Degradation of the herbicide isoproturon by a photocatalytic process

In this study, the adsorption and photocatalytic degradation of isoproturon (one of the most widely used herbicides in agriculture) was investigated in an annular photoreactor packed with a TiO₂ photocatalyst. The results highlighted that the monolayer Langmuir adsorption isotherm model was well obeyed. The isoproturon adsorption equilibrium constant was determined experimentally. The codegradation of isoproturon and of other copollutants such as salicylic acid and phenol occurred, demonstrating that within the catalyst, the same type of sites can be involved in the adsorption of the two pollutants. The heat of adsorption fell in the range of 20 to 50 °C and was found to be ∼43 kJ/mol. As expected, the adsorption constant K_a decreased with increasing the fluid flow due to the temperature rise. The kinetics of the photocatalytic degradation of isoproturon revealed a first-order reaction for initial concentrations between 3 and 43 ppm. In our experimental conditions, no by-products were detected and total disappearance of isoproturon was observed.     

Analysis of n-alkanes at sub microgram per liter level after direct solid phase microextraction from aqueous samples.

This work describes the application of the previously presented solid phase microextraction (SPME) fiber in direct mode for sampling of C10-C20 n-alkanes from aqueous solution. The fiber has simple composition and is constructed from activated charcoal:PVC suspension in tetrahydrofuran. When the composition of the fiber was optimized that the optimum composition was 90:10 (activated charcoal:PVC) for direct mode, whereas it was 75:25 for sampling from the headspace of aqueous samples. This fiber is completely stable in contact with water. The extraction efficiency is improved in the presence of 0.1 M NaCl. The value is between 17.8-38.5% for the first extraction, which better than the efficiency of similar commercial fibers. After seven extractions, all analytes are removed from the aqueous samples nearly 100%. Single fiber repeatability and fiber-to-fiber reproducibility are good and both are less than 13% for all studied alkanes. Finally, direct mode SPME was used in the determination of n-alkanes in the range of sub microg L(-1) without any additional preconcentration procedure. Gas chromatography along with flame ionization detection were used for separation and detection of the studied analytes.     

Determination of iron at ng/ml level by solid phase spectrophotometry after preconcentration on cation exchange filters

A cationic exchanger paper is used to retain analytes in solution and, after drying, to analyze directly by measuring the UV-Vis absorbance of the paper. The method was applied to determination of iron using its known 1,10-phenanthroline complex. Using 100 ml of sample the applicable concentration range was between 1.0 and 10.0 ng/ml with a detection limit of 0.2 ng/ml and a RSD around 2%. The method was applied to determination of iron total in snow, human serum and wine.     

Colorimetric detection of uranium(VI) on building surfaces after enrichment by solid phase extraction

A method for detecting and quantifying uranium(VI) levels on building materials that include concrete, Plexiglas, glass and steel surfaces is presented. Uranium(VI) was extracted from building material surfaces using a pH 2.2 buffer rinse and, subsequently complexed by an organic chelating agent, arsenazo III. The application of a uranium-chelating molecule, arsenazo III, allows for concentration enhancement using C₁₈ solid phase extraction and colorimetric detection of the uranium complex using ultraviolet-visible spectroscopy at 654 nm. The method has a detection limit (based on 3σ) of 40 ng/L (5 ng/cm²) and an overall extraction efficiency greater than 80% for each surface type (concrete, Plexiglas, glass, steel). Methods to prevent interference by metal ions commonly found on building materials are discussed.     

固相萃取-离子色谱法测定地下水中痕量高氯酸根离子

建立了测定地下水中痕量高氯酸根（ClO~4）的固相萃取-离子色谱(SPE-IC)分析方法。0.7 L水样经预处理降低主要干扰离子Cl~、CO2~3和SO2~4的干扰后,使用Cleanert PWAX弱阴离子交换固相萃取小柱对地下水中痕量(μg/L级)的ClO~4进行富集,用6 mL 1%NaOH溶液洗脱,富集液经0.45 μm水膜过滤后,用IonPac AS20阴离子分离柱、50 μL进样环、40 mmol/L KOH溶液淋洗、抑制电导检测分离分析。结果表明,地下水样品中ClO~4的方法检出限和测定下限分别为0.15 μg/L和0.60 μg/L,进样质量浓度在1～15 μg/L范围内有很好的线性关系,线性相关系数为0.9992,回收率为99.7%～100.5%;该方法经济有效,可用于地下水中痕量ClO~4的检测。利用该方法测定了哈尔滨周边部分地区地下水中ClO~4浓度,检测结果与离子色谱-质谱联用法的检测结果的相对误差为1.85%～9.24%。     

Fabrication of a novel immunosensor using functionalized self-assembled monolayer for trace level detection of TNT by surface plasmon resonance

We have developed a new immunosensor based on self-assembly chemistry for highly sensitive and label-free detection of 2,4,6-trinitrotoluene (TNT) using surface plasmon resonance (SPR). A monolayer of amine terminated poly(ethylene glycol) hydrazinehydrochloride (PEG-NH₂) thiolate was constructed on an activated gold surface and immobilized with trinitrophenyl-β-alanine (TNPh-β-alanine) by amide coupling method. The binding interaction of a monoclonal anti-TNT Ab (M-TNT Ab) with TNPh-β-alanine immobilized thiolate monolayer surface was monitored and evaluated for detection of TNT based on the principle of indirect competitive immunoreaction. Here, the competition between the self-assembled TNT derivative and the TNT in solution for binding with antibody yields in the response signal that is inversely proportional to the concentration of TNT in the linear detection range. With the present immunoassay format, TNT could be detected in the concentration range from 0.008 ng/ml (8 ppt) to 30 ng/ml (30 ppb). The response time for an immunoreaction was 2 min and one immunocycle could be done with in 4 min including surface regeneration. Bound antibodies could be easily eluted from the self-assembled immunosurface at high recoveries (more than 100 cycles) using pepsin solution without any damage to the TNT derivatives immobilized on the surface. The compact self-assembled monolayer was highly stable and prevented the non-specific adsorption of proteins on the surface favoring error free measurement.     

A sol-gel immobilization of nano and micron size sorbents in poly(dimethylsiloxane) (PDMS) microchannels for microscale solid phase extraction (SPE)

Sorbent particles consisting of nano and micro silica, and micron size octadecylsilica (ODS) were immobilized using sol-gel chemistry onto poly(dimethylsiloxane) (PDMS) microfluidic channels to serve as μ-chip solid phase extraction (SPE) devices. Extraction, preconcentration and purification of biological and chemical analytes were carried out using these. Micro and nano scale silica-immobilized μ-SPE were used for the extraction/purification of DNA from recombinant Escherichia coli crude lysate. The average DNA recovery was 77 ± 9% (X ± R.S.D.) for the micron size silica particles and 70 ± 5% (X ± R.S.D.) for the nano silica particles. The extracted DNA could be amplified by polymerase chain reaction (PCR) whereas the DNA from the crude lysate solution could not be. This was a testimony to the purification capability of the μ-SPE device. ODS immobilized μ-SPE were used to study the extraction efficiency (EE) and enhancement factor (EF) for three groups of organic compounds, aromatics, phenols and carboxylic acids. They showed poor recovery and low enrichment because the analytes sorbed into the PDMS and were not quantitatively extracted.     

Determination of nine emerging pesticides at trace level in aqueous samples using fully automated on-line solid phase extraction coupled with liquid chromatography-mass spectrometry

On-line solid phase extraction (SPE) coupled to liquid chromatography-mass spectrometry (LC-MS) offers an easy and fast strategy to analyze the organic contaminants in environmental samples with high sensitivity and selectivity. This paper described an in-house designed on-line SPE system and an on-line SPE-LC-MS method for the determination of pesticides at trace levels in water samples. The system was assembled from an eight-position valve, a piston pump, a six-port valve and a C18 SPE column, and significantly reduced analysis time by achieving full automation. Moreover, the use of a large enrichment volume (50?mL) significantly enhanced method sensitivity. Using this on-line SPE system, an on-line SPE-LC-MS method was developed for the determination of nine pesticides at trace levels in lake water and seawater sample. Under optimized conditions, method detection limits (MDLs) were 1.00–10.0?ng?L^?1.     

Study of CsCl incorporation in silica via sol-gel synthesis catalyzed by biogenic compounds

Incorporation of CsCl in silica via sol-gel route catalyzed by biogenic compounds with three different concentrations of CsCl has been carried out by using organic compounds extracted from Nitzschia spp., a freshwater diatom alga. The visual integrity, nitrogen adsorption and electron microscopies were used to characterize the silica gels obtained from the biocatalysts employing sol-gel process with tetraethylorthosilicate (TEOS) as precursor. The usual sequence for the sol-gel process was used: sol preparation, gelation, aging, drying and heat treatment. Differential thermal analysis (DTA), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to characterize the incorporation of CsCl in the biomimetic silica. Chemical analysis of the biocatalysts was used to explain the exothermic behavior of the samples during DTA and DSC. The incorporation of CsCl in the silica matrix with a process using biogenic catalysts proved to be more effective compared to another process using inorganic catalysts.     

Synthesis of carbon nanotube/anatase titania composites by a combination of sol-gel and self-assembly at low temperature

A simple method is described for the synthesis of carbon nanotube/anatase titania composites by a combination of a sol-gel method with a self-assembly technique at 65 °C. This method makes use of polyelectrolyte for wrapping multi-walled carbon nanotube (MWCNT) and providing them with adsorption sites for electrostatically driven TiO₂ nanoparticle deposition. The composites were characterized using X-ray diffraction, transmission electron microscopy, Fourier transform infrared and X-ray photoelectron spectroscopy, and photoluminescence for analyzing their crystal phase, microstructure, particle size, and other physicochemical properties. The results showed that MWCNT were covered with an anatase TiO₂ thin layer or surrounded by an anatase TiO₂ thick coating, which is constructed of TiO₂ particles about 6 nm in size. The composites were rich in surface hydroxyl groups. The excited e⁻ in conduction band of TiO₂ may migrate to MWCNT. Concerning the potential applicability, MWCNT/TiO₂ composites showed excellent photocatalytic activity toward the photodegradation of methyl orange.     

串联固相萃取法选择性富集白花蛇舌草中的环烯醚萜苷类成分

研究了从白花蛇舌草水提取物中选择性富集环烯醚萜苷类成分的方法。该方法采用硅胶基质的寡聚乙二醇(OEG,实验室自合成)和ODS两种填料依次作为固定相,对白花蛇舌草水提醇沉样品进行固相萃取,并以超高效液相色谱(UPLC)系统对在富集的各个阶段得到的产物进行了色谱表征。实验结果表明,采用该方法得到的终产物的产率为8.21%。从UPLC谱图中可以看出固相萃取环烯醚萜苷类成分选择性富集的过程。终产物中14种典型的环烯醚萜苷类化合物含量明显升高,可达白花蛇舌草水提物的6.1倍,回收率为50.1%,富集效果明显。因此,将白花蛇舌草水提物醇沉后依次经过OEG柱与ODS柱的串联固相萃取可选择性地富集环烯醚萜苷类成分。该方法操作步骤较少,操作简便,选择性好,提取效率较高,富集效果明显。     

XRD and SEM characterization of Cu/Co catalysts supported on Si-Al-zeolite made by a modified sol-gel technique

Cu, Co and Cu/Co catalysts supported on a Si-Al-Zeolite matrix, made by a modified sol-gel method, were characterized by XRD and SEM. The formation of some spinels was identified in some of the samples. Of particular interest were those spinels whose composition included Cu and Co in a mixed oxide. The identification of such structures would explain higher activities in those catalysts. This revised version was published online in June 2006 with corrections to the Cover Date.     

Micro-solid phase equilibrium extraction with highly ordered TiO2 nanotube arrays: a new approach for the enrichment and measurement of organochlorine pesticides at trace level in environmental water samples

Ordered TiO₂ nanotube arrays have been widely used in many fields such as photocatalysis, self-cleaning, solar cells, gas sensing, and catalysis. This present study exploited a new functional application of the ordered TiO₂ nanotube arrays. A micro-solid phase equilibrium extraction using ordered TiO₂ nanotube arrays was developed for the enrichment and measurement of organochlorine pesticides prior to gas chromatography-electron capture detection. Ordered TiO₂ nanotube arrays exhibited excellent merits on the pre-concentration of organochlorine pesticides and lower detection limits of 0.10, 0.10, 0.10, 0.098, 0.0076, 0.0097, 0.016, and 0.023 μg L⁻¹ for α-HCH, β-HCH, γ-HCH, δ-HCH, p,p’-DDE, p,p’-DDD, o,p’-DDT, and p,p’-DDT, respectively, were achieved. Four real water samples were used for validation, and the spiked recoveries were in the range of 78–102.8%. These results demonstrated that the developed micro-solid phase equilibrium extraction using ordered TiO₂ nanotube arrays would be very constructive and have a great beginning with a brand new prospect in the analysis of environmental pollutants.     

Boehmite sol properties and preparation of two-layer alumina membrane by a sol-gel process

A two layer ultrafiltration alumina membrane was prepared by a sol-gel process using boehmite sol as precursor. The sol was prepared by hydrolysation of aluminium tri-sec-butoxide. Sol properties, such as viscosity as a function of concentration and acidity, were investigated by using capillary viscometry, transmission electron microscopy and laser scattering photometry etc. The viscosity increased with an increase in concentration and a decrease in pH, while the particle shape and size of the sol were mainly determined by pH. The membrane prepared by a dipping procedure was characterized by both scanning electron microscopy and transmission electron microscopy. The results showed that the membrane thickness and surface morphology were affected by the dipping time, the viscosity and the temperature.     

整体柱在线固相微萃取-高效液相色谱法分析爽肤水中痕量雌激素

以甲基丙烯酸缩水甘油酯(GMA)为功能单体、乙二醇二甲基丙烯酸酯(EDMA)为交联剂,偶氮二异丁腈(AIBN)为引发剂、甲醇及正己烷(14∶5,v/v)为二元致孔剂,通过原位聚合反应制备了聚甲基丙烯酸缩水甘油酯(Poly(GMA-co-EDMA))毛细管整体柱。研究表明,制备的Poly(GMA-co-EDMA)整体柱具有良好的通透性和较低的柱压(1.5×106Pa,冲洗流速0.5 mL/min)。该整体柱对雌二醇、炔雌醇、雌酮和己烯雌酚的富集倍数分别为86、116、77和86。构建了整体柱在线微萃取接口装置,建立了整体柱在线固相微萃取-高效液相色谱(HPLC)测定爽肤水中痕量雌二醇、炔雌醇、雌酮和己烯雌酚的分析方法。该分析方法的检出限(S/N=3)为0.05~0.20μg/L。将方法应用于爽肤水中雌激素的检测,加标回收率为69.3%~111.3%,RSD5.0%。所建立的方法简单、快速、灵敏、准确,可满足爽肤水中痕量雌激素的分析。     

Liquid chromatographic determination of trace levels of nitrophenols in water samples after dispersive magnetic solid phase extraction

An efficient and fast dispersive magnetic solid phase extraction method was developed using MIL‐101(Cr)/poly (mercaptobenzothiazole)@magnetite nanoparticles for the preconcentration and determination of nitrophenols in river and rain water samples. High‐performance liquid chromatography‐Ultraviolet instrument was applied for the analysis of target nitrophenols. The effect of several variables on the extraction performance was explored via design of experiment approach. Limits of detection and linear dynamic ranges were attained in the range of 0.05–0.10 µg/L and 0.2–250 µg/L, respectively. The enrichment factors were in the range of 317–363. The precision (n = 3) of dispersive magnetic solid phase extraction method was in the range of 5.3–6.8%. Eventually, the method was utilized for the analysis of target nitrophenols in river and rain water samples.     

Sample clean-up by sol-gel immunoaffinity chromatography for determination of chloramphenicol in shrimp

The paper describes the characterisation and application of sol-gel columns prepared by entrapping anti-chloramphenicol (CAP) antibodies. Retention of CAP in the column was caused by specific interactions with the anti-CAP antibodies and not by non-specific adsorption to the sol-gel glass. After optimising important operation conditions, e.g. feeding medium, feeding flow-rate, elution medium, elution flow-rate and elution volume, the sol-gel columns were included in a clean-up procedure developed to determine CAP in shrimp. The selectivity of the columns was high enough to efficiently remove interfering matrix compounds. Due to the chromatographic conditions applied retention of cross-reacting substances in the immunoaffinity column did not pose a problem. CAP recovery of the analytical method was 68% with a relative standard deviation of 4% (n=4). In spite of applying highly complex shrimp extracts the columns could be used for clean-up of at least 12 samples. However, when detection of CAP is carried out with an UV detector the analytical method has a relatively poor sensitivity (LOD=1.8 ng/g, S/N=3). The most obvious way is to replace the UV detector by a detector based on an inherently more sensitive and selective detection principle, like a mass spectrometer.     

On the interaction of encapsulated pH indicator species within a silica matrix produced by three sol-gel routes

Solid acid-base sensors were prepared by encapsulating two pH indicators (brilliant yellow or acridine) within a silica matrix by the sol-gel method using three different routes: (1) non-hydrolytic, (2) acid catalyzed and (3) base catalyzed. The interactions of the silica-indicator with the resulting materials were then investigated by cyclic and differential pulse voltammetry. Complementary, ultraviolet-visible, photoacoustic spectroscopy was employed for the characterization of the interactions by monitoring the band shifts (bathochromic or hypsochromic, depending on the sol-gel route) between the neat pH indicators and those encapsulated within the silica network. Furthermore, X-ray photoelectron spectroscopy showed that the N 1s binding energy in brilliant yellow was shifted for the material resulting from the acid route. The electrochemical behavior and the pH indicator interactions with the silica network were dependent on the nature of the employed sol-gel route. For the sensors prepared with acridine, the interactions with the silica network took place through the nitrogen group from the pyridinic ring. For the brilliant yellow indicator, different behaviors were observed depending on the route, suggesting different processes during preparation or analysis. For the basic catalyzed and non-hydrolytic routes, it was not possible to assign a specific interaction. Nevertheless, it seemed that interactions might have taken place through the hydroxyl and/or sulphonic groups. Furthermore, for the brilliant yellow sensor prepared through the acid route, it was possible to show that the interaction probably or partially occurred through the azo groups.     

固相微萃取-气相色谱-质谱联用分析水中的痕量扑草净

研究了固相微萃取－气相色谱－质谱联用测定水中扑草净的方法，采用聚丙烯酸酯（PA）萃取头，对影响固相微萃取萃取效率的萃取时间、搅拌速度、pH值以及盐度等进行了优化。在优化实验条件下，方法线性范围在0．1mg/mL-1000ng/mL之间，检出限为1．5ng/L。用该法分析了合成井水、自来水和湖水样品，回收率在85．4％－89．1％之间，相对标准偏差在1．8％－5．2％之间。本方法适合于水中痕量扑草净的分析。     

Determination of methotrexate in human urine at trace levels by solid phase extraction and high-performance liquid chromatography/tandem mass spectrometry

For biological monitoring of hospital personnel occupationally exposed to antineoplastic agents, highly sensitive and specific methods are required. In order to detect trace MTX urinary concentrations, a precise and accurate high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) procedure, incorporating solid phase extraction, has been developed. Urine samples were purified by solid phase extraction (SPE) on octadecyl bonded, endcapped silica SPE columns. After eluting with methanol, the solvent was evaporated obtaining a 25-fold concentration of the analyte. This procedure was validated by using 7-OHMTX as internal standard. Calibration curves had correlation coefficients always higher than 0.999, and the limit of detection was assessed at 0.2 microg L(-1). High specificity of the HPLC-MS/MS technique assures that no interfering substances are detected rather than the analyte of interest.