VOLUME 15, NO3, SEPT 1993

DETERMINATION OF GADOLINIUM AND SAMARIUM IN AQUEOUS-SOLUTION BY X-RAY-FLUORESCENCE SPECTROMETRY

A simple X-ray fluorescene (XRF) spectrometric method for the determination of gadolinium and samarium in aqueous solution has been developed. The sample solution was introduced to the XRF spectrometer directly in simple polyethylene bottle. Statistical evaluation helped to establish an analytical application of the method. Effects of various cations and anions on gadolinium and samarium intensity have been studied. Matrix effects due to these cations and anions have been rectified using standards of similar composition.read more

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RIAZ QADEER ,M SALEEM ,JAVED HANIF ,M AFZAL ,

AN INFRARED STUDY OF THE ADSORPTION OF CO ON SUPPORTED BIMETALLIC CATALYST SYSTEM

Ruthenium-manganese bimetallic catalysts supported on alumina and silica were prepared by coimpregnation of high surface area alumina and silica with RUCl3 and MnCl2. Infrared spectroscopy was used to investigate the adsorption of CO on the system. The study revealed that the presence of Mn not only produces a low frequency band but also results in the shift of IR bands. The data has been discussed in terms of ensemble and electronic effects and the change in surface geometry produced by the addition of Mn to die catalyst system.read more

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S TAJAMMUL HUSSAIN ,

STABILITY OF RESPONSE OF RED PMMA DOSIMETERS AT DIFFERENT TEMPERATURES

Dosimetric response and post-irradiation stability of commercially available 2 mm thick polymethyl methacrylate sheets have been investigated spectrophotometrically. The response curves at 615, 650 and 700 nm show linear response from 4 to 15 kGy. At 640 nm the response is linear from 4 to 20 kGy and with proper calibration, the dosimeter can be used up to 50 kGy. The stability of response of red PMMA dosimeter during post-irradiation swage at different storage temperature (-10, 26,35, 40, 50-degrees-C) has also been investigated at 640 nn. The dosimeters irradiated to 10 or 20 kGy and stored al room temperature show stable response for about three weeks, which is followed by slight and gradual decrease in response. The response during post-irradiation storage at lower temperature (-10 to 35-degrees-C) is stable over a period of 15 days while at higher temperature (45 and 55-degrees-C), fading of colour takes place which is faster at higher temperatures. These results show that the dosimetric characteristics of commercially available 2 mm thick red PMMA sheets are suitable for its possible application in radiation processing, such as sterilization of medical supplies and food irradiation, however storage of dosimeters at temperatures above 35-degrees-C should be avoided.read more

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GULZAR AHMAD ,SHAD A KHAN ,HASAN M KHAN ,MIAN S WAHID ,

GAS-CHROMATOGRAPHIC DETERMINATION OF CHLORIDE USING 2,4-DICHLOROPHENYLBOROIC ACID AS A DERIVATIZING REAGENT

2,4-Dichlorophenylboronic acid (CPBA) was examined as analytical reagent for the gas chromatographic determination of chloride, bromide and iodide. Flame Ionization Detector (FID) and glass column (90 cm x 4 mm) packed with SE-52 (2.5% w/w) on Universal B (65-85 mesh) were used to evaluate their GC behaviors. 2,4-Dichlorphenylboronic acid in the presence of excess of mercuric salt in the acidic solution (pH 0-2) reacts quantitatively with chloride, bromide and iodide to form dichlorophenylmercuric halides. The halides derivatives are easily extracted in chloroform with transfer of halide from aqueous to organic phase within 92-95%. Linear calibration ranges for GC determination of chloride, bromide and iodide were evaluated and extraction method has been developed for the determination of chloride at trace levels with detection limit of 0.06 mug/ml Cl- in original solution. Method has been used for the determination of chloride in tap water.read more

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W I STEPHEN ,A SARAFRAZ YAZDI ,

SOME ASPECTS OF SOLUTE CONCENTRATION AND ZONE AREA OF THE SPOT FOR DETECTION AND QUANTITATION OF AMINO-ACIDS BY PAPER-CHROMATOGRAPHY

Detection of amino acids at different concentrations have been carried out. R(f) values have been found to change with change of the concentration of amino acids. Quantitative estimation of the separated amino acids from mixture and juices (fruits and vegetables) have been accomplished using area measurement of the spots, both by square-counting and integral evaluation methods. Comparison of zone area with weight of the zone area reveals that the two methods give the same quantitative results.read more

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M AMIN UDDIN ,M AHMAD ,IFFAT HAMEED ,

OXIDATION OF L-METHIONINE BY POLY(PYRIDYL) IRON(III) COMPLEXES IN AQUEOUS-SOLUTIONS

The kinetics of oxidation of L-methionine by poly(pyridyl) iron (III) complexes in aqueous media have been investigated. The reactions are first order each in the oxidant, reductant and hydrogen ion. The immediate products are the respective poly(pyridyl) iron (II) complexes and methionine sulphoxide. Each reaction is discussed in terms of the outer-sphere mechanism.read more

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J FEMIIYUN ,ALLEN T EKUBO ,G ADEFIKAYO AYOKO ,

THE SIMULTANEOUS ANALYSIS OF THEOPHYLLINE, CAFFEINE AND THEIR METABOLITES IN HUMAN PLASMA BY HPLC

Theoplline, caffeine and their important metabolites were extracted from human plasma using newly developed solid support liquid/liquid extraction tubes. These substances were separated on a 3 mum ODS (250 x 4.6 mm i.d) column with a mobile phase gradient and detected with a UV diode array detector set at two wave lengths of 270 and 290 nm. The normal ranges for the plasma drug/metabolite molar ratios have been determined.read more

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A RAZAK SOMO ,S ALI ARBANI ,M Y KHAHAWER ,M A CHIPPA ,G ALI QURSHI ,

QUANTITATION OF AZIDE AND LEAD IN LEAD AZIDE BY VOLTAMMETRIC METHOD

A voltammetric method for quantitative determinations of azide and lead in lead azide is presented. The determination of azide is based on oxidation of azide ions at a carbon paste electrode and that of lead on reduction at a dropping-mercury electrode in a 0.1 M acetate solution at pH 4.6. This voltammetric method is also applied in determination of trace amounts of azide in evinronmental samples. The limit of detection is about 0.05 mg NaN3 per m3 of air, when 25 L of air is passed through 10 ml 0.2 M KOH for absorption of air.read more

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G ALI QURESHI ,A RAZAK SOMO ,SIKANDER ALI ARBANI ,M Y KHAHAWER ,

CIRCULAR-DICHROISM STUDIES ON COMPLEX-FORMING ABILITY OF ANTIBIOTIC D-CYCLOSERINE WITH VO(IV), CO(II) AND NI(II) IONS IN AQUEOUS-SOLUTION

CD studies have been utilized to investigate complex forming ability of antibiotic (+)-cycloserine (CCS) With VO2+, Co2+ and Ni2+ ions in aqueous solution. In solution, complex ions of the type [M(CCS)3]2+ are formed at pH 4.0 which show 2-3 Co''on bands between 16,129-28,011 cm-1 with molar ellipticity values 59.0-1838.6 dm3 mo-1 cm-1. At optimum conditions intensity of CD bands is linearly increased with concentration of the components between 1-10 x 10(-2) mol dm-3. CD bands are assigned to electronic transitions corresponding to lower symmetry of octahedral complexes.read more

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SYED RAUF ,MUHAMMAD JAMIL ,CHRISTY MUNIR ,NASIR AHMAD ,

IMPROVEMENT IN THE ELECTROSTATIC THEORY OF REVERSED-PHASE ION-PAIR CHROMATOGRAPHY TO INCLUDE THE ROLE OF ORGANIC MODIFIER

In this study, the electronic theory of ion-pair chromatography has been extended to include the role of organic modifier. This approach has increased the possibility to use organic modifier in the improvement of separation of ionic, non-ionic and ionized substances. The results accumulated shows that both the slope and the intercept of In K'vs. organic modifier concentration plot are predicted to increase the oppositely charged and to decrease for similarly charged solute ions.read more

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M A CHIPPA ,S A ARBANI ,M Y KHAHAWER ,A RAZAK SOMO ,G ALI QURESHI ,