http://blogs.najah.edu/author/emp_2249 An-Najah Blogs :: en-us Sat, 27 Jul 2024 15:01:33 IDT Sat, 27 Jul 2024 15:01:33 IDT [email protected] [email protected] http://blogs.najah.edu/staff/emp_2249/article/Enhancement-of-n-GaAs-characteristics-by-combined-heating-cooling-rate-and-metalloporphyrin-modification-techniquesPublished ArticlesDifferent modification techniques namely preheating controlling the cooling rate and modification with tetra-4-pyridylporphyrinatomanganeseIII have been used to enhance photoelectrochemical characteristics of n-GaAs electrodes in light-to-electricity conversions Combination of such three techniques together yielded electrodes with better darkcurrent density vs potential plots and photocurrent density vs potential plots Higher efficiency and stability were also observed for electrodes modified by such combined techniques Solid State Sciences Volume 6 Issue 1 January 2004 Pages 139-146 http:dxdoiorg101016jsolidstatesciences200311007 http://blogs.najah.edu/staff/emp_2249/article/Determination-of-Aminophylline-by-Cathodic-Stripping-VoltammetryPublished ArticlesAminophylline is determined by cathodic stripping voltammetry CSV in BR buffer pH 75 at a hanging mercury drop electrode The detection limit was 3x10-8 M after 60 s accumulation at -060 V versus AgAgCl reference electrode The linear range demonstrated up to 5x10-7 M using CSV The interference caused by some purine derivatives anions and some metal cations on the peak current was studied The peak current is enhanced by theophylline some methylguanines and copper II while it decreased or disappeared by citrate chloride and Triton X-100 surfactant The method has good sensitivity and its application to pharmaceutical samples is possible Keywords: Determination of aminophylline stripping voltammetry cathodic stripping voltammetry adsorptive voltammetry dosage forms An-Najah University Journal for Research - Natural Sciences A ISSN: 1727-2114 Volume 15 2001 Pages: 021-028http://blogs.najah.edu/staff/emp_2249/article/Voltammetric-and-spectrophotometric-determination-of-nizatidine-in-pharmaceutical-formulationsPublished ArticlesTwo methods are described for quantitative determination of nizatidine The first is a cathodic stripping voltammetric method which is based on the accumulation of the compound at the hanging mercury drop electrode The adsorptive stripping response was evaluated with respect of accumulation time potential concentration pH and other variables A linear calibration graph was obtained over the range 30 10-8 - 10 10-6 M with a detection limit 30 10-8 M after a 20s accumulation time at -02 V accumulation potential On the other hand it was found that the detection limit could be lowered to 10 x 10 8 M after 180s accumulation time at -02 V accumulation potential The relative standard deviation was in the range 12-20 for six measurements The tolerance amounts of the common excipients have also been reported The second is a spectrophotometric method which is based on the formation and extraction of the ion-pair complex formed between nizatidine and either bromocresol green or bromothymol blue The extracted colored ion-pair complexes absorb at 416 nm The effect of different factors such as: type of organic solvent pH reagent concentration number of extraction times shaking time temperature and the tolerance amount of the common excipients have been reported The calibration graph was linear in the range 60 x 107 - 18 x 10-5 M with a detection limit of 60 10-7 M and molar absorptivity of 21 x 104 l mol-1cm-1 when using bromocresol green while the calibration graph was linear in the range 30 x 10-7 - 11 x 10-5 M with a detection limit of 30 x 10-7 M and molar absorptivity of 32 104l mol-1cm-1 when using bromothymol blue The spectrophotometric methods offer alternative methods with reasonable sensitivity selectivity and accuracy with relative standard deviation in the range 21-60 and 12-47 for six measurements when using bromothymol blue and bromocresol green respectively The proposed two methods were applied for the determination of nizatidine in commercially available dosage forms A comparison between the voltammetric and the extraction-spectrophotometric methods was also reported Mikrochimica acta 2000 vol 134 no3-4 pp 153-160 19 ref http://blogs.najah.edu/staff/emp_2249/article/Electrochemical-study-on-the-determination-of-tinidazole-in-tabletsPublished ArticlesThe electrochemical reduction of tinidazole has been carried out in aqueous solution in the pH range 18113 by differential-pulse DP polarography Tinidazole exhibits one or two reduction peaks depending on pH In strongly acidic solution pH45 one reduction peak was obtained and it was suitable for analytical purposes A method for the determination of tinidazole by DP polarography in BrittonRobinson buffer of pH 30 which allows quantification over the range 003730 gml was proposed The method was successfully applied to the determination of tinidazole in tablets with mean recovery and relative standard deviation of 987 and 3 respectively Excipients did not interfere in the determination Journal of Pharmaceutical and Biomedical Analysis Volume 21 Issue 4 December 1999 Pages 881-886 http://blogs.najah.edu/staff/emp_2249/article/Extractional-spectrophotometric-determination-of-famotidine-in-pharmaceutical-formulationsPublished ArticlesJournal of Pharmaceutical and Biomedical Analysis Volume 21 Issue 2 1 November 1999 Pages 459-465 http:dxdoiorg101016S0731-70859900139-9http://blogs.najah.edu/staff/emp_2249/article/Adsorptive-stripping-voltammetric-determination-of-dimenhydrinate-at-a-hanging-mercury-drop-electrodePublished ArticlesDimenhydrinate exhibits a single adsorptive stripping peak at a hanging mercury drop electrode after accumulation at 00V vs AgAgCl electrode at pH 38 acetate buffer The addition of trace amounts of copper ions enhanced the dimenhydrinate peak and its height depends on the concentration of each dimenhydrinate and Cu2 The adsorptive stripping response was evaluated with respect to accumulation time and potential concentration dependence electrolyte the presence of other purines surfactants and other metal ions and some variables The calibration graph for dimenhydrinate determination is linear over the range 2010820107 M pre-concentration for 60s The correlation factor is found to be 0985 and RSD is 32 at 10107 M Detection limit is 10108 M after 5 min accumulation The determination of dimenhydrinate in pharmaceutical formulations by the proposed method is also reported Microchimica Acta Volume 130 Number 3 September 1999 http:wwwspringerlinkcomcontentp26939m8572p6134 http://blogs.najah.edu/staff/emp_2249/article/Electrochemical--Reduction--and-Determination-of--AzathioprinePublished ArticlesSensitive method for the determination of azathioprine by differential-pulse polarography DPP is described The cyclic voltammograms demonstrate the adsorption of the drug on the mercury electrode The effect of different experimental parameters affecting the drug determination eg pH supporting electrolyte nature accumulation potential accumulation time presence of copper ions and other operational parameters are also mentioned In pH 75 Britton-Robinson buffer the calibration graph for the determination of azathioprine was linear in the range 50x10-5 - 50x10-7 M with RSD of 13 The detection limit was found to be 10x10-8 M The degree of interference from some other purines anions and metal ions on the azathioprine peak was evaluated The method was applied to the determination of drug in commercially available dosage formshttp://blogs.najah.edu/staff/emp_2249/article/Adsorptive-cathodic-stripping-voltammetric-determination-of-theophylline-at-a-hanging-mercury-drop-electrodePublished ArticlesAdsorptive stripping voltammetry was used for the determination of trace amounts of theophylline Theophylline in pH 75 Britton-Robinson buffer gives an adsorptive stripping voltammetric peak at a hanging mercury drop electrode at 038 V at accumulation potential 00 V versus AgAgCl The optimum conditions of pH accumulation potential and accumulation time were studied using differential-pulse voltammetry The calibration graph for the determination of theophylline was linear in the range 0636 g l1 with a relative standard deviation of 2 The detection limit was 06 g l1 after 180 s accumulation at 00 V The effect of some purine compounds and metal ions on the peak height of theophylline was studied The presence of CuII ions enhanced the theophylline peak and the behaviour of the theophyllinecopper complex was investigated The method was applied to the determination of the drug in commercially available dosage forms A comparison of the proposed method with previously reported methods was also made Analyst 1994 119 1967 - 1970 http:wwwrscorgpublishingjournalsANarticleasp?doi=an9941901967 http://blogs.najah.edu/staff/emp_2249/article/Sensitive-adsorptive-stripping-voltammetric-determination-of-xanthine-and-its-derivativesPublished ArticlesSensitive cathodic stripping voltammetric procedures for trace determination of xanthine I 7-methylxanthine II and 17-dimethylxanthine III are reported The methods are based on the accumulation of the copperI complexes of the compounds on the hanging mercury drop electrode The adsorptive stripping response was evaluated with respect to accumulation time potential concentration pH and other variables Linear calibration graphs were obtained over the range from 20 10-8 to 20 10-9 M; the limits of detection with accumulation times of 4 min for I and III and of 6 min for II were calculated to be 50 l0-10 10 10-9 and 5 10-10 M respectively Possible interferences by other purine derivatives were examined The simultaneous determination of 17-dimethylxanthine paraxanthine and theophylline is possible by the proposed method Electroanalysis Volume 7 Issue 10 Pages 975 - 979 1994 http:www3intersciencewileycomjournal110447221abstract?CRETRY=1SRETRY=0 http://blogs.najah.edu/staff/emp_2249/article/Determination-of-nanomolar-levels-of-guanine-by-differential-pulse-adsorptive-cathodic-stripping-voltammetry-of-its-copperII-complex-Published ArticlesGuanine is determined at the 501010 20107 moll level by differential-pulse adsorptive stripping voltammetry at a hanging mercury drop electrode using the reduction peak of its copper II complex at 021 V vs Ag-AgCl electrode The optimum analytical conditions were found to be Britton-Robinson buffer solution pH 48 an accumulation potential of 00 V and an accumulation time of 3 min Under these conditions the detection limit is 501010 moll and the relative standard deviation 26 for 10107 moll guanine The method is compared with the previous voltammetric methods The presence of some purine derivatives does not interfere Fresenius Journal of Analytical Chemistry Volume 348 Number 11 November 1994 http:wwwspringerlinkcomcontentw23164221r40383t