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Abstract
DETERMINATION OF 2′,3′‐DIDEOXYINOSINE USING IRON (II) PHTHALOCYANINE MODIFIED CARBON PASTE ELECTRODE by Kenneth I. Ozoemena and Raluca‐Ioana Stefan, Department of Chemistry, University of Pretoria, Pretoria, South Africa and Tebello Nyokong, Department of Chemistry, Rhodes University, Grahamstown, South Africa
ABSTRACT: An amperometric sensor, based on carbon paste impregnated with iron (II) phthalocyanine complex (FePc), has been constructed for the assay of anti‐HIV agent dideoxyinosine (didanosine, DDI). Using chronoamperometry (E = +1.04 V versus Ag/AgCl) technique, the amperometric sensor can be used reliably for dideoxyinosine assay at pH 7.4 phosphate buffer in the 1.5–9.5 nmol/L concentration range with a detection limit of 5.7 × 10−10 mol/L. The surface of the electrode can easily be regenerated by simple polishing, obtaining a fresh surface ready for use in a new assay. The new amperometric sensor proved to be highly reliable for the assay of dideoxyinosine purity in raw material as well as for the uniformity content test of Videx® tablets.
Analytical Letters, 37(13), 2641–2648, 2004
Abstract
CHEMOMETRIC OPTIMIZATION OF A RP‐HPLC METHOD FOR THE SIMULTANEOUS ANALYSIS OF ABACAVIR, LAMIVUDINE, AND ZIDOVUDINE IN TABLETS by Predrag Djurdjevic, Faculty of Science, Chemistry Department, Kragujevac; Aleksandra Laban and Slavko Markovic, Institute of Pharmacy of Serbia, Belgrade and Milena Jelikic‐Stankov, Faculty of Pharmacy Belgrade, State Union of Serbia and Montenegro
ABSTRACT: A method has been developed and validated for the separation of abacavir, lamivudine, and zidovudine by high‐performance liquid chromatography (HPLC) on a C18 column with uv detection at 270 nm. The optimal conditions for separation were determined with the aid of a “critical resolution map” technique using the program DryLab®. The effect of simultaneously varying the pH and proportion of methanol in the mobile phase was studied to optimize the separation. A response surface diagram was used to study the interaction between factors determining the separation. The mobile phase composition that provides an optimal resolution of components in an acceptable elution time is water:methanol (60:40 v/v) + 0.2% TEA and pH = 3.20 (pH adjusted with H3PO4). A method is applied for the analysis of Trizivir® tablets (Glaxo Wellcome, UK). The powdered tablets were extracted with methanol:water (50:50 v/v) mixture and after addition of stavudine as an internal standard subjected to HPLC analysis and assayed by comparison of analyte to internal standard peak areas to concentration ratios.
Analytical Letters, 37(13), 2649–2667, 2004
Abstract
MEMBRANE PRECONCENTRATION OF NALIDIXIC AND PIROMIDIC ACIDS AND SIMULTANEOUS DETERMINATION USING A SYNCHRONOUS SOLID‐PHASE PHOSPHORESCENCE APPROACH by L. F. Capitán‐Vallvey, Osama M. A. Al‐Barbarawi, M. D. Fernández‐Ramos, and R. Avidad, Department of Analytical Chemistry, Research Group Solid Phase Spectrometry, Faculty of Sciences, University of Granada, Granada, Spain
ABSTRACT: A preconcentration membrane for the retention and phosphorimetric determination of pharmaceuticals nalidixic and piromidic acids is proposed. The membrane has a circular zone of plasticized PVC adhered to the surface of a polyester strip, which constitutes the preconcentration area where the analytes are retained by absorption from a solution that contains it. Measurement of intrinsic phosphorescence in the synchronous phosphorescence spectra performed at 281/371 nm for nalidixic acid and 331/471 nm for piromidic acid make the resolution of the mixture possible. The applicable concentration range, detection limit, and precision (as relative standard deviation) are from 0.3 to 3.0 mg · l−1, 0.08 mg · l−1, and 5.1% for nalidixic acid and from 0.03 to 0.15 mg · l−1, 0.002 mg · l−1, and 5.2% for piromidic acid. The method was applied to the determination of residues of both pharmaceuticals in cow milk and human urine.
Analytical Letters, 37(13), 2669–2683, 2004
Abstract
GRAPHITE FURNACE ATOMIC ABSORPTION SPECTROMETRIC DETERMINATION OF RHODIUM AFTER ONLINE ION‐EXCHANGE PRECONCENTRATION by Fuensanta Sánchez Rojas, Catalina Bosch Ojeda, and José M. Cano Pavón, Department of Analytical Chemistry, Faculty of Sciences, University of Málaga, Málaga, Spain
ABSTRACT: A method for the determination of rhodium in different samples at trace levels is presented. The investigated metal is preconcentrated on a chelating resin microcolumn [1,5‐Bis(2‐pyridyl)‐3‐sulphophenyl methylene thiocarbonohydarzide (PSTH) immobilized on an anion‐exchange resin (Dowex 1x 8‐200)] placed in the autosampler arm. The modification of the autosampler in the tubing line and circuit allowed either the flow of the sample through the column or the operation of the autosampler in the normal mode, where microlitres of 4 M HNO3, which acts as the elution agent, pass through the microcolumn eluting Rh(III), which is directly deposited in the graphite tube as a drop of a precisely defined volume. The detection limit is 0.3 ng mL−1. Linearity is maintained in the concentration range 0–50 ng mL−1 for rhodium, with correlation factor of 0.999 and relative standard deviation of 1.8% for 10 ng mL−1 of Rh. The effects of various parameters such as pH, concentration and volume of eluent, sample loading time, sample flow rate, and interference of a large number of metal ions and anions on the determination of this metal was studied in detail to optimize the conditions for their determination in various samples. The method is found to be highly selective, fairly sensitive, simple, rapid and economical, and may be safely applied to their determination in different complex materials, such as environmental samples and catalysts.
Analytical Letters, 37(13), 2685–2700, 2004
Abstract
DETERMINATION OF MAJOR AND RARE EARTH ELEMENTS IN BASTNASITE ORES BY ICP‐AES by Serpil Yenisoy‐Karakaş, Eftade O. Gaga, Aysun Doğangün, and Semra G. Tuncel, Chemistry Department, Middle East Technical University, Ankara, Turkey
ABSTRACT: Analytical procedure for direct determination of La, Ce, Sm, Eu, Y, Yb, Pr, and Nd by ICP‐AES in bastnasite ores without need for the initial separation or preconcentration of the rare earth elements (REEs), has been developed. Besides rare earth elements, five major elements (Al, Ca, Ba, Fe, and Mg) were also measured. Two standard reference materials (GSP‐2 and STM1 purchased from the U.S. Geological Survey) were selected to test the accuracy of the method. Good agreement was generally achieved. Based on these experiments it appeared that direct ICP‐AES method should be attractive and well suited for the routine determination of REEs in rare earth ores.
Analytical Letters, 37(13), 2701–2709, 2004
Abstract
ADDING AUXILIARY ELECTRODE—AN EFFECTIVE METHOD FOR ENHANCING SIGNAL‐TO‐NOISE RATIO IN NANOSPRAY MASS SPECTROMETRY by Xuejiao Xu, Jianjun Zhai, Wenqing Shui, Guobin Xu, and Pengyuan Yang, Department of Chemistry, Fudan University, Shanghai, China and Jianjun Zhai, Department of Chemistry, Lanzhou University, Lanzhou, China
ABSTRACT: A simple arrangement for improving signal‐to‐noise ratio (S/N) in a nanoelectrospray procedure using an auxiliary electrode has been investigated. The auxiliary electrode (aluminium plate in the present experiments) with different size and shape was placed near the home made nanoelectrospray tip and various electrical potential was added, which could dramatically disturb nanoelectrospray properties. This arrangement was employed to enhance S/N of tips spraying reserpine solution at different concentrations under the control experimental conditions. The comparison of S/N of nanoelectrospray with and without auxiliary electrode gives an explicit trend that auxiliary electrode could improve sensitivity of nanoelectrospray to at least twofold.
Analytical Letters, 37(13), 2711–2720, 2004
Abstract
BATCH AND FIA SPECTROPHOTOMETRIC DETERMINATION OF SODIUM AND POTASSIUM IONS VIA REACTION WITH SULFOPHTHALEIN DERIVATIZED CROWN ETHERS by Irena Nemcova, Petr Rychlovský, and Lenka Antalova, Department of Analytical Chemistry, Faculty of Sciences, Charles University of Prague, Prague, Czech Republic; and Simon Cihelník; Department of Organic Chemistry, Institute of Chemical Technology, Prague, Czech Republic; and Department of Chemistry and Chemistry Didactics, Faculty of Education, Prague, Czech Republic
ABSTRACT: The mono‐ and bis‐ monoaza‐15‐crown‐5‐ethers and monoaza‐18‐crown‐6‐ethers, bound to the sulphophthalein dyes phenol and bromophenol red, were synthesized. Their complexing properties were studied and, on this basis, these substances were found to be suitable spectrophotometric reagents for nonextraction batch and flow‐through (FIA) determination of Na+ and K+ ions in ethanol medium. The optimal reaction and flow conditions were found and a method was developed for determination of both ions. Although the reactions are not fully selective toward both ions, it is possible to carry out the determination of both ions simultaneously by using a suitably selected reagent at certain concentration ratios. The results are comparable for both dyes and for the mono‐ and bis‐compounds; the size of the cavity in the crown ether is decisive.
Analytical Letters, 37(13), 2721–2738, 2004
Abstract
ENHANCED FLUORESCENCE OF EU‐GD‐OXOLINIC ACID‐CTMAB SYSTEM AND ITS APPLICATION TO THE DETERMINATION OF EUROPIUM (III) AT ULTRA‐TRACE AMOUNT by Xia Wu, Yuebo Wang, Shuna Sun, Jinghe Yang, Changying Guo, Yunxiao Han, and Aiqin Du, Key Lab of Colloid and Interface Chemistry of Education Ministry, School of Chemistry and Chemical Engineering, Shandong University, Shandong, P. R. China
ABSTRACT: A fluorescence enhancement phenomenon in the europium‐oxolinic acid (OA)‐CTMAB fluorescence system was observed when Gd3+ was added. The fluorescence intensity of the systems was measured (λex = 345 nm, λem = 612 nm) at pH 7.25. Under optimum conditions, a linear relationship between the enhanced fluorescence intensity and the Eu3+ concentration in the range of 2.0 × 10−10 − 1.0 × 10−7 mol/l was observed. The detection limit of Eu3+ was 5.2 × 10−12 mol/l (S/N = 3). This method was used for the determination of trace amounts of europium in rare earth samples with satisfactory results.
Analytical Letters, 37(13), 2739–2752, 2004
Abstract
POLAROGRAPHIC AND VOLTAMETRIC DETERMINATION OF CARCINOGENIC NITROBIPHENYLS AT A STATIC AND HANGING MERCURY DROP ELECTRODE by Radek Štěpán, Jiří Barek, and Jiří Zima, UNESCO Laboratory of Environmental Electrochemistry, Department of Analytical Chemistry, Charles University, Prague, Czech Republic; Viktor Mejstřík, Center for Ecology, Toxicology and Analysis, Research Institute for Organic Syntheses, Pardubice‐Rybitví, Czech Republic; and Josino C. Moreira, CESTEH/ENSP/FIOCRUZ, Rio de Janeiro, Brazil
ABSTRACT: A number of environmentally important substances exhibit genotoxic or ecotoxic properties leading to the need for sensitive and selective methods for their determination. Differential pulse polarography (DPP) and DC tast polarography (DCTP) at a static mercury drop electrode (SMDE) were used for the determination of trace amounts of carcinogenic nitrobiphenyls, namely 2‐nitrobiphenyl (2‐NBP), 3‐nitrobiphenyl (3‐NBP), and 4‐nitrobiphenyl (4‐NBP) within the concentration range from 2 · 10−7 to 1 · 10−4 mol · l−1 for DC tast polarography and from 2 · 10−8 to 1 · 10−4 mol · l−1 for DPP using a Britton‐Robinson buffer—methanol (1:1) mixture with resulting pH 12 as a base electrolyte. Differential pulse voltammetry (DPV) at a hanging mercury drop electrode (HMDE) is applicable within the concentration range from 2 · 10−8 to 1 · 10−5 mol · l−1. The above mentioned techniques were used for the analysis of mixtures of carcinogenic nitrobiphenyls.
Analytical Letters, 37(13), 2753–2770, 2004
Abstract
RAPID CAPILLARY ELECTROPHORETIC METHOD FOR TRACE CHROMIUM SPECIATION USING A ZWITTERIONIC ISOELECTRIC POLYMER COATED CAPILLARY AND PHOTODIODE ARRAY DETECTION by Marion King and Brett Paull, National Centre for Sensor Research, School of Chemical Sciences, Dublin City University, Dublin, Ireland and Mirek Macka, Australian Centre for Research on Separation Science, School of Chemistry, Faculty of Science, Engineering and Technology, University of Tasmania, Australia
ABSTRACT: A capillary electrophoretic method has been developed for the rapid screening of water samples for chromium (III) and chromium (VI). Chromium (III) and (VI) were separated as the anionic species, chromate and chromium pyridinedicarboxylate (CrL2 −1), utilising simple precapillary complexation with 2,6‐pyrinedicarboxylic acid (PDCA). The two species were separated using a 30 mM phosphate buffer (pH 6.4) containing 10 mM of N‐carboxymethylated polyethyleneimine (CMPEI) to totally suppress the EOF. The relatively high buffer concentration allowed large sample volumes to be injected electrokinetically without introducing substantial peak broadening. Using a short 31 cm capillary, chromate, excess PDCA and chromium‐PDCA were separated in under 2.5 min, without interference from other matrix anions or cations present in nonsaline natural water samples. Photodiode array detection allowed the two chromium species to be simultaneously monitored at their optimum absorbance wavelengths (270 and 370 nm) and allowed enhanced peak identification. Detector response was shown to be linear over the range 0.2–1.6 mg/L and detection limits for both species of 20 µg/L in standard solutions were possible.
Analytical Letters, 37(13), 2771–2787, 2004
Abstract
DETERMINATION OF PHENOLIC COMPOUNDS IN THE HULL AND FLOUR OF BUCKWHEAT (FAGOPYRUM ESCULENTUM MOENCH) BY CAPILLARY ELECTROPHORESIS WITH ELECTROCHEMICAL DETECTION by Youyuan Peng, Fanghua Liu, and Jiannong Ye, Department of Chemistry, East China Normal University, Shanghai, P R China and Youyuan Peng, Department of Chemistry, Quanzhou Normal University, Fujian, P.R. China
ABSTRACT: A simple, reliable and reproducible method, based on capillary electrophoresis with electrochemical detection (CE‐ED), for the determination of phenolic compounds of buckwheat (Fagopyrum esculentum Moench) hulls and flour was reported. The mainly phenolic components consist of (−)‐epicatechin, rutin, hyperoside, and quercetin. Operated in a wall‐jet configuration, a 300 µm diameter carbon disk electrode was used as the working electrode, which exhibits good response at +0.90 V (versus SCE) for all relevant analytes. The potential effects of working electrode, pH and concentration of buffer, separation voltage, and injection time on CE‐ED were investigated. Under the optimum conditions, the analytes can be separated in a 50 mmol/L borate buffer (pH = 8.7) within 16 min. The response was linear over three orders of magnitude with detection limit (S/N = 3) ranging from 2 × 10−7 g/mL to 5 × 10−7 g/mL for all analytes. This method has been used for the determination of phenolic compounds in buchwheat (Fagopyrum esculentum Moench) hulls and flour, and the assay result was satisfactory.
Analytical Letters, 37(13), 2789–2803, 2004
Abstract
HPLC SEPARATION OF NEUTRAL, ACIDIC, AND BASIC COMPOUNDS ON A P‐TERT‐BUTYL‐CALIX[8]ARENE‐BONDED STATIONARY PHASE by Lai‐Sheng Li, Shi‐Lu Da, Yu‐Qi Feng, and Min Liu, Department of Chemistry, Wuhan University, Wuhan, P. R. China and Lai‐Sheng Li, College of Chemistry and Material Sciences, Nanchang University, Nanchang, P.R. China
ABSTRACT: The preparation and the structural characterization of a p‐tert‐butyl‐calix[8]arene‐bonded silica gel stationary phase (CABS) have been reported. Subsequently, in this paper, the investigation of its HPLC performance was carried out using neutral, basic, and acidic solutes as probes. Meanwhile, the compared study with conventional RP‐C18 also was done under the same conditions. The results show that CABS can behave a reversed‐phase material with weaker hydrophobicity relative to ODS. Additionally, hydrogen bonding, π‐π and inclusion interaction between CABS and polar analytes, such as N‐substituted anilines, phenols, and so on, also can be observed. The versatile performance should be related to the calix[8]arene ligand, which can provide different sites for solutes. An advantage of CABS over ODS lies in its high selectivities for polar aromatics and the fast separation of nonpolar hydrocarbons.
Analytical Letters, 37(13), 2805–2817, 2004
Abstract
STATISTICAL TREATMENT OF TRACE ELEMENT DATA FROM MODERN AND ANCIENT ANIMAL BONE: EVALUATION OF ROMAN AND BYZANTINE ENVIRONMENTAL POLLUTION by Patrick Degryse and Philippe Muchez, Fysico‐chemische Geologie, K.U. Leuven, Heverlee, Belgium; Bea De Cupere and Wiu Van Neer, Koninklijk Museum voor Midden‐Afrika, Tervuren, Belgium; and Marc Waelkens, Departement Archeologie, K.U. Leuven, Leuven, Belgium
ABSTRACT: Through chemical analysis of ancient animal bone found at the archaeological site of Sagalassos, and through comparison of the analytical data with that from modern bone and feed from the same location, conclusions on the ancient livestock are made. Samples of ancient and modern goat bone as well as Quercus coccifera were analyzed using Inductively Coupled Plasma–Mass Spectrometry (ICP‐MS). After evaluation of the consistency of the chemical characteristics of different types of modern bone in one individual, it is decided to use the trace element data of long bone for statistical treatment. After evaluation of the degree and effects of diagenesis in the fossil bone, it is concluded that trace element data are useful indicators for anthropogenic palaeoenvironmental pollution, as a distinction could be made between elements that occur naturally in the bedrock and those that can be linked to industrial pollution. The occurrence or depletion of the latter elements in fossil bone, show diachronic changes in the chemical composition of the goat bones which can be explained in function of the changing catchment area from which the animals were obtained through time. It is conceivable that during periods of insecurity, such as the fifth to sixth century A.D. in the area of Sagalassos, animal herds were kept closer to the ancient town and would hence take up more pollutants with the ingested food. A lower uptake of pollutants during the fourth century, a rich and secure period in the history of the city, can be explained by a wider catchment area from which the goats were obtained.
Analytical Letters, 37(13), 2819–2834, 2004
Abstract
AN IMPROVED PRESSURIZED LIQUID EXTRACTION METHOD FOR THE DETERMINATION OF POLYCYCLIC AROMATIC HYDROCARBONS IN FRESHWATER SEDIMENTS BY GAS CHROMATOGRAPHY‐MASS SPECTROMETRY by Jason G. Harb and Joseph H. Aldstadt, III, Department of Chemistry, University of Wisconsin‐Milwaukee, Milwaukee Wisconsin, USA
ABSTRACT: An improved pressurized liquid extraction (PLE) method for polycyclic aromatic hydrocarbons (PAHs) in freshwater sediment is described. The optimized method is simple, fast, efficient, and requires small amounts of sample and generates small amounts of secondary waste. Five optimization factors were chosen for study: extraction temperature, extraction time, sample mass, solvent volume, and post‐extraction cooling time. Method development was performed using authentic PAH‐contaminated (“aged”) sediment samples; optimal conditions were identified based upon a response function (recovery/precision) for three representative PAHs (naphthalene, pyrene, and benzo[g,h,i]perylene). In the optimized method, 3.00 mL of n‐hexane and 0.500 g of sediment were heated in a closed stainless steel extraction cell for 60.0 min at 200°C. The cell was then placed in an ice bath for 5.0 min, and the PAH content of the collected extract was determined by gas chromatography‐mass spectrometry (GC‐MS). Detection limits for this method range from 0.0511 ± 0.0110 to 0.963 ± 0.0792 µg per gram of dried sediment sample for the sixteen PAHs classified by the U.S. Environmental Protection Agency (U.S. EPA) as “priority pollutants.” The method was validated by applying it to National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1944. The concentrations determined were, on average, within ±11% of the certified values (at the 95% confidence level). The PLE method described herein requires ∼90% less extraction solvent and yields a ∼45% improvement in precision compared to existing methods.
Analytical Letters, 37(13), 2835–2850, 2004
Abstract
CATALYTIC ABSTRACTION OF CYANIDE IN HEXACYANOFERRATE(II) BY MERCURY(II) IN THE PRESENCE OF α‐NITROSO‐β‐NAPHTHOL AS INDICATOR REACTION FOR DETERMINATION OF MERCURY(II) BY KINETIC METHOD by Surendra Prasad, Department of Chemistry, School of Pure and Applied Sciences, The University of the South Pacific, Suva, Fiji
ABSTRACT: The abstraction of cyanide ion from hexacyanoferrate(II) by Hg(II) as a catalyst has been studied spectrophotometrically in the presence of α‐Nitroso‐β‐Naphthol (αNβN). When Hg(II) is present in different stoichiometric amounts with [Fe(CN)6]4−, abstraction of two cyanide ions per ion of Hg(II) takes place with the formation of three different green colored complexes [Fe(CN)4(αNβN)]2−, [Fe(CN)2(αNβN)2], and [Fe(αNβN)3]2+. However, when Hg(II) is present in catalytic amounts in the range of 1 × 10−6 − 1 × 10−5 mol l−1a single ternary complex of the type [Fe(CN)4(αNβN)2]2− is formed which is intensely green in color and quite stable. The effects of pH, concentration of reactants, and temperature have been studied. A detailed kinetic study of cyanide abstraction is reported and a probable mechanism consistent with the experimental data has been proposed. This catalytic observation formed the basis for development of a catalytic kinetic method for determination of Hg(II) using the titled ligand exchange reaction. The reaction has been well suited for the determination of Hg(II) in various spiked water samples with 97 ∼ 103% recoveries. The relative standard deviation and percentage error in various determinations of Hg(II) have been reported. The effect of various interfering ions have been studied and discussed. The interference by various closely associated metal ions on the determination of Hg(II) have been studied using synthetic water samples.
Analytical Letters, 37(13), 2851–2867, 2004
Abstract
MANGANESE (II)–1,10‐PHENANTHROLINE–AZO DYE–POTASSIUM PERIODATE SYSTEM FOR KINETIC SPECTROPHOTOMETRIC DETERMINATION OF NANOGRAM LEVELS OF MANGANESE by Konstantin L. Mutaftchiev, Department of Chemistry and Biochemistry, Higher Medical Institute, Pleven, Bulgaria
ABSTRACT: The catalytic effect of manganese (II) on the oxidation of the azo dye 3‐methyl‐6‐(2‐hydroxyethoxy)‐2‐[4‐N(N‐methyl‐N‐phenylamino) phenylazo] benzothiazolium methylsulphate, with potassium periodate in the presence of 1,10‐phenanthroline in weakly acidic media is studied. The reaction is followed spectrophotometrically by measuring the decrease in the absorbance of the dye at 610 nm. Under the optimum conditions (1 × 10−4 mol dm−3 azo dye, 1 × 10−3 mol dm−3 potassium periodate, 4 × 10−4 mol dm−3 1,10‐phenanthroline, 0.1 mol dm−3 buffer–pH 3.0, 70°C, 7 min) manganese (II) in the range 0.1–5 ng cm−3 can be determined by the fixed‐time method with a detection limit of 0.035 ng cm−3. The developed method is highly sensitive, selective, and simple. The method was applied successfully to the determination of manganese in peas, carrots, and peppers.
Analytical Letters, 37(13), 2869–2879, 2004