Microdetermination of oxygen in organic compounds using a glassy carbon pyrolysis tube and nondispersive infrared detection

A glassy carbon pyrolysis tube holding a filling of carbon granules, protected from atmospheric oxygen by the carrier gas and an aluminum oxide ceramic mantle tube, has been successfully used for the first time in the microdetermination of oxygen. The reaction temperature of 1300 °C assures the quantitative transformation of oxygen to carbon monoxide, which is measured by infrared detection. The analysis of fluorine, phosphorus and alkali metal containing compounds is now possible. A 10% hydrogen content in the nitrogen carrier gas enhances liberation of oxygen in organometallic compounds. The method is applicable to sample weights between 0.1 and 5 mg and the time required for one analysis is 100 s.     

流化床热解过程中煤中氟的挥发性研究

采用大同、平朔、霍林河、义马四种煤研究了热解过程中煤中氟的挥发行为。研究表明，随热解温度的升高，氟的挥发率有增加趋势。但其行为不仅取决于元素氟及其化合物本身的挥发性，同时还受其赋存形态、共存矿物离子等原生条件和热解条件的影响。氟磷灰石类矿物质并非四种煤中氟的主要赋存形态。除大同煤外，难挥发性氟的含量均高于65％，难挥发性氟至少部分是以CaF2或CaF2基的多元络合物形式存在的。     

Automatic microanalyzers: II. Automatic analyzer for rapid microdetermination of oxygen

A commercially available analyzer for the microanalytic determination of oxygen in organic and some inorganic compounds is described. The technique rests upon the application of the Schütze-Unterzaucher principle; it involves flash pyrolysis of the sample in nitrogen atmosphere and reduction of pyrolitic gases with carbon black at 1120 °C in order to produce carbon monoxide which is oxidized into carbon dioxide; the latter is finally titrated by protonometric coulometry.The use of a vertical reactor makes possible a complete automation of the technique and besides it preserves the initial properties of the aging carbon black filling which is a very important feature for correct oxygen determination. The flash pyrolysis of samples in the vertical tube makes also possible a very important shortening of analysis time: for routine operation, a 7 min duration is generally chosen by the operator but it can be reduced to only 5 min at will.This technique covers a very broad analytical field and the apparatus can be provided with an automatic sample dispenser now commercially available, so that series determinations are carried out without operator save for the previous weighing out of all samples.     

Fluorine ion selective electrode for microdetermination of fluorine in organic compounds

A simple procedure is described for the decomposition of organic fluoro-compounds by a quartz oxygen flask, with auxiliary combustible adhesive paper and in combination with the fluorine ion selective electrode's new measuring technique. Polymers of high F content, fluorocarbons, and compounds of the ---CF₃ functional group can be quantitatively decomposed. The presence of N, Cl, Br, I, S, P, As, B, Si, K, Na, Hg, Mg, Al, Fe, Pb, Ag, Cu, and Zn do not interfere with the quantitative microdetermination of organic fluorine element. The absolute error is ±0.30%.     

A new method for the determination of oxygen in organic compounds

Oxygen in compounds of carbon, hydrogen, and oxygen can be determined by heating the sample with an excess of strontium oxide and graphite in. a nickel bomb or sealed Vycor glass tube. During the heating period, three hours at 650° C, the oxygen of the sample is converted to carbonate. The carbonate is then determined volumetrically. The accuracy of the method was found to be ± 0.3% (absolute percentage error) for several types of compounds. Most elements other than carbon, hydrogen, and oxygen interfere. Compounds like phenol, that are exceedingly resistant to complete pyrolysis, yield low resuilts. Carbon in organic compounds can be determined by heating the sample with barium nitrate, and subsequently determining carbonate in the mixture.     

CaO伴随生物质热裂解制油同时脱氧的小型流化床实验研究

在小型流化床反应器中,对CaO伴随生物质快速热裂解制油过程中的直接脱氧效果进行了研究。当反应温度为520℃、载气流量8000L/h时,在纯白松粉末和CaO伴随条件下分别制出了生物油样品。实验结果表明,当采用纯白松与CaO/白松质量比分别为1、2、4时,生物油样品中有机组分的含氧量依次为39.38%、39.15%、39.04%和32.29%;在CaO/白松质量比为4时,生物油有机组分含氧量的下降幅度达18.0%（相对变化）。GC-MS分析结果表明,CaO加入后左旋葡聚糖和甲酸、乙酸等高含氧量物质相对含量明显下降,证实了CaO伴随生物质热裂解过程中“富氧中间体”固氧路径的存在;与此同时,糠醛类等主要来源于脱水反应的产物相对含量上升,说明CaO的加入也促进了脱水反应的发生。     

Determination of trace levels of total fluorine in water using combustion ion chromatography for fluorine: a mass balance approach to determine individual perfluorinated chemicals in water

Perfluorinated compounds (PFCs) such as perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) have received worldwide attention because of their environmental persistence and widespread distribution. Because of the lack of robust analytical methods and standards to detect all of the PFCs, and their precursors and metabolic intermediates, a mass balance approach involving the determination of total fluorine (TF), followed by fractionation of samples to separately determine inorganic and organic fluorine, is needed. In this study, we have developed a method to determine low microg/L levels of total fluorine (TF) in seawater samples. Further, seawater samples were fractionated into organic and inorganic fractions by extraction with organic solvents, which were then analyzed for TF, extractable organic fluorine (EOF) and inorganic fluorine (IF; i.e., fluoride). Concentrations of known perfluorinated compounds (PFCs) including PFOS and PFOA were also determined in water samples by liquid chromatography-tandem mass spectrometry (LC-MS/MS) to enable calculation of the fraction of fluorine that is contributed by PFCs to TF. A major proportion of fluorine in seawater was in the form of fluoride (>90% in locations not affected by direct discharges). Nevertheless, within the organofluorine fraction, a major percentage (60-90%) of fluorine still remains unknown in water samples, suggesting the occurrence of other fluorinated acids in addition to known perfluorinated acids. Further studies are needed to identify and quantify the unidentified organofluorines in seawater. Mass balance analysis of total organic fluorine (TOF) and EOF is important, if we are to understand transport and fate of fluorinated compounds in the environment, and if we are to identify the sources of unidentified fluorinated compounds.     

Manometric submicro determination of carbon and hydrogen in organic materials

A method is described for the determination of carbon and hydrogen in quantities of organic material ranging from 5 to 50 μg. The method involves catalytic combustion of the sample in oxygen and measurement of the pressures of the resulting carbon dioxide and water. Special attention has been paid to the reduction of the effect of water adsorption in the apparatus. The present submicro method can be applied to non-volatile, non-hygroscopic samples and is free from interferences by nitrogen, sulphur and halogens (except fluorine). The standard deviation in the 50-μg sample range is 0.13% for carbon and 0.10% for hydrogen. The average duration per analysis when carried out in series is 20 min.     

Microdetermination of fluorine in organic compounds by oxygen flask combustion and conductometric titration

For the conductometric titration of fluoride with calcium acetate, solvent system in sample solution and titrant, concentration, and acidity of sample solution were examined to establish the titration conditions. Results of these examinations were transferred to the microdetermination of fluorine in organic compounds using oxygen flask combustion method.Comparative examination between quartz and Pyrex flasks for the combustion of fluorine samples indicated that good results were obtained by the use of the former flask, whereas the use of the latter one gave negative values of 1.0–1.6% due to the formation of boron fluoride during the combustion.     

Microdetermination of carbon and hydrogen in organofluorine compounds

A simple method is described for the elimination of the interferences of fluorine in carbon and hydrogen determination of fluorinated organic compounds. Samples are burnt in a rapid flow of oxygen using the cobalto-cobaltic oxide, rapid straight empty tube, rapid empty tube of Belcher-Ingram, and flash combustion methods.The combustion products are passed through Anhydrone, silica gel-thorium nitrate, and soda asbestos absorption tubes, respectively. Carbon and hydrogen are determined gravimetrically. Acceptable results are generally obtained for a wide range of partially and highly fluorinated organic compounds.     

A titrimetric method for estimation of fluorine in organic compounds

A simple and rapid titrimetric method for estimation of fluorine in organic compounds and fluoropolymers is reported. It involves combustion of the sample in oxygen, absorption of the combustion products in an aqueous solution of Ce(III) nitrate and glycerol, containing hexamethylenetetramine, and finally titration with EDTA, with Xylenol Orange and Methylene Blue as screened indicator.     

Microdetermination of oxygen at traces level in organic sulfur compounds

We have described an original method allowing us to determine traces of oxygen in organic compounds such as polymers modified through grafting of functions containing oxygen.The method allows us to obtain oxygen contents included between a few hundred ppm and 7 to 8%. It consists in the pyrolysis of the sample, the reduction of oxygen to carbon monoxide and, finally the detection of the latter in an infrared analyzer.     

The Submicrodetermination of Oxygen in Organic Compounds by a Gas-Chromatographic Method

Abstract

Preliminary studies of a method for the determination of oxygen in 30–80 μ;g samples of organic compounds are described. Organic oxygen is converted to carbon monoxide by pyrolysis through platinized graphite wool and the monoxide is measured by thermal conductivity.     

Application of the unterzaucher method to the determination of oxygen in coke

The Unterzaucher method, used for the determination of oxygen in organic compounds and coal, has been adapted to the determination of oxygen in coke. Modifications were made to the conventional apparatus in order to eliminate any contribution made by the coke moisture to the determined oxygen content. The carbon dioxide produced from the combustion of the oxygen in the coke was estimated by a sensitive conductimetric method. Evidence is presented which indicates that additional liberation of oxygen from the coke mineral matter does not make a significant contribution to the total oxygen determined under the prescribed experimental conditions. The error of the determination is approximately 0.1%. A comparison is made between results obtained for a series of cokes and chars by the direct method and by an independent determination, based on neutron activation.     

离子色谱在有机物和高分子材料分析中的应用

介绍了用氧瓶燃烧，高温炉分解有机化合物、高分子材料等样品，用去离子水或Na2CO3／NaHCO3溶液吸收分解产物，用离子色谱测定吸收液中F^-、C1^-、Br^-、SO4^2-、PO4^3-，计算出样品中氟、氯、溴、硫、磷等元素含量的方法。     

Differences of fluorine in cements determined by photometric methods after distillation and pyrolysis.

Using a spectrophotometric method after distillation separation is a standard test method widely employed for the determination of fluorine (F) in cement. Using a flow injection (FI) method after pyrolysis separation for quantification of fluorine in cement has recently been developed. Differences between the fluorine content values obtained by each method have been noted. This paper documents the differences between fluorine content (distillation F) measured spectrophotometrically after distillation and that (pyrolysis F) determined using the FI method after pyrolysis for fourteen commercial Portland cements and identifies a factor contributing to the differences between distillation F and pyrolysis F values. A highly significant relationship existed between distillation F and pyrolysis F values for fourteen cements (r(2) = 0.998, p < 0.001).     

Trace analysis of total fluorine in human blood using combustion ion chromatography for fluorine: a mass balance approach for the determination of known and unknown organofluorine compounds

The number of perfluorochemicals (PFCs) that have been found in biological and environmental matrices is increasing as analytical standards and methods evolve. Perfluorooctanesulfonate (PFOS) and perfluorooctanoate (PFOA) constitute only a fraction of the total suite of PFCs found in environmental and biological matrices. A robust method and approach is needed to evaluate the mass of fluorinated compounds in biological matrices. In this study, we developed a method to measure total fluorine (TF) and organic fluorine (TOF) in human blood matrices using combustion ion chromatography (CIC). Blood matrices (whole blood, serum, and plasma) were analyzed in bulk to determine TF. An aliquot of the blood was also extracted with organic solvents such as methyl-tert-butyl ether (MTBE) and hexane, and organic and aqueous extracts were separated, to fractionate organofluorines from inorganic fluorine. The organic layer was analyzed for TF by CIC, and for known PFCs by high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). PFCs measured by HPLC-MS/MS accounted for >80% of the TF in the organic fraction. The aqueous fraction contained inorganic fluorine and other non-extractable organofluorines. However, in the bulk sample, fluoride and non-extractable organofluorines accounted for >70% of the TF in blood samples from the general population. In occupationally exposed individuals, known organofluorines accounted for a major proportion of the TF. These results suggest the existence of yet uncharacterized fluorine fraction in human blood. Further studies are needed to characterize the aqueous fraction that contains inorganic fluorine and non-extractable forms of fluorine.     

A step toward direct fullerene synthesis: C60 fullerene precursors with fluorine in key positions

Several fluorine containing polycyclic aromatic hydrocarbons with exact carbon atom topology of the C₆₀ fullerene have been synthesized. Different numbers of fluorine atoms were introduced in the key positions, as needed for an efficient intramolecular condensation to the fullerene molecule. The polycyclic aromatic compounds obtained represent attractive precursors for rational, high-yield fullerene synthesis by flash vacuum pyrolysis.     

A rapid automatic method for the determination of oxygen in organic substances, using coulometry at controlled potential

An Unterzaucher apparatus for the determination of oxygen in organic compounds is used. The iodine vapour formed in the anhydroiodic acid tube is led by a stream of nitrogen to the cathodic chamber of an electrolysis cell. Here the iodine is reduced at controlled potential at a rotating Pt-eiectrode. The amount of electricity used is determined by an electronic integrator and read from a digital voltmeter. For weights of samples in the range 0.5-6 mg the standard deviation is about 0.08% oxygen.     

Precise,non-destructive determination of fluorine by 14-MeV neutron activation analysis

A procedure is described for the precise determination of fluorine in organic and metal-organic compounds by 14-MeV neutron activation analysis using the reaction: ¹⁹F(n,2n)¹⁸F (β +, t_{$\text{1}\text{2}$} = 110 min).A relative standard deviation of better than ±0.5% is achieved by irradiating samples and standard simultaneously. Uniform neutron exposures were ensured by rotating the samples during irradiation. Positron emitters of short half-life are allowed to decay before counting. In metal-organic compounds, Sc, Zn, Ga and Ag cause the most serious interference; for organic compounds the method is rapid, and specific for fluorine.