环境监测中两种原位被动采样技术——薄膜扩散平衡技术和薄膜扩散梯度技术

介绍了近年来环境监测中两种新的原位被动采样技术.薄膜扩散平衡(DET)技术和薄膜扩散梯度(DGT)技术.综述了DET技术的原理、装置的组成和构造、特点及在环境监测中的应用.关于DGT技术着重论述了对被监测物质有效态的累积原理,总结了扩散相和结合相的发展,并展望了未来的发展方向.     

A new form of analytical chemistry: distinguishing the molecular structure of photo-induced states from ground-states

This paper introduces a new analytical technique from the field of crystallography, and the optoelectronics motivation that underpins this effort. The essence of the photocrystallography technique is explained in the context of a four-dimensional (space-time) structural probe, and the four technically distinct time-windows of enquiry are presented. This features the complementary needs of laboratory, synchrotron and Free-electron laser based X-ray diffraction experiments. The different scales of atomic resolution required for the technique to be able to probe various photochemical phenomena are described. Sample requirements for photocrystallography experiments are also considered. The paper concludes by forecasting the prospective fortune of this new analytical technique to respond to major current challenges in the photovoltaic, optical data storage, and non-linear optics industries.     

A critical review of vacuum-assisted headspace solid-phase microextraction for environmental analysis

Vacuum-assisted headspace solid-phase microextraction (Vac-HSSPME) is an emerging analytical technique, which further advances HSSPME by providing lower detection limits of analytes with poor volatility at shorter extraction times. This review discusses the theoretical aspects and possibilities of the Vac-HSSPME technique for analysis of environmental samples. Optimization of key parameters, currently available equipment and methods for quantification of organic pollutants in water and soil are considered. Key problems and limitations of the technique are discussed along with possible approaches for its future development. The technique has a well-developed theory, which could be used for modeling of the extraction process, faster method development, and optimization. Wider application of the technique is limited by the lack of automation, which, however, seems possible to develop and implement by manufacturers of commercial multi-purpose autosamplers for gas chromatography instruments. It has been shown that Vac-HSSPME allows decreasing cross-contamination of samples from the laboratory air, which is advantageous for identification and quantification of trace environmental pollutants. Simple equipment for the technique makes it possible to apply for on-site sample preparation and analysis of environmental samples.     

Measurement of anions in ambient particulate matter by ion chromatography: A novel sample preparation technique and development of a generic uncertainty budget

A novel sample preparation technique for the measurement of anions in particulate matter by ion chromatography is presented. The technique uses the eluant from the ion chromatography analysis stage to perform the extraction of the anions from the particulate matter. The demonstrated advantages of the new technique are manifold: faster sample throughput, minimised sample preparation, and a matrixed-matched sample for analysis. The repeatability of the technique has been tested using nominally identical ambient particulate matter samples (sub-sampled from one large filter) and the uncertainty of the technique has been estimated. The uncertainty estimate is transferable to other similar methods used to measure ions in particulate matter. Real data obtained using the new method are also presented.     

Applications of automated amino acid analysis using 9-fluorenylmethyl chloroformate.

A rapid and sensitive fully automated method for the determination of primary and secondary amino acids in different matrices is described. Amino acids are derivatized with 9-fluorenylmethyl chloroformate using an automated precolumn derivatization technique. Data are presented to show that the technique is both reproducible and highly sensitive. Applications of the technique are presented, including the analysis of peptide and protein hydrolysates and the profiling of free amino acids in physiological fluids.     

Application of the reference-element technique for fast sequential flame atomic-absorption spectrometry

Fast sequential flame atomic-absorption spectrometry (FS-FAAS) is able to measure a sequence of analyte wavelengths in one monochromator scan and so achieves or exceeds the analysis speed of sequential ICP–OES. The requirements and implementation of an FS-FAAS instrument are presented in detail. FS-FAAS is a sequential multi element technique which retains the advantages of conventional FAAS, for example ease of use. While the FS-FAAS technique is an ideal tool for routine determination of elements in the mg L^–1 concentration range, it is still subject to common sources of error such as transport problems and long-term drift. The reference-element technique can be used to correct for these types of common interference; other advantages include correction of some errors which are induced during sample preparation, and improved analytical accuracy and precision. The reference-element technique when utilizing the FS- FAAS technique is described in detail and benefits of the technique will be demonstrated by comparing performance for selected applications, for example a mineral sample and a scrap wood digest.     

Applications of an optimization technique in submolecular biology

Some applications of an optimization technique due to Levenberg in theoretical submolecular biology are described. This technique has proved a very useful tool for the generation of three-dimensional structures of molecules having cyclic components or other constrained regions. The generated molecular structures provide the starting point for quantum chemical calculations of great value in solving problems of biological interest. The mechanism of transport of alkali metal cations by valinomycin is one such example and this paper describes briefly how various conformations of valinomycin were obtained using the optimization technique. A variant of the same method has been suggested as a new technique for the detection of topographical similarities between apparently dissimilar molecules which are substrates for the same enzyme or receptor site. The technique is illustrated with a comparison of a tricyclic antidepressant with norepinephrine both of which have been postulated to compete for a common receptor site in the “amine pump” of peripheral adrenergic nerve cell membranes. Another area in which the optimization technique has proved useful is in developing an optimum separable localized bond function method designed for rigorous calculations on large saturated molecules. This method is briefly described.     

Microcoulometric determination of protonation constants of nuphar alkaloids

The coulometric titration technique is applied for evaluation of protonation constants of substances available in micromolar amounts. The validity of the procedure was checked by studying several well-known systems. Unknown constants were evaluated for naturally isolated alkaloids. The advantages of the microcoulometric technique are discussed.     

HPLC柱切换技术在临床药物分析中的应用

综述了近十年来高效液相色谱柱切换技术在药物分析中的应用情况，主要介绍了柱切换技术在生物样品纯化，富集和手性分离方面的实际应用，该技术可用于直接进样分析，特别适用于临床药物分析，可和于药代动力学，生物利用度等研究。     

Joint determination of fluorine and chlorine in granitic rocks with ion-selective electrodes

This enables both fluorine and chlorine in granitic rocks to be determined with a single sample. A rapid technique, using fusions in culture tubes, and a slower technique, employing fusions in platinum crucibles are described. The culture-tube technique is suitable for geochemical exploration and employs an oxidizing flux so that sulphide-bearing rocks can be analysed. The platinum-crucible technique yields fluorine and chlorine results for the standard rocks G-2 and GSP-1 that are comparable in value and precision to those obtained by other analytical methods. It is faster, easier to manipulate and yields higher fluorine values than the existing joint spectrophotometric method.     

Sub-micro methods for the analysis of organic compounds

Summary A new technique is described which enables organic compounds to be analysed for elements and functional groups using sample weights of 30–50 micrograms (0.03 to 0.05 mg). These amounts are only just visible to the naked eye. The accuracy is similar to that of the microscale, and the technique is fairly simple.It is expected that these methods will be of value in biochemistry and associated fields where amounts of sample are often limited. The new technique is not intended to replace micro-methods. Investigations are still proceeding to develop further methods for the determination of functional groups and to refine earlier procedures.     

Investigation of liquid–solids fluidized bed of different particle size through radioactive particle tracking techniques

Radioactive particle tracking technique (RPT) has proven to be a powerful and versatile technique both in terms of the richness of information it provides as well as the variety of multiphase flow situations it has been successfully employed. This work reports the execution of RPT technique for investigation of liquid–solids fluidized bed of different particle sizes (1.2 and 0.6 mm). Experiments are performed in a 10 cm ID cylindrical column for different liquid velocities. Further, RPT experiments are performed for both the solids and effect of liquid velocity and particle size on flow behaviour of liquid–solid fluidized bed is quantified.     

Real-time measurements of polychlorinated biphenyls using laser ionization time-of-flight mass spectrometry.

Polychlorinated biphenyls (PCBs) are hazardous compounds for which there are few methods involving real-time measurement. Recently, the development of the pulsed-laser technique has enabled us to measure aromatic hydrocarbons quite rapidly. In particular, the LI-TOFMS (laser ionization time of flight mass spectrometry) technique is expected to be a powerful method for on-line, selective and sensitive measurements. In the context of developing a highly selective and sensitive technique, the effective laser wavelength and pulse duration for laser ionization of 2-4 chlorinated PCBs are considered. Excitation at lambda = 266 nm was found to be substantially more effective than at lambda = 280, 300 or 320 nm. Also, picosecond excitation for PCBs underwent more efficient ionization (by a factor of over 10) and less fragmentation than nanosecond excitation. The achievable sensitivity for trichlorinated biphenyl in a real-time (1 min) measurement using the LI-TOFMS technique was estimated to be in the sub-ppbV range (< 0.01 mg/Nm3).     

Estimation of pore size distribution in MCM-41-type silica using a simple desorption technique

A recently developed dynamic desorption technique is used for obtaining vapor isotherms on porous materials. This gravimetric technique does not require any preliminary calibration and is based on analyzing the kinetics of liquid evaporation from a porous sample under quasi-steady state conditions. The crucial feature of the technique is concerned with the fact that no vapor pressure measurements are necessary. The technique is illustrated by desorption of benzene vapors from mesoporous silica MCM-41. To calculate the pore size distribution, the Derjaguin–Broekhoff–de Boer theory in its combination with the Wheeler model for capillary condensation is used. In the calculations, the reference data on benzene adsorption on a nonporous silica gel from two different sources (published by different authors) are applied. The mean mesopore sizes estimated from desorption isotherms are shown to be in a fair agreement with the calculations through the geometrical method based on the X-ray diffraction data. The dynamic desorption technique can serve as an additional tool for the characterization of a porous media.     

A comparison of the performance of two chromatographic and three extraction techniques for the analysis of PAHS in sources of drinking water

The aim of this work is to establish a sensitive and reliable method for the analysis of the 16 priority Environmental Protection Agency-defined polycyclic aromatic hydrocarbons (PAHs) found in water samples. Gas chromatography (GC)-mass spectrometry (MS) and high-performance liquid chromatography (HPLC)-fluorescence detection (FLD)-UV techniques are optimized to obtain an adequate resolution of all compounds. Validation of the methods is carried out, and a good performance is observed for both techniques. The HPLC-FLD-UV technique is somewhat more sensitive than the GC-MS technique for the determination of PAHs; thus, the HPLC-FLD-UV method is used to follow up both the solid-phase extraction (SPE) analysis using cartridges and discs and the liquid-liquid extraction (LLE), which are also evaluated for the extraction of the PAHs. Low recoveries between 43% and 79% are obtained using SPE cartridges, and higher values are obtained using SPE discs (56-96%) and LLE (60-105%). Better results are obtained using the LLE technique, and, thus, analysis of real water samples is carried out using this technique. LODs between 0.6 and 21 ng/L and relative standard deviations less than 15% are obtained using a spiked water sample analyzed using the full LLE HPLC-FLD-UV method.     

The detection of hidden proton magnetic resonance signals by means of INDOR

The INDOR technique appears to be a very useful and rapid tool for the detection of hidden proton lines as an aid in the elucidation of the structure of complex organic molecules. The experimental conditions for obtaining optimum results in a limited time are discussed. Analysis of the INDOR spectra of a number of selected spin systems are given; these show the capabilities of this method. Examples are given in which this technique is applied.     

Simple and rapid methods for on-site determination of radon and thoron in soil-gases for seismic studies

The determination of soil-gas anomalies especially ²²²Rn anomalies, are important to precisely locate fault traces, as well as to investigate earthquake precursors. In this paper, we have studied and compared new rapid methods for on site determinations of radon (²²²Rn), thoron (²²⁰Rn) and total radon (²²²Rn+²²⁰Rn) in soil-gas. These new techniques pump the soil-gas continuously from the soil through a simple sampling tube to the counting cell for one-minute with discarding the excess. Then, either four one-minute counting periods (5-minute technique) or nine one-minute counting intervals (10-minute technique) are followed immediately. In all the methods, conversely to Morse"s method, the first counting period (C1) was not employed for calculations. Three calculation methods for the five-minute technique, two for the ten-minute technique and a modified Morse"s method are compared with theoretical values and different real soil-gases with different radon/thoron ratios. The affect of different flow rates of soil-gases into the counting cell was also investigated. Finally, the ten-minute technique seems to be a little more accurate, but the 5-minute technique is much more suitable for seismic field studies when a much larger number of determinations are required in a short time.     

Absolute absorption measurements of polymer films for optical waveguide applications by photothermal deflection spectroscopy

A self‐contained experimental technique is proposed for measuring the absolute optical absorption spectra, thermal diffusivity, and thermal conductivity of polymer thin films. The technique is based on photothermal deflection spectroscopy and provides sensitivity that is high enough to quantify the very small optical absorption losses in polymer films used for optical waveguide applications. The capabilities of the technique are demonstrated with measurements performed on thin films of poly(methyl methacrylate) and a fluorinated polymer (CYTOP). An error analysis is presented, and the factors are discussed that influence the accuracy of the technique. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 39: 2717–2726, 2001     

阿达玛变换光谱和成像技术的应用和研究进展

阿达玛变换(HT)作为一种多通道光谱调制技术，具有多通道同时检测能力、多通道成像能力以及适用于数据处理等优点。综述了近十年来HT光谱和成像技术在分析科学中的应用和研究进展。主要从HT模板编码技术和HT激发序列应用技术等方面讨论了其最新发展和存在的问题，并展望了其发展前景。     

Embossing of organic thin films using a surfactant assisted lift-off technique

A simple technique for patterning organic materials using a surfactant assisted lift-off method is proposed. Thin films of various organic materials are prepared, and areas in contact with a surfactant coated poly(dimethylsiloxane) (PDMS) stamp are selectively removed. The general applicability of this technique is shown for materials containing nitrate, amine, and carboxylic acid functional groups. This technique provides a new methodology for fabricating patterns with vertical dimensions ranging from 30 nm up to 3 μm on organic thin films with specific functional groups.