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Njuguna NM, Abuga KO, Kamau FN, Thoithi GN. "A liquid chromatography method for simultaneous determination of diphenhydramine, promethazine, chlorpheniramine and ephedrine in cold-cough syrups." Pharmaceutical Chemistry Journal. 2017;51(2):153-158. Abstract

A simple, rapid isocratic liquid chromatography method was developed for the simultaneous determination of diphenhydramine, promethazine, chlorpheniramine, and ephedrine in cold-cough syrups commonly available in the Kenyan market. The influence of the percentage of organic modifier, ion pairing agent, buffer concentration as well as pH and column temperature on the selectivity with respect to analytes was investigated. Optimum chromatographic separation was achieved using a C18 Gemini NX column (250 mm × 4.6 mm, 5 μm) maintained at 40°C and a mobile phase comprising methanol –triethylamine-0.2 M ammonium acetate pH 5.0 -water mixture (50:0.15: 40:9.85, v/v) delivered at a flow rate of 1.0 mL/min. Upon validation, the proposed liquid chromatography method satisfied the International Committee on Harmonization acceptance criteria for linearity, sensitivity, precision, and robustness. The method was applied in the analysis of commercial samples obtained from Nairobi County, Kenya. The method can be used in routine analysis of cold-cough syrups containing the specified compounds.

Keywords: diphenhydramine; promethazine; chlorpheniramine; ephedrine, cold-cough syrups.

Gachangaga PN, Amugune BK, Ogeto JO, Abuga KO. "A liquid chromatographic method for the simultaneous determination of amlodipine, valsartan and hydrochlorothiazide in tablets." East Cent. Afr. J. Pharm.. 2014;17(2):25-34. Abstract

A simple, rapid, sensitive, specific, accurate, precise and fast high performance liquid
chromatographic method for the determination of antihypertensive drugs amlodipine,
valsartan and hydrochlorothiazide singly or in combination was developed and
validated. Separation of the analytes was achieved on a Hypersil C-18 (250 mm × 4.6
mm, 5 μm) column using a mobile phase consisting of acetonitrile-KH2PO4 pH 3.0-
water (75:6:19 % v/v/v) delivered at 1 ml/min, UV detection at 229 nm and 40 oC
column temperature. The precision of the method was demonstrated through
repeatability (coefficient of variation = 0.298-0.724) as well as intermediate precision
(coefficient of variation = 0.435-1.412). The detector response was linear over the 25-
150 % range with R2 ≥ 0.99 for each of the three analytes. The limit of detection for
hydrochlorothiazide, valsartan and amlodipine were 10.72, 21.20 and 14.45 ng, while
the limits of quantification were 35.76, 71.23 and 48.16 ng, respectively. The method
showed satisfactory robustness and accuracy with a recovery of 99.7-100.6 %. The
method was applied in the assay of 6 commercial products containing drugs under
study. The results obtained revealed quality problems among the samples analyzed.

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