An integrated GC/FT-IR system for the analysis of environmental pollutants

An integrated gas chromatography/Fourier transform infrared spectrometry (GC/FT-IR) system developed for the analysis of environmental pollutants is described. The versatility of the system allows the utilization of many different techniques of sample introduction and manipulation during analysis. The sample can be introduced by direct injection or thermal desorption from an adsorbent cartridge, and can then be separated on one of two capillary columns and detected by FT-IR or an FID. Cold traps and collection cartridges incorporated in the system permit recovery and additional fractionation of samples. Recovered sample and sample fractions can then be re-analyzed by GC/FT-IR or subsequently analyzed by GC/MS or other methods.     

Chromatographic determination of the rate and extent of absorption of air pollutants by sea water

Summary A simple chromatographic method is developed to determine the rate constant for expulsion of an air pollutant from water or its diffusion parameter in the liquid, the rate constant for chemical reaction of the pollutant with water, its mass transfer coefficient in the liquid, and the partition coefficient between liquid water and air. From these physicochemical parameters, the absorption rate by sea water and, therefore, the depletion rate of a polluting substance from the air can be calculated, together with the equilibrium state of this absorption. The method has been applied to nitrogen dioxide being absorbed by triple-distilled water and by sea water, at various temperatures. From the temperature variation of the reaction rate constant and of the partition coefficient, the activation energy for the reaction and the differential heat of solution were determined.     

Benzene charge exchange at atmospheric pressure for low-level detection of pollutants in ambient air

Charge exchange using the benzene molecular ion in a corona discharge atmospheric pressure ionization source is shown to be extremely sensitive for detecting low proton affinity compounds in air. Experiments performed on an Extrel API tandem mass spectrometric system indicated a limit of detection of 12.7 ppt for the detection of 2-chloroethyl ethyl sulfide in air.     

Dry ice-originated supercritical and liquid carbon dioxide extraction of organic pollutants from environmental samples

Packed in a high-pressure vessel and under calculated conditions, dry ice can be used as a source of carbon dioxide for supercritical CO₂ extraction or liquid CO₂ of organic compounds from environmental samples. Coupled with a fluid modifier such as toluene, dry ice-originated supercritical CO₂ (Sc CO₂) achieves quantitative extraction of many volatile organic compounds (VOCs) and semivolatile organic compounds (SOCs) including polycyclic aromatic hydrocarbons (PAHs), n-alkanes, and polychlorinated biphenyls (PCBs) from solid matrices. Compared to contemporary manual or automated supercritical fluid extraction (SFE) technologies, this novel technique simplifies SFE to a minimum requirement by eliminating the need of a high-pressure pump and any electrical peripherals associated with it. This technique is highly suitable to analytical areas where sample preservation is essential but difficult in the sampling field, or where sample collection, sample preparation, and analysis are to be done in the field.     

固相微萃取在水样污染物检测中的应用

固相微萃取是一种具有高灵敏度、回收率和重复性等优点的前处理技术,广泛应用于水中痕量污染物的处理,本文从固相微萃取装置、基本原理及其在水样污染物检测的中应用展开介绍,并以固相微萃取作为主题检索词,利用ISI Web of Knowledge中Web of Science引文数据库,对1998年到2012年间的相关文献进行计量分析。结果表明,固相微萃取主要应用于水样前处理,杀虫剂是主要的富集对象,气相、液相色谱以及质谱是常使用的检测器。     

Enhanced visible light photodegradation of water pollutants over N-, S-doped titanium dioxide and n-titanium dioxide in the presence of inorganic anions

The potential application of waste water treatment by photocatalysis is very likely to find its place in the near future. We have studied the photocatalytic degradation of three dyes (Eosin B, Rhodamine 6G, Rhodamine B) in the presence of doped n-TiO₂ in water and found that anchoring groups are favorable to the photodegradation of the pollutants. Taking Rhodamine B as a model pollutant, this study points out an alternative route to enhance photodegradation in invisible light, which consumes energy to synthesize, but addition of 0.1 mM of I⁻ or S₂O₃²⁻ increases the discoloration by up to three folds. For example, KI increased degradation to 36% while Na₂S₂O₃ enhanced it by 61%, which was higher than that of pure n-TiO₂ after sun light irradiation of 40 min. The enhancement of degradation by I⁻ and S₂O₃²⁻ may be linked to the scavenging of the holes by the inorganic anions, thus inhibiting recombination between h⁺/e⁻ after excitation of the semiconductor. The degradation is more effective in the presence of S₂O₃²⁻. In the presence of 0.1 mM KI, the rate constant increased from 0.0231 s⁻¹ to 0.0325 s⁻¹.Peroxodisulphate increases degradation, however, this is attributed to the sulfate radicals.     

Analysis of kaolin by sedimentation field-flow fractionation and electrothermal atomic absorption spectrometry detection

Summary Electrothermal (graphite furnace) atomic absorption spectrometry (ETAAS), as off-line detector for sedimentation field-flow fractionation (SedFFF) is exploited in clay analysis. Quantitation limits of coupled SedFFF-ETAAS for the determination of a submicron kaolin sample, considered a representative model of natural water suspended particulate, are theoretically established and experimentally validated with reference to Al and Si determination by ETAAS. Complete sample recovery for a 4 μg injected kaolin sample was obtained by keeping adsorption in the SedFFF apparatus to a minimum under control. The best experimental conditions, ensuring sample integrity, were low ionic strength (Na₂CO₃, 10⁻⁵ M), pH 8 and a Teflon covered accumulation wall. Several different runs, revealing the various experimental parameters affecting quantitative recovery, are reported and the different physico-chemical processes affecting such recovery are discussed. The advantages and drawbacks of SedFFF-ETAAS coupling compared with inductively coupled plasma-mass spectrometry (ICP-MS) technique are also discussed.     

Preparation and performances of small bore columns packed with reversed-phase materials and their use for the evaluation of air pollutants

Summary The preparation of small bore columns (1 mm i.d.) packed with reversed-phase materials is described. High efficiency (H_min=2 dp), coupled with a small C term (0.005 sec) have been obtained so that high speed can be combined with sufficient resolution for the separation of complex organic mixtures. These columns have been used for the separation of air pollutants dispersed in different matrices (air, particulate matter and rain water). Practical applications include the determination of aldehydes in air and emission samples, PAHs, nitrated and oxygenated PAHs in dust sampled from the stack of an industrial emission or collected in a urban area and the analysis of organic components dissolved in rain water collected at a rural site. Specific detection of these pollutants has been achieved by connecting small bore columns to UV absorbance, voltammetric and fluorimetric detectors. Mass spectra of some specific components have been recorded using the off-line technique.This work has been performed as a part of a Research Doctorate thesis to be discussed at the University of Rome.Dedicated to Prof. Dr. A. Liberti on the occasion of his 70th birthday.     

Development and validation of a rapid and wide-scope qualitative screening method for detection and identification of organic pollutants in natural water and wastewater by gas chromatography time-of-flight mass spectrometry

In this work, a multiclass screening method for organic contaminants in natural and wastewater has been developed and validated for qualitative purposes, i.e. to ensure the reliable and sensitive identification of compounds detected in samples at a certain level of concentration. The screening is based on the use of GC-TOF MS, and the sample procedure involves solid phase extraction with C(18) cartridges. Around 150 organic contaminants from different chemical families were investigated, including PAHs, octyl/nonyl phenols, PCBs, PBDEs and a notable number of pesticides, such as insecticides (organochlorines, organophosphorus, carbamates and pyrethroids), herbicides (triazines and chloroacetanilides), fungicides and several relevant metabolites. Surface water, ground water and effluent wastewater were spiked with all target analytes at three concentration levels (0.02, 0.1 and 1 μg/L). Influent wastewater and raw leachate from a municipal solid waste treatment plant were spiked at two levels (0.1 and 1 μg/L). Up to five m/z ions were evaluated for every compound. The identification criterion was the presence of, at least, two m/z ions at the expected retention time, measured at their accurate mass, and the accomplishment of the Q/q(i) intensity ratio within specified tolerances. The vast majority of compounds investigated were correctly identified in the samples spiked at 1 μg/L. When analyte concentration was lowered down to 0.1 μg/L the identification was more problematic, especially in complex-matrix samples like influent wastewater. On the contrary, many contaminants could be properly identified at the lowest level 0.02 μg/L in cleaner matrices. The procedure was applied to the screening of water samples of different origin and matrix composition and allowed the detection of several target contaminants. A highly reliable identification could be carried out thanks to the sensitive full-spectrum acquisition at accurate mass, the high selectivity reached with the use of narrow-mass window extracted ion chromatograms, the low mass errors observed in the positive detections and the Q/q ratio accomplishment.     

Separation and preconcentration of persistent organic pollutants by cloud point extraction

Persistent organic pollutants (POPs) are recognized as a class of poisonous compounds which pose risks of causing adverse effects to human health and the environment. Thus, it is very important to detect POPs in environmental and biological samples. The identification and determination of very low levels of POPs in complex matrices is extremely difficult. Recently a promising environmentally benign extraction and preconcentration methodology based on cloud point extraction (CPE) has emerged as an efficient sample pretreatment technique for the determination of trace/ultra-trace POPs in complex matrices. The purpose of this paper is to review the past and latest use of CPE for preconcentrating POPs and its coupling to different contemporary instrumental methods of analysis. First, the comparison of various extraction techniques for POPs is described. Next, the general concept, influence factors and other methods associated with CPE technique are outlined and described. Last, the hyphenations of CPE to various instrumental methods for their determination are summarized and discussed.     

基于色谱-质谱联用的新型有机污染物分析方法与技术

新型有机污染物是目前国内外关注的热点。在发现和分析新型有机污染物方面色谱-质谱联用技术发挥着至关重要的作用。本文对5类新型有机污染物(全氟化合物、药物、饮用水消毒副产物、农药转化产物和新农药、溴化阻燃剂)的主要色谱-质谱联用技术进行了介绍和评价,并对色谱-质谱联用的发展趋势进行了展望。     

Complexes of dihydroxybenzenes with carbon monoxide by DFT calculations and FT-IR matrix spectroscopy

Weakly bound complexes of dihydroxybenzenes and nitrophenols with carbon monoxide were the objects of theoretical studies based on the Becke–Lee–Parr density functional. Stability and vibrational spectra of all stable bimolecular complexes were determined and the theoretical results were integrated by matrix isolation FT-IR spectroscopy measurements.     

Vapor+liquid equilibrium of water, carbon dioxide, and the binary system, water+carbon dioxide, from molecular simulation

NVT- and NpT-Gibbs ensemble Monte Carlo (GEMC) simulations were applied to describe the vapor–liquid equilibrium of water (between 323 and 573 K), carbon dioxide (between 230 and 290 K) and their binary mixtures (between 348 and 393 K). The properties of supercritical carbon dioxide were determined between 310 and 520 K by NpT-MC simulations. Literature data for the effective pair potentials (for water: the SPC-, SPC/E-, and TIP4P potential models; for carbon dioxide: the EPM2 potential model) were used to describe the properties of the pure substances. The vapor pressures of water and carbon dioxide are calculated. For water, the SPC- and TIP4P models give superior results for the vapor pressure when compared to the SPC/E model. The vapor–liquid equilibrium of the binary mixture, carbon dioxide–water, was predicted using the SPC- as well as the TIP4P model for water and the EPM2 model for carbon dioxide. The interactions between carbon dioxide and water were estimated from the pair potentials of the pure components using common mixing rules without any adjustable binary parameter. Agreement of the predicted data for the compositions of the coexisting phases in vapor–liquid equilibrium and experimental results is observed within the statistical uncertainties of the simulation results in the investigated range of state, i.e. at pressures up to about 20 MPa.     

Monitoring the air quality around an oil refinery through the use of diffusive sampling

Diffusive sampling has been used to study the spatial distribution of SO₂, NO₂, NO_x, NH₃ and BTX (benzene, toluene and xylenes) near an oil refinery located in Falconara, Italy, over the period from March to October 2001. Three different categories of sampling sites (roadside, residential and background) were studied. In total, 56 sites were monitored. The results were evaluated on the basis of the limit values found in the European Directives. The results of the defined study indicate that the measured concentrations were substantially lower than the ambient air quality standard with the maximum concentrations being generally found much closer to emission sources. The monitoring method described here can be used to assess integrated concentration levels over long periods of time and to identify pollution hotspots where concentrations are likely to be consistently high. Identification of these hotspots may help to assess air quality and to implement proper action plans, especially in locations where industrial and urban pollution coexist.     

Atmospheric pressure chemical ionization in gas chromatography-mass spectrometry for the analysis of persistent organic pollutants

Atmospheric pressure chemical ionization (APCI) was primarily applied as the ion source for liquid chromatography-mass spectrometry (LC–MS). While APCI started to be used in gas chromatography-mass spectrometry (GC–MS) in 1970s, GC-APCI-MS was not widely used until recently. As a soft ionization technique, APCI provides highly diagnostic molecular ions, which is favored for the wide-scope screening. With the capability of tandem mass spectrometry (MS/MS), GC-APCI-MS methods with high sensitivity and selectivity have been developed and applied in the analysis of persistent organic pollutants (POPs) in environment and biological samples at trace levels. The present review introduces the history of the APCI source, with emphasis on mechanisms of ionization processes under the positive and negative ionization modes. Comparison between GC-APCI-MS and GC–MS with traditional electron ionization (EI) and chemical ionization (CI) are provided and discussed for selectivity, sensitivity and stability for the analyses of POPs. Previous studies found that the GC-APCI-MS methods provided limits of detection (LODs) around 10–100 times lower than other methods. An overview of GC-APCI-MS applications is given with the discussions on the advantages and drawbacks of various analytical methods applied for the analyses of POPs.     

高效液相色谱-串联质谱法同时测定废水中18种酚类污染物

建立了上清液直接进样-高效液相色谱-串联质谱同时测定废水中18种酚类污染物的分析方法。取5.0 mL水样置于具塞离心管中,加氨水调节pH≥12,摇匀,加入1.0 mL二氯甲烷-正己烷(2: 1, v/v)混合溶液并振摇5 min, 4000 r/min离心5 min,用玻璃针筒抽取上清液并经0.22 μ m聚四氟乙烯滤膜过滤,用甲酸调节水样pH至中性;然后采用Thermo Hypersil ODS柱(100 mm×2.1 mm, 5.0 μ m)分离,以甲醇-0.01 mol/L甲酸铵-甲酸水溶液(pH 4.0)为流动相进行梯度洗脱,流速0.2 mL/min,柱温30℃,进样10 μ L,电喷雾负离子电离(ESI^-)模式、多反应监测(MRM)模式进行检测,外标法定量。18种酚类化合物的峰面积与其质量浓度在一定浓度范围内均呈良好的线性关系(r²≥0.9991),方法检出限为0.10~0.88 μ g/L。测定低、中、高加标浓度的样品,18种酚类化合物的相对标准偏差为2.5%~9.9%(n=6);火工药剂废水与石油化工废水样品中的平均加标回收率为68.7%~118%(n=3)。此方法操作简单,灵敏度高,干扰小,分析速度快,可适用于环境废水中18种酚类污染物的同时分析。     

Nondestructive determination of crystallinity by diffuse reflectance FT-IR in composites made from polyphenylene sulphide and carbon fibres

Diffuse reflection Fourier transform infrared spectroscopy can be used for nondestructive determination of the degree of crystallinity at the surface of composite materials made from polyphenylene sulphide reinforced with carbon fibres. In particular, the ratio of the heights of the peaks at 1075 and 1093 cm^–1 can be used as a quantitative indicator of the crystallinity. This has been confirmed by annealing highly amorphous prepreg to give samples of varying degrees of crystallinity, in which case a good linear relationship is observed between the peak ratio and the enthalpy of crystallization as determined by differential scanning calorimetry.     

金属有机骨架材料在吸附分离大气污染物中的应用

大气污染问题是关系人民生命健康和经济社会和谐发展的重大问题.因此需要开发高效的吸附材料用于大气污染物的吸附和分离.金属有机骨架材料(MOFs)是一类新型的多孔材料,该材料具有结构多样、孔结构有序、大比表面积和高孔隙率等结构特点.MOFs通过调节有机配体的长度和官能团调节孔径和孔道尺寸,并进行功能化修饰在孔道中引入功能性...     

Voltammetric and FT-IR studies of modified activated carbon systems with phenol, 4-chlorophenol or 1,4-benzoquinone adsorbed from aqueous electrolyte solutions

Cyclic voltammetric and spectral FT-IR studies of the influence of surface chemistry on the adsorption and electrochemical behaviour of powdered activated carbon electrodes (PACE) in the presence of phenol, 4-chlorophenol and 1,4-benzoquinone were carried out. The variety of surface chemical properties was achieved through modification of the carbon samples by heat treatment under vacuum and in an oxygen–ammonia atmosphere as well as by oxidation with conc. nitric acid. Adsorption processes were carried out from aqueous solutions (in air and an oxygen-free atmosphere) in the presence acidic, neutral or basic electrolytes. Some electrochemical parameters of electrode systems with adsorbed organics were estimated and correlated with the adsorption ability of carbon materials. The changes in FT-IR spectra of the carbons caused by adsorption and/or coupling organic molecules are presented and discussed.     

Use of FT-IR Spectrometry for On-Line Detection in Temperature Rising Elution Fractionation

Summary: Temperature rising elution fractionation (TREF) has become a popular analytical technique that is able to determine the chemical composition distribution (CCD) of an ethylene/α-olefin copolymer. An infrared (IR) detector is commonly used in TREF detection to measure the concentration of the polymer solution exiting the column as a function of elution temperature. The chemical composition of the eluting polymer at a given elution temperature can be predicted from the relationship between comonomer content and TREF elution temperature pre-established through ¹³C nuclear magnetic resonance (NMR) analysis of TREF fractions. In this article, a Fourier transform infrared (FT-IR) spectrometer has been coupled with a TREF instrument to provide a more powerful tool for characterizing complex olefin copolymers. The Partial Least Squares (PLS) technique is used when analyzing the FT-IR spectra of the eluting polymer solutions. The power of on-line FT-IR detection in TREF is demonstrated using a few complex copolymer systems, such as ethylene-octene copolymer, polystyrene grafted ethylene-vinyl acetate copolymer and ethylene-methyl acrylate copolymer.