Peroxynitrous-acid-induced chemiluminescence of fluorescent carbon dots for nitrite sensing

In this work, chemiluminescent (CL) property of the carbon dots in the presence of peroxynitrous acid was studied. Peroxynitrous acid is formed by online mixing of nitrite and acidified hydrogen peroxide. The CL intensity was increased linearly with nitrite concentration in the range from 1.0 × 10(-7) M to 1.0 × 10(-5) M, and the detection limit was 5.3 × 10(-8) M (signal-to-noise ratio of S/N = 3). This method has been successfully applied to the determination of nitrites in pond water, river water, and pure milk, with recoveries in the range of 98%-108%. The CL mechanism of the peroxynitrous acid-carbon dots system was investigated using the CL, ultraviolet-visible light (UV-vis), and electron paramagnetic resonance (EPR) spectra. The electron-transfer annihilation of hole-injected and electron-injected carbon dots could mainly account for the CL emission, which sheds new light on the optical properties of the carbon dots.     

Chemiluminescence detection systems for the analysis of explosives

The objective of this paper is to provide a comprehensive review of explosive detection by chemiluminescence (CL) through a summary of the relevant literature in the last 5 years and a synopsis of current research topics and developments. The literature reviewed is specially addressed for the detection of a group of high explosives, containing nitrogen compounds. Most explosives compounds contain either nitro or nitrate groups which make possible their detection and quantification using detection systems based on chemiluminescent reactions. Practical considerations and experimental requirements are indicated, and the possibilities and limitations are evaluated.     

Carbon dioxide effects on luminol and 1,10-phenanthroline chemiluminescence

Luminol and 1,10-phenanthroline are widely used chemiluminescent (CL) reagents for the analysis of a wide range of metals and inorganic and organic complexes. While the fundamental mechanism for luminol and 1,10-phenantholine chemiluminescence is understood, the analytical application of these reagents is largely empirical and often poorly described mechanistically. For example, CL signals observed from metal-luminol systems are strongly dependent on the pH of the sample, even though the final pH of the reaction mixture is controlled to a narrow range by a buffer. Other investigators report significant changes in CL signal due to freshness and the acidity of reagents. Our work shows that many of these effects are due to dissolved CO2 present or formed in the analytical system. The hypothesis that carbon dioxide plays a pivotal role in enhancing luminol CL is supported by direct manipulation of CO2(aq) concentrations by the addition of CO2(g) or carbonic anhydrase. In contrast, Cu(II) analysis using the CL reagent 1,10-phenanthroline is completely quenched in the presence of CO2(aq). A plausible mechanism for these observations involves the reaction between superoxide, produced in these analytical systems, and CO2(aq) to form the peroxycarbonate radical, *C04-. The formation of *CO4- has very important analytical implications since this species appears to enhance or quench the CL signal from luminol and 1,10-phenanthroline, respectively.     

Integration of electrokinetics and chemical oxidation for the remediation of creosote-contaminated clay

Remediation of clayey soils that are contaminated with polycyclic aromatic hydrocarbons (PAHs) is a challenging task that may require integration of several technologies. The benefits of integrating in situ electrokinetic remediation with chemical oxidation were evaluated in laboratory-scale experiments lasting for 8 weeks. A voltage gradient of 48 V/m of direct current and 4.7 V/m of alternating current and periodic additions of chemical oxidants were applied to creosote-contaminated soil. Electrokinetically enhanced oxidation with sodium persulphate resulted in better PAH removal (35%) than either electrokinetics (24%) or persulphate oxidation (12%) alone. However, the improvement was shown only within 1/3 (5 cm) of the soil compartment. Electrokinetics did not improve the performance of Fenton oxidation. Both chemical oxidants created more positive oxidation-reduction potential than electrokinetic treatment alone. On the other hand, persulphate treatment impaired the electroosmotic flow rate. Elemental analyses showed reduction in the natural Al and Ca concentrations, increase in Zn, Cu, P and S concentrations and transfer of several metal cations towards the cathode. In conclusion, the results encourage to further optimisation of an integrated remediation technology that combines the beneficial effects of electrokinetics, persulphate oxidation and Fenton oxidation.     

Protein sensing and cell discrimination using a sensor array based on nanomaterial-assisted chemiluminescence

Cross-reactive sensor arrays, known as "chemical noses", offer an alternative to time-consuming analytical methods. Here, we report a sensor array based on nanomaterial-assisted chemiluminescence (CL) for protein sensing and cell discrimination. We have found that the CL efficiencies are improved to varied degrees for a given protein or cell line on catalytic nanomaterials. Distinct CL response patterns as "fingerprints" can be obtained on the array and then identified through linear discriminant analysis (LDA). The sensing of 12 kinds of proteins at three concentrations, as well as 12 types of human cell lines among normal, cancerous, and metastatic, has been performed. Compared with most fluorescent or colorimetric approaches which rely on the strong interaction between analytes and sensing elements, our array offers the advantage of both sensitivity and reversibility.     

Room temperature sonolysis-based advanced oxidation process for degradation of organomercurials: application to determination of inorganic and total mercury in waters by flow injection-cold vapor atomic absorption spectrometry

A new oxidation method based on room-temperature ultrasonic irradiation (sonolysis) is proposed for conversion of organomercurials into inorganic mercury and subsequent determination by flow injection-cold vapor atomic absorption spectrometry. This advanced oxidation process eliminates the need for chemical oxidants, high temperature, and pressure for degradation of organomercurials so that total mercury can be determined with sodium tetrahydroborate(III) or tin(II) chloride as reducing agents. Complete oxidations can be accomplished within 3 min, using a 40% sonication amplitude (100 W nominal power) provided by a probe ultrasonic device (20 kHz frequency) and a 1 mol L(-1) HCl liquid medium. The presence of HCl was seen to be necessary for fast oxidation of organomercurials, in contrast to other chemical oxidants such as H2O2 or HNO3 which yielded incomplete oxidation. Further advantages of the proposed method over existing methods which are currently employed for oxidation prior to total Hg determination are the removal of hazardous wastes and the decreased risk of Hg losses by volatilization. Oxidation kinetics indicated a pseudofirst-order reaction with apparent rate constants (k) of 3.2 x 10(-2) and 1.6 x 10(-2) s(-1) for methylmercury and phenylmercury, respectively. Oxidation experiments in the presence of foreign substances acting as OH radical scavengers showed a tolerance at least up to a concentration of 1000 mg L(-1). Likewise, model wastewaters with chemical oxygen demand of up to 1000 mg L(-1) could be processed without diminishing the oxidation efficiency. The method was applied to determination of inorganic and total mercury in simulated wastewaters and spiked environmental waters in combination with selective reduction.     

Atmospheric pressure chemical ionization source. 2. Desorption-ionization for the direct analysis of solid compounds

The flowing afterglow-atmospheric pressure glow discharge (APGD) ionization source described in part 1 of this study (in this issue) is applied to the direct analysis of condensed-phase samples. When either liquids or solids are exposed to the ionizing beam of the APGD, strong signals for the molecular ions of substances present on their surfaces can be detected without compromising the integrity of the solid sample structure or sample substrate. As was observed for gas-phase compounds in part 1 of this study, both polar and nonpolar substances can be ionized and detected by mass spectrometry. The parent molecular ion (or its protonated counterpart) is usually the main spectral feature, with little or no fragmentation in evidence. Preliminary quantitative results show that this approach offers very good sensitivity (detection limits in the picogram regime are reported for several test compounds in part 1 of this study) and linear response to the analyte concentration. Examples of the application of this strategy to the analysis of real-world samples, such as the direct analysis of pharmaceutical compounds or foods is provided. The ability of this source to perform spatially resolved analysis is also demonstrated. Preliminary studies of the mechanisms of the reactions involved are described.     

Dynamic component chemiluminescent sensor for assessing circulating polymorphonuclear leukocyte activity of peritoneal dialysis patients

Recurrent bacterial peritonitis is a major complication in peritoneal dialysis (PD) patients, which is associated with polymorphonuclear leukocyte (PMN) functional changes and can be assessed by a chemiluminescent (CL) reaction. We applied a new approach of a dynamic component chemiluminescence sensor for the assessment of functional states of PMNs in a luminol-amplified whole-blood system. This method is based on the evaluation of CL kinetic patterns of stimulated PMNs, while the parallel measurements of intracellular and extracellular production of reactive oxygen species (ROS) from the same sample can be conducted. Blood was drawn from diabetic and nondiabetic patients during follow-up, and during peritonitis. Healthy medical personnel served as the control group. Chemiluminescence curves were recorded and presented as a sum of three biological components. CL kinetic parameters were calculated, and functional states of PMNs were assessed. Data mining algorithms were used to build decision tree models that can distinguish between different clinical groups. The induced classification models were used afterward for differentiating and classifying new blind cases and demonstrated good correlation with medical diagnosis (84.6% predictive accuracy). In conclusion, this novel method shows a high predictive diagnostic value and may assist in detection of PD-associated clinical states.     

Effect of metal ions on the molecular weight distribution of humic substances derived from municipal compost: ultrafiltration and size exclusion chromatography with spectrophotometric and inductively coupled plasma-MS detection

The effect of metal ions (Co, Cu, Ni, Pb, Zn) on the molecular weight distribution of humic substances (HSs) obtained from compost is studied. We believe this is the first of this type of study applied in this way to humic substances. Size exclusion chromatography is coupled with two on-line detection systems (spectrophotometric and ICPMS) to study the binding of metal ions by humic substances leached from compost. ICPMS provided highly specific, sensitive, and multielement analytical information that enabled obtaining direct experimental evidence for the participation of metal ions in molecular size distributions of humic compounds. The compost extract or its high molecular weight fraction (>5,000) was put in contact with EDTA or citrate ions, thereby competing with HSs for binding metals. The experiments were carried out by varying the pH maintained by Tris-HCl or CAPS buffer (pH 8.0 and 10.3) and keeping the ionic strength constant. The elution profile of humic substances using UV/ visible detection was compared with those from ICPMS detection of Co, Cu, Ni, Pb, and Zn in the same chromatographic runs. The results obtained suggested that both bridging between small molecules and complexation/ chelation by individual molecules are involved in metal ion binding to humic substances. The use of ICPMS to study the role of metal ions in aggregation/disassociation of humic substances proposed in this work is promising. Coupling element-specific detection with SEC or other separation systems allows better understanding of the mobility and bioaccessibility of elemental species in the environment and further elucidation of the dissolved humic structure.     

Chemiluminescence detection for hybridization assays on the flow-thru chip, a three-dimensional microchannel biochip.

Chemiluminescence (CL) detection is seldom used in two-dimensional solid support microarray platforms because adequate sensitivity and spatial resolution is difficult to achieve. The three-dimensional ordered microchannels of the Flow-thru Chip increase both the sensitivity and spatial resolution required for quantitative CL measurements on microarrays. Enzyme-catalyzed CL reactions for the detection of hybridizations on microchannel glass were imaged using a CCD camera. Signal uniformity, sensitivity, and dynamic range of the detection method were determined. The relative standard deviation of signal intensities across an array of 64 spots was 8.1%. A detection limit of 250 amol of target with a linear dynamic range of 3 orders of magnitude was obtained for a 3-h assay. Similar to two-color fluorescence measurements, multiple enzyme labels were employed to demonstrate two-channel chemiluminescence. A unique method for measuring the relaxation time of a chemiluminescent species is also described.     

Lab-on-valve system integrating a chemiluminescent entity and in situ generation of nascent bromine as oxidant for chemiluminescent determination of tetracycline

A novel configuration of a lab-on-valve (LOV) system was fabricated and applied for chemiluminescence (CL) detection by integrating a demountable Z-type flow cell onto the LOV unit. A bismuthate immobilized microcolumn was incorporated in one port of the LOV for in situ oxidation of KBr and generation of bromine as oxidant for the bromine-hydrogen peroxide-tetracycline (TC) chemiluminescent reaction. The nascent bromine reacts with hydrogen peroxide and produces a weak CL signal, the intensity of which was significantly enhanced in the presence of TC following an energy-transfer mechanism. A novel procedure for tetracycline quantification was therefore developed based on the present system. When compared with the reported flow injection-CL methods for TC, this procedure not only provided an improved detection limit of 2.0 microg L(-)(1) but also minimized sample and reagent consumption. A linear range of 6.0-10 000 microg L(-)(1) was derived along with RSD values of 5.9 (at the concentration level of quantification limit) and 2.2% (at 50 microg L(-)(1)), and a sampling frequency of 120 h(-)(1) was achieved. The system was validated with a National Standard Procedure (GB/T 18932.4-2002, HPLC with UV detection) by measuring TC contents in commercial milk samples.     

Oxidation Reaction between Periodate and Polyhydroxyl Compounds and Its Application to Chemiluminescence

The oxidation reaction between periodate and polyhydroxyl compounds was studied. A strong chemiluminescent (CL) emission was observed when the reaction took place in a strong alkaline solution without any special CL reagent. However, in acidic or neutral solution, it was hard to record the CL with our instrument. It was interesting to find that in the presence of carbonate the CL signal was enhanced significantly. When O(2) gas and N(2) gas were blown into the reagent solutions, both background and CL signals of the sample were enhanced by O(2) and decreased by N(2). The spectral distribution of the CL emission showed two main bands (λ = 436-446 and 471-478 nm). Based on the studies of the spectra of CL, fluorescence and UV-visible, a possible CL mechanism was proposed. In strongly alkaline solution, periodate reacts with the dissolved oxygen to produce superoxide radical ions. A microamount of singlet oxygen ((1)O(2)*) could be produced from the superoxide radicals. A part of the superoxide radicals acts on carbonates and/or bicarbonates leading to the generation of carbonate radicals. Recombination of carbonate radicals may generate excited triplet dimers of two CO(2) molecules ((CO(2))(2)*). Mixing of periodate with carbonate generated were very few (1)O(2)* and (CO(2))(2)*. These two emitters contribute to the CL background. The addition of polyhydroxyl compounds or H(2)O(2) caused enhancement of the CL signal. It may be due to the production of (1)O(2)* during the oxidized decomposition of the analytes in periodate solution. This reaction system has been established as a flow injection analysis for H(2)O(2), pyrogallol, and α-thioglycerol and their detection limits were 5 × 10(-)(9), 5 × 10(-)(9), and 1 × 10(-)(8) M, respectively. Considering the effective reaction ions, IO(4)(-), CO(3)(2)(-), and OH(-) could be immobilized on a strongly basic anion-exchange resin. A highly sensitive flow CL sensor for H(2)O(2), pyrogallol, and α-thioglycerol was also prepared.     

Determination of fluorine in inorganic substances (Overview)

This is a review of physical and chemical methods of determination of fluorine in inorganic substances which have been published in the last decade. Promising new indirect variants of molecular absorption spectrometry are presented, as well as widely applied methods of ion chromatography, potentiometry with fluoride selective electrode, and others.     

包装材料中化学物质迁移分子动力学模拟研究进展

概述了分子动力学模拟的基本原理及其应用方法,在此基础上,综述了分子动力学模拟在高阻隔包装材料、缓释包装材料、高性能聚合包装材料中化学物质迁移的研究现状,并提出分子动力学技术在包装材料化学物质迁移方面未来的应用方向:深入研究模型处于缺陷状态、复杂环境下的建模方法,不断完善迁移模型库,采用更高性能的计算机来构建更大分子量的模型,以验证和改进模型并提供更多的物性数据,得到一些极限条件或实验无法实现情况下的信息。     

化学衍生化技术在毒品分析中的应用研究进展

衍生化是一种利用化学变换把化合物转化成类似化学结构物质的技术.样品进行衍生化的作用主要是把难于分析的物质转化为与其化学结构相似但易于分析的物质,便于量化和分离.本文简要介绍了化学衍生化技术,并对该技术在毒品检验中的应用进行综述,以期为法庭科学相关领域研究提供理论依据,为公安实践业务开展提供参考.     

Development of an aerosol chemiluminescent detector coupled to capillary electrophoresis for saccharide analysis

A novel aerosol chemiluminescent (CL) detector coupling to capillary electrophoresis (CE) for the detection of saccharides is reported. This CL detector is composed of a postcapillary nebulizer and porous alumina as catalyzer in quartz tube. The CL emission could be generated due to the catalyzing oxidization of saccharides on the surface of porous alumina. The saccharides such as sucrose, alpha-lactose, maltose, raffinose, galactose, xylose, and glucose with only weak UV absorbance can be successfully detected. The linear ranges of those saccharides are from 30-2000 to 50-2000 mg/L; relative standard deviations range from 2.1 to 3.7% (200 mg/L, n = 11). Compared with the traditional UV detector currently used in CE, this novel detector shows the advantage of high sensitivity to the compounds with only weak UV absorption. Thus, it could be an important supplement of CE detectors for UV-lacking compounds.     

Molecular connectivity parameter and enthalpy of mixing

The molecular connectivity functions for Van der Waals constants a and b, Flory's characteristic pressure p¹ and reduced volume ? and the ratio $\text{P}{}^1\text{V}\text{?}$ are obtained through regression analysis of data on n-alkanes and isomeric alkanes. Such functions are very useful in predicting the desired property of a compound for which experimental data are lacking. Such connectivity functions, however, fail to describe the properties of mixtures or thermodynamic functions of mixing.Thus, the enthalpies of mixing ΔH^M calculated through the use of these connectivity functions, differ largely in sign and/or magnitude from the observed data. Reasons for the discrepancies are discussed.     

Optical sensors for vapors, liquids, and biological molecules based on porous silicon technology

The sensing of chemicals and biochemical molecules using several porous silicon optical microsensors, based both on single-layer interferometers and resonant-cavity-enhanced microstructures, is reported. The operation of both families of sensors is based on the variation of the average refractive index of the porous silicon region, due to the interaction with chemical substances either in vapor or liquid state, which results in marked shifts of the device reflectivity spectra. The well established single-layer configuration has been used to test a new chemical approach based on Si-C bonds for covalent immobilization of biological molecules, as probe, in a stable way on the porous silicon surface. Preliminary results on complementary oligonucleotide recognition, based on this technique, are also presented and discussed. Porous silicon optical microcavities, based on multilayered resonating structures, have been used to detect chemical substances and, in particular, flammable and toxic organic solvents, and some hydrocarbons. The results put in evidence the high sensitivity, the reusability, and the low response time of the resonant-cavity-enhanced sensing technique. The possibility of operating at room temperature, of remote interrogation, and the absence of electrical contacts are further advantages characterizing the sensing technique.     

Nanoscale heterogeneity if glass-forming liquids: experimental advances

Recent evidence indicates that in supercooled liquids the cooperativity of molecular motion extends over certain temporal and spatial ranges. A key advance is the experimental and theoretical exploration of higher-order correlation functions that can track the molecular coordinates for more than just two points in time or space. Uncontested experimental determinations of the heterogeneity length scale at the glass transition remain a major goal.     

Differentiation between viral and bacterial acute infections using chemiluminescent signatures of circulating phagocytes

Oftentimes the etiological diagnostic differentiation between viral and bacterial infections is problematic, while clinical management decisions need to be made promptly upon admission. Thus, alternative rapid and sensitive diagnostic approaches need to be developed. Polymorphonuclear leukocytes (PMNs) or phagocytes act as major players in the defense response of the host during an episode of infection, and thereby undergo functional changes that differ according to the infections. PMNs functional activity can be characterized by quantification and localization of respiratory burst production and assessed by chemiluminescent (CL) byproduct reaction. We have assessed the functional states of PMNs of patients with acute infections in a luminol-amplified whole blood system using the component CL approach. In this study, blood was drawn from 69 patients with fever (>38 °C), and diagnosed as mainly viral or bacterial infections in origin. Data mining algorithms (C4.5, Support Vector Machines (SVM) and Na?ve Bayes) were used to induce classification models to distinguish between clinical groups. The model with the best predictive accuracy was induced using C4.5 algorithm, resulting in 94.7% accuracy on the training set and 88.9% accuracy on the testing set. The method demonstrated a high predictive diagnostic value and may assist the clinician one day in the distinction between viral and bacterial infections and the choice of proper medication.