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Analytical and Bioanalytical Chemistry (v.372, #4)
No Title by C. Masalles; S. Borrós; C. Viñas; F. Teixidor (pp. 513-518).
Cobaltabis(dicarbollide) [3,3′-Co(1,2-C2B9H11)]–-doped polypyrrole (PPy) films have been prepared galvanostatically on glassy carbon electrodes in acetonitrile solution. The potential response behavior of the film of this new material has been investigated in some common pH buffers and in acid–base titrations. The potentiometric characteristics of the resulting films are indicative of a quasi-Nernstian response (approximately 50 mV/pH unit), a linearity range from pH 12 to 3 and correlation coefficients (r2) of approximately 0.98. The electrode is suitable for pH measurements and for monoprotic titrations of strong alkalis with strong acids, and weak bases with strong acids, but the long response time hinders the use of this electrode for multiprotic titrations. The time response has been dramatically improved by reducing the film thickness by using the template effect of a non-conducting polymer (PVC) cast over the graphite surface before PPy deposition. PPy polymerization occurs in the free channels of PVC leading to the formation of PPy wires. The morphological change of PPy does not affect the slope or linearity range. The response of the PVC–PPy electrochemical sensor is rapid and the sensor is easy to prepare, at low cost, and its performance is comparable with that of commercial glass electrodes.
Keywords: Conducting polymers pH Electrode Polypyrrole Sensor Titration
No Title by Cheng-Gang Niu; Zhi-Zhang Li; Xiao-Bing Zhang; Wei-Qi Lin; Guo-Li Shen; Ru-Qin Yu (pp. 519-524).
By replacing the hydrogen of the 4-amino group of a 4-amino-1,8-naphthalimide derivative with an N-acryloxyethyl group, the fluorophore has been covalently immobilized on an optical sensor surface by UV photopolymerization. The optical sensor obtained can be used for the determination of picric acid. The linear range and detection limit of the sensor are 9.80×10–7–1.96×10–4 mol L–1 and 7.1×10–7 mol L–1, respectively. Leaching of the fluorophore from the membrane is effectively prevented by covalent immobilization, resulting in a sensor with a relatively long lifetime. The response time of the sensor is short, and the reproducibility and reversibility are good. The sensor has been used for the indirect determination of the chloroquine content of pharmaceutical tablets.
Keywords: Optical fiber sensor Aminonapthalmide Covalent immobilization Fluorescence quenching
No Title by Hui-Chun Yeh; Wann-Yin Lin (pp. 525-531).
The use of m-chloroperoxybenzoic acid (mCPBA) in stead of hydrogen peroxide causes an increase in chemiluminescence (CL) of luminol oxidation catalyzed by microperoxidase 8 (MP8) by an order of magnitude. The accelerated formation of an intermediate plays a major role in the CL enhancement, which also leads to a significant reduction in CL duration. The presence of guanidine hydrochloride, sodium carbonate, or sodium chloride further increases the CL emission drastically. The CL emission enhancement is strongly pH dependent. The enormous enhancement of the CL signal is due to an accelerated CL cycle and an improved CL efficiency in the presence of the enhancer. The CL signal covers several orders of magnitude over a wide range of concentrations of luminol and mCPBA. The intense CL of MP8-luminol-mCPBA in the presence of the enhancer will have great potential for extremely sensitive CL assays.
Keywords: Chemiluminescence Stopped-flow Microperoxidase 8 m-Chloroperoxybenzoic acid Enhancer
No Title by Mitsuo Itoh; Kazuo Watanabe; Mutsuo Hatakeyama; Mitsuo Tachibana (pp. 532-536).
An X-ray spectrometric method has been developed for the determination of 41Ca in the biological-shield concrete of nuclear reactors. The concrete sample was first decomposed with nitric, hydrofluoric, and perchloric acids. Calcium was then separated from other radionuclides by ion-exchange chromatography and recovered as an oxalate precipitate. X-rays at 3.3 keV from 41Ca in the calcium oxalate pellet were measured. The detection efficiency of the X-ray measurement at 3.3 keV was calculated from those obtained by measuring 55Fe standard pellets at 5.9 keV using mass-absorption coefficients of the calcium oxalate pellet at each X-ray energy. A lower limit of determination of 8 Bq g–1 was obtained for a sample weight of 1 g.
Keywords: X-ray spectrometry 41Ca Biological-shield concrete Ion-exchange chromatography
No Title by E. Borai; M. Eid; H. Aly (pp. 537-541).
Ion chromatographic techniques were investigated for the separation and the quantitative determination of some rare earth elements (REEs) in monazite and xenotime minerals. The influences of selected eluents containing complexing acids including oxalic and α-hydroxy isobutyric acid (α-HIBA) on the retention and hence the separation efficiency of REEs was studied. Different variables affecting the separation of different REEs such as pH, type, and concentration of the mobile phase were investigated. Gradient elution, using an advanced gradient pump, was controlled automatically by the Dionex AI-450 computer software. Separation of REEs was carried out using an Ion Pac CS5A column followed by a post column derivatization reaction with 4-(2-pyridylazo)resorcinol (PAR) and UV-VIS spectrophotometric detection. Mineral dissolution was carried out using sulfuric acid. A comparative evaluation of REE distribution in monazite and xenotime minerals using both ion chromatography (IC) and inductively coupled plasma atomic emission spectrometric (ICP-AES) techniques was carried out.
Keywords: REEs Monazite Xenotime IC ICP-AES
No Title by Shuji Kozono; Shigeto Takahashi; Hiroki Haraguchi (pp. 542-548).
An on-line matrix separation/inductively coupled plasma mass spectrometry (ICP-MS) method is proposed for the determination of trace amounts of phosphorus in high purity tantalum metal, tantalum (V) oxide, and tantalum pentaethoxide. In the present method, the matrix tantalum in the sample solution was adsorbed on the anion exchange resin, and phosphorus (phosphate ion) was eluted with the carrier solution of HF and HNO3 mixture. Then, the effluent solution was subsequently mixed with bismuth solution and aqueous ammonia solution to coprecipitate phosphate together with bismuth hydroxide. The precipitate formed was collected on the in-line membrane filter to wash out nitric acid with pure water, and then dissolved with hydrochloric acid. The obtained phosphorus sample solution was introduced directly into the nebulizer of ICP-MS for the determination of phosphorus. Phosphorus was determined at the molecular ion signal of 31P16O+ (m/z 47). The detection limit (3σ) of phosphorus in the present method was 1.3 ng mL–1 as the sample solution basis, and the relative standard deviation for 30 ng mL–1 of phosphorus in the standard solution was 4.3% in the replicate measurements (n=11). The present method was applied to the analysis of high purity tantalum materials. The concentrations of phosphorus in tantalum samples were in fairly good agreement with those obtained by glow discharge mass spectrometry (GDMS).
Keywords: Phosphorus traces Tantalum High purity Inductively coupled plasma mass spectrometry Matrix separation Anion exchange
No Title by Radmila Milačič; Janez Ščančar; Janez Tušek (pp. 549-553).
The applicability of an anion-exchange fast protein liquid chromatographic-electrothermal atomic absorption spectrometric procedure (FPLC-ETAAS) was investigated for the determination of Cr(VI) in welding fumes after alkaline extraction of aerosols loaded on filters. Gas tungsten arc welding (GTAW) of stainless steel was applied. Samples of welding fumes were collected during regular welding on polycarbonate membrane filters of 8 µm and 0.4 µm pore size (inhalable and respirable aerosols). Alkaline extraction (2% NaOH-3% Na2CO3) of filters in a heated ultrasonic bath was applied to leach Cr from the airborne particulate matter. 0.5 cm3 of sample extract was then injected onto an anion-exchange FPLC column. Tris-HCl buffer (0.005 mol dm–3, pH 8.0) and the same buffer with NaCl (0.5 mol dm–3) were employed in gradient elution (15 min, flow rate 1 cm3 min–1). The separated Cr species were determined "off line" by ETAAS in 0.5 cm3 fractions. Cr(VI) was reproducibly and quantitatively eluted from 12.0 to 13.0 min with a maximum peak at 12.5 min. Good repeatability of measurement (±3.0%) of alkaline extracts was obtained for Cr(VI). The LOD (3s) was found to be 0.035 µg m–3 Cr(VI), when 2 m3 of aerosols were collected on the filter. Validation of the procedure was performed by spiking alkaline extracts and by the analysis of standard reference material CRM 545, Cr(VI) in welding dust loaded on a filter. The technique was successfully applied for the determination of Cr(VI) in welding fumes.
Keywords: Chromium(VI) Welding fumes Anion-exchange fast protein liquid chromatography Electrothermal atomic absorption spectrometry
No Title by Takuma Takasu; Alexander Iles; Kiyoshi Hasebe (pp. 554-561).
A simple, accurate and reproducible reversed-phase high-performance liquid chromatography (HPLC) method was developed for the separation and characterisation of alkylphenols (APs) and alkylphenol polyethoxylates (APEOs), using a C18 octadecyl silica (ODS) column. APs and each APEO oligomer were separated successfully within a reasonable time without gradient elution. An excellent resolution was obtained, even for mixtures of APs and low EO number APEOs, which are otherwise difficult to separate using conventional normal-phase HPLC methods. This method, combined with solid-phase extraction, was highly applicable for the simultaneous determination of alkylphenols and alkylphenol ethoxylates in real samples.
Keywords: Reversed-phase HPLC Alkylphenol ethoxylate Endocrine disruptor Non-ionic surfactant
No Title by D. Martens; M. Gfrerer; T. Wenzl; A. Zhang; B. Gawlik; K.-W. Schramm; E. Lankmayr; A. Kettrup (pp. 562-568).
The performance of various enhanced extraction techniques, such as accelerated solvent extraction, microwave-assisted extraction, Soxhlet extraction, ultrasonic extraction and fluidized-bed extraction for the determination of polychlorinated organic compounds in dry sediment was investigated in two laboratories. The results of the two laboratories were in good agreement. The extraction yields from the batch extraction methods were lower than those from the dynamic techniques. Accelerated solvent extraction, especially, exhibited higher extraction efficiency than the standard procedure, Soxhlet extraction, whereas the results of fluidized-bed extraction were comparable.
Keywords: Soxhlet extraction ASE Microwave-assisted extraction Ultrasonic extraction Fluidized-bed extraction Chlorinated compounds
No Title by C. Zwiener; S. Seeger; T. Glauner; F. Frimmel (pp. 569-575).
The three metabolites hydroxyibuprofen (OH-Ibu), carboxyibuprofen (CA-Ibu), and carboxyhydratropic acid (CA-HA), also known from human metabolism of ibuprofen, could be identified in biodegradation experiments. Identification was based on EI mass spectra and comparison with literature data. Detection was performed by selective MS–MS measurements by GC–ion-trap MS and online methylation. Ibuprofen (Ibu), OH-Ibu, and CA-Ibu could be detected with a signal-to-noise ratio of 10:1 at a concentration of 2 nmol L–1, CA-HA at 0.5 nmol L–1. Degradation experiments in both biofilm reactors (BFR) and batch experiments with activated sludge (BAS) reveal OH-Ibu as the major metabolite under oxic conditions, and CA-HA under anoxic conditions. CA-Ibu was found under oxic and anoxic conditions almost only in the BAS. The metabolites together do not account for more than 10% of the initial concentration of Ibu.
Keywords: Biodegradation Pharmaceutical residues Ibuprofen Biofilm reactors Sewage sludge
No Title by Jiří Machát; Viktor Kanický; Vítězslav Otruba (pp. 576-581).
The possibility of determining selenium in blood serum using inductively coupled plasma emission spectrometry with conventional pneumatic nebulization was studied. A high-resolution spectrometer (SBW=6 pm) with laterally viewed ICP was employed. Analysis with conventional pneumatic nebulization could overcome laborious and demanding digestion, which is necessary for hydride generation. A pressure digestion with nitric acid at 160 °C was sufficient to decrease the carbon content in the serum sample to 5%–10% of its original value. Spectral interference of the CN band was observed and mathematically corrected. It was found that the carbon-induced selenium line emission enhancement occurred even under ICP optimized conditions. A method of determination was developed and applied to the analysis of blood serum. True limit of detection in real samples is 0.01–0.02 mg/L and the limit of quantification (RSD 10%) is 0.03–0.07 mg/L using Se I 196.090 nm line at an integration time of 10–2 s. The method was tested by analysis of porcine blood serum and the serum reference material Seronorm MI 0181.
Keywords: Selenium speciation Spectrometry ICP-AES Pneumatic nebulization
No Title by Sibel A. Özkan; Bengi Uslu (pp. 582-586).
The oxidation of fluvastatin sodium on a glassy carbon electrode has been studied by use of a variety of voltammetric techniques. Different conditions were investigated to optimize the determination of fluvastatin sodium. The dependence of the intensities of currents and potentials on pH, concentration, scan rate, and nature of the buffer was investigated. Oxidation of fluvastatin sodium was found to be diffusion-controlled and irreversible. The best results for the determination of fluvastatin sodium were obtained by using differential pulse and square-wave voltammetric techniques in Britton–Robinson buffer at pH 10.04. Differential pulse and square-wave voltammetry at a glassy carbon electrode resulted in linear calibration in the range 8×10–6 to 6×10–4 mol L–1 and detection limits of 1.07×10–6 and 7.99×10–7 mol L–1, respectively. The proposed methods were successfully applied to the determination of the drug in capsules and biological fluids. Excipients did not interfere with the determination. Statistical validation revealed that the methods were free from significant systematic errors.
Keywords: Voltammetry Fluvastatin sodium Human serum Simulated gastric juice Pharmaceuticals
No Title by Ignacio López-García; Jesús Arroyo; P. Viñas; Manuel Hernández-Córdoba (pp. 587-592).
A fully computer-controlled manifold is described which enables the automatic dilution and measurement of solutions which are too concentrated to be measured by direct aspiration in FAAS. The sample solution is propelled by a peristaltic pump equipped with two pump tubes of different diameters, the difference between the nebulizer uptake rate and the flow rate supplied by both tubes being compensated by solvent provided through a T-piece. The absorbance is averaged and the pump turning speed automatically increased or reduced until an absorbance value within the linear response of the spectrometer is obtained. To furnish very high dilution, the system automatically reverses the direction of the flow moved through one of the pump tubes, so that the net flow delivered by the pump is the difference between the flows propelled through the two pump tubes. In these circumstances, in addition to absorbance, the module of the Fourier transform obtained from the absorbance–time profile can be used as the analytical signal. Calibration is performed by use of a single standard solution. In this way, it is possible to determine copper in the 1–10,000 µg mL–1 range with an RSD of 1.3–3%. Copper, zinc, calcium, and magnesium were determined in different samples to check the reliability of the procedure.
Keywords: Automatic dilution Concentrated solutions Flame atomic absorption spectrometry
No Title by Beata Godlewska-Żyłkiewicz (pp. 593-596).
Losses of palladium in weakly acidic solutions during storage process, which occur by its hydrolysis and/or adsorption onto the surface of storage vessels, are studied and ways of overcoming them are proposed. A fast and effective procedure for cleaning of laboratory ware with 0.2 mol L–1 thiourea in 0.1 mol L–1 HCl is described. Preparing palladium solutions in quartz vessels as well as using autosampler cups made from quartz glass, enabled to diminish the detection limit of palladium in synthetic solutions by GFAAS from 0.94 ng/mL to 0.27 ng/mL.
Keywords: Palladium GFAAS Storage Adsorption
No Title by Bolin Gong; Yan Wang (pp. 597-600).
A new polyacrylacylaminothiourea chelating fiber was synthesized simply and rapidly from nitrilon (an acrylonitrile-based synthetic fiber) and aminothiourea. This fiber was used for the pre-concentration and separation of traces of AuIII, PtIV, PdIV, and IrIV ions from aqueous samples. Factors effecting and parameters for the adsorption of these ions onto the resin, such as acidity, rate, reuse, capacity, and interference of other ions, were investigated using inductively-coupled plasma atomic emission spectrometry (ICP-AES). Conditions of desorption of these ions from the resin were similarly investigated. The enrichment factor was 100. The relative standard deviation for the determination of AuIII, PtIV, PdIV, and IrIV were in the range of 0.7–3.0% for 20.0 ng/mL of each. The recoveries of a standard from real solution samples were between 96% and 100%. The concentrations of analyzed ions in a digested metal powder sample processed with the method proposed were in good agreement with the certified values.
Keywords: Noble metal traces ICP-AES Pre-concentration Polyacrylacylaminothiourea fibers
No Title by Hua Cui; Shifeng Li; Feng Li; Yugang Sun; Xiangqin Lin (pp. 601-604).
A new flow-injection procedure has been developed for the determination of salicylic acid based on the enhancement of the chemiluminescence from the cerium(IV)–Tween 20 reaction by salicylic acid in acidic medium. The method is simple, selective and sensitive with a detection limit of 2.5×10–9 g mL–1. It is applicable to the determination of salicylic acid in the concentration range of 4.0×10–9–1.1×10–6 g mL–1. The relative standard deviation (RSD) is 0.85% for 4.0×10–7 g mL–1 salicylic acid (n=11). The method has been successfully applied to the determination of salicylic acid in bactericidal solutions. Furthermore, it is suggested that light emission from cerium(IV)–Tween 20 reaction is probably because of the formation of singlet oxygen 1O2 * and the emitter is excited oxygen molecular pairs O2(1Δg)O2(1Σg –).
Keywords: FIA Chemiluminescence Cerium(IV) Salicylic acid Tween 20