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Analytica Chimica Acta (v.532, #1)
Monitoring arsenic in the environment: a review of science and technologies with the potential for field measurements by Dan Melamed (pp. 1-13).
This review examines available field assays and other technologies with the potential to measure and monitor arsenic in the environment. The strengths and weaknesses of the various assays are discussed with respect to their sensitivity, ability to detect the chemical states of arsenic, performance in various media, potential interferences, and ease of operation. The state of the science and development efforts of selected technologies is presented.
Keywords: Anodic stripping voltammetry; Arsenic; Arsenate; Arsenite; Arsenomolybdate; Bioassay; Capillary electrophoresis; Colorimetric; Microcantilever; Organoarsenic; Surface enhanced Raman spectroscopy; X-ray fluorescence
Chemometric data analysis of pollutants in wastewater—a case study by Kunwar P. Singh; Amrita Malik; Dinesh Mohan; Sarita Sinha; Vinod K. Singh (pp. 15-25).
In this study, chemometric techniques such as cluster analysis (CA), discriminant analysis (DA), principal component analysis (PCA) and partial least squares (PLS) were used to analyse the wastewater dataset to identify the factors which affect the composition of sewage of domestic origin, spatial and temporal variations, similarity/dissimilarity among the wastewater characteristics of cis- and trans-drains and discriminating variables. Samples collected from 24 wastewater drains in Lucknow city and from three sites on Gomti river in the month of January/February, May, August and November during the period of 5 years (1994–1999) were characterized for 32 parameters. The multivariate techniques successfully described the similarities/dissimilarities among the sewage drains on the basis of their wastewater characteristics and sources signifying the effect of routine domestic/commercial activities in respective drainage areas. Spatial and seasonal variations in wastewater composition were also determined successfully. CA generated six groups of drains on the basis of similar wastewater characteristic. PCA provided information on seasonal influence and compositional differences in sewage generated by domestic and industrial waste dominated drains and showed that drains influenced by mixed industrial effluents have high organic pollution load. DA rendered six variables (TDS, alkalinity, F, TKN, Cd and Cr) discriminating between cis- and trans-drains. PLS–DA showed dominance of Cd, Cr, NO3, PO4 and F in cis-drains wastewater. The results suggest that biological-process based STPs could treat wastewater both from the cis- as well as trans-drains, however, prior removal of toxic metals will be required from the cis-drains sewage. Further, seasonal variations in wastewater composition and pollution load could be the guiding factor for determining the STPs design parameters. The information generated would be useful in selection of process type and in designing of the proposed sewage treatment plants (STPs) for safe disposal of wastewater.
Keywords: Wastewater; Sewage treatment; Multivariate analysis; Cluster analysis; Principal component; Discriminant analysis; Partial least squares
Slope comparison method (SCM) for the determination of trace amounts of silicate in ultrapurified water by Akhmad Sabarudin; Mitsuko Oshima; Shoji Motomizu (pp. 27-35).
A sensitive analytical method for the determination of trace amounts of silicate in ultrapurified water was developed. The method is based on the formation of an ion associate of molybdosilicate with malachite green (MG) and the collection of the ion associate on a tiny membrane filter (diameter: 5mm, and effective filtering diameter: 1mm). The ion associate formed on the membrane filter is dissolved together with the membrane filter in 1ml of methyl cellosolve (MC) and the absorbance of MC solution is measured at 627nm by a flow injection-spectrophotometric detection technique. In this method, silicate in the original sample (ultrapurified water) is concentrated as the ion associate into a small volume of MC to get high sensitivity. As sample concentration takes place, the small amounts of silicate contained in the reagents used also become concentrated as the ion associate into MC. The original sample volumes are varied and evaporated to an identical volume. Therefore, the reagent added is fixed to the same volume. The absorbance increase linearly with increase in the original sample volume will be due only to silicate in the original samples (ultrapurified water). The resulting slopes obtained by varying the sample volumes are compared with the slope of the calibration graph, and thus named the slope comparison method (SCM). The SCM facilitates a more sensitive and accurate evaluation of silicate concentration in the samples than either common calibration method (CCM) or standard addition method (SAM) because it compensates for the influence of trace amounts of silicate contained in chemicals, reagent solution and solvent used. The calibration graph was constructed from 0 to 0.25ngml−1 of Si and the detection limit was 10pgml−1 (ppt) when 30ml of samples was used. The standard deviation and relative standard deviation from six measurements of the reagent blanks were 0.0012 and 3.5%, respectively.
Keywords: Slope comparison method; Ultrapurified water; Ion associate; Molybdosilicate; Malachite green; Membrane filter
Separation efficiency of a chemical warfare agent simulant in an atmospheric pressure ion mobility time-of-flight mass spectrometer (IM(tof)MS) by Wes E. Steiner; William A. English; Herbert H. Hill Jr. (pp. 37-45).
An electrospray ionization atmospheric pressure ion mobility orthogonal reflector time-of-flight mass spectrometer (IM(tof)MS) that routinely achieves mobility and mass separation efficiencies in line with theoretical limits is reported. The maximum IM(tof)MS efficiency for a given instrumental design depends widely upon the various key parameters such as voltage, temperature, initial pulse width, interface and reflectron energies. Optimization of the current IM(tof)MS instrument, resulted in an IMS separation efficiency over 133,000 theoretical plates (a resolving power of 155) and a resolving power of 1200 for the TOFMS using a singly charged G/V-type chemical warfare agent (CWA) nerve simulant (dimethyl methylphosphonate (DMMP)) in less than 12ms.
Keywords: Ion mobility spectrometry; Time-of-flight mass spectrometry; Chemical warfare agent simulant; Resolving power
Uranium emission spectra with a low power microwave plasma source by Yixiang Duan; Susan T. Scherrer; Sudip P. Koirala; Chuji Wang; Christopher B. Winstead (pp. 47-54).
This work presents the first report of uranium spectra generated by a low power microwave plasma source to conduct emission measurements. Distinct uranium peaks in the wavelength range examined from 320 to 430nm have been successfully obtained with a 200W plasma utilizing low gas flow rates. The influence of temperature on the uranium behavior in the plasma source is discussed, and the intensity of the spectral lines obtained with this low power source is systematically compared with the results reported in literature, in which high power plasma sources were employed. Concentration effects are studied and the calibration curves are made for some strong spectral lines. The detection limits of uranium are also estimated to be at the 0.4ppm level, with linear dynamic range at least two and half orders of magnitude. This research establishes a method to effectively generate uranium atoms and ions at a low power and low gas flow rate, which should be useful for uranium fundamental characteristic studies and on-site uranium monitoring work.
Keywords: Microwave plasma; Emission spectrometry; Uranium; Spectral line; Measurement
A comparison of high accuracy isotope dilution techniques for the measurement of low level sulfur in gas oils by Ruth Hearn; Michael Berglund; Markus Ostermann; Nusa Pusticek; Philip Taylor (pp. 55-60).
A comparison of high accuracy methods for the analysis of total sulfur in gas oils by three metrology institutes is described. The work contains a comparison of three different aspects of the analysis: sample digestion, instrumental measurement and isotope dilution strategies.Thermal ionisation mass spectrometry (TIMS) in combination with high pressure asher (HPA) or Carius tube digestion has traditionally been used for such high accuracy analysis. However, this paper demonstrates that the faster, less laborious technique of ICP-MS in combination with microwave digestion is equally capable. Results from the comparison experiments show excellent agreement for fuel samples containing sulfur concentrations in the range 11–200μgg−1. This excellent agreement across the different sample preparation, measurement and isotope dilution techniques has been exploited in the certification of two new diesel fuel reference materials.
Keywords: Sulfur; Gas oil; Isotope dilution; ICP-MS; TIMS; Uncertainty
Imaging fiber microarray fluorescent ion sensors based on bulk optode microspheres by Katarzyna Wygladacz; Eric Bakker (pp. 61-69).
Optical imaging fibers with micrometer-sized wells were used as a sensing platform for the development of microarray optical ion sensors based on selective bulk extraction principles established earlier for optodes. Uniform 10μm sized microspheres based on plasticized poly(vinyl chloride) containing various combinations of ionophores, fluoroionophores and lipophilic ion-exchangers were prepared for the detection of sodium, potassium, calcium and chloride, and deposited onto the wells of etched fiber bundles. Specifically, sodium sensing particles were based on tert-butylcalix[4]arene tetraacetic acid tetraethylester, potassium particles on 2-dodecyl-2-methyl-1,3-propanediyl bis[ N-[5′-nitro(benzo-15-crown-5)-4′-yl]carbamate] (BME-44), calcium particles on an acrylic derivative of ETH 129 (AU-1) covalently attached to a methacrylic polymer, and chloride particles based on the anticrown ionophore [9]mercuracarborand-3 (MC-3). The fluorescence emission characteristics of individual microspheres were observed from the backside of the fibers and were found to selectively and rapidly change as a function of the sample composition. The optical characteristics of the particles were found to be comparable to that of corresponding thin optode films and particles deposited onto microscope glass slides. The measuring ranges (logarithmic molar concentrations) at pH 7.0 were found as −3 to 0 for sodium, −3.5 to −0.5 for potassium, −7 to −2 for calcium, and −5 to 0.5 for chloride. Selectivities were determined over other common electrolytes and found to be sufficient for physiological applications. The simultaneous deposition of sodium and chloride sensing particles was successfully performed, demonstrating that such microarray sensors are capable of simultaneously sensing multiple analytes. This technology is compatible with other microsphere-based fluorescent sensing principles, forming a promising total analysis platform for a variety of applications.
Keywords: Optode microspheres; Ionophore; Human saliva; Imaging fiber bundles; Total analysis system
Fabrication of polyaniline/carbon nanotube composite modified electrode and its electrocatalytic property to the reduction of nitrite by Manli Guo; Jinhua Chen; Jia Li; Bo Tao; Shouzhuo Yao (pp. 71-77).
A polyaniline (PANI)/carbon nanotubes (CNTs) composite modified electrode was fabricated by galvanostatic electropolymerization of aniline on multi-walled carbon nanotubes (MWNTs)-modified gold electrode. The electrode thus prepared exhibits enhanced electrocatalytic behavior to the reduction of nitrite and facilitates the detection of nitrite at an applied potential of 0.0V. Although the amperometric responses toward nitrite at MWNTs/gold and PANI/gold electrodes have also been observed in the experiments, these responses are far less than that obtained at PANI/MWNTs/gold electrode. The effects of electropolymerization time, MWNTs concentration and pH value of the detection solution on the current response of the composite modified electrode toward sodium nitrite, were investigated and discussed. A linear range from 5.0×10−6 to 1.5×10−2M for the detection of sodium nitrite has been observed at the PANI/MWNTs modified electrode with a sensitivity of 719.2mAM−1cm−2 and a detection limit of 1.0μM based on a signal-to-noise ratio of 3.
Keywords: Polyaniline; Carbon nanotube; Amperometric detection; Electrocatalytic reduction; Nitrite
Potentiometric flow injection analysis of dicyclomine hydrochloride in serum, urine and milk by H. Ibrahim; Y.M. Issa; Hazem M. Abu-Shawish (pp. 79-88).
Five plastic membrane electrodes for the determination of dicyclomine hydrochloride (DcCl) were fabricated and fully characterized in terms of composition, life span, usable pH range, working concentration range and temperature. The membranes of these electrodes consist of dicyclominium-silicotungstate (Dc-ST), silicomolybdate (Dc-SM), phosphotungstate (Dc-PT), phosphomolybdate (Dc-PM) or tetraphenylborate (Dc-TPB) ion-associations dispersed in PVC matrix with dibutyl phthalate plasticizer. The electrodes showed near-Nernstian response over the concentration range of 4.0×10−6 to 1.0×10−2M DcCl and applied to the potentiometric determination of dicyclominium ion in pharmaceutical preparations, serum, urine and milk in batch and flow injection (FI) conditions with average recoveries of 96.1–102.7% and relative standard deviation of 0.055–1.994%. The electrodes exhibit good selectivity for DcCl with respect to a large number of inorganic cations, organic cations, sugars and amino acids. The sensitivities of these electrodes are high enough to measure as low as 1.73μg/ml of DcCl which permit the determination of the Ksp values of the ion-associates used. The proposed potentiometric methods offer the advantages of simplicity, accuracy, automation feasibility and applicability to turbid and colored sample solutions.
Keywords: Ion-selective electrode; Ion-association; PVC membrane electrode; Dicyclomine hydrochloride; FI conditions; Biological fluids
An electropolymerized aniline-based fiber coating for solid phase microextraction of phenols from water by Habib Bagheri; Ali Mir; Esmaeil Babanezhad (pp. 89-95).
An aniline-based polymer was electrochemically prepared and applied as a new fiber coating for solid phase microextraction (SPME) of some priority phenols from water samples. The polyaniline (PANI) film was directly electrodeposited on the platinum wire surface in sulfuric acid solution using cyclic voltammetry (CV) technique. The efficiency of new coating was investigated using a laboratory-made SPME device and gas chromatography with flame ionization detection for the extraction of some phenols from the headspace of aqueous samples. The scanning electron microscopy (SEM) images showed the homogeneity and the porous surface structure of the film. The results obtained proved the ability of this polymer as a suitable SPME fiber coating for trapping the selected phenols. Influential parameters affecting the extraction process were optimized and an extraction time of 50min at 50°C gave maximum efficiency, when the aqueous sample was saturated with NaCl and adjusted at pH 2. This new coating can be prepared easily in a reproducible manner and it is rather inexpensive and stable against most of organic solvents. The PANI thickness can be precisely controlled by the number of CV cycles. At the optimum conditions, the R.S.D. for a double distilled water spiked with phenol and chlorophenols at ppb level were 4.8–17% ( n=3) and detection limits for the studied compounds were between 0.69 and 3.7ngml−1, except for phenol and 4-chlorophenol. The optimized method was successfully applied to some real-life water samples.
Keywords: Water analysis; Environmental analysis; Solid phase microextraction; Polyaniline; Chlorophenols; Gas chromatography
Quantitative and qualitative analysis of flavonoids in leaves of Adinandra nitida by high performance liquid chromatography with UV and electrospray ionization tandem mass spectrometry detection by Jie Zhang; Jun Yang; Jicheng Duan; Zhen Liang; Lihua Zhang; Yushu Huo; Yukui Zhang (pp. 97-104).
The extract of Adinandra nitida leaves, named as Shiyacha in China, was studied by high performance liquid chromatography (HPLC)–ultraviolet detection–electrospray ionisation (ESI) tandem mass spectrometry (MS). Under the optimized condition, the analysis could be finished in 45min on a Hypersil C18 column combined with negative ion detection using information-dependent acquisition (IDA) mode of a Q TRAP™ instrument. Six flavonoids were identified as epicatechin, rhoifolin, apigenin, quercitrin, camellianin A, and camellianin B among which rhoifolin was for the first time found in Shiyacha. And the fragment pathways of these flavonoids were elucidated. Furthermore, with epicatechin, rhoifolin, and apigenin as markers, the quality control method for Shiyacha and its relevant product was firstly established. Calibration linearity was good ( R2>0.9992) over a three to four orders of magnitude concentration range with an S/N=3 detection limit of 2.5ng.
Keywords: Adinandra nitida; Flavonoid; High performance liquid chromatography; Electrospray ionization; Tandem mass spectrometry; Quality control