Preservation of accuracy and precision in the analytical practice of low power ICP-AES

In an inductively coupled argon plasma (ICAP) matrix effects caused by elements constituting major inorganic components in samples of widely different nature have been studied under experimental conditions not primarily aimed at achieving maximum detection power and minimum matrix effects but at optimum reproducibility of the analytical signals. Separate and combined matrix effects on thirteen ICAP analysis lines were investigated. From the results conclusions could be drawn of interest for the practice of ICP analysis. A close examination of acid effects revealed the appearance of an “adaptation” effect.     

The influence of ethanol addition on the determination of trace elements in aqueous solutions by ICAP

The effect of the addition of ethanol to aqueous solutions of various trace elements (Ca, Cd, Mg, Cu and Ni) on their spectral line intensities in inductively coupled argon plasma (ICAP) was investigated. Using a relatively low ethanol content (up to 10%, v/v) an enhancement of both atomic and ionic lines was found but to a different extent. By optimization of experimental parameters, an improvement of the sensitivity of the multielemental analysis was obtained.     

Qualitative and semi-quantitative ICAP-AES analysis using a computer-controlled monochromator

This paper describes the hardware adaptations and the developed software which enable qualitative and semi-quantitative analysis to be performed by means of a computer-controlled monochromator in combination with an inductively coupled argon plasma (ICAP) excitation source. First, the required hardware features are discussed, especially with respect to the use of a plasma torch extension, the wavelength characteristics and effective spectral line width of the monochromator, and the long-term instrument stability. The general computer program concept is described and the various routines are also dealt with in more detail. Finally, the developed analysis method is critically evaluated as to its accuracy, speed, user-friendliness and dependency on instrumental parameters.     

An inductively coupled plasma using 1 lmin of argon

The development and preliminary evaluation of an ICAP consuming only 1 $\text{l}\text{min}$ of argon is described. External cooling of the torch with pressurized air and a two tube plasma torch arrangement are essential. Detection limits and matrix effects are comparable to those of a conventional ICAP.     

Some considerations on the excitation mechanism in the inductively coupled argon plasma

The excitation conditions in the analytical observation zone of the inductively coupled argon plasma cannot be described by the model of partial local thermal equilibrium. After some general remarks on excitation models the paper analyses in tutorial fashion four alternative models proposed in the literature, featuring metastable argon atoms, radiation trapping, reaction rates and ambipolar diffusion.It is concluded that none is completely satisfactory, but that they are complementary rather than contradictory. Finally, some elements of the four models are integrated into a new model that considers the ICAP as a plasma decaying from conditions of heterogeneous disequilibrium to a situation of homogeneous thermal equilibrium.     

New In-Situ Sampling and Analysis of the Production of CeO<Subscript>2</Subscript> Powders from Liquid Precursors in a rf Thermal Plasma Reactor. Part 2: Analysis of CeO<Subscript>2</Subscript> Powders,Fuel Addition,and Image Analysis

A novel reactor design, sampling probe and wet collection system were used to investigate the combined effects of plasma operating parameters and particle collection mechanisms on the synthesis of CeO₂ particles from liquid precursors. The sampling of particles in-flight and the collection of particles at several reactor regions were used to provide experimental evidence of particle size at different reactor locations at various plasma operating conditions, i.e., power and plasma gas flow rates. This information provided a picture of how CeO₂ particles were formed and how these particles were collected in various locations. The effect of adding water-soluble fuels (alanine and glycine) to the original cerium nitrate solutions was also investigated. Fuel addition decreased the temperature of CeO₂ formation by acting as a local heat source as a result of fuel auto-ignition. Photographs of the particles in-flight were taken using a fast speed CCD camera.     

Numerical Modeling of Thin Film Deposition in Expanding Thermal Plasma

Expanding thermal plasma (ETP) is a widely used technique for deposition of a thin layer of ceramic materials and metal oxide on a substrate for a wide range of applications including abrasion resistance, UV absorption, as well as conductive and optical coatings. The coating quality is found to be dependent on operating parameters as well as reactor designs. In this article, we have presented a CFD based model of the ETP process to simulate the deposition of silica-like coatings on a polycarbonate substrate. Along with the flow-thermal model of plasma jet expansion process, the study also reports the development of a simplified gas phase and surface reaction model to simulate the coating phenomena. The model has been used further to study the effect of various operating conditions on the coating thickness, viz. reactor pressure, reagent flow rate, distance of the substrate from the arc and substrate alignment.     

Plasma Spray Process Operating Parameters Optimization Based on Artificial Intelligence

During plasma spray process, many intrinsic operating parameters allow tailoring in-flight particle characteristics (temperature and velocity) by controlling the plasma jet properties, thus affecting the final coating characteristics. Among them, plasma flow mass enthalpy, flow thermal conductivity, momentum density, etc. result from the selection of extrinsic operating parameters such as the plasma torch nozzle geometry, the composition and flow rate of plasma forming gases, the arc current intensity, beside the coupled relationships between those operating parameters make difficult in a full prediction of their effects on coating properties. Moreover, temporal fluctuations (anode wear for example) require “real time” corrections to maintain particle characteristic to targeted values. An expert system is built to optimize and control some of the main extrinsic operating parameters. This expert system includes two parts: (1) an artificial neural network (ANN) which predicts an extrinsic operating window and (2) a fuzzy logic controller (FLC) to control it. The paper details the general architecture of the system, discusses its limits and the typical characteristic times. The result shows that ANN can predict the characteristics of particles in-flight from coating porosity within maximal error 3 and 2 % in temperature and velocity respectively. And ANN also can predict the operating parameters from in-flight particle characteristics with maximal error 2.34, 4.80 and 8.66 % in current intensity, argon flow rate, and hydrogen flow rate respectively.     

An Optical Emission Study on Expanding Low-Temperature Cascade Arc Plasmas

The optical emission spectra from expanding low-temperature cascade arc plasmas were studied. The objective of this study was to examine the distinctive features of low-temperature cascade arc plasmas in comparison with a radio frequency (RF) plasma source. The principal results obtained in this study were: (1) in an expanding cascade arc plasma jet, active heavy particles (mainly excited argon or helium neutral species under our operating conditions), rather than electrons, are responsible for the excitation of reactive species when a reactive gas is injected into the plasma jet, (2) the excitation of reactive species was found to be controlled by the electronic energy levels of these excited argon or helium neutrals, (3) changing the operating parameters affected only the emission intensities of excited species, and no effect on the emission nature of plasmas was observed.     

The effect of plasma operating parameters on analyte signals in inductively coupled plasma-mass spectrometry

Utilizing the SCIEX ICP-MS an extensive study of the effects that plasma operating parameters have on analyte ion signals in ICP-MS has been carried out. Parameters studied included aerosol flow rate (nebulizer pressure), auxiliary flow rate, power and sampling depth (sampling position from the load coil). The two key parameters are aerosol flow rate (nebulizer pressure) and power. Elements can be grouped into characteristic behaviour patterns based on the overall dependence of their ion count signal on these two parameters. The nebulizer pressure-power behavior patterns allow a sensible selection of compromise operating conditions and significantly clarify single parameter observations which often indicate confusing trends in behavior. In addition to characterizing analyte ion signals the parameter behavior plots have also been used to study oxide species and plus two ions in ICP-MS. While aerosol flow rate and power appear to be the key ICP parameters in ICP-MS, ion signals are dependent on sampling depth and auxiliary flow rate and some data are also presented illustrating the signal dependence on these two parameters.     

水中铀的电感耦合等离子体发射光谱法测定

建立了电感耦合等离子体发射光谱法测定水中铀的方法。优化了仪器工作条件,通过基体匹配消除了无机酸基体干扰。方法检出限为0.15 mg/L,对5.000 0 mg/L铀标准溶液测定的相对标准偏差(RSD)为0.98%(n=10),加标回收率为95%~106%,方法准确可靠。     

Carrier distillation-ICAP approach for trace metal assay of U3O8 powder

Summary A new approach for the trace metal assay of U₃O₈ powder has been described. The carrier distillation technique used for selective volatilization of trace metals in U₃O₈ with d.c. arc excitation is adapted for the release of analytes from the solid sample into the ICAP source by inductively heating the sample. The experimental parameters have been optimised for the direct determination of Cd, Cu, K, Na, Ni and Pb. The performance of the method developed here is tested for the precision and accuracy of determinations by analysing spiked U₃O₈ samples and NBL U₃O₈ reference standards (standard deviation 2–9%). The method appears promising to be developed as a highly precise analytical optical emission spectrometric method as it adds to the ingenuity of the carrier distillation method, the advantages of ICAP.

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Bestimmung von Metallspuren in U₃O₈-Pulver durch Trägerdestillation/ICAP

Zusammenfassung Das Trägerdestillationsverfahren zur selektiven Verdampfung von Spurenmetallen in U₃O₈ im Gleichstrombogen wurde mit induktiver Probeerhitzung für ICAP angepaßt. Die experimentellen Parameter wurden für die direkte Bestimmung von Cd, Cu, K, Na, Ni und Pb optimiert. Die Leistungsfähigkeit des Verfahrens wurde mit Hilfe von Proben mit bestimmten Zusätzen sowie mit zertifiziertem Referenzmaterial überprüft (Standardabweichung 2–9%). Durch die Verbindung der Vorteile von Trägerdestillation und ICAP bietet sich eine Methode von hoher Präzision.

     

Determination of refractory elements in atmospheric particulates using slurry sampling electrothermal vaporization inductively coupled plasma optical emission spectrometry and inductively coupled plasma mass spectrometry with polyvinylidene fluoride as chemical modifier

Electrothermal vaporization (ETV) inductively coupled plasma optical emission spectrometry (ICP-OES) and inductively coupled plasma mass spectrometry (ICP-MS) with polyvinylidene fluoride (PVDF) as chemical modifier are critically compared for the determination of refractory elements in coal fly ash and airborne particulates. The atmospheric particulates that collected on a PVDF filter were introduced into the graphite furnace in the form of a slurry by dissolving the filter in dimethylformamide, and the dissolved filter PVDF, along with additional added PVDF powder, was used as a chemical modifier for subsequent ETV-ICP-OES and ETV-ICP-MS determination. The vaporization behaviors of analytes (Ti, Zr, V, Mo, Cr, La) in ETV-ICP-OES/MS were studied in detail, and the optimal ETV operating parameters were obtained. Under the optimized operating conditions, the detection limits of target elements were 0.08-2.7 ng m(-3) for ETV-ICP-OES and 0.5-50 pg m(-3) for ETV-ICP-MS, respectively, with analytical precisions of 3.5-7.3% for ETV-ICP-OES and 3.9-9.6% for ETV-ICP-MS, respectively. The tolerable amounts of matrix elements for ETV-ICP-OES are higher than for ETV-ICP-MS. Both ETV-ICP-OES and ETV-ICP-MS were used to directly determine the trace refractory elements in coal fly ash and airborne particulates and the analytical results are comparable.     

Parametric study of the flow and temperature fields in an inductively coupled r.f. plasma torch

A theoretical investigation of the effect of different parameters on the flow and the temperature fields in a radiofrequency inductively coupled plasma is carried out. The parameters studied are: central injection gas flow rate, total gas flow rate, input power, and the type of plasma gas. The results obtained for argon and nitrogen plasmas at atmospheric pressure indicate that the flow and the temperature fields in the coil region, as well as the heat flux to the wall of the plasma confinement tube, are considerably altered by the changes in the torch operating conditions.     

毛细管电泳-电化学发光间接测定人血浆中盐酸甲氯芬酯

建立了一种毛细管电泳-电化学发光间接测定人血浆中盐酸甲氯芬酯(MFX)的新方法.在碱性条件下,三联吡啶钌在铂电极上的弱电化学发光信号可以被MFX增敏,且MFX水解后灵敏度比未水解的灵敏度提高了6倍.研究了工作电极电位、磷酸盐缓冲溶液浓度及其pH值、分离电压、进样电压和进样时间等实验参数对MFX水解产物N,N-二甲氨基乙醇测定的影响.在优化实验条件下,其浓度线性范围为0.020～50 μg/mL,检出限(3σ)为6.3 ng/mL,峰高的相对标准偏差为3.1%(10 μg/mL MFX,n=11).利用该法间接地测定了人血浆中MFX的含量,回收率为95.9%～96.9%.     

Plasma diagnostics of an analytical Grimm-type glow discharge in argon and in neon: Langmuir probe and optical emission spectrometry measurements

Comparative investigations were performed on a Grimm-type glow discharge source by Langmuir probe measurements and by optical emission spectrometry. The Langmuir probe measurements yielded electron temperatures and number densities of electrons, whereas the optical emission spectrometry measurements resulted in data for excitation and ionization temperatures of different species. The results confirm that there is no local thermal equilibrium in the discharge plasma. The operating conditions of the glow discharge source and also the working gas and the cathode material were varied to investigate their influence on the plasma parameters. The outcome of the plasma diagnostics will be used to improve the modelling of relevant excitation and ionization processes by computer simulation. The major physical processes in the low pressure glow discharge plasma should be better understood if the analytical capability of this spectrochemical excitation and ionization source has to be further enhanced.     

A rate model of inductively coupled argon plasma analyte spectra

A model which explicitly considers the various rates of excitation, deexcitation, ionization and recombination for analyte species in an ICAP of defined electron density and temperature is presented. The model reveals that radiative decay, radiative recombination and radiative absorption affect the level populations of a fundamentally collisionally dominated plasma. In addition. Penning ionization is shown to have a negligible effect on spectrally derived temperatures except for elements of high second ionization potential.     

Fast analysis by gas-liquid chromatography. Perspective on the resolution of complex fatty acid compositions

Separation of fatty acids as methyl ester (FAME) derivatives has been carried out using short and highly polar capillary column developed for fast gas-liquid chromatography (GLC) applications. The GLC parameters have been optimized in order to achieve separation of FAME ranging from 4:0 (butyric acid) to 24:1 in less than 5 min. Milk fat that has by far the most complex fatty acid composition among edible fats and oils has been used to optimize the method. The volume of the oven has been reduced in order to allow for a heating rate of 120 degrees C/min and to rapidly cool-down to the initial temperature (50 degrees C) of the GLC program. The GLC conditions developed are not suitable to achieve separation of positional and geometrical isomers of octadecenoic acid but are useful to perform separation of major fatty acids in milk fat. The conditions developed could be used to analyze edible fats and oils or biological samples such as plasma or red blood cell lipids. The results confirmed that short and highly polar fast columns operating under optimal conditions could be used to separate the fatty acids in various matrices.     

GD-MS法和ICP-MS法测定高纯铌中痕量元素

采用辉光放电质谱法(GD-MS)对高纯铌中Ta,Mo,W等痕量杂质元素进行了测试,并对GD-MS工作参数进行了优化,部分元素与采用电感耦合等离子体质谱法(ICP-MS)定量分析的结果进行比较,对某些元素含量差别较大的原因进行了分析,论述了Element GD辉光放电质谱仪的特点及其在痕量杂质分析上的优势。     

Introduction of high carbon content solvents into inductively coupled plasma mass spectrometry by a direct injection high efficiency nebuliser

A preliminary investigation on the introduction of high carbon content solvents into inductively coupled plasma mass spectrometry (ICP-MS) by a direct injection high efficiency nebuliser (DIHEN) is presented. Ethanol, hexane, toluene and a natural gas condensate were introduced using a flow injection system. The performance for determinations of total concentrations of mercury present in organic solvents as different species was evaluated. The most critical operating parameters were the nebuliser gas flow rate and amount of oxygen added to the plasma. For the DIHEN a nebuliser gas flow rate of 0.3 L min(-1) and 50 mL min(-1) of oxygen added to the plasma auxiliary gas flow gave stable conditions and high analyte sensitivity. Species recoveries for HgCl(2), CH(3)HgCl, (CH(3))(2)Hg and Hg(0) in hexane were 99+/-4, 101+/-4, 95+/-4 and 104+/-7%, respectively. Detection limit for mercury in hexane was 85 pg mL(-1) based on 3 sigma of a (201)Hg-spiked blank. A gradual deposition was observed at the nebuliser tip, partly blocking the gas annulus. The rate of deposition seemed to be related to the amount of carbon introduced through the nebuliser. With the optimised conditions used in this work, the nebuliser could be used for approximately 50 hexane samples before cleaning was necessary.