Time-resolved Optical Emission Spectroscopy in Water Electrical Discharges

The characteristics of the plasma initiated in ultrapure water between pairs of tungsten and tantalum electrodes were investigated by time-resolved optical emission spectroscopy. The deexcitation processes of the reactive species formed in the water plasma depended on the electrode material, but had been independent on the polarity of the applied voltage pulses. All the reactive species presented the same evolution with time and have been identified with high concentration in the emission spectra between the pulses. The current–voltage characteristics showed the features of a spark discharge for the both types of electrodes used in the process. When tantalum electrodes were used to generate the discharge, a broad emission continuum (350–940 nm) dominated the spectrum due to a transition to arc discharge.     

Nitrate and Hydrogen Peroxide Generated in Water by Electrical Discharges Stimulate Wheat Seedling Growth

This paper reports the stimulation of wheat seedling growth by using plasma-treated water. A nanosecond pulsed generator in a gas bubble-in-liquid system with a point-to-plate electrode was employed to treat de-ionised (DI) water, producing mainly hydrogen peroxide (H₂O₂) in the water when argon gas was used, and nitrate (\({\text{NO}}_{3}^{ - }\)) when air was used. The H₂O₂ and \({\text{NO}}_{3}^{ - }\) generated, respectively, in argon and air plasma-treated water significantly increased the growth parameters such as biomass, leaf length, and the relative chlorophyll content of the wheat seedling. The total biomass of the seedlings grown in potting mix after 4 weeks was augmented by 61 and 87%, respectively, for argon plasma-treated water and air plasma-treated water compared with the control (untreated DI water). In hydroponics, the biomass of the seedling increased 27 and 38%, respectively, for the argon and the air after 2 weeks in comparison to the control. In potting mix, the shoots and roots of the seedlings responded differently to the treated water: the biomass of shoot increased 33% for air plasma-treated water compared with the argon, while that of root increased 17% for argon plasma-treated water compared with the air. A separate experiment in hydroponics with chemical solutions of H₂O₂ and \({\text{NO}}_{3}^{ - }\) matching with the concentrations of the H₂O₂ and \({\text{NO}}_{3}^{ - }\) generated in the plasma-treated water showed similar stimulation of wheat seedling growth.     

Water in polymer membranes. Part I : Water sorption and refractive index of cellulose acetate

The dependence of water absorption of 2 to 4 μm thick membranes of cellulose acetate on relative humidity was determined by measuring small changes in their asymmetric waveguide properties in the visible spectral region. Simultaneous measurements of changes in film thickness provide a direct method for obtaining the change in film volume as a function of water concentration and a new measure of polymer porosity. Data are presented for a typical film fabricated from cellulose acetate (CA398-30) which illustrate the usefulness of studying water absorption by integrated optics techniques.     

Transport Coefficients in Water Plasma: Part I: Equilibrium Plasma

Knowledge of the transport coefficients of steam water plasma is important for modeling plasma flow processes and heat transfer. In this study, calculations of these properties were performed in a temperature range from 400 to 30,000 K and at pressures of 0.5, 1.0, 5.0 and 10 bar. Herein the composition of water plasma was determined at equilibrium. First, the most recent data on potential interactions and elastic differential cross sections for interacting particles were carefully examined in order to choose those most appropriate for determining the collision integrals. Second, we restricted the number of species to ten (e, H, O, H⁺, O⁺, O⁺⁺, H₂, O₂, OH and H₂O) and tested our collision integrals by comparing the thermal conductivity and viscosity to experimental data for water (at low temperatures). Finally, the total thermal conductivity, viscosity and electrical conductivity were calculated for different pressures.     

Chemical Reactions in Electrical Discharges: Preparation of perfluorinated acetylenes and nitriles. Preliminary communication

Several fluorinated acetylenes and nitriles have been isolated from the reaction mixture obtained from Tesla excited fluorinated aromatic compounds. Differences in product distributions using Tesla or radio frequency discharges are discussed.     

Selectivity tuning of serially connected open-tubular (capillary) columns in gas chromatography. Part I: Fundamental relationships

Summary The evolution of the use of mixed phases or serial column combinations is outlined, leading to systems with fixed-length columns to be used in selectivity tuning (“multi-chromatography”). The difference between multi-chromatography and multi-dimensional gas chromatography is outlined. After discussing the system used in subsequent work, the fundamental relationships of multi-chromatography are detailed. Among the basic relationships the additivity of retention data, the relationship between the individual and composite capacity factors and the relative retentivity serving as the fundamental parameter of a multi-chromatography system are discussed. The relative retentivity is derived as a function of gas holdup times, pressures, and average velocities or flow rates. Finally, the relationships between individual vs. composite relative retention, efficiency, and resolution values are deduced. We dedicate this paper to the memory of our dear friend, Dr. S. R. Lipsky. Consolidated and enlarged text of part of the papers presented at the 37th Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy (Atlantic City, NJ, March 10–14, 1986) (92–94), and at the Seventh International Symposium on Capillary Chromatography (Gifu, Japan, May 11–14, 1986) [95]. Part II will follow in the December issue.     

Fundamental studies on a planar-cathode direct current glow discharge. Part I: characterization via laser scattering techniques

A laser-scattering-based instrument was used to study an argon d.c. planar-diode glow discharge. The gas-kinetic temperature (T_g) was determined via Rayleigh scattering and the electron number density (n_e), electron temperature (T_e), and shape of the electron energy-distribution function were determined by Thomson scattering. Axial profiles of these parameters were obtained as the discharge current, voltage, and pressure were varied. Trends in the profiles of T_g and in the other parameters show the interdependence of these plasma species and properties. The results will be compared with current theoretical computer models in order to improve our understanding of the fundamental processes in glow discharges sustained under conditions appropriate for spectrochemical analysis.     

Fundamental aspects of contactless conductivity detection for capillary electrophoresis. Part I: Frequency behavior and cell geometry

A better understanding of the characteristics of the axial contactless conductivity cell could be obtained by carefully studying the effect of the cell geometry on its frequency behavior. A good fit between theoretical and experimental results shows that the axial contactless conductometric detector can effectively be described by the simplest possible equivalent circuitry consisting of a capacitor, resistor, and a second capacitor. The cell constant is largely defined by the length of the gap between the electrodes. The effective electrode size is thus not related to the dimensions of the real electrodes but more closely to the cross-sectional area of the internal diameter of the capillary. Typical experimental values of 20 MOmega and 0.1 pF were obtained for the resistance and capacitances, respectively, of a cell formed by a 2 mm gap between two 4 mm long electrodes fitted with a capillary of 50 microm ID. It could be shown that the diameter of the electrode is not critical and tight coupling of the electrodes to the outer wall of the capillary is not needed. The peak overshoot phenomenon, which has frequently been reported, is an artefact that can be minimized by optimizing the frequency for cell excitation. The frequency setting has to be optimized for each cell design, operational amplifier, electrolyte solution and capillary.     

Interpretation of the Mechanisms of Chromatographic Separation on CN-Silica. Part I: TLC of Metal Complexes

JPC – Journal of Planar Chromatography – Modern TLC - The chromatographic behavior of four mixed tris(β-diketonato) complexes of the type [Co(acac)3-n(phacphac)n] (n = 0-3), three...     

Influence of Surface-Active Compounds on Starch Dispersion in Water. Part I. Starch Pasting

The influence of native lipids and additives of surface-active compounds on starch paste rheology was investigated. The aim of the study was to gain better understanding of mechanisms involved in starch gelatinization and how these structure changes of granules later affect rheological properties of pastes and gels. Starches from three main sources—potato, maize, and wheat—were tested; sodium dodecylsulfate, oleate, and benzalkonium chloride were employed as additives. Starch pasting was examined by a rheometer to get a viscosity profile, also pastes were analyzed by differential scanning calorimetry, for particle size using a light scattering technique. Results revealed that there was a competition between native lipids and added surfactants for amylose complexation. Complexes formed during gelatinization were strongly affecting granule swelling and dissolution of starch polymers, and viscosity of pastes was mainly dependent on the particle size of a disperse phase in the paste. Addition of strong ionic surfactants to cereal starches resulted in smaller granular remnants and, therefore, decreased viscosity, while the weak anionic surfactant promoted an increase in the particle size and paste viscosity for both cereal and tuber starches. The mechanism of the effect of surfactants on the particle size in pastes is discussed.     

Removal of Model Pollutants in Aqueous Solution by Gliding Arc Discharge: Determination of Removal Mechanisms. Part I: Experimental Study

The respective roles of short and long-life oxidant species in the degradation of model organic pollutants in water have been investigated in a gas–liquid gliding arc plasma reactor. Three different model pollutants were treated in two configurations: direct discharge mode and spatial post discharge mode. In each case the pollutants were classified according to their ease of removal, from easier to more difficult to remove. The results were as follows: phenol >> 1-heptanol >> pCBA. The removal mechanisms also are different depending on the characteristics of the pollutant treated. Phenol (100 % of phenol was removed for energy density = 1.20 × 10⁵ J/L) was supposed to react strongly with NO₂° radicals produced by the dissociation of N₂O₄ in liquid phase. The degradation of 1-heptanol would proceed by desorption of the liquid phase to the gas phase, where oxidation occurs due to the plasma active short-lived species. In the case of pCBA, oxidation occurs in the liquid solution, but the degradation is low because of its low reactivity with species such as ozone and °NO₂ and insufficient production of OH° radicals in the solution.     

Amperometric enzyme electrodes: Part I. Theory

The theory of the steady state operation of an amperometric enzyme is derived. The reaction scheme includes diffusion of substrate and product through a membrane, the kinetics of the enzyme substrate reaction and the electrochemical regeneration of the enzyme. A simple diagnostic plot is derived which allows the rate limiting process to be identified, and the balance between the transport of substrate through the membrane and the enzyme and electrochemical kinetics to be determined. The effects of inhibition by the accumulation of product behind the membrane are also considered.     

Decomposition of Methylene Blue in Water by Corona Discharges

The decomposition of methylene blue (MB) in aqueous solution was investigated using a pulsed corona discharge. The discharge was ignited in the gas bubbled in the solution through several needle electrodes. The influence of treatment time, volume of the treated solution and initial concentration of the dye in solution on MB degradation was studied. The effect of the nature of the gas introduced was also investigated. For the same energy input, MB conversion increased in the order air < argon < oxygen. When using oxygen, the decomposition of MB exceeded 95% after ~20 min plasma treatment. Higher efficiency was obtained for higher treated volume and higher initial concentration. At 90% conversion the yield obtained with oxygen was ~5 g/kWh for an initial concentration of 150 mg/l and a treated volume of solution of 100 ml.     

Degradation of Acetophenone in Water by Pulsed Corona Discharges

Degradation of acetophenone in dilute aqueous solution has been studied using pulsed corona discharges in water. Higher conversions of acetophenone were obtained with the addition of oxygen or ozone than with the addition of nitrogen and without the addition of any gas. Intermediates of acetophenone degradation, as determined by gas chromatography–mass spectroscopies (GC–MS), were phenethyl alcohol, toluene, and 2-acetylphenol. In addition, the degradation reaction pathways of acetophenone in water are discussed.     

Transient processes in photogalvanic cells: Part I. Fundamentals

The theory of transient processes in photogalvanic cells is developed. The systems treated consist of a photoactive species B which can be oxidized (or reduced) to A in its excited state B^* by a one-electron acceptor Z which itzelf is reduced (oxidized) to Y. It is further assumed that both redox couples undergo one-electron transfer reactions at the metal electrodes. The electrode kinetics for both redox couples is taken into account. A computer program is described with which the following data can all be obtained as functions of time, after illumination has started: current, potential of the illuminated electrode, potential of the dark electrode, power, and the concentration profiles of A, B, Z and Y near the electrodes.     

Nitric Oxide Production by High Voltage Electrical Discharges for Medical Uses: A Review

Nitric oxide (NO) is a vasodilator and antihypertensive agent as well as a universal anti-microbial factor killing bacteria, fungi and parasites without killing human cells provided that an appropriate dose level and treatment time are applied. Exogenous NO is often employed in inhalation therapies for treating pulmonary hypertension in children and adults. NO generation from air in high voltage electrical discharges is being developed for medical uses because it is technologically simple, economical and portable. The related literature is reviewed here. The plasma can be a thermal plasma, where the temperature is of the order of 10,000 K, or it can be a non-thermal plasma, where the electron temperature is very high but the average gas temperature can vary over a wide range from close to room temperature to thousands of degrees above room temperature. The plasma temperature has significant effects on the chemical composition of the treated gas. These effects are explained based on the chemical reaction mechanism. Further, NO generated by electrical discharges is usually contaminated with nitrogen dioxide and sometimes with ozone and particulate matter. The techniques that have been successfully hybridized with the electrical discharge devices or that can potentially be hybridized for the purification of NO are also reviewed. Recent successful testing of electrical discharge-based NO generators for inhalation therapy on animal models in the US and routine use of them in Russia and east Europe for wound decontamination and fast heeling suggests that the technique has a great potential for applications in future.     

Chlorpromazine metabolism in humans. Part I

Summary A direct scan technique employing quantitative thin-layer chromatography for color samples of chlorpromazine and its metabolites by spectro-photometric method with the use of double-beam spectrodensitometer is described. Chlorpromazine and 17 metabolites have been analyzed qualitatively and quantitatively. This method can be applied for the assay of phenothiazines in both human plasma and urine. Extraction procedures for chlorpromazine and its metabolites in blood plasma and urine are presented. Advantages and disadvantages of this technique are discussed.

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Zusammenfassung Ein direktes Abtastverfahren für quantitative Dünnschichtchromatogramme von Chlorpromazin und seinen Metaboliten mit Hilfe eines Doppelstrahl-Spektrodensitometers wurde beschrieben. Chlorpromazin und 17 seiner Metaboliten wurden qualitativ und quantitativ analysiert. Das Verfahren eignet sich zur Phenothiazinbestimmung in Plasma und Harn. Extraktionsmethoden wurden angegeben. Vor- und Nachteile des beschriebenen Verfahrens wurden besprochen.

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This work was supported by USPHS Grant MH 17968.     

Metrology in chemistry: Part I. Current activities in Europe

 The paper (Parts I and II) reports the results of a survey carried out to assess the current situation in the field of metrology in chemistry within Europe and to identify future needs for work at the European level. Responses to a questionnaire covering 17 economic sectors and distributed to 17 countries plus the European Commission Joint Research Centre (EC JRC), together with input from a project group, EURACHEM and EUROMET provided the basis of the study. The questionnaire responses clearly indicated that only a minority of countries had clearly defined responsibilities for policy, funding and technical leadership. Similarly only a small number of countries was able to provide any information about levels of funding. Nonetheless, a variety of work is in progress and in some countries the effort is considerable. In other countries discussion is in progress and /or work is beginning. Part I covers the protocol for the study and reports current activities. Part II reports suggestions for future work, a strategy for metrology in chemistry and recommendations for the EC Fifth Framework Programme. Received: 11 January 1999 / Accepted: 4 January 2000