Determination of sulphur in petroleum products after sulphur dioxide generation and of sulphur dioxide in air by chemiluminescent flame emission

The determination of sulphur in petroleum products by combustion, concentration of the sulphur dioxide in sodium tetrachtoromercurate solutions and cool flame molecular emission is described. Improvements in burner design and optimization of analytical conditions result in a minimum detectable amount of 6 ng of sulphur. The absorption of sulphur dioxide from air samples and its determination by a similar method gives a detection limit of 1.3 μg SO₂ m^-3.     

Simultaneous microdetermination of sulphur,carbon and nitrogen by reaction gas chromatography

Summary A simultaneous microdetermination of C, N and S, based on reaction GC, with a commercial analyser for the microdetermination of C, H, N and O, is described. The sample, covered with a mixture of WO₃ and SnO₂, is combusted in a stream of helium with added oxygen, and the mixture of pyrolysis products is oxidized completely by passage through a layer of granulate SnO₂. Conversion of SO₃ into SO₂, reduction of nitrogen oxides and absorption of unreacted oxygen proceed in a layer of Cu, and halogens are trapped by metallic antimony. Particular attention is paid to determination of sulphur in liquid samples without weighing.

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Simultane Mikrobestimmung von Schwefel, Kohlenstoff und Stickstoff mittels Reaktions-Gaschromatographie

Zusammenfassung Die simultane Mikrobestimmung von C, N und S mittels Reaktions-Gaschromatographie unter Benutzung eines kommerziellen Analysators für die Mikrobestimmung von C, H, N und S wurde beschrieben. Eine Probe wird nach Überschichtung mit einer Mischung aus WO₃ und SnO₂ im Heliumstrom unter einmaligem Sauerstoffzusatz verbrannt. Das Gemisch der Pyrolyseprodukte wird mit Hilfe einer Schicht aus granuliertem SnO₂ zu Ende oxydiert. Die Konversion von SO₃ in SO₂, die Reduktion von Stickstoffoxiden und die Absorption nicht verbrauchten Sauerstoffs verlaufen in der Cu-Schicht, Halogene werden in der Endphase von metallischem Antimon eingefangen. Besondere Aufmerksamkeit wird auch der Bestimmung von Schwefel in flüssigen Proben ohne Wägung gewidmet.

     

Measurement of non-methane hydrocarbons in Taipei city and their impact on ozone formation in relation to air quality

Air pollutants data from semi-continuous measurements at multiple sampling sites in Taipei metropolitan area of Taiwan was obtained by collecting air samples in canisters. The hydrocarbon composition was determined by using GC/MS and GC/FID. The air samples were pre-concentrated onto glass beads prior to separation by PLOT and DB-1 columns of GC. The method showed detection limit of <1 ppb and relative standard deviation in the range of 5-30% for different compounds. Aromatic hydrocarbons (toluene, benzene, etc.) and aliphatic hydrocarbons (ethylene, acetylene, propane, etc.) were correlated primarily to determine the source of emission. The estimated hydrocarbons were ranked according to their abundance and photochemical reactivity. The criteria pollutants, ozone and NO₂ were measured by UV-differential optical absorption spectroscopy (UV-DOAS), and were utilized to determine the relative importance of non-methane hydrocarbons (NMHC) and significant contribution of NO₂ in limiting ozone formation. The obtained results suggest that ozone formation in Taipei city is probably limited by the supply of non-methane hydrocarbons. The concentration profile of targeted pollutants was compared to other metropolitan areas to determine air quality and the pollutant sources.     

Volatile sulphur compounds in wines related to yeast metabolism and nitrogen composition of grape musts

The influence of nitrogen compounds in grape musts on the content of sulphur compounds of wines was studied. Different vinifications were performed with the addition of methionine (20 mg l⁻¹) and/or cysteine (40 mg l⁻¹) to grape musts before alcoholic fermentation. Six grape musts, with different nitrogen composition, from cultivars of the ‘Vinhos Verdes’ Region, in Portugal, were used. Addition of methionine to grape musts enhanced the content of wines in 3-(methylthio)-1-propanol, acetic acid-3-(methylthio)propyl ester, 3-(methylthio)propionic acid and some unidentified sulphur compounds. Increase of cysteine concentration in musts led to the production of wines with high levels of hydrogen sulphide and cis-2-methyltetrahydro-thiophene-3-OL and also unidentified sulphur compounds; however, the content of 3-(methylthio)propionic acid in the wines decreased considerately with the addition of cysteine to grape musts. This work showed that cultivars from the Vinho Verde Region show different sulphur compound contents. Avesso wines, elaborated from grape musts with low amino acids level, presented the highest total sulphur compounds content. Wines from Azal branco and Alvarinho were characterised by high contents of 4-(methylthio)-1-butanol and 3-(methylthio)propionic acid, respectively. A high content of N-(3-(methylthio) propyl)-acetamide and dimethylsulphone characterise the Loureiro wines. In contrast, Trajadura wines, produced from a must rich in amino acids, presented a low total sulphur compounds content; however, these wines were also characterised by high concentrations of 4-(methylthio)-1-butanol, acetic acid-3-(methylthio)propyl ester and hydrogen sulphide.     

Production of nitrogen oxides in a positive column of a glow-type discharge in air flow

This paper deals with the investigations of a low-current glow-type discharge in air flow as applied to the problem of nitrogen oxide production. The electrode configurations correspond to the classical coaxial plasmatron and to the so-called gliding arc. The discharge burns in a regime of constricted positive column with a typical current density from 47 to 120 A/cm² and with the related electron density from 0.53?10¹⁴ to 2.3?10¹⁴ 1/cm³. The gas temperature changes from 3000 to 3610 K. The described conditions provide a flow of NO molecules from the plasma column with the energetic cost for production of one molecule of (30–50) eV. Maximum content of NO molecules [NO]?=?4 g/m³ (3500 ppm) was obtained. In spite of a rather high gas temperature, the plasma is still nonequilibrium. The high vibrational levels of the nitrogen molecules are populated, and the main channel of the nitric oxide production is associated with the reaction in which the vibrationally excited nitrogen interacts with atomic oxygen.

     

抗生素菌渣热解N官能团变化特征及其与NO_x前驱物关系研究

以青霉素菌渣(PMW)和土霉素菌渣(TMW)为对象,在水平管式反应器中进行快速热解,采用X射线光电子能谱(XPS)表征和化学吸收-分光光度定量分析方法,研究了抗生素菌渣热解N官能团变化特征及其与NO_x前驱物的关系。结果表明,菌渣燃料N官能团分为无机N(N-IN)和蛋白质及其水解产物N(N-A)两种。决定菌渣NO_x前驱物以NH_3-N为主,N官能团主要为N-A,PMW占81.1%、TMW占59.0%。在低温区间,N-IN在150-250℃分解和N-A在250-450℃转化,为NH3-N主要来源;PM W和TM W产率分别为20.9%和25.6%,而HCN-N产率小于2%,基本与燃料N官能团特征无关;该阶段伴随吡啶N(N-6)和吡咯N(N-5)的生成及转化,峰值在350-400℃。在高温区间,半焦N反应,主要是N-6和N-5的转化,为NH_3-N和部分HCN-N的来源;该阶段伴随少量更稳定质子化吡啶N(N-Q)和氮氧化物N(N-X)生成。由于N-IN和不稳定N-A低温下会快速分解,250-300℃下菌渣半焦N去除高达40%、能量损失可控制在25%,因此,采用合适低温热解处理菌渣,在保证能量前提下可有效去除燃料中的N。     

Determination of sulphur species arising from the reaction of sulphur and sulphide in a (K, Na)SCN eutectic melt

Sulphur and sulphide ions react in (K,Na)SCN eutectic melt with the formation of polysulphide. The electrolytic oxidation of SCN(-) at 155 degrees forms S(4) which gives S(2-)(5) with S(2-); at 165 degrees the sulphur electrogenerated is S(2) that reacts according to S(2) + S(2-) = S(2-)(3). The equilibrium constants of these reactions have been obtained by voltammetric measurements. The formation of S(2) at 155 degrees by irradiation from a xenon lamp was confirmed. The S(2) reacts with S(2-) to give S(2-)(3), and the equilibrium constant for this reaction is the same as that found for the reaction at 165 degrees .     

Determination of passive-sampled sulphur dioxide in ambient air as sulphate ion by flow injection analysis with an in-line reaction column

A modified FIA method was developed for the determination of sulphur dioxide (SO(2)) in ambient air collected by a passive sampler. SO(2) was oxidized by hydrogen peroxide and determined as sulphate ion in solution. Barium-dimethylsulfoazo-III complex was used as spectrophotometric reagent. A BaSO(4)-immobilized in-line reaction column was introduced into the flow system to increase the sensitivity and reproducibility. An in-line cation exchange column was used to eliminate triethanolamine, which was used as the absorbent reagent in the passive sampler. Sulphate ions can be analyzed in the range of 0.08-10.00 mg l(-1) with the R.S.D. less than 1.6% at the rate of 15 samples h(-1). It was satisfactory to apply this method to the analysis of sulphur dioxide in ambient air and the results agreed with those obtained by ion chromatography.     

The preferred conformations of 2,4-dichlorophenol, 2,4-dichloroanisole and their sulphur analogues

Analysis of the benzene dipole moments of 2-chloroanisole and 2,4-dichloroanisole, 2-chlorothioanisole and 2,4-dichlorothioanisole shows these compounds to exist as trans. 2-Chlorophenol and 2,4-dichlorophenol, and their sulphur analogues, are mixtures of Cis and trans conformers. The populations of the cis conformers are, at 25°C, 86 and 78% for the phenols, and ca. 70 and 50% for the corresponding thiophenols. The influence of various factors, such as the non-additivity of the (2-ClC₆H₄X)-group moment and torsional oscillation of the H-X bond (especially the H-S bond), on the calculated populations has been discussed. Incidentally it has been shown that p-dimethoxybenzene and p-di-(methylthio)benzene, as well as p-phenylenediamine and p-diformylbenzene, are equimolecular mixtures of cis and trans conformers.     

Synthesis and characterization of dichlorodicarbonylruthenium(II) complexes of oxygen,sulphur and nitrogen donor ligands

Complexes of dichlorodicarbonylruthenium(II) of formula [RuCl₂(CO)₂L₂] (L = tetramethylthiourea, monomethylthiourea, dimethylthiourea, pyridine 2-thiol, piperidine or pyridine) and [RuCl₂(CO)₂L′ (L′= 1,2-diaminoethane or tetramethylurea), have been prepared. The complexes were characterized by their IR, NMR and elemental analyses.     

Polydimethylsiloxane-based permeation passive air sampler. Part I: Calibration constants and their relation to retention indices of the analytes

A simple and cost effective permeation passive sampler equipped with a polydimethylsiloxane (PDMS) membrane was designed for the determination of time-weighted average (TWA) concentrations of volatile organic compounds (VOCs) in air. Permeation passive samplers have significant advantages over diffusive passive samplers, including insensitivity to moisture and high face velocities of air across the surface of the sampler. Calibration constants of the sampler towards 41 analytes belonging to alkane, aromatic hydrocarbon, chlorinated hydrocarbon, ester and alcohol groups were determined. The calibration constants allowed for the determination of the permeability of PDMS towards the selected analytes. They ranged from 0.026 cm² min⁻¹ for 1,1-dichloroethylene to 0.605 cm² min⁻¹ for n-octanol. Further, the mechanism of analyte transport across PDMS membranes allowed for the calibration constants of the sampler to be estimated from the linear temperature programmed retention indices (LTPRI) of the analytes, determined using GC columns coated with pure PDMS stationary phases. Statistical analysis using Student's t test indicated that there was no significant difference at the 95% probability level between the experimentally obtained calibration constants and those estimated using LTPRI for most analyte groups studied. This correlation allows the estimation of the calibration constants of compounds not known to be present at the time of sampler deployment, which makes it possible to determine parameters like total petroleum hydrocarbons in the vapor phase.     

Spectrophotometric determination of nitrogen dioxide in air

Summary A sensitive spectrophotometric method for the determination of trace amounts of nitrogen dioxide, after fixing it as nitrite in alkaline sodium arsenite solution, is described. The reaction is based on the diazo-coupling of p-nitroaniline with chromotrophic acid in acetate medium (pH 6±0.5). The azo dye formed has its absorption maximum at 515 nm, with a molar absorptivity of 3.7×10⁴ l mol^–1 cm^–1. Beer's law is obeyed over the range 0–20 g of nitrite. The relative standard deviation is 2.5% for ten determinations of 10 g of nitrite. The effect of interfering gases and ions on the determination is discussed. The method has been applied to the determination of residual nitrogen dioxide in a laboratory fume cupboard and the results are compared with those obtained by the widely used sulphanilamide — NEDA method. Down to 0.5 g of nitrite can be determined.     

Thermal destruction of rice hull in air and nitrogen

In this study, we ashed rice hull in air and nitrogen, respectively, and systematically investigated the effects of ashing temperature and atmosphere on the structures, morphologies, and pore characteristics of rice hull ash (RHA). All RHA samples are amorphous materials with porous structures. IR spectra revealed that RHA that ashed in air (WRHA) exhibit more polar groups on the surface than that of ashed in nitrogen (BRHA). The silica and carbon contents, BET surface area, and pore volume of BRHA increase with ashing temperature. When ashed in air, however, the silica content of WRHA increases and carbon content decreases with temperature. The BET surface area and pore volume of WRHA increase with temperature firstly and decline subsequently due to the closure of pores. Compared with WRHA, BRHA shows higher surface areas, micropore volumes, carbon contents, and lower mesopore fractions and silica contents. This study provides essential information for choosing a suitable thermal treatment of rice hull for a given adsorbate.     

Thermal degradation of cereal straws in air and nitrogen

Multigram quantities (2.5-10 g) of highly purified IgG were obtained within 4 h from serum by using Avid AL packed in a radial-flow column. Avid AL is an affinity gel containing a synthetic, low-mol-wt ligand capable of selectively binding IgG from serum of all animal species tested. By packing the gel in a radial-flow column up to 500 mL, a high flow rate of 50 mL/min can be achieved without adversely affecting the performance of the gel and the purity of the isolated antibody.     

白石湖煤液化粗油加氢精制过程硫、氮化合物转化规律

采用实沸点蒸馏仪对白石湖煤液化油进行馏分切割,切取<170℃液化粗油进行加氢精制脱除其中硫、氮化合物,采用硫化学发光气相色谱仪（GC-SCD）、氮化学发光气相色谱仪（GC-NCD）对液化粗油和精制油中硫、氮化合物进行分析表征,研究加氢精制过程硫、氮化合物的转化规律。结果表明,液化粗油中含硫化合物主要是噻吩类化合物和硫醇,经过加氢精制后基本消失,苯并噻酚类化合物脱除比例要低于噻吩类化合物,属于较难脱除含硫化合物。液化粗油中含氮化合物主要是苯胺类化合物,其次是吲哚类化合物,经过加氢精制吲哚类化合物全被脱除,苯胺和喹啉类化合物属于碱性含氮化合物,是精制油中残留的主要含氮化合物,含量达1.61 mg/kg。     

Intake of different chemical species of dietary arsenic by the japanese,and their blood and urinary arsenic levels

We calculated the intake of each chemical species of dietary arsenic by typical Japanese, and determined urinary and blood levels of each chemical species of arsenic. The mean total arsenic intake by 35 volunteers was 195±235 (15.8-1039) μg As day^?1, composed of 76% trimethylated arsenic (TMA), 17.3% inorganic arsenic (As_i), 5.8% dimethylated arsenic (DMA), and 0.8% monomethylated arsenic (MA): the intake of TMA was the largest of all the measured species. Intake of As_i characteristically and invariably occurred in each meal. Of the intake of As_i, 45-75% was methylated in vivo to form MA and DMA, and excreted in these forms into urine. The mean measured urinary total arsenic level in 56 healthy volunteers was 129±92.0 μg As dm^?3, composed of 64.6% TMA, 26.7% DMA, 6.7% As_i and 2.2% MA. The mean blood total arsenic level in the 56 volunteers was 0.73±0.57 μg dl^?1, composed of 73% TMA, 14% DMA and 9.6% As_i. The urinary TMA levels proved to be significantly correlated with the whole-blood TMA levels (r = 0.376; P<0.01).     

Chemometric studies in the Lagoon of Venice, Italy. Annual evolution of sulphur species and relationship to biogeochemical cycles in lagoon water

During the period March 1997-March 1998 dimethyl sulphide (DMS), dimethylsulphoniopropionate (DMSP) and carbon disulphide (CS2) were determined weekly in the water of the Lagoon of Venice, Italy (at three stations located in the Giudecca Canal, the San Secondo Canal and the Rio di San Nicolò). At the same time, the following hydrological and biological variables were also measured: tide height, temperature, transmittance, fluorescence, pH, salinity, chlorinity, sulphate, ammonia, nitrite, nitrate, phosphate, silicate, chlorophyll a, phaeopigments, phytoplankton (abundance and biomass). Principal component analysis (PCA), applied as a dimension reduction tool, made it possible to summarize multivariate information in a small number of components, which highlighted the relationships between the temporal evolutions of the sulphur compounds with hydrological and biological variables in the seasonal biogeochemical cycle of the lagoon. In particular the overall temporal cycle, which begins with the development of biological activity in late winter and spring, followed by the predominance of degradation processes during the late summer and the remineralization of nutrients in autumn, is clearly described in the plane of the first two principal components, together with the interrelationships between all the relevant variables.