Background corrections, plasma

Minimizing Spectral Interferences The most important spectral interference is a continuous source of background emission from the flame or plasma and emission bands from molecular species. This background emission is particularly severe for flames in which the temperature is insufficient to break down refractory compounds, such as oxides and hydroxides. Background corrections for flame emission are made by scanning over the emission line and drawing a baseline (Figure 10.51). Because the temperature of a plasma is... 

To produce an analytical method, the operator must select the power level of the plasma, the wavelength for each element (preferably free from spectral interferences), and the vewing height at which the plasma is to be seen for each element. Further, it may be necessary to apply background correction intervals are set using the graphics capability. 

Chapters 5 and 6 discuss the application of new techniques such as atomic absorption spectrometry with and without graphite furnace and Zeeman background correction, inductively coupled plasma mass spectrometry, X-ray fluo-... 

Many of the published methods for the determination of metals in seawater are concerned with the determination of a single element. Single-element methods are discussed firstly in Sects. 5.2-5.73. However, much of the published work is concerned not only with the determination of a single element but with the determination of groups of elements (Sect. 5.74). This is particularly so in the case of techniques such as graphite furnace atomic absorption spectrometry, Zeeman background-corrected atomic absorption spectrometry, and inductively coupled plasma spectrometry. This also applies to other techniques, such as voltammetry, polarography, neutron activation analysis, X-ray fluroescence spectroscopy, and isotope dilution techniques. 

Volume 1 consists of chapters covering the development. Instrumentation, and results of a wide range of materials, including background correction lasers, inductively coupled-mass sp>ectroscopy plasmas, electrothermal vaporizers, sample introduction, and Fourier transform atomic spectrocopy. 

CONTENTS Preface, Joseph Sneddon. Analyte Excitation Mechanisms in the Inductively Coupled Plasma, Kuang-Pang Li and J.D. Winefordner. Laser-Induced Ionization Spectrometry, Robert B. Green and Michael D. Seltzer. Sample Introduction in Atomic Spectroscopy, Joseph Sneddon. Background Correction Techniques in Atomic Absorption Spectrometry, G. Delude. Flow Injection Techniques for Atomic Spectrometry, Julian F. Tyson. 

E. H. Van Veen and M. T. C. De Loos-Vollebregt, Application of mathematical procedures to background correction and multivariate analysis in inductively coupled plasma-optical emission spectrometry, Spectrochim. Acta, Part B, 53(5), 1998, 639-669. 

Zinc. AAS analysis of zinc by P CAM 173 is a standard application of the method as seen in NIOSH PAT. Zinc in the divalent state has been analyzed by dithiozonate (13). This colorimetric method suffers interferences from many other dithi-zone complexing metals. Zinc is easily determined after nitric acid wet ashing with an oxidizing air-acetylene flame using the 213.9 nm analytical line and background correction. The AAS analysis for Zn is as sensitive as more complex activation or plasma techniques. 

Procedure Use an Inductively Coupled Plasma Atomic Emission Spectrometer (ICP-AES), or equivalent instrumentation with similar capabilities. Follow the instrument manufacturer s instructions for setting instrument parameters for assay of cadmium. Select appropriate background correction points for the cadmium analyte according to the recommendations of the instrument manufacturer. Select analytical wavelengths to yield adequate sensitivity and freedom from interference. 

The measured intensities of the selected analytical lines are influenced by the various settings such as the plasma operation conditions (the generator output and the gas flow rates), the observation height of the plasma, the sample feed rate, the measurement integration time and the spectral background correction points. The choice of operational settings has to take into account the sample type, the elements analysed and the level of precision required for the analysis. 

Inductively coupled plasma-atomic emission spectrometry was investigated for simultaneous multielement determinations in human urine. Emission intensities of constant, added amounts of internal reference elements were used to compensate for variations in nebulization efficiency. Spectral background and stray-light contributions were measured, and their effects were eliminated with a minicomputer-con-trolled background correction scheme. Analyte concentrations were determined by the method of additions and by reference to analytical calibration curves. Internal reference and background correction techniques provided significant improvements in accuracy. However, with the simple sample preparation procedure that was used, lack of sufficient detecting power prevented quantitative determination of normal levels of many trace elements in urine. 

For the analytical determination of metals (Cd, Cu, Fe, Mn, Pb and Zn) in surface sediments, suspended particulate matter and biological matrices, digestion with a 3 1 HNO3-HCIO4 mixture under controlled temperature was used (36). Analysis of sediments and suspended particulate matter were made by Flame Atomic Absorption Spectrometry (FAAS) with air-acetylene flame and deuterium background correction. The analysis of metals in lichens and molluscs were performed by ICP-AES. The operating conditions for FAAS and Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) analysis are shown in Tables 6.1 and 6.2, respectively. 

For the homogeneity studies, the extractants (0.05 mol L EDTA, 0.43 mol L" acetic acid and 0.005 mol L DTPA) were prepared as laid out in the certification reports [15, 17], The trace element contents (Cd, Cr, Cu, Ni, Pb and Zn) in the extracts were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES) for the CRMs 483/484, flame atomic absorption spectrometry (FAAS) or electrothermal atomic absorption spectrometry with Zeeman background correction (ZETAAS) for the CRM 600. In the case of the CRM 483, little analytical difficulty was experienced as illustrated by the good agreement obtained between the within-bottle and between-bottle CVs for the CRM 484, lower extractable contents, closer to the detection limits and consequent poorer analytical precision was observed in particular for Cr (EDTA extractable contents), Cd and Pb (acetic acid extractable contents). No particular difficulties were experienced for the CRM 600. On the basis of these results, the materials were considered to be homogeneous at a level of 5 g for EDTA- and acetic acid-extractable contents and 10 g for DTPA-extractable contents (as specified in the extraction protocols). 

Lewis SA, Hardison NW, Veillon C. 1986. Comparison of isotope dilution mass spectrometry and graphite furnace atomic absorption spectrometry with Zeeman background correction for determination of plasma selenium. Anal Chem 58 1272-1273. 

A major difficulty encountered with atomic absorption techniques is the presence of incompletely absorbed background emission from the source and scattered light from the optical system. As the background becomes more intense relative to the absorption of the analyte, the precision of the measurement decreases dramatically. For this reason, several background correction techniques have been implemented. A commonly used method is the method of proximity, which was discussed in relation to inductively coupled plasma spectroscopy. 

Analytical Methods and Speclatlon Electrothermal atomic absorption spectrophotometry (ETAAS), differential pulse adsorption voltammetry (DPAV), isotope-dilution mass spectrometry (ID-MS), and inductively coupled plasma mass spectrometry (ICP-MS) furnish the requisite sensitivity for measurements of nickel concentrations in biological, technical and environmental samples (Aggarwal et al. 1989, Case et al. 2001, Stoeppler and Ostapczuk 1992, Templeton 1994, Todorovska et al. 2002, Vaughan and Templeton 1990, Welz and Sperling 1999). The detection limits for nickel determinations by ETAAS analysis with Zeeman background correction are approximately 0.45 jg for urine,... 

Zeeman background correction. Continuum source (D2) may be applied for plasma/ serum matrices... 

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