General criteria for assessing the accuracy of approximate wave functions and their densities

Master equations for propagators in quantum open systems and their spectral resolutions are derived. The Zwanzig partitioning scheme along the superoperator algebra are used to derive equations of motion for partitioned operators in a Liouville space. The reservoir influence on the dynamical evolution of operators is shown to lead explicitly to dissipative effects arising from memory terms in the evolution equations of such operators. It is also shown that spectral representations may be written in a self-consistent analytic way by means of the self-energy fields for transition energies of the system by taking into account the lack of the complete knowledge about the reservoir. A kinematic fluid interpretation of the resultant equations is given and an explicit form of the “collision” superoperator is obtained. Finally, a simple example to illustrate the determination of self-energy fields for the system–reservoir interaction corrections is given. © 1995 John Wiley & Sons, Inc.     

Heavy metal levels and physico--chemical quality of potable water supply in Warri, Nigeria

The interaction between man's activities and the environment is gaining world wide attention. Warri an oil producing community in Delta State of Nigeria is faced with environmental oil pollution. Since open and underground water bodies are regarded as final recipients of most environmental pollutants, this study sought to provide data on the levels of the physico-chemical parameters and contaminants in Warri metropolitan water supply. This study investigated the cadmium, lead and chromium using Atomic Absorption Spectrophotometer, physico-chemical properties such as pH, temperature, total suspended solid TSS, total dissolved solid TDS, electrical conductivity EC, biological oxygen demand BOD, dissolved oxygen DO, chemical oxygen demand COD, and total coliform count of potable water sources in Warri. Ekpan River was found to have 1.2 mg/L of cadmium, 1.0 mg/L of chromium, 1.20 mg/L of lead and 2.0 mg/L of manganese. The heavy metals levels and the pollution parameters were lowest in the borehole water samples, except pH which is more acidic in borehole water samples and conductivity which is more in well water samples in all the sampling stations. Some of the parameters were above WHO standards.     

Continuous electrophoretic separation of106Ru species in sea water and uptake of the separated fractions by sea algae

¹⁰⁶Ru chloro and nitrosyl-nitrato complexes in sea water were separated into several species by continuous electrophoresis on a filter paper curtain. Biological uptake experiments were carried out on sea algae Fucus virsoides with fractionated¹⁰⁶Ru chloro and nitrosyl-nitrato complex species in sea water. The biological uptake of¹⁰⁶Ru chloro complex species was about 8 times higher than the uptake of¹⁰⁶Ru nitrosyl-nitrato species. Electrophoretically most mobile electrically positively charged cationic species in both systems also showed about 8 times higher biological uptake than the most mobile negatively charged anionic species. A close relation of the biological uptake to the sign of the electrical charge and the electrophoretic mobility of the species is demonstrated. The results are discussed with respect to possible danger to the biological environment as a consequence of the aging of ruthenium species in sea water resulting from¹⁰⁶Ru waste disposal to the sea from a nuclear reprocessing plant. On leave of absence from the National Institute of Radiological Sciences, 9-1, 4-chome, Anagawa, Chiba-shi, Japan, on a fellowship from The Science and Technology Agency of the Japanese Govemment.     

ICP-OES法与石墨炉原子吸收法测定饮用水中重金属元素比较

通过对比电感耦合等离子体发射光谱法(ICP-OES)与石墨炉原子吸收法(AAS)测定水中重金属的检出限、重复性、加标回收率等实验,验证两种方法的准确性,从而为饮用水中重金属的测定提供可靠的方法。结果表明,石墨炉原子吸收法测定饮用水中砷、镉、铬、铅、汞、硒检出限均低于ICP-OES法,但ICP-OES法测定线性范围宽,重复性和加标回收率均优于石墨炉原子吸收法,分析速度快,操作便捷,结果满意,是目前饮用水中重金属的测定非常可靠的方法。     

Evaluation criteria for the quality of published experimental data on nanomaterials and their usefulness for QSAR modelling

Nowadays nanotechnology is one of the most promising areas of science. The number and quantity of synthesized nanomaterials increase exponentially, therefore it is reasonable to expect that comprehensive risk assessment based only on empirical testing of all novel engineered nanoparticles (NPs) will very soon become impossible. Hence, the development of computational methods complementary to experimentation is very important. Quantitative structure-property relationship (QSPR) and quantitative structure-activity relationship (QSAR) models widely used in pharmaceutical chemistry and environmental science can also be modified and adopted for nanotechnology to predict physico-chemical properties and toxicity of empirically untested nanomaterials. All QSPR/QSAR modelling activities are based on experimentally derived data. It is important that, within a given data set, all values should be consistent, of high quality and measured according to a standardized protocol. Unfortunately, the amount of such data available for engineered nanoparticles in various data sources (i.e. databases and the literature) is very limited and seldom measured with a standardized protocol. Therefore, we have proposed a framework for collecting and evaluating the existing data, with the focus on possible applications for computational evaluation of properties and biological activities of nanomaterials.     

Trace metal analysis of sediments and particulate matter in sea water by energy-dispersive X-ray fluorescence

Summary The capability of energy-dispersive X-ray fluorescence was investigated for fast and simple chemical analysis of trace elements in sediments and particulate matter in sea water. Nuclepore 0.4 m pore-size membranes are recommended as optimal filters for a straightforward collection of suspended material. The collection of suspended trace metals by filtration seemed to give a sufficiently homogeneous filter load (s% <2.5). Data are presented on the concentrations of K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Pb, Rb and Sr with a fair precision (s% < 5.6) and accuracy.

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Bestimmung von Metallspuren in Ablagerungen und Schwebstoffen von Meerwasser mit Hilfe der energiedispersiven Röntgenfluorescenz

Zusammenfassung Ein Verfahren zur raschen und einfachen Analyse der Metallspuren wird vorgeschlagen. Zur Sammlung der Schwebstoffe werden als optimal Nuclepore-Membranen (Porengröße 0,4 m) empfohlen. Dabei wird eine ausreichend homogene Filterbeladung erhalten (s% < 2,5). Mit befriedigender Reproduzierbarkeit (s% < 5,6) und Richtigkeit wurden folgende Elemente bestimmt: K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Pb, Rb und Sr.

     

Preparation of candidate certified reference materials for the quality control of EDTA-and acetic acid-extractable trace metal determinations in sewage sludge-amended soil and terra rossa soil

The determination of extractable trace metal contents in soil using single extraction procedures is currently performed in many laboratories to assess the bioavailable metal fraction (and related phytotoxic effects) and the accessability to the environment (e.g. contamination of ground waters). Owing to the need for validation of the extraction schemes used and of the analytical techniques, the EC Measurements and Testing Programme (formerly BCR) has organized a project for improving the quality of determination of extractable trace metal contents in soil, the first step being an interlaboratory study to adopt common extraction procedures and the second being a certification campaign to certify two soils for their extractable trace element contents following these procedures. This paper gives a brief overview of the project organisation and describes the preparation, homogeneity and stability studies of two soil candidate reference materials (sewage sludge-amended and terra rossa soils).     

Calibration in atomic spectrometry: A tutorial review dealing with quality criteria,weighting procedures and possible curvatures

Calibration is required to obtain analyte concentrations in atomic spectrometry. To take full benefit of it, the adequacy of the coefficient of determination r² is discussed, and its use is compared with the uncertainty due to the prediction bands of the regression. Also discussed from a tutorial point of view are the influence of the weighting procedure and of different weighting factors, and the comparison between linear and quadratic regression to cope with curvatures. They are illustrated with examples based on the use of ICP-AES with nebulization and laser ablation, and of LIBS. Use of a calibration graph over several orders of magnitude may be problematic as well as the use of a quadratic regression to cope with possible curvatures. Instrument softwares that allow reprocessing of the calibration by selecting standards around the expected analyte concentration are convenient for optimizing the calibration procedure.     

Heavy water reactions with alkaline-earth metal dications in the gas phase: Kinetics at room temperature

Room temperature rate coefficients and product distributions are reported for the reactions initiated in D₂O with dications of the alkaline-earth metals Mg, Ca, Sr and Ba. The measurements were performed with a selected-ion flow tube (SIFT) tandem mass spectrometer and electrospray ionization (ESI). Mg²⁺ reacts with water by a fast electron transfer leading to charge separation with a rate coefficient of 1.4 × 10⁻⁹ cm³ molecule⁻¹ s⁻¹. Ca²⁺ reacts with D₂O in a first step to form the adduct Ca²⁺(D₂O), with an effective bimolecular rate coefficient of 2.3 × 10⁻¹¹ cm³ molecule⁻¹ s⁻¹, which then undergoes rapid charge separation by deuteron transfer to form CaOD⁺ and D₃O⁺ in a second step with k = 7.9 × 10⁻¹⁰ cm³ molecule⁻¹ s⁻¹. The CaOD⁺ ion reacts further by clustering up to five more D₂O molecules. Sr²⁺ clusters up to eight D₂O molecules and Ba²⁺ up to seven D₂O molecules, with the first addition of D₂O being rate determining in each case and the last addition being distinctly slower, as might be expected from a transition in the occupation of the added water molecules from an inner to an outer hydration shell.     

Algorithm and criterion of quality for assessing the packing of polymer microspheres

An algorithm for assessing the quality of the packing of two-dimensional ordered structures, prepared using polymer microspheres 20 μm in diameter on a water surface, is proposed. An analysis is performed on the basis of optical microscopy images. The area of the largest ordered microsphere domain in an image is used as the quality criterion. The algorithm simplifies analysis of the ordered structures.     

An improved metal extraction procedure for the determination of trace metals in sea water by atomic absorption spectrometry with electrothermal atomization

A rapid carbamate extraction method with pyrrolidinedithiocarbamate and diethyldithiocarbamate is described for the simultaneous determination of Cd, Co, Cu, Fe, Ni, Pb and Zn in sea water by atomic absorption spectrometry with a graphite atomizer. The metal—carbamate complexes are extracted from 500 ml of sea water into Freon TF and back-extracted into 10 ml of 0.3 M nitric acid. The method has considerable advantages over previously recommended extraction procedures. The metals are transferred to a solution in which their concentrations do not change with time, and which can be easily stored for transportation. The sensitivity is high enough for analysis of open ocean waters.     

Chelating resins for the concentration of trace elements from sea water and their analytical use in conjunction with atomic absorption spectrophotometry

An investigation has been made of the uptake of trace elements from both distilled water and sea water by the chelating ion-exchange resins Chelex-100 and Permutit S1005. The resins retained the following elements with an efficiency of ca. 100%: Ag, Bi, Cd, Cu, In, Pb, Mo, Ni, rare earths, Re (90% only), Sc, Th, W, V, Y and Zn. Manganese was retained quantitatively only by the Chelex resin. The following elements are removed with 100% efficiency by means of₂N mineral acids: Bi, Cd, Co, Cu, In, Ni, Pb, rare earths, Sc, Th, Y and Zn. Ammonia (4 N) completely removes molybdenum, tungsten, vanadium and rhenium. The resins have been used in conjunction with atomic absorption spectrophotometry for the simultaneous determination of zinc, cadmium, copper, nickel and cobalt in sea waters.     

Bulk optode sensors for batch and flow-through determinations of lead ion in water samples

A sensitive optode consisting of highly lead-selective ionophore (Lead IV), proton-selective chromoionophore (ETH 5294) and lipophilic anionic sites (KTpClPB) in plasticized polyvinyl chloride (PVC) membrane was fabricated. The optode membranes were used for determination of Pb²⁺ by absorption spectrophotometry in batch and flow-through systems. The influence parameters such as pH, type of buffer solution, response time and concentration of regenerating solution were optimized. The membrane responded to Pb²⁺ by changing its color from blue to pinkish purple in Tris buffer containing different concentration of Pb²⁺ at pH 7.0. The optode provided the response range of 3.16 × 10⁻⁸ to 5.00 × 10⁻⁵ mol L⁻¹ Pb²⁺ with the detection limit of 2.49 × 10⁻⁸ mol L⁻¹ in the batch system within the response time of 30 min. The dynamic range of 1.26 × 10⁻⁸ to 3.16 × 10⁻⁵ mol L⁻¹ Pb²⁺ with detection limit of 8.97 × 10⁻⁹ mol L⁻¹ were obtained in the flow-through system within the response time of 15 min. Moreover, the proposed optode sensors showed good selectivity towards Pb²⁺ over Na⁺, K⁺, Mg²⁺, Cd²⁺, Hg²⁺ and Ag⁺. It was successfully applied to determine Pb²⁺ in real water samples and the results were compared with well-established inductively coupled plasma optical emission spectrometry (ICP-OES). No significant different value (t_critical = 4.30 > t_exp = 1.00-3.42, n = 3 at 95% of confidence level) was found.     

A fascinating new field in colloid science: small ligand-stabilized metal clusters and their possible application in microelectronics

Small metal clusters, like Au₅₅(PPh₃)₁₂Cl₆, which fall in the size regime of 1–2 nm are colloidal nanoparticles with quantum properties in the transitional range between metals and semiconductors. These chemically tailored quantum dots show by the Quantum Size Effect (QSE) a level splitting between 20 and 100 meV, increasing from small particle sizes to the molecular state. The organic ligand shell surrounding the cluster acts like a dielectric spacer generating capacitances between neighboring clusters down to 10^–18F. Therefore, charging effects superposed by level spacing effects can be observed. The ligand-stabilized colloidal quantum dots in condensed state can be described as a novel kind of artificial solid with extremely narrow mini or hopping bands depending on the chemically adjustable thickness of the ligand shell and its properties. Since its discovery, the Single Electron Tunneling (SET) effect has been recognized to be the fundamental concept for ultimate miniaturization in microelectronics. The controlled transport of charge carriers in arrangements of ligand-stabilized clusters has been observed already at room temperature through Impedance Spectroscopy (IS) and Scanning Tunneling Spectroscopy (STS). This reveals future directions with new concepts for the realization of simple devices for Single Electron Logic (SEL). Part II presents models and connections between microscopic and macroscopic level, regardless of whether there already exist suitable nanoscale metal cluster compounds, and is aimed at the ultimate properties for a possible application in microelectronics.     

Effects of ammonium nitrate on sensitivity for determinations of copper,iron, and manganese in sea water by atomic absorption spectrometry with pyrolytically coated graphite tubes

Ammonium nitrate, used as a matrix modifier in sea-water analysis to eliminate the interference of sodium chloride, degrades the pyrolytic coating on graphite-furnace tubes. The initially increased sensitivities for copper, manganese and iron are maintained for up to 15 atomizations; there is then a rapid decline to a constant lower sensitivity. The characteristics depend strongly on the particular lot of furnace tubes. To decrease the NaCl interference without using matrix modifier, estuarine samples must be diluted (1 + 1) with pure water. Blanks and standards are prepared and diluted with Gulf Stream water containing low amounts of trace metals to match the estuarine matrix.     

In situ electrodeposition for the determination of lead and cadmium in sea water

Electrodeposition techniques for the direct determination of lead and cadmium in sea water at the natural pH and in the presence of dissolved oxygen are examined. Anodic stripping voltammetry, at either the hanging mercury drop electrode or glassy carbon thin film electrode, is suitable for the determination of labile lead and cadmium. The presence of dissolved oxygen increases the height of the lead wave with a shift to more negative potentials. A more versatile technique is in situ deposition of labile metals on a mercury-coated graphite tube electrode. The mercury film, deposited in the laboratory, is stable on the dried tubes which are used later for field electrodeposition. The deposited metals are determined by electrothermal atomic absorption spectrometry.     

Development of protective polymer coatings for silver halide fibers and their application as threshold level sensors for chlorinated hydrocarbons in sea water

The stability of silver halide fibers in artificial sea water (ASW) with and without a protective polymer coating and the influence of high salt concentrations on the sensor response was investigated. In contrast to bare silver halide fibers, the polymer coated fibers remain stable in contact with chloride solutions. This enables the application of a recently presented mid-IR fiber evanescent wave spectroscopy (FEWS) sensor system for the quantitative detection of chlorinated hydrocarbons (CHC) also in sea water.     

A modified nitroso-r method for the determination of cobalt in sea water

The existing colorimetric nitroso-R method for the determination of biologically important cobalt in sea water described by Thompson and Laevastu has been studied in detail, modified and improved. A procedure is recommended in which an approximately five-fold increase in sensitivity is achieved in the measurement of the nitroso-R chelate through close control of : pH, development time of complex, conditions for decomposition of excess reagent, and employment of a wavelength of 425 mμ. The size of the water sample required for an analysis is reduced from 10 to 21. For optimum results it was found necessary for a minimum period of 7 days to elapse following precipitation with sodium carbonate prior to filtration and analysis. A previously unreported salt effect in the procedure is described which requires either construction of a calibration curve from sea water spiked with cobalt or a correction in use of standards in distilled water.A precision was obtained with a 1–2% relative standard deviation throughout range of concentrations used, with an accuracy of 3.0% at 0.5 p.p.b.     

n-Alkanes, PAHs and surfactants in the sea surface microlayer and sea water samples of the Gerlache Inlet sea (Antarctica)

Sea surface microlayer (SML) and sea water samples (SSW) collected in the Gerlache Inlet Sea (Antarctica) were analysed for n-alkanes and polycyclic aromatic hydrocarbons (PAHs). The SML is a potential enrichment site of hydrophobic organic compounds compared to the underlying water column. Total concentration ranges of n-alkanes and PAHs (dissolved and particulate) in subsurface water (− 0.5 m depth) were 272-553 ng l^− 1 (mean: 448 ng l^− 1) and 5.27-9.43 ng l^− 1 (mean: 7.06 ng l^− 1), respectively. In the SML, the concentration ranges of n-alkanes and PAHs were 353-968 ng l^− 1 (mean: 611 ng l^− 1) and 7.32-23.94 ng l^− 1 (mean: 13.22 ng l^− 1), respectively. To evaluate possible PAH contamination sources, specific PAH ratios were calculated. The ratios reflected a predominant petrogenic input. A characterisation of surface active substances was also performed on SML and SSW samples, both by gas bubble extraction, and by dynamic surface tension measurements. Results showed a good correlation between n-alkanes, PAHs and refractory organic matter.     

A modified dimethylglyoxime method for the determination of nickel in sea water

A colorimetric dimethylglyoxime (DMG) method for the determination of nickel in sea water was studied in detail, and improved through close control of experimental conditions. For a maximum precipitation of 90% of the nickel a minimum period of 7 days was necessary between treatment with sodium carbonate and filtration. A salt effect resulted from: (1) a gain in absorbance due to soluble ions not precipitated by sodium carbonate, which increased with increasing salt concentration, (2) an offsetting loss in absorbance due to incomplete precipitation of nickel. The transition 3d ions precipitated by sodium carbonate exerted no discernible effect on the absorbance.A procedure is recommended by which a relative standard deviation of 0.7% was achieved. Consistent recovery yields of 97% were obtained from samples of sea water spiked with nickel collected over a period of several months.