Dielectric Barrier Discharge in Analytical Spectrometry

Abstract

Dielectric barrier discharge is a nonequilibrium plasma, and its industrial application has been on a large scale. Similarly, its prominent features of high dissociation ability at low working temperature and low power consumption, simple and adjustable configuration, ambient working conditions, and long lifetime are favorable for developing a wide array of analytical devices as well. This review addresses the basics of dielectric barrier discharge and emphasizes their analytical applications in analytical atomic spectrometry, chemiluminescence, gas chromatographic detectors, ion source for mass spectrometry, and ion mobility spectrometry with 103 references.     

Air Analysis: Determination of Ozone by Chemiluminescence

SUMMARY

The present review is devoted to applications of chemiluminescence for ozone analysis in air. Methods including gas phase determination and solution measurements are summarised. Practical considerations and experimental requirements are indicated. The literature revised covers the papers of analytical interest which have appeared in aproximately the last ten years.     

Luminol Chemiluminescence in Urine Analysis

Abstract

The purpose of the present review is to sketch out the scope of luminol chemiluminescence in human urine analysis. Practical considerations and experimental requirements are indicated. The literature revised covers the papers of analytical interest that have appeared in approximately the last six years.     

Evolved Gas Analysis by Mass Spectrometry

Abstract: Periodic publications have been published that address advances in evolved gas analysis techniques, because the correct interpretation for the mechanism of a thermally induced reaction, involving the formation of gaseous species, is strongly dependent on the characterization of the evolved products.

When the nature of volatile products released by a substance subjected to a controlled-temperature program are online determined, the results allow one to prove a supposed reaction, either under isothermal or under heating conditions.

Very recent analytical applications of evolved gas analysis performed by mass spectrometry, selected among those published in 2012 and 2013, are collected in this review.     

Vapor Flows Along a Plane Condensed Phase with Weak Condensation in the Presence of a Noncondensable Gas

A steady flow of a vapor in a half space condensing at incidence onto a plane condensed phase is considered in the case where another gas that does not condense (the noncondensable gas) is present near the condensed phase. A systematic asymptotic analysis of the Boltzmann equation for hard-sphere molecules is performed in the case where condensation is weak, and the relation among the parameters of the vapor flow at infinity, those associated with the plane condensed phase, and the amount of the noncondensable gas is derived in an analytical form. The result supplements the numerical result for the relation for arbitrarily strong condensation obtained on the basis of a model Boltzmann equation and under the restriction that the vapor molecules are mechanically identical with the noncondensable-gas molecules [Taguchi et al., Phys. Fluids 15: 689 (2003)]. PACS numbers: 47.45.-n, 51.10.+y, 05.20.Dd, 05.60.-k     

Evolved Gas Analysis by Mass Spectrometry

Abstract

The analytical applications of the evolved gas analyses (EGAs) performed by mass spectrometry for the period extending from 2005 to 2010 are collected in this review. By EGA, the nature of volatile products released by a substance subjected to a controlled temperature program are determined on-line, with the possibility to prove a supposed reaction either under isothermal or under heating conditions.     

Microplasma-Based Detectors for Gas Chromatography: Current Status and Future Trends

Abstract: Microplasma is a useful detector for analyzing the effluent of gas chromato-graphy due to its remarkable capacity for portability, high sensitivity, and excellent multielement selectivity. Compared to classical detectors, microplasma detectors have the advantages of small size, low cost, and low energy consumption in design and operation. We aim to provide an overview of microplasma detectors and show their applications in various chemical analyses. The operational characteristics and analytical performance of different microplasma detectors, such as capacitively coupled microplasma, glow discharge microplasma, and microhollow-cathode microplasma, are presented in detail to reveal the current status of microplasma detectors for gas chromatography. In addition, several approaches for the design of microplasma are discussed and the future trends in the development of microplasma detectors are highlighted at the end of this review. Various applications of microplasma detectors for gas chromatography systems are also presented in this review.     

Formation of argon cluster with proton seeding

ABSTRACT

We employ force-field molecular dynamics simulations to investigate the kinetics of nucleation to new liquid or solid phases in a dense gas of particles, seeded with ions. We use precise atomic pair interactions, with physically correct long-range behaviour, between argon atoms and protons. Time dependence of molecular cluster formation is analysed at different proton concentration, temperature and argon gas density. The modified phase transitions with proton seeding of the argon gas are identified and analysed. The seeding of the gas enhances the formation of nano-size atomic clusters and their aggregation. The strong attraction between protons and bath gas atoms stabilises large nano-clusters and the critical temperature for evaporation. An analytical model is proposed to describe the stability of argon-proton droplets and is compared with the molecular dynamics simulations.     

Recent Advances in Analytical Applications of Nanomaterials in Liquid-Phase Chemiluminescence

Abstract

In recent years, many nanomaterials-assisted chemiluminescence (CL) systems have been developed to improve the sensitivity and to expand the scope of their analytical applications. In these new systems, nanomaterials participate in CL reactions as catalysts, labels, reductants, luminophors, or energy acceptors. This review mainly focuses on the recent analytical applications of metal nanoparticles, magnetic nanoparticles, quantum dots (QDs), and carbon-based nanomaterials (carbon nanotubes and graphene) in liquid-phase CL systems. Recent advances in electrochemiluminescence based on nanotechnology and its analytical applications, especially in immunoassay, DNA analysis, and other biological analyses, are also summarized. Finally, we discuss some critical challenges in this field and speculate about their solutions. A total of 177 references mainly in the last 5 years are included in this review.     

Sensitive Chemiluminescence Assay for Patulin in Apple Juice by Flow Injection

Abstract

A sensitive chemiluminescence (CL) procedure for the determination of patulin by flow injection is described. It was found that patulin inhibits the CL generated from the luminol–dissolved oxygen system significantly. The decrement of chemiluminescence intensity was linear with the patulin concentration over the range from 0.04 to 10.0 ng mL^?1 with a detection limit of 0.01 ng mL^?1 (3σ_noise). At a flow rate of 2.0 mL min^?1, a complete analytical process could be performed within 0.5 min, including sampling and washing, with a relative standard deviation of less than 3.0% (n=5). The proposed method was applied successfully in the determination of patulin in apple juice, and the recovery was between 96.9% and 103.9%.     

Vibrational Spectroscopy in Clinical Analysis

Abstract: Vibrational spectroscopy includes several different techniques, the most important of which are mid-infrared (IR), near-IR, and Raman spectroscopy. Raman and mid-IR spectroscopy are complementary techniques and usually both are required to completely measure the vibrational modes of a molecule. Vibrational spectrometry covers a series of well-established analytical methodologies suitable to be employed for both qualitative and quantitative purposes. In the first part of this review, we will focus on theoretical aspects related to vibrational techniques; in the second part, the most important papers, published during the period 2005–2014, related to clinical analysis performed with vibrational spectroscopy techniques will be critically discussed.     

Microplasma Technology and Its Applications in Analytical Chemistry

Abstract

This review article describes some existing microplasma sources and their applications in analytical chemistry. These microplasmas mainly include direct current glow discharge (DC), microhollow-cathode discharge (MHCD) or microstructure electrode (MSE), dielectric barrier discharge (DBD), capacitively coupled microplasmas (CCμPs), miniature inductively coupled plasmas (mICPs), and microwave-induced plasmas (MIPs). The historical development and recent advances in these microplasma techniques are presented. Fundamental properties of the microplasmas, the unique features of the reduced size and volume, as well as the advantageous device structures for chemical analysis are discussed in detail, with the emphasis toward detection of gaseous samples. The analytical figures of merit obtained using these microplasmas as molecular/elemental-selective detectors for emission spectrometry and as ionization sources for mass spectrometry are also given in this review article.     

Binding Study of Phenformin with Bovine Serum Album Using a Combined Technique of Equilibrium Dialysis with Flow-Injection Chemiluminescence Detection

ABSTRACT

The interaction between phenformin hydrochloride and bovine serum albumin (BSA) was investigated by the methods of chemiluminescence combined with equilibrium dialysis technique. A novel N-bromosuccinimide (NBS)–eosin Y (EY) chemiluminescence (CL) method was established for the determination of phenformin. The mechanism of this chemiluminescence system was proposed. Optimization studies were performed to determine the phenformin. Under the optimal conditions, the CL intensity was linear for a phenformin concentration over the range of 4.6 × 10^?8 to 5.0 × 10^?5 g/mL. The detection limit was 1.5 × 10^?8 g/mL. The data obtained by the present equilibrium dialysis–CL system were analyzed using the Klotz plot and the Scatchard analysis. The results showed that the Klotz plot and the Scatchard plot are linear with good correlation coefficient, indicating that the phenformin has only one type of binding site on BSA. The binding parameters were the number of the binding sites n (1.02) and the estimated association constant K (2.66 × 10⁴ L/mol). The chemiluminescence system combined with equilibrium dialysis developed in this work demonstrated its use for determination of interaction between drug and protein by using relatively simple instrument.     

Molecular Emission Spectrohetry ih a Low Pressure Electrical Discharge

A low pressure electrical discharge for excitation of polycyclic aromatic hydrocarbons, PAHs, without fragmentation is described. The discharge characteristics as well as the plasma background spectra are given. The application of the discharge for the excitation of molecular spectra of PAHs is described. Difficulties with correction of the analyte emission spectrum for the background emission spectrum of the gas (He) are mentioned. Analytical use of the discharge for detection of PAH3 introduced by gas chromatography is described and is shown to be of marginal analytical use because of the rather poor detection limits of about 1 μg.

Jurgensen and Winefordner¹ have reviewed both reduced pressure and atmospheric pressure nitrogen discharges for detection of atomic and molecular species. The same authors² have also described an active nitrogen-induced chemiluminescence system for detection of polycyclic aromatic hydrocarbons, PAHs, and achieved detection limits in the range of 0.01 - 2000 ng. The intriguing aspect of the active nitrogen—induced chemiluminescence approach² for detection of PAHs was that the discharge was gentle resulting in little fragmentation of the PAHs and in the appearance of emission spectra characteristic of the parent molecules. Because of the poor understanding of the mechanism of excitation of the large organic molecules and the minimal fragmentation and because of the lack of control of the direct discharge as opposed to the afterglow in the studies of Jurgensen and Winefordner², the present authors began a careful study of the physical and analytical characteristics of this discharge in the fall of 1984. The physical characteristics were reported by Yu and Winefordner³ and indicated that the previous workers², were using the direct discharge plasma as a result of llpoorlv grounding. In addition, the same workers³ showed that the active nitrogen afterglow was not capable of exciting PAHs. In this note, we report on the analytical capabilities of an improved active gas (nitrogen or helium) electrical discharge system for gaseous PAHs.     

Evolved Gas Analysis by Infrared Spectroscopy

Abstract

The analytical applications of the evolved gas analysis (EGA) performed by infrared spectroscopy, for the period extending from 2005 to 2009, are collected in this review. By this technique, the nature of volatile products released by a substance subjected to a controlled temperature program are on-line determined, with the possibility to prove a supposed reaction, either under isothermal or under heating conditions.     

Density-Dependent Diffusion in the Periodic Lorentz Gas

We study the deterministic diffusion coefficient of the two-dimensional periodic Lorentz gas as a function of the density of scatterers. Based on computer simulations, and by applying straightforward analytical arguments, we systematically improve the Machta–Zwanzig random walk approximation [Phys. Rev. Lett. 50:1959 (1983)] by including microscopic correlations. We furthermore, show that, on a fine scale, the diffusion coefficient is a non-trivial function of the density. On a coarse scale and for lower densities, the diffusion coefficient exhibits a Boltzmann-like behavior, whereas for very high densities it crosses over to a regime which can be understood qualitatively by the Machta–Zwanzig approximation.     

Fluorescence Microscopy and Flow Cytofluorometry of Reactive Oxygen Species

Abstract

The effects of reactive oxygen species on cell function and health have driven the development of numerous detection methodologies to assess oxidative stress. In this article, we review the detection of reactive oxygen species by fluorescence microscopy and flow cytofluorometry over the last seven years. Emphasis is placed on the variety of sample matrices analyzed and the diverse biomedical questions and oxidative stress mediated diseases that benefit from the information provided by these fluorescence-based analytical techniques.     

The Combination of Gas Chromatography With Mass Spectrometry

Abstract

The coupling of the techniques of gas chromatography and mass spectrometry has provided the chemist with one of his most powerful analytical methods. The analysis of such diverse substances as fuels, air pollutants, food flavors, smokes, protein hydrolyzates, pesticides, lipid extracts, etc. may all require the separation and identification of the components of extremely complex mixtures.     

Spectrophotometric Determination of Ammonia in Estuarine Waters by Hybrid Reagent‐Injection Gas‐Diffusion Flow Analysis

Abstract

A flow‐injection gas‐diffusion technique is described for the online determination of ammonia in estuarine waters covering a salinity range of S=0 to 36. The flow analysis system, which is a hybrid of reagent injection and conventional sample‐injection flow systems, avoids the need for a rotary injection valve. Whereas gas‐diffusion techniques have been widely applied in conventional sample‐injection flow analysis, reagent‐injection flow analysis involving gas diffusion has been little used because it is susceptible to interference from dissolved gaseous species such as carbon dioxide coexisting with ammonia in the sample. This source of interference has been overcome by online adjustment of sample to pH 8.4 prior to the injection of the base that initiates gas diffusion of ammonia. The pore sizes of hydrophobic membranes used in gas diffusion were characterized by a bubble‐point test prior to use in the flow analysis system. These showed wide variation in pore size, and grading and careful selection was necessary in order to obtain reliable gas diffusion measurements of ammonia. The proposed flow‐injection system can be operated in a continuous flow mode, at a sample throughput of 135 measurements hr^?1 with a typical limit of detection (LOD) of 9 µg N L^?1, or in stopped‐flow mode at 60 measurements hr^?1 with a LOD of 3 µg N L^?1. The technique was validated using water samples containing a wide range of dissolved carbon dioxide concentrations, salinity, and pH. Excellent agreement (r=0.999) was observed between results obtained using the reagent‐injection system and an approved reference method.     

Influence of ro-vibrational and isotope effects on the dynamics of the C(3 P)+ OD(X 2Π) → CO(X 1 Σ+) + D(2 S) reaction

The C(³ P)+OD(X ²Π) reaction has been studied by means of quantum mechanical real wave packet (RWP) and quasiclassical trajectory (QCT) methodologies on the ground potential energy surface of Zanchet et al. [J. Phys. Chem. A 110, 12017 (2006)]. Initial state selected total reaction probabilities at J?=?0 total angular momentum have been calculated for a wide range of collision energies. Product state-resolved integral cross-sections at selected collision energies and excitation functions have been determined from the RWP calculations using the J-shifting approximation and from QCT calculations. State-specific and thermal rate coefficients have been calculated using both methodologies up to 500 K. The effect of reagent rotational excitation on the dynamics for the C(³ P)+OH(X ²Π) and C(³ P)+OD(X ²Π) reactions has been investigated and interesting discrepancies between the QCT and RWP results have been found. The RWP results are found to be in an overall good agreement with the corresponding QCT results, although the QCT integral cross-section and rate coefficients are slightly smaller than those obtained from the RWP calculations.