Analyse par activation aux photons gamma et aux particules chargees

The activation methods, nuclear reactions and chemical separation processes used to determine traces of carbon, nitrogen and oxygen in the metals and semiconductors considered are described briefly. The results obtained are reviewed. They mainly concern the following analyses: (1) determination of carbon and oxygen in alkaline metals; (2) determination of nitrogen and oxygen in refractory metals; (3) determination of carbon, nitrogen and particularly oxygen in various other metals; (4) determination of these same elements in semiconducting materials. In some cases the concentrations measured by γ photon or charged particle activation methods are compared with the results obtained by other techniques.     

Determination of traces of carbon, nitrogen and oxygen in molybdenum and tungsten

The determination of carbon and nitrogen in molybdenum and of carbon, nitrogen and oxygen in tungsten, is described. The analytical techniques applied were charged-particle activation (carbon, nitrogen and oxygen), photon activation (carbon and oxygen), combustion (carbon) and vacuum-fusion extraction (nitrogen and oxygen). Chemical methods yielded upper limits in the 2-5 mug/g range. Activation analysis yielded 100 and 8 ng/g for carbon in molybdenum and tungsten respectively, 500 and 74 ng/g for nitrogen in molybdenum and tungsten respectively and 70 ng/g for oxygen in tungsten. The results obtained by charged-particle and photon activation agreed satisfactorily.     

Inter-laboratory comparison of the chemical analysis of silicon nitride

Summary The results of a round robin for the determination of nitrogen, oxygen and carbon and the common metallic impurities like Al, Ca, Fe, Mg and Na in silicon nitride are reported. The following analytical methods have been tested: nitrogen by acid decomposition under pressure followed by Kjeldahl distillation; oxygen by carrier-gas hot extraction; carbon by combustion in oxygen and infrared detection; metallic impurities after acid decomposition under pressure and evaporation of silicon fluoride by AAS or ICP-OES.     

Determination of trace organic carbon and nitrogen in the presence of carbonates in anorganic bovine bone graft materials

The widespread concern of bovine spongiform encephalopathy (mad cow disease) has raised questions about the possibility of residual organic material in bovine-derived bone graft materials. Conflicting reports have shown both the presence and the absence of organic materials in bone derived products. This study compared residual organic levels in two commercial bone graft products: a bovine bone product treated chemically and at low temperature, and a bovine bone product treated at high temperature. In this study, organic carbon, the primary constituent of organic materials, is defined as carbon that is not liberated as CO₂ upon acidification (i.e. non-carbonate carbon). Three approaches to the determination were used: (1) organic carbon was calculated as the difference between total carbon determined by high temperature combustion and carbonate carbon determined by acid evolution of CO₂. (2) Organic carbon was determined by measuring total carbon by high temperature combustion of a sample that had been pretreated with acid to remove all carbonate. (3) The total organic carbon remaining in solution after acid dissolution was determined. In addition, organic nitrogen was determined as the difference between total Kjeldahl and ammonia nitrogen. Total nitrogen values were confirmed using an instrumental nitrogen analyzer. No detectable organic carbon or organic nitrogen was observed in the high temperature bone product. In the low temperature treated bovine product, however, approximately 2000 μg/g organic carbon was measured by all three methods, as well as 15 μg/g organic nitrogen.     

Determination of carbon, hydrogen and nitrogen in inorganic compounds by means of an automatic organic elemental microanalyzer

The Hewlett Packard Model 185 CHN Analyzer, which is based on an automated modified Dumas combustion technique and was designed for the analysis of organic materials, has been applied to the determination of carbon, nitrogen and hydrogen in inorganic compounds.With minor modifications to the procedure routinely used for the organic analysis, the instrument has proved to be able to broaden its original application field giving in general good performances in the inorganic domain.A particular emphasis has been put in testing nitrates, carbonates, ammonium salts and different kinds of carbon. Till now it appears that the only materials really difficult to analyze are the refractory nitrides, carbides and carbonitrides.Finally some considerations have been made in respect of the determination of the percent weight composition of mixtures through their carbon, nitrogen and hydrogen content.     

Distribution of carbon nanotube sizes from adsorption measurements and computer simulation

The method for the evaluation of the distribution of carbon nanotube sizes from the static adsorption measurements and computer simulation of nitrogen at 77 K is developed. We obtain the condensation/evaporation pressure as a function of pore size of a cylindrical carbon tube using Gauge Cell Monte Carlo Simulation (Gauge Cell MC). To obtain the analytical form of the relationships mentioned above we use Derjaguin-Broekhoff-deBoer theory. Finally, the pore size distribution (PSD) of the single-walled carbon nanohorns (SWNHs) is determined from a single nitrogen adsorption isotherm measured at 77 K. We neglect the conical part of an isolated SWNH tube and assume a structureless wall of a carbon nanotube. We find that the distribution of SWNH sizes is broad (internal pore radii varied in the range 1.0-3.6 nm with the maximum at 1.3 nm). Our method can be used for the determination of the pore size distribution of the other tubular carbon materials, like, for example, multiwalled or double-walled carbon nanotubes. Besides the applicable aspect of the current work the deep insight into the problem of capillary condensation/evaporation in confined carbon cylindrical geometry is presented. As a result, the critical pore radius in structureless single-walled carbon tubes is determined as being equal to three nitrogen collision diameters. Below that size the adsorption-desorption isotherm is reversible (i.e., supercritical in nature). We show that the classical static adsorption measurements combined with the proper modeling of the capillary condensation/evaporation phenomena is a powerful method that can be applied for the determination of the distribution of nanotube sizes.     

Characterisation and quantification of organic phosphorus and organic nitrogen components in aquatic systems: a review

This review provides a critical assessment of knowledge regarding the determination of organic phosphorus (OP) and organic nitrogen (ON) in aquatic systems, with an emphasis on biogeochemical considerations and analytical challenges. A general background on organic phosphorus and organic nitrogen precedes a discussion of sample collection, extraction, treatment/conditioning and preconcentration of organic phosphorus/nitrogen from sediments, including suspended particulate matter, and waters, including sediment porewaters. This is followed by sections on the determination of organic phosphorus/nitrogen components. Key techniques covered for organic phosphorus components are molecular spectrometry, atomic spectrometry and enzymatic methods. For nitrogen the focus is on the measurement of total organic nitrogen concentrations by carbon hydrogen nitrogen analysis and high temperature combustion, and organic nitrogen components by gas chromatography, high-performance liquid chromatography, gel electrophoresis, mass spectrometry, nuclear magnetic resonance spectrometry, X-ray techniques and enzymatic methods. Finally future trends and needs are discussed and recommendations made.     

Interferences in the determination of total nitrogen in natural waters by photo-oxidation to nitrate-nitrite mixture

The method proposed by Armstrong, Williams and Strickland for the photo-oxidation of total nitrogen in sea-water to nitrate and nitrite has been studied in some detail, to extend its use to fresh and brackish waters, applying a more accurate method for the determination of the reaction products. Variables influencing the yield of nitrate and nitrite are irradiation time, pH and type of buffer, kind of nitrogen compound and its concentration, and the concentrations of oxygen, carbon dioxide, organic matter and salts, especially bromides, even at the low concentrations found in brackish waters. All these variables interact in a rather complicated way. Interferences from halides, organic matter and carbon dioxide are considerably reduced by ensuring that the pH is kept at 8.5-9 during the irradiation. Because pure solutions of many substances give quantitative yields (> or = 98%) in the pH-range 7-9 usually recommended, whereas others require lower pH for maximal oxidation, a method has been developed involving photo-oxidation first at pH 2.1 and then at pH 8.5-9. In the absence of interfering concentrations of halides the relative increase in yield by an initial irradiation at low pH is especially large (10-36%) for proteins, organic nitrogen in fresh waters, uric acid and urea. A comparison is made between determination of total nitrogen in some natural waters by using photo-oxidation and by a Kjeldahl method modified to give total nitrogen. By making use of the optimal conditions presented in this paper, a negative error of less than 8% is expected in the determination of total nitrogen in fresh waters. For saline waters the error will probably be larger, at least at a high ratio of organic to inorganic nitrogen.     

有机化合物对电感耦合等离子体质谱(ICP-MS)法测定食品中总砷的影响

目的 研究有机化合物对电感耦合等离子体质谱法（ICP-MS）测定食品中总砷的影响,分析总结一般规律,为食品中总砷的准确测定提供理论依据。方法 研究了甲醇和乙醇等14种有机化合物对ICP-MS测定砷的动能歧视模式（KED）信号值和动态反应模式（DRC）信号值的影响,通过分析各有机化合物的电离能、极性和溶解度等性质,推测其在ICP-MS测定体系中对砷响应信号值增敏或者抑制的可能机理。结果 有机化合物对ICP-MS的KED模式测定砷离子As+的信号值有增敏效应,对DRC模式测定氧化砷离子AsO+信号值的影响小于KED模式测定As+的信号值,而且过程也更为复杂。相反,氮氧化物会减弱As+和AsO+的信号值。锗、铟等内标元素原子与砷原子在等离子体中电离行为和灵敏度的差异,使得内标元素校准砷测定信号的漂移受到干扰。结论 推测有机化合物影响ICP-MS测定砷响应信号值的可能机理是：有机化合物和氮氧化物经电离或裂解之后分别生成碳离子或多原子碳离子和氮氧离子或氮氧基团,碳离子或多原子碳离子会与砷原子发生电荷转移反应,增强As+或AsO+的信号值,同时有机化合物也可能会与As+竞争氧气而降低AsO+的信号值,而具有强电负性的氮氧基团可能会与As+和AsO+发生电荷转移反应而减弱其信号值。有机化合物对砷的ICP-MS响应信号值的影响可能是受到有机化合物电离能、溶解度、极性和分子结构等综合因素的结果。     

The submicro determination of carbon,hydrogen and nitrogen by a gas-chromatographic method

A method for the determination of carbon, hydrogen and nitrogen in organic samples weighing 40–80 μg is described. The sample is decomposed conventionally in a helium stream and the water formed is converted to acetylene. Nitrogen, carbon dioxide and acetylene are then separated on a silica-gel column, and the acetylene is burned to carbon dioxide by passage through copper oxide at 900° because the acetylene peak itself is not easily measured. Water from the second combustion is removed on silica gel and the three peaks emerging are measured by means of a micro thermistor cell. The standard deviations obtained for acetanilide are 0.31% for carbon, 0.28% for hydrogen and 0.11% for nitrogen. Results for other compounds are given and the parameters relevant to precision are discussed.     

Determination of light elements in metals and semiconductors by charged particle activation analysis

The determination of boron, carbon, nitrogen and oxygen in metals and semiconductors by charged particle activation analysis (CPAA) is reviewed. It is shown that CPAA is a sensitive and accurate method suitable for the analysis of reference materials.     

Determination of Deltamethrin in Water Samples Using Sulfur and Nitrogen Co-Doped Carbon Quantum Dots as a Chemiluminescence Probe

Journal of Analytical Chemistry - The application of sulfur and nitrogen co-doped carbon quantum dot?potassium permanganate chemiluminescence (CL) system for the determination of trace...     

Automation in organic analysis II. Simultaneous microdetermination of oxygen and nitrogen

A simple, rapid, and accurate method of simultaneous determination of oxygen and nitrogen in organic compounds, containing (in addition to C, H, and O) Cl, Br, and I, is described. The principle of the method consists in the pyrolytic decomposition of the analyzed compound in a current of hydrogen at 1000–1100 °C and the conducting of the hydropyrolytic product through layers of nickel and platinized carbon (50% Pt) heated at 1050 °C. On this filling the nitrogen-containing products are transformed to elementary nitrogen, the oxygen-containing products are transformed to carbon monoxide, the halogens to hydrohalogenides, and methane is decomposed. After removing hydrohalogenides by soda asbestos, carbon monoxide and nitrogen are separated on a chromatographic column filled with Porapak Q, and determined with a catharometer. The whole analysis, including the weighing of the sample, requires 25 min. Sulfur interferes with the determination.     

Green Emission Carbon Nanodots as Fluorescence Turn-on Probe for Detecting Picolinic Acid

Journal of Analytical Chemistry - A new strategy for the determination of picolinic acid (PLA) is developed by utilizing green-emissive boron and nitrogen co-doped carbon nanodots (BNCNDs) and Cu2+...     

Automation in organic analysis III. Micro- and ultramicrodetermination of nitrogen

A simple, rapid and accurate method of nitrogen determination in organic substances containing in addition to C, H, N also O, S, F, Cl, I, Se and Hg was elaborated. The method is based on pyrolytic decomposition of the substance in a flow of hydrogen at 1000–1100 °C and passing the hydropyrolytic products through layers of managenese-II oxide (absorbing sulfur and selenium) and nickel at 950 °C. On nickel elementary nitrogen is liberated from the nitrogenous hydropyrolytic products and the pyrolytic methane also decomposes on it. After elimination of interfering substances (carbon monoxide, water, hydrogen halides) the content of nitrogen is determined with a catharometer.The whole determination, including the sample weighing, requires 12 min and the precision is ±0.30% absolute.     

Kobalt(II,III)-oxid als Verbrennungskatalysator bei der Bestimmung von Kohlenstoff und Wasserstoff in Organosiliciumverbindungen

Summary Cobalt(II, III) oxide is recommended as combustion catalyst for the determination of carbon and hydrogen in organosilicon compounds. If required (i.e. to avoid deflagration in certain cases), the oxidation can also be performed in a stream of nitrogen.     

氮掺杂碳纳米管的合成及活化过一硫酸盐的性能与机理

以多壁碳纳米管(MWCNT)为原材料, 三聚氰胺为氮前体, 采用高温煅烧法制得了含氮量约3.33%(摩尔分数)的氮掺杂碳纳米管(N-CNT-700), 该纳米管为一维材料. N-CNT-700活化过一硫酸盐(PMS)体系60 min内对苯酚的降解效率可达100%, 总有机碳(TOC)去除率可达61.6%, 体系的活化能为35.4 kJ/mol. 通过电子顺磁共振(EPR)检测、 掩蔽实验及PMS浓度测定等方式确定了体系降解机制为自由基(·OH, SO₄^·-)与非自由基共同作用, 除去9%的吸附去除外, 91%的氧化降解中自由基作用占比约49%, 单线态氧(¹O₂)作用占比约18%, 活性中间体作用占比约24%. N-CNT-700的反应活性随着重复利用次数的增加而降低, 高温处理可以恢复其高反应活性. 煅烧温度影响材料中的氮含量及种类, N-CNT的反应活性与氮含量成正比, 且与石墨氮含量密切相关.     

Use of data-processing in modern rapid methods of elemental analysis

Automated methods for the rapid determination of carbon, hydrogen, nitrogen, and oxygen have been developed for use in conjunction with modern data processing equipment. Details as to the methods, apparatus, programming of procedures, and evaluation of the results are presented.     

Contribution to the study of carbon and nitrogen determination by activation,using the nuclear reactions12C(α, n)15O and14N(d,n)15O

The carbon and nitrogen activation curves were determined for the nuclear reactions¹²C(α, n)¹⁵O and¹⁴N(d, n)¹⁵O, within the limits of the following maximum energies: 40 MeV for α-particles, and 21 MeV for deuterons. Inferences are made concerning the potential possibilities of these activation methods, from the sensitivity aspects, for the determination of carbon and nitrogen, with reference to the problem of the main interferences which have also been studied experimentally. The chemical separation process used to isolate¹⁵O after irradiation is described. Concrete examples of carbon and nitrogen determinations by these methods are given.     

元素分析仪测定土壤氮、碳含量的不确定度评定

用实例对元素分析仪测定土壤氮、碳含量不确定度进行评定.分析讨论了测定过程中不确定度的来源、不确定度分量的计算.结果表明,影响土壤碳、氮含量测定不确定度的主要因素是标准物质的引入和标准曲线的绘制.