顺序注射化学发光联用技术测定空气中的SO2

基于在酸性溶液中SO32-被Ce4 氧化成SO42-产生很强的化学发光的原理,将顺序注射(SI)进样和化学发光(CL)检测方法联用,以0.012%三乙醇胺作吸收液,成功地测定了空气中的SO2。其浓度与发光信号强度在6.40×10-9～1.28×10-5mol/L范围内呈线性关系。方法的检出限(3σ)为4.80×10-9mol/L,对3.20×10-7mol/L的SO32-溶液9次测定的相对标准偏差为2.9%,方法回收率为98.45～103.6%。分析频率为90样/h。     

镁-美他环素胶束体系荧光特性及美他环素的测定

研究了在金属离子存在下美他环素在胶柬体系中的荧光特性,实验结果表明：在pH 9.50～11.30的H3PO4-HAc-H3BO3-NaOH缓冲溶液中,镁离子和非离子表面活性剂曲通X-100对美他环素的荧光具有显著的协同增敏作用.据此建立了测定药物制剂中美他环素的荧光光谱法.定量线性范围为0.16～16μg/mL,检出限为0.0036μg/mL,相对标准偏差为1.9%.     

Absorption, concentration and determination of trace amounts of air pollutants by flow injection method coupled with a chromatomembrane cell system: application to nitrogen dioxide determination

The concentration distribution of an analyte in a chromatomembrane cell (CMC) was examined by using various air samples of different air pollutant (NO₂) concentrations and volumes, and the results obtained could be explained by a proposed principle of the concentration distribution of the analyte in the CMC. This principle was for the first time proved experimentally in the present study. On-line preconcentration and continuous determination of the air pollutant (NO₂) in air samples were realized by coupling a three-hole CMC with a flow injection analysis (FIA) system, where a triethanolamine (TEA) aqueous solution (2 g l⁻¹) was used as an absorbing solution for NO₂ in the air samples. A calibration method with standard nitrite aqueous solutions was developed for the determination of NO₂ in the air samples. Concentrations of NO₂ in indoor air and its diluted air samples were determined by the proposed CMC/FIA method. The volume of air sample necessary for the measurement was decreased to only 5 ml. The measuring time for one sample was about 5–6 min even when a 20 ml air sample was used.     

A Study on the Location and Aggregation of Tetrahydrophenylporphyrin with a Single Hexadecyl Chain in Triton X-100 Micelle

The location and aggregation of 5,10,15-tris(4-hydroxyphenyl)-20-(hexadecyloxyphenyl)porphyrin (P) in nonionic polyoxyethylene (9.5) octylphenol (Triton X-100) micelle solutions were studied by means of UV–Vis and fluorescence spectra. P forms premicelle surfactant–porphyrin aggregates when the surfactant concentration is below and approaching the CMC. In Triton X-100 micelle solutions, different types of H-aggregates of P were formed when the concentration of P is higher than 3.9×10^-6?mol?dm^-3. As the bulk pH is changed, a transfer process for the porphyrin moiety in Triton X-100 micelle occurs. In neutral Triton X-100 micelle solutions, P may be located at the inner layer of the micelle; in basic conditions, the porphyrin moiety may transfer to the outer surface of the micelle. The kinetic study of porphyrin complexed with Cu(II) in Triton X-100 micelle solutions shows that the metalation rate could be controlled by changing the pH.     

Air quality monitoring network design to control nitrogen dioxide and ozone, applied in Malaga, Spain

Air monitoring networks are necessary to assess air quality in order to reduce pollution to levels which minimize harmful effects on human health and the environment. This paper describes a method to design or optimize air quality monitoring networks for nitrogen dioxide and ozone and its application in Malaga, a medium large city located in Andalusia, southern Spain, with traffic being the main source of air pollution. The completion of this method revealed that the old assessment network in Malaga was badly designed and made it possible to determine that one traffic-orientated and one background control station were necessary for NO₂ assessment in Malaga, as well as two control stations for O₃. First the number of stations necessary is obtained from historical data. Sampling campaigns with passive diffusion samplers at 74 sites were then carried out to obtain information on the pollution distribution in Malaga. The average concentrations found for NO₂ and O₃ were 22.8 μg/m³ and 64.3 μg/m³ respectively. Maximum values of up to 42.2 μg/m³ NO₂ were found in Malaga city centre and O₃ reached 91.5 μg/m³ downwind from the emission source. After spatial interpolation of the obtained values with Geographical Information Systems, a selection of the best locations for the monitoring stations was made, in line with the macro- and microscale siting requirements of the European Directive 2008/50/EC on ambient air quality and cleaner air for Europe.     

Continuous chemiluminescence determination of formaldehyde in air based on Trautz-Schorigin reaction

A new continuous method for the determination of formaldehyde in air is described. A cylindrical wet effluent diffusion denuder is used for the collection of formaldehyde from air into a thin film of absorption liquid (distilled-deionized water). Formaldehyde in the denuder concentrate is on-line detected employing a chemiluminescence flow method based on a reaction of formaldehyde and gallic acid with hydrogen peroxide in an alkaline solution. The collection efficiency of formaldehyde is quantitative at the air flow rate of 0.5 L min⁻¹ (absorption liquid flow rate of 336 μL min⁻¹). The limit of detection (S/N = 3) is 0.60 μg m⁻³ HCHO (0.49 ppb). The calibration graph is linear up to 300 μg m⁻³ HCHO (244 ppb). The relative standard deviations of chemiluminescence method for 1 × 10⁻⁶ and 5 × 10⁻⁶ M HCHO are 2.87% and 1.49%, respectively. Acetaldehyde interferes negligible, other compounds do not interfere. The method was employed for formaldehyde measurement in ambient air. The comparison measurement illustrates the good agreement of results obtained by proposed method with those obtained by reference fluorimetric method.     

Sequential injection spectrophotometric determination of zinc(II) in pharmaceuticals based on zinc(II)–PAN in non-ionic surfactant medium

A sequential injection analysis (SIA) spectrophotometric method for the determination of trace amounts of zinc(II) with 1-(2-pyridylazo)-2-naphthol (PAN) is described. The method is based on the measurement of absorbance of the zinc(II)–PAN chelate solubilized with a non-ionic surfactant, Triton X-100, no extraction procedure is required in the proposed method, yielding a pink colored complex at pH 9.5 with absorption maximum at 553 nm. The SIA parameters that affect the signal response have been optimized in order to get the better sensitivity and minimum reagent consumption. A linear relationship between the relative peak height and concentration was obtained in the concentration range of 0.1–1.0 μg ml⁻¹. The limit of detection (LOD, defined as 3σ) and limit of quantification (LOQ, defined as 10σ) were 0.02 and 0.06 μg ml⁻¹, respectively. The sample throughput about 40 samples/h was obtained. The repeatability were 1.32 and 1.24% (n = 10) for 0.1 and 0.5 μg ml⁻¹, respectively. The proposed method was successfully applied to the assay of zinc(II) in three samples of multivitamin tablets. The results were found to be in good agreement with those obtained by flame atomic absorption spectrophotometric method and with the claimed values by the manufactures. The t-test showed no significant difference at 95% confidence level.     

Sensitive and ultra-fast determination of arsenic(III) by gas-diffusion flow injection analysis with chemiluminescence detection

A novel chemiluminescence gas-diffusion flow injection system for the determination of arsenic(III) in aqueous samples is described. The analytical procedure involves injection of arsenic(III) samples and standards into a 0.3 mol L⁻¹ hydrochloric acid carrier stream which is merged with a reagent stream containing 0.2% (w/v) sodium borohydride and 0.015 mol L⁻¹ sodium hydroxide. Arsine, generated in the combined carrier/reagent donor stream, diffuses across the hydrophobic Teflon membrane of the gas-diffusion cell into an argon acceptor stream and then reacts with ozone in the flow-through chemiluminescence measuring cell of the flow system. Under optimal conditions, the method is characterized by a wide linear calibration range from 0.6 μg L⁻¹ to 25 mg L⁻¹, a detection limit of 0.6 μg L⁻¹ and a sample throughput of 300 samples per hour at 25 mg L⁻¹ and 450 samples per hour at 25 μg L⁻¹.     

Simultaneous cloud point extraction and spectrophotometric determination of carmoisine and brilliant blue FCF in food samples

A novel simultaneous cloud point extraction method for the determination of carmoisine and brilliant blue FCF by spectrophotometry has been developed. The method is based on the cloud point extraction of carmoisine and brilliant blue FCF from aqueous solution using Triton X-100, diluting the extracted surfactant rich phase with water and measuring the absorbance at 522 and 640 nm for carmoisine and brilliant blue FCF, respectively. The effects of different parameters such as pH, concentration of surfactant and temperature on the cloud point extraction of both dyes were investigated and optimum conditions were established. Linear calibration curves were obtained in the range of 0.02-3.50 μg mL⁻¹ for carmoisine and 0.05-3.50 μg mL⁻¹ for brilliant blue FCF under optimum conditions. Detection limit based on three times the standard deviation of the blank (3S_b) was 0.017 and 0.016 μg mL⁻¹ (n = 10) for carmoisine and brilliant blue FCF, respectively. The relative standard deviation (RSD) for 0.1 μg mL⁻¹ was 4.14 and 3.30% (n = 10), for carmoisine and brilliant blue FCF, respectively. The method was applied to the simultaneous determination of the dyes in different food samples.     

Determination of cysteine in a pharmaceutical formulation by flow injection analysis with a chemiluminescence detector

A simple and convenient flow injection-chemiluminescence (FI-CL) method for the determination of cysteine is reported, based on a fast and strong CL in a basic luminol-cysteine-NaIO₄ solution. The linear range was 1.0×10⁻⁸ to 1.0×10⁻⁶ M with a detection limit (3s) of 5×10⁻⁹ M, which was 100 times more sensitive than previously reported CL methods. Singlet oxygen, hydroxyl radical and hydrogen peroxide were suggested to be produced in this reaction and were responsible for the CL of cysteine. This simple method has been successfully applied for the determination of cysteine in a pharmaceutical formulation.     

The Micellization and Clouding Phenomena of a Nonionic Surfactant,Poly(ethylene glycol) t-octylphenyl ether (Triton X-100): Effect of (Chloride Salt) Electrolytes

Herein, we report the micellization and the clouding of a nonionic surfactant, poly(ethylene glycol) t-octylphenyl ether (Triton X-100), in aqueous solutions in the absence and presence of (chloride salt) electrolytes. In the absence and presence of electrolytes, the critical micelle concentration (CMC) of Triton X-100 was measured by surface tension measurements. Upon increasing the temperature as well as the concentration of electrolytes, the CMCs decreased. The surface properties and the thermodynamic parameters of the micellar systems were evaluated. From these evaluated thermodynamic parameters, it was found that in the presence of an electrolyte, the stability of the micellar system is high. The cloud points (CPs) of Triton X-100 were also measured in the absence and presence of metallic ions of electrolytes. Upon the addition of metallic ions of chloride salts (electrolytes), the decrease in CP values was observed and the order was found to be: K⁺ > Na⁺ > Li⁺ > NH⁺₄.     

Study on the Activity and Kinetic Characteristics of Glucoamylase in W/O Microemulsion Systems

The activity and kinetic characteristics of glucoamylase has been investigated in W/0 microemulsion systems of AOT/isooctane/buffer, CTAB/isooctane/l-pentanol/buffer and TX-100/ibooctane/I-pentanol/buffer, and compared with that in aquous solution. The effect of various parameters, such as pH optimum, To ptimum and water content, on the activity of the enzyme in microemulsion was determined. The results obtained show that the structure of the microemulsion has strong effect on enzyme activity compared to the k_cat, in aquous solution, the apparent turnover number k'_cat values were decreased in AOT, TX- 100 based system, and in creased in CTAB based system.     

Features of stable radical generation in lignin on exposure to nitrogen dioxide

The mechanism of stable radical generation in lignin under the action of nitrogen dioxide and NO₂ - air mixture is considered. The formation of phenoxyl, iminoxyl and acylaminoxyl radicals has been detected by EPR. The proposed mechanism involves a primary oxidative reaction of phenol groups with dimers of NO₂ (nitrosyl nitrate) resulting in the formation of phenoxyl radicals and nitric oxide. In the subsequent recombination of phenoxyl radicals and nitric oxide, nitroso compounds and oximes are formed. By reaction of oximes with radicals NO₂, stable iminoxyl radicals are formed. This mechanism is confirmed by kinetic dependencies obtained over a wide range of NO₂ concentrations. From IR spectroscopy measurements it follows that hydroxyl groups of non-phenolic structures of lignin are oxidised to aldehydes producing acylaminoxyl radicals by reaction with NO₂. The kinetic data show that the adsorption of NO₂ on the lignin surface is the rate-determining factor in stable radical formation.     

Spectrophotometric determination of cationic and anionic surfactants with anionic dyes in the presence of nonionic surfactants,part II: Development of batch and flow injection methods

On the basis of the changes in absorption spectra of azo dyes on the addition of an organic onium ion, spectrophotometric methods for the determination of organic onium salts and anionic surfactants were developed, and applied to flow injection method. Propyl orange (PO^–) was used for the determination of organic onium ions. Pairs of PO^– and Zeph⁺ (tetradecyldimethyl-benzylammonium ion) or PO^– and nC₁₈TMA⁺ (n-octadecyltrimethylammonium ion) were used for the determination of anionic surfactants. The determination range of organic onium ions were (0–3) × 10^–5 M by a batch method and were (0–2) × 10^–5 M by a flow injection method. The determination ranges of anionic surfactants were (0–2) × 10^–5 M by the batch method, and were (0–5) × 10^–5 M by the flow injection method, and the detection limit corresponding toS/N = 3 was 3 × 10^–7 M by the flow injection method. By the proposed flow injection method, anionic surfactants in water samples were determined.     

Triton X-100对血红蛋白/利巴韦林/H2O体系中血红蛋白性质和药物释放的影响

通过紫外光谱、荧光光谱、zeta电位、电导率、高效液相色谱和影像分析等方法研究了Triton X-100对血红蛋白/利巴韦林/H2O体系中血红蛋白性质和药物控制释放的影响. 研究结果表明, 随着Triton X-100浓度的增大, 荧光强度、荧光偏振、zeta电位和蛋白的形貌均发生较大的变化, Triton X-100能使增溶定位在蛋白表面中的利巴韦林逐渐游离出来. 当Triton X-100浓度大于1×10^-5 mol·L-1 时, Triton X-100 与血红蛋白的作用占主导地位, 血红蛋白开始明显变性. 少量Triton X-100能保护蛋白免受药物的影响.     

Effects of Triton X-100 on Properties of Hemoglobin and Controlled Release of Drug in Hemoglobin/Ribavirin/H2O System

Effects of Triton X-100 on the properties of hemoglobin (Hb) and on the controlled release of ribavirin were studied using the methods of UV-Vis spectrum, fluorescence spectrum, zeta potential, conductivity, high-performance liquid chromatographic (HPLC), and image morphology in Hb/ribavirin/H₂O system. With the increase of concentration of Triton X-100 in the system, the intrinsic fluorescence intensity, synchronous fluorescence intensity, fluorescence polarization, zeta potential, and morphology of Hb all changed gradually, and the ribavirin located on the Hb surface was dissociated and released out. When the concentration of Triton X-100 was higher than 1×10⁻⁵ mol·L⁻¹, the stronger interaction of Triton X-100 with Hb was predominant. Hb was unfolded and denaturized. A little Triton X-100 can protect Hb from the effects of ribavirin.     

Mechanism of stable radical generation in aromatic polyamides on exposure to nitrogen dioxide

By using the example of poly-m-phenylene isophthalamide, the mechanism of generation of stable nitrogen-containing radicals in aromatic polyamides in the presence of nitrogen dioxide is considered. The proposed mechanism is based on the reactions of dimers of nitrogen dioxide in the form of nitrosyl nitrate. As a result of a primary reaction of electron transfer from donor functional groups of macromolecules to nitrosyl nitrate, macromolecular radical cations and nitric oxide are formed. Amide groups and phenyl rings can act as electron donors. In the subsequent reactions with participation of radical cations, nitric oxide and nitrogen dioxide oximes, nitroso compounds and nitrites are formed. Generation of stable iminoxyl radicals occurs by reactions of oximes with nitrogen dioxide. Thermolysis of the polymer nitration products gives iminoxyl and acylarylaminoxyl radicals. The structure of iminoxyl radicals and features of dynamics of their formation have been confirmed by ab initio quantum-chemical calculations.     

Direct determination of acrylamide in food by gas chromatography with nitrogen chemiluminescence detection

A method of gas chromatography with nitrogen chemiluminescence detection and using standard addition is described for the determination of acrylamide in heat‐processed foods. Using a modified QuEChERS (quick, easy, cheap, effective, rugged, and safe) sample preparation method removes the acrylamide precursors completely, and the risk of overestimating acrylamide concentration due to additional analyte formation in the hot gas chromatograph inlet is also avoided. Sample preparation is rapid and inexpensive. A Deans switch device is utilized to heart‐cut acrylamide and to prevent interferences from the solvent and matrix from reaching the detector. The pre‐column is backflushed at high temperature to maintain a clean baseline and shorten the cycle time compared to baking out the column. Quantitation using standard addition is employed for compensation of potential variability in the acrylamide extraction efficiency in acetonitrile. The limit of detection and the limit of the quantification obtained for this method are 27 and 81 μg/kg, respectively, in food samples (equivalent to 3.5 and 10.6 μg/L in acetonitrile, respectively), and the linear range is 76–9697 μg/kg in food samples (equivalent to 10–1280 μg/L in acetonitrile) with an R² value of 0.9999.     

Validating the correlation of traffic-associated hydrocarbon and nitrogen dioxide with distance from a trunk road within a rural environment in UK

This study monitored traffic-associated air pollutants at four sampling sites within the A49 trunk road. Measurements of the gaseous air pollutants were carried out at various distances (roadside, 50 m, and 100 m) from the A49 trunk road using short term tubes at breathing heights. Data was collected over a 23-month period (June 2008-April 2010). Statistical analyses of hydrocarbon (HC) and nitrogen dioxide (NO₂) show positive r² and p-values, and suggest seasonal, intra- and inter-site variations in a distance-decay relationship. Higher mean concentrations were obtained within the winter season and near the roadside with a gradual decline with distance from the emission source. However, at some locations with increased vehicular activities, this relationship was altered. Elevated mean concentrations were observed within 50 m at Craven Arms (CA 50) and Strefford Road (SR 50); suggesting the influence of traffic on the concentration levels of the contaminants.     

Adsorption and selectivity of carbon dioxide with methane and nitrogen in slit-shaped carbonaceous micropores: Simulation and experiment

We have used the grand canonical Monte Carlo method to study the adsorption and selectivity of mixtures of carbon dioxide with methane and nitrogen at high (i.e., ambient) temperatures in model slit pores with graphitic surfaces. Experimental data, including new high pressure measurements for carbon dioxide and methane on a non-porous graphitic standard, were used to test the potential models. The mixture simulations predict that carbon dioxide is preferentially adsorbed in both systems. The results are discussed in terms of competing energetic and entropic effects and the underlying molecular mechanisms.