ACS spectrophotometric grade, ≥99.8%, contains 0.5-1.0% ethanol as stabilizer
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咖啡因, meets USP testing specifications, anhydrous
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氯仿, ReagentPlus®, ≥99.8%, contains 0.5-1.0% ethanol as stabilizer
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甲醇, puriss., meets analytical specification of Ph Eur, ≥99.7% (GC)
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氯仿, biotech. grade, ≥99.8%, contains 0.5-1.0% ethanol as stabilizer
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甲醇, HPLC Plus, ≥99.9%, poly-coated bottles
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甲醇 溶液, NMR reference standard, 4% in methanol-d4 (99.8 atom % D), NMR tube size 5 mm × 8 in.