Fe3O4–SiO2 nanocomposites obtained via alkoxide and colloidal route

The magnetic nanocomposite materials represent an important class of nanomaterials extensively studied nowadays due to their varied applications from medical diagnostic to storage information. The iron oxides in silica matrix systems are highly investigated. The sol-gel method is a suitable way of preparation of Fe₃O₄-SiO₂ nanocomposite materials, since this method allowed the preparation of nanocomposite materials with narrow size distribution of magnetite in silica matrix. In the present work, nanocomposite materials in the Fe₃O₄-SiO₂ system were prepared by sol-gel method via alkoxide and aqueous route. As SiO₂ sources, tetraethoxysilan (TEOS) for the alkoxide route, as well as silica sol Ludox (30%) for the aqueous route, were used. This study shows the influence of the type of silica matrix on the structure, size, and distribution of the Fe₃O₄ nanoparticles in the Fe₃O₄-SiO₂ systems. The gels were annealed at 550°C in order to consolidate the matrices. The structural characterization of the obtained materials via the two preparation routes was performed by DTA/TGA analysis, X-ray diffraction, IR and Mössbauer spectroscopy, Transmission Electron Microscopy (TEM) and Selected Area Electron Diffraction (SAED).     

Determination of Arsenic and Phosphorus in Doped Polysilicon Layers

Abstract

The method is based on polysilicon dissolution with a water-hydrofluoric-nitric acid etchant mixture followed by matrix volatilization as hexafluorosilicic acid. Losses of arsenic through volatilization are avoided by its oxidation with permanganate. Phosphorus is determined by the molybdenum blue method with direct addition of a mixed reagent to the residue. Spectrophotometric evaluation at 882 nm provides a detection limit of 10 ng P ml^?1 with a precision better than 3%. Arsenic is determined by reducing As(V) to electroactive As(III) on addition of sulphite in 2 M hydrochloric acid. Differential-pulse polarography of this solution provides a precision of 2% and a detection limit of 20 ng As ml^?1.     

Zeeman Effect Electrothermal Atomic Absorption of Arsenic with Platinum as a Matrix Modifier

Abstract

Since the charring temperature of As in environmental samples can be raised to 1320°C with Pt, the sensitivity of determining As by ET-AAS is increased about 50% using Ni salt as a matrix modifier. The interference of most foreign ions is avoided, but PO^[dbnd] and SO^[tbnd] cause a depression and F^? and SiO^[dbnd] produce an enhancement of the As absorption. The method has been applied to pollution control and river sediment samples with satisfactory results.     

Synthesis of Thin-Film Acidic Ti(IV) and Zr(IV) Phosphates Deposited on Surface of Fiber and Investigation their Properties

Abstract

Cellulosic fibres present great interest as matrix for non-organic synthesis with the use of ion-molecular layering method [I]. This method consists in realization of the successive reactions with the surface functional groups. Synthesized materials can he of scientific and technical interest.     

Synthetic modifications in ethyl 2-amino-4-methylthiazole-5-carboxylate: 3D QSAR analysis and antimicrobial study

Ethyl 2-amino-4-methylthiazole-5-carboxylate (1) is a very substantial derivative of the thiazole group. This derivative has been modified and has been synthesized using readily available materials. The structures of synthesized derivatives were confirmed by IR, ¹H NMR, ¹³C NMR, and mass spectral techniques. The newly prepared compounds (5a–k) were studied for their antimicrobial activities against strains of bacteria (Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, and Streptococcus pyogenes) and fungi (Candida albicans, Aspergillus niger, and Aspergillus clavatus) using serial dilution method. Structure-activity relationship was carried out by CoMFA and CoMSIA with the help of 3D-QSAR analysis. As per the database alignment, the CoMFA and CoMSIA models were developed. Information based on these models is useful for structure-activity relationships of the reported molecules.     

Developed Method for Spectroscopic Studies of Viscous Samples

Abstract

In this work, the trace elements in phosphoric acid, which has been considered an example of the proposed viscous sample, were measured accurately by a developed method. Samples were diluted to decrease matrix and background interferences. Quantitative analysis of As, Ca, Cd, Cu, Fe, Hg, K, Mg, Na, Pb, and Zn were carried out using flame atomic absorption spectrometry (FAAS). A comparison with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) proves the validity of the developed method. The change of the electronic transition due to diluted of the viscous samples was demonstrated using UV-VIS spectroscopy.     

Synthesis and Thermal Characterizations of Pmma Nanocomposite Functionalized by Polyhedral Oligomeric Silsesquioxane

Abstract

A novel polyhedral oligomeric silsesquioxane/polymethyl methacrylate (POSS/ PMMA) hybrid nanocomposite was synthesized by using potassium persulfate and sodium dodecyl sulfate as the initiator and emulsifier, respectively. The structures of prepared nanocomposites were characterized with X-ray photoelectron spectroscopy, laser particle size analysis, and X-ray diffraction. The thermal properties of the POSS/PMMA nanocomposites were studied by differential scanning calorimetry, and thermogravimetric analysis. The results indicate that POSS could be incorporated into the PMMA matrix at molecular lever and the incorporation of POSS molecules can improve the thermal stability of PMMA.

[Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the following free supplemental files: Additional figures]     

Spectral Interference in Antimony Analysis with High Temperature Furnace Atomic Absorption

Abstract

Background correction in atomic absorption spectrophotometry using a high temperature furnace has a close relation to the chemical treatment and the detection limit. Conventionally used for this correction is the D₂ lamp method, but spectral interference is inevitable in this method because the spectral bandwidth of the light from the D₂ lamp after passing through a monochromator is as wide as 0.1 to 5 nm. In the analysis of Sb in lead alloy or in steel, there is spectral interference due to high concentration of elements such as Pb, Cu or Fe, in the matrix, so accurate measurement is impossible unless these elements are removed at the pretreatment stage.

In polarized analyte Zeeman atomic absorption spectrophotometry developed by the authors, the wavelength of the measuring beam is the same as that of the reference and they are identical in spectral line profile as well as in geometrical shape. They differ only in the direction of polarization. For these reasons, we found that there is no spectral interference like that recognized in the D₂ lamp correction technique. As a result, a direct analysis was done simply by dissolving gunmetal or steel in acid without removing the matrix elements Pb, Cu or Fe.     

The Emerging Role of Titrimetry in Late Nineteenth-Century Industrial Problem Solving: The Example of Trace Analysis for Perchlorate in Chile Saltpetre

Abstract

Trace analysis is usually associated with high-sensitivity analysis instrumentation. It became fully established from the 1960s following consensus among different groups of practitioners over protocols, reference materials, sensitivity, and accuracy and precision. As a consequence, wet chemical methods have been relegated to a secondary role, contrasting with their tremendous historical significance in detecting, identifying, and estimating small amounts of material. This is particularly relevant to the state-of-the-science analytical determinations stimulated by the effect of minor components in commodities of commercial importance. Here, I select a single example: attempts made during the 1890s to determine the amount of potassium perchlorate (KClO₄) that occurs in Chile saltpetre (sodium nitrate). The application of titrimetry, particularly the adaptation of Volhard's method for chloride analysis, was crucial in the efforts to estimate perchlorate in the nitrate used for explosives and to track the impact of perchlorate concentrations on certain important agricultural crops.     

An estimation of the measurement uncertainty for an optical emission spectrometric method

 A validation procedure based on the ISO/IEC 17025 standard was used to demonstrate the long-term stability of a calibration process and to assess the measurement uncertainty of a standard test method for optical emission vacuum spectrometric analysis of carbon and low-alloy steel (ASTM E 415–99a). The validation was used to provide documented evidence that the selected method fulfils the requirements and that the method is ”fit for purpose”. A test for drift was applied to determine statistically whether the analytical results vary systematically with time. The accuracy and traceability of the optimised method were tested by an analysis of closely matched matrix certified reference materials (CRMs). The measurement uncertainty estimations took account of the precision study, the bias and its uncertainty, and the qualification of uncertainties not considered in the overall performance studies. Received: 2 November 2002 Accepted: 2 January 2003 Acknowledgement The author expresses gratitude to Dr. Aleš Fajgelj for helpful discussions during the 3rd Central European Conference on Reference Materials and Measurements. Presented at CERMM-3, Central European Reference Materials and Measurements Conference: The function of reference materials in the measurement process, May 30–June 1, 2002, Rogaška Slatina, Slovenia Correspondence to T. Drglin     

Atomic Fluorescence Determination of Selenium Using Hydride Generation Technique

Abstract

Hydride generation followed by atomic fluorescence spectrometry, a simple and very sensitive technique, has been evaluated for selenium analysis in different environmental and biological samples. Research is focused on the interfering effects of several selected anions, cations, and acids on the selenium determination and the sample preparation procedures. Besides some transition metals such as Ni²⁺ Co²⁺ and Cu²⁺ HNO₃ acid, the digestion medium used for sample preparation, shows strong interference. In order to reduce this interfering effect, matrix match or standard addition is recommended. This technique is validated by analyzing a number of standard reference materials. Results for selenium analysis in some biological samples are also presented.     

Multi-Target Classification Pattern Recognition Applied to Computer-Aided Materials Design

Abstract

A multi-target classification pattern recognition method based on the principal component analysis (PCA) has been proposed for computer-aided materials design considering the multiple specialties of materials. The designed sample with probable optimal specialties is determined in such way that its representing point should be at the optimal region in the PC sub-space, where most optimal samples can be discriminated from non-optimal samples by means of features. The experimental parameters of the sample represented by this point can be obtained using a non-linear inverse mapping method from the PC sub-space to the original space. Based on the information provided using the method, several samples of V-PTC materials with optimal multiple specialties are synthesized.     

Cesium Salt of Tungstosilicic Acid Fabricated by Nano-Casting Strategy: An Efficient Catalyst for the Three-Component Hosomi–Sakurai Reaction

Abstract

We have used SBA-15 silicas as hard templates for the nano-fabrication of Cs_1.8H_2.2SiW₁₂O₄₀ (CsHSiW) salt nanocrystal. The elimination by HF (or NaOH 90 °C) in the silica matrix from the composites occurred by a two-step reaction deposition of CsHSiW salt nanocrystal. The nano-casted CsHPW materials were characterized by several techniques: chemical analysis (atomic absorption, neutron activation analysis, and inductively coupled plasma) and spectroscopic methods (FT-IR spectrum, X-ray diffraction, transmission electron microscopy, and energy dispersive x-ray analysis measurement). In addition to the complete characterization of CsHSiW nanocrystal samples, their catalytic performances are shown for the three-component Hosomi–Sakurai reaction. The reaction proceeds efficiently under ambient conditions with good to excellent yields.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.     

Study of Matrix Effects on Determination of Trace Elements in Aluminum,Using Inductively Coupled Plasma Atomic Emission Spectrometry, 1) Selection of Spectral Lines.

Abstract

The effect of an aluminum matrix on the determination of B, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Si and Zn was studied. These elements are expected to be present in high purity Al base materials. 45 spectral lines of these elements were scanned in a spectral window of 60 pm. Background equivalent concentrations were calculated and compared with existing data. Interference free spectral lines, one for each element, have been recommended to be used for analysis. Depression effects due to the Al matrix were calculated at the selected lines.     

A diagnostic tool for determining the quality of accuracy validation. Assessing the method for determination of nitrate in drinking water

Realistic internal validation of a method implies the performance validation experiments under intermediate precision conditions. The validation results can be organized in an X _Nr×Ns (replicates×runs) data matrix, analysis of which enables assessment of the accuracy of the method. By means of Monte Carlo simulation, uncertainty in the estimates of bias and precision can be assessed. A bivariate plot is presented for assessing whether the uncertainty intervals for the bias (E ± U(E)) and intermediate precision (RSDi ± U(RSDi) are included in prefixed limits (requirements for the method). As a case study, a method for determining the concentration of nitrate in drinking water at the official level set by 98/83/EC Directive is assessed by use of the proposed plot.     

Direct Determination of Aluminum in Archaeological Clays by Laser‐Induced Breakdown Spectroscopy

Abstract

Instrumental techniques that allow the direct analysis of solids with little or no sample preparation are particularly important for the evaluation of samples that are difficult to analyze such as refractory or geological materials. Laser‐induced breakdown spectroscopy (LIBS) is a promising technique for the direct, rapid analysis of elements in solid materials with minimal sample preparation. The main advantages over wet techniques are virtual nondestructiveness and analysis speed. The goal of this work is the direct determination of aluminum of archaeological pieces using laser‐induced breakdown spectroscopy. The corresponding signals of metals were interpolated from calibration graphs of different salts of the metals. The matrix effects from the direct determination of these elements were thoroughly investigated. The potential of this technique for direct quantitative analysis of real archaeological materials (from Department of Ancient Science, University of Zaragoza) was evaluated, and the reproducibility of LIBS spectra from different archaeological samples was measured as a function of the number of laser shots. Finally, the results from LIBS are compared with those obtained by laser ablation inductively coupled plasma mass spectrometry.     

The influence of different factors on exploitation properties of nonlinear optical polymeric materials based on an epoxy matrix doped with flavonoids

The paper is devoted to investigations of exploitation properties of nonlinear-optical (NLO) polymer film materials based on an epoxy matrix doped with flavonoids. Adhesion of the polymer films to a glass substrate is investigated. Also, the influence of photoinduced destruction on functional properties of these polymer composites by UV–Vis spectroscopy method is studied. Effect of various microorganisms such as mold fungi of Aspergillus niger (A. niger) and Pinicillum chrysogenum (P. chrysogenum) species on the polymer NLO materials are analyzed by evaluation of the fungistatic effect and fungicidal resistance and using the FTIR spectroscopy. As a result it is established that the NLO polymer film materials based an epoxy matrix doped with flavonoids have a very good adhesion to the glass substrate, and they are stable to the photoinduced destruction. These materials do not have the fungistatic effect but they demonstrate some fungicidal resistance. This phenomenon is explained by the presence of flavonoids, which are natural antiseptics.     

Sub-Microdetermination of Antimony (Iii) and Antimony (V) In Natural and Polluted Waters and Total Antimony In Biological Materials By Flameless Aas Following Extractive Separation With N-P-Methoxyphenyl-2-Furylacrylohydroxamic Acid

Abstract

Antimony (III) was separated from antimony (V) by extractive separation from 2–10^?6 M HC1 media with N-p-methoxyphenyl-2-furylacrylohydroxamic acid (MFHA) in chloroform and determined by graphite furnace atomic absorption spectroscopy at 2600°C using copper as matrix modifier. Antimony (V) was subsequently reduced to the trivalent form with acidic (-1M HC1) potassium iodide solution and determined as above. the mutual tolerance between antimony (III) and antimony (V) in the present mothod was very high-either of the species could be determined in presence of 15 times higher concentration of the other species. the sepatation-AAS determination system enabled accurate differential analysis of the metalloid in natural/ polluted waters down to 10^?2 ppb (ug 1^?1) levels. the method was also applied to the analysis of antimony in vehicle exhaust particulates, plant tissues, and animal tissues. the method was validated by analysing several certified reference materials with and without standard addition of antimony. MFHA was chosen from amongst thirteen new hydroxamic acids.     

Inorganic arsenic speciation in various water samples with GFAAS using coprecipitation

A simple, economic and sensitive method for selective determination of As(III) and As(V) in water samples is described. The method is based on selective coprecipitation of As(III) with Ce(IV) hydroxide in presence of an ammonia/ammonium buffer at pH 9. The coprecipitant was collected on a 0.45 µm membrane filter, dissolved with 0.5 mL of conc. nitric acid and the solution was completed to 2 or 5 mL with distilled water. As(III) in the final solutions was determined by graphite furnace atomic absorption spectrometry (GFAAS). Under the working condition, As(V) was not coprecipitated. Total inorganic arsenic was determined after the reduction of As(V) to As(III) with NaI. The concentration of As(V) was calculated by the difference of the concentrations obtained by the above determinations. Both the determination of arsenic with GF-AAS in presence of cerium and the coprecipitation of arsenic with Ce(IV) hydroxide were optimised. The suitability of the method for determining inorganic arsenic species was checked by analysis of water samples spiked with 4–20 µg L^?1 each of As(III) and As(V). The preconcentration factor was found to be 75 with quantitative recovery (≥95%). The accuracy of the present method was controlled with a reference method based on TXRF. The relative error was under 5%. The relative standard deviations for the replicate analysis ( n?=?5) ranged from 4.3 to 8.0% for both As(III) and As(V) in the water samples. The limit of detection (3σ) for both As (III) and As(V) were 0.05 µg L^?1. The proposed method produced satisfactory results for the analysis of inorganic arsenic species in drinking water, wastewater and hot spring water samples.     

Determination of227Ac in geological materials through neutron activation and alpha-spectrometric assay of induced228Th

A new route has been developed for the micro-determination of²²⁷Ac in geological materials by neutron activation. The method is based on intense neutron irradiation of the analysed samples followed by separation and α-spectrometric determination of²²⁸Th, the β-decay product of the 6.1 hrs²²⁸Ac isotope formed. Two alternatives are considered for analysis related to the origin of the analysed matrix. The high sensitivity of the method is documented by the determination of 10^?17 g²²⁷Ac/g sample. The method is successfully applied for age determination of five uranium containing materials and old uranium glass from Bohemia, CSSR.