The spectrographic determination of total barium in bone ash

Samples of bone ash are mixed with graphite and anhydrous copper sulphate as spectrographic buffer and lanthanum oxide as internal standard. The mixture is pressed into 30-mg pellets and burnt in a d.c. arc surrounded by a mantle of oxygen and argon. The spectra are evaluated by non-recording microphotometry. The effective concentration range is 2–25 p.p.m. of barium in the ash, and the coefficient of variation is 8% for single exposures at the 8-p.p.m. level     

Direct spectrographic determination of impurities in uranium tetrafluoride

A direct spectrographic method for tlic determination of some impurities in UF₄ is described. The sample in the graphite electrode was covered with a layer of alumina before the arc was struck; alumina prevents the volatilization of UF₄ and thus avoids high spectral and background interferences. To stabilize the discharge, a controlled atmosphere of argon and oxygen was used. The impurity elements were divided into 3 categories according to their volatility: high (B, Si), medium (Co, Mn, V, Mo, Ti, etc.), and low (Ni, Pb, alkaline earths, etc.). Impurities of high and medium volatility could be determined with germanium or aluminum as internal standard. The sensitivities found for this method generally agreed with those of the carrier distillation method. The coefficients of variation varied from 8 to 25% at the 25 p.p.m. level.     

Graphite Supported Preparation (GSP) of α-Cyano-4-Hydroxycinnamic Acid (CHCA) for Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry (MALDI-MS) for Peptides and Proteins

Graphite as MALDI matrix or in combination with other substances has been reported in recent years. Here, we demonstrate that graphite can be used as target coating supporting the crystallization of the ??-cyano-4-hydroxycinnamic acid matrix. A conventional dried-droplet preparation of matrix and analyte solution on a graphite-coated metal target leads to a thin, uniform layer of cubic crystals with about 1???m edge length. Commercially available graphite powder of 1?C2???m particle size is gently wiped over the target using a cotton Q-tip, leading to an ultra-thin, not-visible film. This surface modification considerably improves analysis of peptides and proteins for MALDI MS using conventional dried-droplet preparation. Compared with untreated targets, the signal intensities of standard peptides are up to eight times higher when using the graphite supported crystallization. The relative standard deviation in peak area of angiotensin II for sample amounts between 1 and 50?fmol is reduced to about 15?% compared with 45?% for untreated sample holders. For a quantification of 1?fmol of the peptide using an internal standard the coefficient of variation is reduced to 3.5?% from 8?%. The new graphite supported preparation (GSP) protocol is very simple and does not require any technical nor manual skills. All standard solvents for peptides and proteins can be used.     

Determination of boron,beryllium and lithium in coal ash and geological materials by spark optical emission spectrometry

A method is described for the accurate and precise determination of boron, beryllium and lithium in coal ash and geological materials by a point-to-plane high-voltage spark optical emission spectrometric technique. A 200-mg sample is crushed and blended with graphite, copper oxide internal standard and cellulose powders, and briquetted. Synthetic calibration standards are prepared from spectrographically pure materials blended into graphite. Corrections are made for spectral interference by iron and silicon on boron. Accurate results are presented for certified reference materials. The precision of the method, about 5%, is superior to that obtained by d.c. arc optical emission.     

D.C. arc spectrochemical determination of rhenium in molybdenite ores

Rhenium is isolated as tetraphenylarsonium perihenate from solutions of molybdenite ores. It is excited in a mixture with an alumina/graphite buffer directly on the cathode in an oxygen atmosphere. Oxygen acts as a protective atmosphere and as a carrier to sweep into the discharge the highly refractory rhenium in the form of easily volatilized oxides Intensity ratios of Re 346473, 346046, 345188 and 3399 30 Å lines with Co 3453.50 Å internal standard line cover the range 0.1–3.2μg of rhenium on the electrode. The relative deviation of the method, computed by a routine regiession analysis program, is+16-—14% for the best analytical line The detection limit is 6·10^-8 g of rhenium Several Canadian and other molybdenites with a rhenium content from 8 to 250 p.p.m. have been analysed.     

The spectrochemical determination of total strontium in bone,milk and vegetation

Samples of bone ash are mixed with anhydrous copper sulphate and graphite and pelleted A d c. arc is used to excite the spectra which are then evaluated by microphotometry The effective concentration range is 50 – 350 p p. m of strontium in the ash and the coefficient of variation is 6% for single exposures at the 90 p p m levelIn the case of milk and vegetation, strontium and calcium are separated as insoluble oxalates and the strontium content of this fraction determined by a method similar to that used for bones, with a similar range and accuracy. An alternative flame photometric method is described for the determination of strontium in the calcium-strontium oxalate fraction, thc coefficient of variation of the whole analytical operation being 5% per determination     

Spectrographic analysis of boron nitride for trace impurities

A d.c. arc emission spectrographic method has been developed for the determination of nine trace impurities in boron nitride. The charge for exciting the sample contains equal quantities of boron nitride and graphite (containing 2% NaF as carrier and 1% La(2)O(3) as an internal standard). The method is useful in the determination of impurities in the range 2-1000 ppm, with a mean relative standard deviation of 13%.     

Determination of trace impurities at the p.p.b. level in fused silica by spark-source mass spectrometry

A sample dissolution-concentration technique for the determination of trace elements in fused silica by spark-source mass spectrometry (s.s.m.s.) is described. The fused silica is dissolved by ultra-pure hydrofluoric acid, and most of the silicon tetrafluoride formed is then removed at 80–100° C, leaving behind the impurities in the solution as fluorides. After addition of ultrahigh-purity graphite and internal standards (Tl and Rb), the mixture is dried to give a sample suitable for pressing into electrodes. The method not only concentrates the trace impurities but also reduces the interferences originating from silicon oxide and carbide species in the mass spectra and thus allows the determination of a larger number of elements at p.p.b. levels. More than 30 trace impurities in 6 fused silica boules and J.T. Baker's Ultrex silicon dioxide are determined and compared with data obtained by other methods.     

Studies of the cathode layer of a d.c. arc

Some factors which affect the cathode layer of a d.c. arc were investigated. It is shown that: (i) varying concentrations of elements with low ionisation potentials in the sample can markedly affect the distribution of atoms in the cathode layer and hence the detection limits of the technique; (ii) variations in arc current and arc gap have only a small effect on the cathode layer provided that these factors are maintained at values above certain minimum levels; (iii) the use of artifical atmospheres and inhomogeneous magnetic fields generally increase detection limits; (iv) detection limits obtained with samples containing relatively high concentrations of elements with low ionisation potentials can be two or three times better than those obtained with conventional anode evaporation techniques provided wandering of the cathode spot is kept to a minimum, a condition which often cannot be realised in practice.     

Evaluation and application of bismuth as an internal standard for the determination of lead in wines by simultaneous electrothermal atomic absorption spectrometry

A method for the direct determination of Pb in wines by simultaneous multi-element atomic absorption spectrometry (SIMAAS) using a transversely heated graphite atomizer, Zeeman-effect background corrector and internal standardization is proposed. Bismuth was used as an internal standard and Pd(NO3)2 plus Mg(NO3)2 as chemical modifier to stabilize both the analyte and the internal standard. The implementation of two pyrolysis steps avoided any build-up of carbonaceous residues on the graphite platform. All diluted samples (1 + 1 v/v) in 0.2% v/v HNO3 and reference solutions (5.0-50 microg l(-1) Pb in 0.2% v/v HNO3) were spiked with 25 microg l(-1) Bi. For a 20 microl aliquot dispensed into the graphite tube, a good correlation (r = 0.9997) was obtained between the ratio of the analyte signal to the internal standard signal and the analyte concentration of the reference solutions. The electrothermal behaviour of Pb and Bi in red, white and rosé wines were compared. In addition, absorbance variations due to changes in experimental conditions, such as atomizer temperature, integration time, injected sample volume, radiation beam intensity, graphite tube surface, dilution and sample composition, were minimized by using Bi as internal standard. Relative standard deviations of measurements based on integrated absorbance varied from 0.1 to 3.4% and from 0.5 to 7.3% (n = 12) with and without internal standard correction, respectively. Good recoveries (91-104%) for Pb spikes were obtained. The characteristic mass was 45 pg Pb and the limit of detection based on integrated absorbance was 0.9 microg l(-1) Pb. Internal standardization increased the lifetime of the tube by 25%. Direct determinations of Pb in wines with and without internal standardization approaches were in agreement at the 95% confidence level. The repeatability and the tube lifetime were improved when using Bi as internal standard. The improvement in accuracy using an internal standard was only observed when the analytical results were affected by errors.     

Emission spectrochemical determination of chromium in organic acids

An emission spectrochemical procedure is described which directly determines the chromium concentration in organic materials in the p.p.m. range. The only preparation of the sample which is necessary is dilution with a graphite matrix which contains the internal standard element and the spectral buffer, lithium carbonate. The effect of sodium on spectral line intensities of cobalt and chromium is shown. The effectiveness of lithium carbonate as a spectral buffer is illustrated. The precision of the technique is estimated to be ± 11.8% and the accuracy estimated to be 10.9%.     

Critical assessment of a new in situ spectroelectrochemical cell designed for the study of interfacial reactions between a porous graphite anode and alkyl carbonate solution

This article critically evaluates the characteristics of a new in situ spectroelectrochemical cell with an optimized path of the IR beam, designed in our laboratory for study of the solid electrolyte interphase (SEI) layer formed between a porous graphite anode and alkyl carbonate solution for lithium-ion batteries. The cell was designed in view of the optical principles underlying the way the in situ cell works, to give depth of penetration of the evanescent IR beam through the attenuated total internal reflectance crystal into the electrolyte at such a small value, ranging from 0.277 to 2.77 μm, that it was possible to minimize the "masking effect" of the ethylene carbonate/diethyl carbonate solvent. Moreover, the "local compositional change" which may arise significantly from the "thin layer electrolyte configuration" cell also could be fairly avoided, since only the electrolyte in the vicinity of the electrode composed of graphite particles is reduced to form the SEI layer to a thickness of at most 0.1 μm during the application of potentials. Thus, it was possible to measure the in situ FT-IR spectra in the cell, which represents the real chemical composition and structure of the SEI layer. Taking the application of the designed in situ cell as an example, this article reports the effect of salt type and electrolyte temperature on the chemical composition and structure of the SEI layer between graphite particles and alkyl carbonate solution with the help of various measured in situ FT-IR spectra. Electronic Publication     

Spectrographic Determination of Eleven Trace Impurities in High Purity Cadmium

Abstract

Eleven trace impurities are determined in high purity cadmium by employing d. c. arc emission spectrographic technique. Cadmium ie converted t o its oxide and ground with high purity conducting graphite powder which acts as a buffer. Forty milligrammes of the above mixture is excited in a d. c. arc set at 12 amperes. The spectra of the sample and synthetic standards are photographed on a Jarrell-Ash 3.4 meter Ebert plane grating spectrograph in the region 2175 - 3425 A using a 1200 lines per mm grating in the first order. The detection limits obtained range from 1 to 10 ppm for different elements. The average coefficient of variation ranges from 8.0 to 15.7% for the impurities.     

The application of differential pulse polarography to the determination of a pharmacologically active benzhydrylpiperazine derivative and its major electroactive metabolites in the plasma and urine of animals.

A method for the determination of 1–500 p.p.m. of acid-soluble aluminium and 2–500 p.p.m. of acid-insoluble aluminium in low-alloy and stainless steels by flameless atomic absorption with a HGA 74 graphite furnace is described. A typical value of the relative standard deviation for acid-soluble aluminium at concentrations larger than 10 p.p.m. was 5 %. The steel sample was dissolved in hydrochloric and nitric acid and filtered. Ammonium sulphate was added to the filtered sample in order to overcome interferences caused by hydrochloric acid. No concentration steps were used. Acid-soluble aluminium was determined within 20 min. The influence of iron, chromium, nickel, molybdenum, hydrochloric acid, nitric acid and ammonium sulphate respectively was investigated.     

Characteristics of carbon nanoparticles synthesized by a submerged arc in alcohols, alkanes, and aromatics

Fullerene-related carbon nanostructures can be synthesized by an arc-in-liquid system as a cost-effective technique. In this work, we investigated the effects of additional carbon sources from liquid media that were alcohols (C(m)H(2m+1)OH, m = 1-8), alkanes (C(m)H(2m+2), m = 6-7), and aromatic compounds (C6H6-C(n)H(2n), n = 1-2) on the product structures and the yield of nanocarbon-rich deposits. It was found that carbon nanoparticles (CNPs) that included multi-walled carbon nanotubes (MW-CNTs) and multi-shelled carbon nanoparticles were produced at high concentrations in the hard deposit at the cathode tip formed by the arc in the alcohols and alkanes, similar to that in a water environment. Importantly, not only graphite electrodes but also these organic compounds played a role of a carbon source to produce CNPs that led to an approximately 8-100 times higher yield than the arc-in-water system. There was a tendency that the increase in alcohol concentration and carbon content in the organic molecules positively affected the yield and production rate of the CNPs. However, the selectivity of MW-CNTs was significantly reduced when aromatic compounds were used. Structural analyses by dynamic light scattering and Raman spectroscopy revealed the dependency of the hydrodynamic particle sizes of CNPs and their crystallinity on the liquid components. For a discussion on the reaction mechanism, optical emission spectra of the arc plasma were analyzed to estimate the arc temperature. In addition, liquid byproducts were analyzed by a UV-vis absorbance spectrometer.     

预嵌锂用穿孔集流体对锂离子电容器电化学性能的影响

将石墨涂覆于传统铜箔(CCC)与穿孔铜箔(PCC)集流体表面,通过内部短路的方式进行预嵌锂处理,再以商业化的活性炭及预锂化的石墨分别为正、负极材料组装成锂离子电容器(LIC)。以PCC为集流体的LIC在0.1和2.0 A?g~(-1)的电流密度下,能量密度分别为118.2和51.7 Wh?kg~(-1),并且在0.5 A?g~(-1)的电流密度下循环1000次后的能量密度保持率为90%;以CCC为集流体的LIC在0.1和2.0 A?g~(-1)的电流密度下的能量密度分别为125.5和43.3 Wh?kg~(-1),在同等电流密度下2.0-3.8 V之间循环1000次后的能量密度保持率仅为73.2%。进一步研究表明,石墨采用PCC在预嵌锂的过程中避免了金属锂沉积,生成了均一且稳定的固体电解质膜(SEI),有效防止充放电过程中SEI膨胀,活性物质与集流体间粘结力降低,活性物质脱落等现象发生。因此,LIC通过PCC完成预嵌锂后的自放电及内阻更小,具有更佳的倍率性能和循环性能。     

On a general spectrochemical method for the direct arcing of liquid-liquid extraction residues in a D.C. arc

A considerable reduction in volume of the enriched sample is combined with the high absolute sensitivity of a mixed cathode layer—cathode excitation, which is applied directly to organic extraction residues in a 1: 1 mixture with an aluminagraphite base. An oxygen protective atmosphere is used to increase the arc temperature, stabilize the column, and reduce cyanogen band interference. The method eliminates the need for subsequent mineralization or burning. Its application is discussed with reference to liquid-liquid extraction systems.     

Software algorithm for automatic interpretation of mass spectra of glycerolipids

A new software algorithm for automatic interpretation of mass spectra of glycerolipids has been developed. The algorithm utilizes a user-specified list of parameters needed to process the spectra. The compounds in mass spectra are identified according to range of measured m/z values, after which the spectra are automatically corrected by the content of naturally occurring isotopes and ion intensities of identified compounds by response correction factors. Automatic processing of the spectra was shown to be accurate and reliable by testing with numerous spectra of glycerophospholipids obtained by liquid chromatography/electrospray ionization mass spectrometry and by comparing the results with manual interpretation of the spectra. If quantitative analysis using internal standards is performed, all the identified compounds in the sample are quantified automatically. A dilution factor may be defined for each sample and is applied to correct the alterations in sample concentration during sample preparation. Processing of several replicate spectra simultaneously produces mean results with standard deviations. The software may also be used to subtract the results of two analyses and to calculate the mean result of replicate subtractions. The algorithm was shown to save time and labor in repetitive processing of mass spectra of similar type. It may be applied to processing of spectra obtained by various mass spectrometric methods.     

Chemical separation and spectrographic estimation of rare earths and yttrium in PuO(2) and (U,Pu)O(2)

An emission spectrographic method for the estimation of rare-earth impurities in plutonium oxide and the mixed oxide (U,Pu)O(2) (30% PuO(2)-70% UO(2)) has been developed. Rare-earth impurities are separated from the matrix by solvent extraction with tri-n-octylamine in xylene and are estimated after concentration. Thulium is used as internal standard and LiF-AgCl as carrier. The spectra are excited in a d.c. arc. The detection limits lie in the range 0.004-0.1 mug and the coefficient of variation ranges from 5 to 23%.     

交流放电法合成多种形态的碳纳米管

碳纳米管的发现［１］引起了科学界的广泛重视,人们对于这种新型材料在纳米导线、高强纤维、超导等方面的应用寄予厚望．目前,合成碳纳米管的方法主要是采用不等径石墨棒直流放电,在阴极上得到含有碳纳米管的沉积物［２］．对于碳纳米管的应用,有关的理论研究［３］及...