Evaluation of Carbon Rod Atomizer for Routine Analysis of Vanadium in Crude Oil by Atomic Absorption Spectroscopy

Abstract

The Carbon Rod Atomizer (CRA) was evaluated for routine trace analysis of vanadium in crude oil by atomic absorption spectroscopy with a carbon (graphite) tube as a micro-furnace. Two crude oil samples were analyzed, both by standard addition and standard working curve methods, and the results confirmed by analysis with flame atomic absorption spectroscopy using a fuel-rich nitrous oxide-acetylene flame. Because of the relative involatility of vanadium at the temperature of the CRA, quantitative recoveries of vanadium in crude oil occur only when the vanadium content of the sample injected into the CRA does not exceed the limit of about 1 × 10^?8 g. A sensitivity (weight/1% absorption) of 7.0 × 10^?11 g and detection limit (signal-to-root-mean-square-noise equal to two) of 6.9 × 10^?12 are reported.     

A New Approach to Determining the Content and 15N Abundance of Total Dissolved Nitrogen in Aqueous Samples: TOC Analyser-QMS Coupling

Abstract

The standard method for determining the ¹⁵N abundance of total dissolved nitrogen (TDN) in aqueous samples (e.g., soil leachate, sewage, urine) is currently Kjeldahl digestion followed by steam distillation or diffusion to isolate the ammonium, and then ¹⁵N measurement using IRMS. However, this technique is both time-consuming and laborious. One way of overcoming these disadvantages could be to couple a TOC analyser to determine the TDN with a sufficient quadrupole MS to determine the ¹⁵N abundance. The highTOC analyser (Elementar Analysensysteme Hanau, Germany), which catalytically oxidises the sample's total nitrogen with a high, constant yield to nitrogen monoxide (NO), appeared particularly suitable. The quadrupole-MS ESD 100 (InProcess Instruments Bremen, Germany) proved to be a suitable mass spectrometer for the ¹⁵N determination of NO. This combination of instruments was found to provide a workable method in numerous measurements of standard and actual samples. The detection limit concerning the N amount required per analysis is 2 μg, corresponding to an N concentration of 0.7mg/l in a maximum sample volume of 3ml. Depending on the N concentration, ¹⁵N abundances starting from 0.5 at.% can be measured with the required precision of better than 3% (simple standard deviation). For example, measuring the abundance of 0.5 at.% requires about 50 μg N, whereas for 1 at.% or more only about 5 μg N is needed per analysis.     

Determination of elements in some lichens growing in Giresun and Ordu province (Turkey) using energy dispersive X-ray fluorescence spectrometry

The concentration of five different elements in six lichens species of different regions in Giresun and Ordu (Turkey) was determined using the energy dispersive X-ray fluorescence method. A radioisotope excited X-ray fluorescence analysis using the method of multiple standard addition is applied to the elemental analysis of lichens. An annular 50 mCi ²⁴¹Am radioactive source and an annular 50 mCi ⁵⁵Fe radioactive source were used for excitation of characteristic K X-rays. An Si(Li)detector which has a 147 eV full-width at half-maximum for 5.9 keV photons was used for intensity measurements. A qualitative analysis of spectral peaks showed that the samples contained potassium, calcium, titanium, iron, and barium.     

土壤重金属铬元素的激光诱导击穿光谱定量分析研究

利用Nd ∶YAG脉冲激光器(波长:1064 nm)作为光源,在实验室自然大气环境下诱导产生土壤激光等离子体,通过等离子体原子发射光谱法定量分析了国家标准土壤样品中元素Cr的含量.实验上研究了在最佳实验条件下土壤中Cr的LIBS分析谱线,测定了Cr元素的定标曲线.实验结果表明,Cr元素浓度在(60—400)×10^-6范围内,元素含量与光谱线强度之间有较好的线性关系;元素Cr浓度分析测量的相对标准偏差(RSD)为7.89%,定量分析结果与标准值的相对偏差为5.3%,Cr元素的检测限为1 关键词： 土壤污染 定量分析 激光诱导击穿光谱 定标曲线     

基于单细胞拉曼技术鉴定非结核分枝杆菌的方法研究

非结核分枝杆菌（NTM）是除结核分枝杆菌复合群（MTC）和麻风分支杆菌以外的分枝杆菌总称。近年来NTM导致人类感染的发病率不断上升,其感染的临床症状与MTC感染极为相似,但两者治疗方案却存在差异,临床亟须快速、准确的鉴定方法用于诊断NTM感染。单细胞拉曼光谱技术（SCRS）具有非标记、免培养、快速、准确、低成本等优势。据此,我们提出了一种基于显微共聚焦单细胞拉曼光谱技术鉴定NTM的方法。通过对临床常见的六种NTM（脓肿分枝杆菌、戈登分枝杆菌、偶发分枝杆菌、土分枝杆菌、鸟分枝杆菌以及堪萨斯分枝杆菌）的拉曼光谱进行处理比较,并结合峰位注释进行分析。采用无监督低维可视化的t-分布式随机邻域嵌入方法展示六种NTM的拉曼数据结构,证明其数据在低维空间上的可分性后,比较分类中常用的六种分类器[支持向量机分析(SVM)、K最近邻分类算法(KNN)、偏最小二乘判别分析(PLS-DA)、随机森林(RF)、线性判别分析(LDA)、XG Boost]的效果。SVM和LDA在NTM分类中效果最好,分别达到了99.4%和98.8%的测试准确率;SVM仅对于堪萨斯分枝杆菌（97.96%,48/49）的分类准确性略低,其余均为100%;LDA对于脓肿分枝杆菌（95.65%,22/23）和戈登分枝杆菌（96.30%,26/27）,其余也均为100%。因此,单细胞拉曼检测结合SVM分类器为NTM快速准确鉴定提供了富有潜力的新工具。     

Interference method of measuring the extinction coefficient of birefringent optical fibers

The extinction coefficient of a birefringent optical fiber (the ratio between the radiation power output of the polarization mode and the radiation power transferred from this mode to another one) characterizes the capability of a birefringent fiber to retain the polarization state of the radiation. In relatively short birefringent fibers (1–100 m), the extinction coefficient may reach 10⁴–10⁶. Such high values of the extinction coefficient are difficult to measure by standard techniques (excitation of one polarization mode by an incoherent source with subsequent recording of the light intensity at the output of the analyzer). An interference method of measuring the extinction coefficient of birefringent fibers is suggested. It is based on using a coherent source and measuring interference oscillations caused by an additional phase modulation at the input of the fiber. This method does not require precise polarization matching between the laser source and fiber and considerably loosens requirements for the polarizer-analyzer extinction and resolution of the photodetector. As a result, using simple standard components (semiconductor laser, film polarizer, and photodetector), one can measure extinction coefficient as high as 10⁶. The suggested interference method of measuring the extinction coefficient of birefringent fibers receives a theoretical analysis, and experimental data obtained for 2- to 1000-m-long fibers are presented.     

Sample preparation techniques for the determination of natural 15N/14N variations in amino acids by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS)

In order to identify natural nitrogen isotope variations of biologically important amino acids four derivatization reactions (t-butylmethylsilylation, esterification with subsequent trifluoroacetylation, acetylation and pivaloylation) were tested with standard mixtures of 17 proteinogenic amino acids and plant (moss) samples using GC-C-IRMS. The possible fractionation of the nitrogen isotopes, caused for instance by the formation of multiple reaction products, was investigated. For biological samples, the esterification of the amino acids with subsequent trifluoroacetylation is recommended for nitrogen isotope ratio analysis. A sample preparation technique is described for the isotope ratio mass spectrometric analysis of amino acids from the non-protein (NPN) fraction of terrestrial moss. ¹⁴N/¹⁵N ratios from moss (Scleropodium spec.) samples from different anthropogenically polluted areas were studied with respect to ecotoxicologal bioindication.     

Prospects for the measurement of the structure of the coupling of a Higgs boson to weak gauge bosons in weak boson fusion with the ATLAS detector

The prospects for the measurement of the tensor structure of the vertex between a standard model Higgs boson and two weak gauge bosons using the distribution of the azimuthal angles between the two tagging jets in the weak boson fusion channel are studied in a Monte Carlo analysis using the fast simulation of the ATLAS detector. The decay channels H→τ⁺τ^-→ll+4ν, H→τ⁺τ^-→lh+3ν at m_H=120 GeV and H→W⁺W^-→llνν at m_H=160 GeV are used in the analysis. For a standard model Higgs boson it is found that purely anomalous couplings are expected to be excluded at a confidence level corresponding to 2σ or more at m_H=120 GeV and more than 5σ at m_H=160 GeV from 30 fb^-1 of data. With a value of 1 roughly reproducing the standard model cross section for a purely anomalous coupling, the standard deviation in a measurement of a contribution of a CP even anomalous coupling in addition to the standard model coupling is estimated to be 0.20 at m_H=120 GeV and 0.09 at m_H=160 GeV.     

On Line Dissolution of ZnS For Sulfide Determination in Stabilized Water Samples with Zinc Acetate,Using Spectrophotometry by Methylene Blue Method

Abstract

Stabilization of sulfide as zinc sulfide is a strategy widely used in batch analysis of this ion in water. A FIA/spectrophotometry system to determine sulfide in stabilized water samples is proposed in this paper. The methodology is based on the formation of methylene blue by the reaction of H₂S with a mixture of Fe³⁺ solution and N,N-dimethyl-p-phenylenediamine (DMPD) in acidic medium. In the system, the sample (480 μL) containing stabilized sulfide (as ZnS slurry) is injected in a carrier stream formed by mixing acidic Fe³⁺ and DMPD. In the reactor coil of 1280 μL, the sulfide is drifted by acid used in the preparation of solutions, releasing H₂S that reacts with Fe³⁺ and DMPD forming methylene blue. The absorbance is measured at 662 nm. The performance of the FIA system was optimized in relation to chemical and flow parameters. The stability of the solutions were studied throughout the period of the experiment. The results did not show any loss of sulfide over a 7 day period. However, in complex matrices an analysis by using the standard addition method is recommended. The analysis of effluent sample through the time showed good agreement between the results obtained each day. The developed system presented the following figures of merit: detection limit of 50 μg L^?1; RSD of 6% at 0.5 μg mL^?1 (using ultrasonic homogenization) and analytical throughput of 60 samples per hour.     

Dark resonances in 87Rb atomic vapors interacting with the field of copropagated linearly polarized waves of various frequencies

The results of theoretical and numerical analysis of resonances of coherent population trapping in ⁸⁷Rb atomic vapors, obtained using copropagated linearly polarized waves, are presented. Various schemes for exciting dark resonance are compared with a view to obtaining a new-generation small-size quantum frequency standard.     

Detection of melamine in liquid milk using surface‐enhanced Raman scattering spectroscopy

Melamine, a nitrogen‐rich chemical, has recently caused enormous economic losses to the food industry due to the cases of milk products adulterated by melamine. This has led to an urgent need of rapid and reliable methods for detection of melamine in food. In this study, surface‐enhanced Raman scattering (SERS) spectroscopy was used to detect melamine in liquid milk. The sample preparation with liquid milk is very easy; it has to be only diluted with double‐distilled water followed by centrifugation. By using a silver colloid, at least a 10⁵‐fold enhancement of the Raman signal was achieved for the measurement of melamine. The limit of detection by this method was 0.01 µg ml⁻¹ for melamine standard samples. Based on the intensity of the Raman vibrational bands normalised to that of the band at 928 cm⁻¹ (CH₂), an external standard method was employed for quantitative analysis. The linear regression square (R²) of the curve was 0.9998; the limit of quantitation using this approach was 0.5 µg ml⁻¹ of melamine in liquid milk; the relative standard deviation was ≤10%; and recoveries were from 93 to 109%. The test results for SERS were very precise and as good as those obtained by liquid chromatography/tandem mass spectrometry. The method was simple, fast(only needs about 3 min), cost effective, and sensitive for the detection of melamine in liquid milk samples. Therefore, it is more suitable for the field detection of melamine in liquid milk. Copyright © 2010 John Wiley & Sons, Ltd.     

A Gas Diffusion Technique Coupled with Flow Injection Systems. Optimization of the Process in its Application to the Fluorimetric Determination of Ammonium in Water Samples

A novel flow injection-gas-diffusion (GD-FI) system has been developed for the on-line analysis of ammonium ion in waters with fluorimetric detection, using an acceptor solution containing the Eosin-Bluish (EB) acid-base indicator. This, together with optimization of the process of gas transfer through the membrane, increases the sensitivity of the method to a considerable extent. Under optimum conditions, it is possible to determine the analyte within the 0.02–1.5 mg l^-1 range, with a limit of detection of 5 μg l^-1 and relative standard deviations (n = 12, [NH₄⁺] = 50 μg l^-1 and 0.05 μg l^-1) of 3.4% and 3.0% respectively. The determination rate was 15 samples per hour.     

Density functional theory calculations and vibrational spectra of p‐bromonitrobenzene

FT‐IR and FT‐Raman spectra of p‐bromonitrobenzene (p‐BNB) have been recorded in the region 4000–400 cm⁻¹ and 4000–50 cm⁻¹, respectively. The molecular structure, geometry optimization, vibrational wavenumbers have been investigated. The spectra were interpreted with the aid of normal coordinate analysis based on the density functional theory (DFT) using the standard B3LYP/6‐31G method and basis set combination and was scaled using multiple scale factors yielding good agreement between observed and calculated wavenumbers. The results of the calculations are applied to simulate infrared and Raman spectra of the title compound which showed reasonable agreement with the observed spectra. Copyright © 2009 John Wiley & Sons, Ltd.     

Quadratic augmented plane wave method for self-consistent band structure calculations

Recently linearized versions of the augmented plane wave (APW) method have been introduced. The quadratic-APW (QAPW) method is presented which is a more general formulation of the linear-APW (LAPW) methods. Here the exact radial solution inside the muffin-tin (MT) sphere is replaced by its Taylor expansion with respect to the energy, truncated after the quadratic term, i.e. with higher accuracy when compared with the standard LAPW method which uses only the linear term. The standard LAPW method is obtained as a special case from our formulation. Similarly to the standard LAPW method, the energy independent APW's are formed from approximate radial wave functions which lead to the secular equations linear in energy. The analysis of the solution inside the MT-sphere shows that the eigenvalue error is proportional to (E-E ₀)⁶ in the method suggested as compared with (E-E ⁰)⁴ for the standard LAPW method. As an application both non-self-consistent and self-consistent calculations are presented for the band structure of FCC copper metal.     

On the condensate values in QCD

Conclusions The sets (3) and (4) of condensates have been compared using the QCD sum rules (2) with indefinite weight functions. A bad matching between both sets of condensates and experimental data has been obtained. The standard values (3) appear to be closer to data but some increase ofQ is necessary to improve the agreement. Only higher values ofm ₀ ² could change the results of this analysis. It is interesting that negative values ofm ₀ ² considerably improve the agreement with data; note that this quantity cannot be determined with a sufficient accuracy. We conclude that the QCD sum rules (2) cannot definitely determine a privileged set of condensates.Dedicated to Academician Václav Votruba on the occasion of his eightieth birthday.     

Comparative analysis of deuterium ions implanted and deuterium atoms saturated at high pressure in pure pd and Pd diluted alloys

Pd and its diluted alloys (Pd-Ag, Pd-Pt, Pd-Ru, Pd-Rh) were implanted by 25 keV deuterium ions at a fluence interval of (1.2–2.3) × 10²² m⁻². The same property alloys were saturated by deuterium atoms using high pressure chamber during long period with temperature stabilization and electrical resistance measurement of standard Pd wire. The post-treatment depth distributions of deuterium and accompanied hydrogen atoms were measured immediately after implantation (ten days) and after definite time period (three months) after saturation with the usage of elastic recoil detection analysis (ERDA). After two months, the measurements were repeated. The comparison of obtained results in both series of studies allowed one to make an important observation of a relative stability of deuterium and hydrogen atoms in pure Pd and its diluted alloys.     

Stabilization of neoclassical tearing modes by an externally applied static helical field

The effect of a static helical magnetic field on the nonlinear growth of the neoclassical tearing mode (NTM) is investigated. The NTM is found to be stabilized by an externally applied helical field of a different helicity if the field magnitude is sufficiently large, suggesting a very simple method for stabilizing the NTM. The mechanism responsible for this stabilization is the decreased fundamental harmonic pressure perturbation of the NTM in the presence of the helical field.     

Neutron inelastic scattering from 40Ca at 21.7 and 25.5 MeV

Differential cross sections for the scattering of neutrons from ⁴⁰Ca for states up to 5 MeV excitation energy have been measured at 21.7 and 25.5 MeV. The analysis is done using a coupled channel formalism in terms of a vibration collective model. The results using a usual standard Woods-Saxon form factor for the transitions are compared with those obtained using form factors derived from a model-independent analysis to the elastic cross sections.     

Quantitative analysis of chromate (CrVI) by normal Raman spectroscopy and surface-enhanced Raman spectroscopy using poly(diallyldimethylammonium) chloride-capped gold nanoparticles

Chromate (Cr^VI) has emerged as a widespread environmental contaminant found in groundwater and surface water, and there is a great need for rapid detection and monitoring of this contaminant. Normal Raman scattering (NRS) spectroscopy with a detection limit of Cr^VI at concentrations of 0.2 g/L was attached. And surface-enhanced Raman scattering (SERS) spectroscopy technique was found to be capable of detecting Cr^VI at concentrations as low as 2.5 mg/L using poly(diallyldimethylammonium) chloride modified gold nanoparticles (PDDA-AuNPs) as a substrate. The SERS substrate was successfully fabricated by combining the selfassembly technique with a heat-treatment-based strategy using poly(diallyldimethylammonium) chloride (PDDA) as the reducing and stabilizing agents. With the 520 cm^?1 band of silicon as internal standard, band intensity ratios of Cr^VI to silicon, that is I ₉₀₂/I ₅₂₀, were found to have a quantitative relationship with a large concentration range of Cr^VI from 0.2 to 20.0 g/L for NRS (R ² = 0.994) and from 2.5 to 25.0 mg/L for SERS (R ² = 0.980), respectively. Besides, the SERS methodology was reproducible, and susceptible to the interference of pH value. The optimum pH for Cr^VI detection by SERS was 3.38. The application of NRS and SERS showed high practical potential for rapid screening and routine analysis of Cr^VI in environmental samples.     

Pressure-induced line broadening for the (30012)←(00001) band of CO2 measured with tunable diode laser photoacoustic spectroscopy

Pressure-induced foreign-broadening lineshape parameters of the carbon dioxide rovibrational transitions belonging to the (30012)←(00001) overtone band near the 1.573 μm wavelength region are measured by using a tunable diode laser photoacoustic spectrometer. The spectroscopic analysis has concerned the first 11 lines of the R branch. For these lines, the air- and Ar-broadening coefficients are measured at room temperature (∼298 K). The measured broadening coefficients of all the transitions of ¹²C¹⁶O₂ are compared with those given in the HITRAN04 database and former measurements with a different spectroscopic method. Agreements and discrepancies are underlined and briefly discussed. The recorded lineshapes are fitted with standard Voigt line profiles in order to determine the collisional broadening coefficient of carbon dioxide transitions.