Quality assurance in operating a multielement ICP emission spectrometer

In the industrial laboratory environment, quality assurance in the operation of a multielement inductively coupled plasma emission spectrometer (ICPES) must often be entrusted to laboratory technicians with little or no technical background in spectrochemical analysis. Therefore, to be successful, a quality assurance program must be reduced to a simple, routine practice. Essential components of the quality assurance program described in this paper are (1) An atom-to-ion emission intensity ratio for multielement optimization and for reproducing optimum analysis conditions. (2) A concise, easily applied specification for sensitivity and for precision. (3) A regimen for monitoring of, and correcting for, calibration and background drift. (4) A set of comprehensive spectral interference calibrations maintained using the emission intensity ratio. (5) A high resolution spectrometer for minimizing spectral interferences. (6) A program of long term performance monitoring and maintenance/record keeping.Each of these components is described in detail. Adherence to this program enhances analytical reliability by helping to ensure that raw concentrations are generated consistently under optimum instrumental conditions, and that corrections for spectral interferences are applied accurately even though interference calibrations may be several months old.The importance of adequate resolution and the proper choice of positions for off-line background measurements is borne out by a detailed study of the determination of toxic trace elements in National Bureau of Standards fly ash samples. As, Be, Cd, Pb, Sb, and Se were determined accurately without isolation/preconcentration from the aluminosilicate matrix. Several determinations required corrections for residual spectral interferences amounting to 100–500% of the resultant concentration, underscoring the accuracy of the interference correction procedures.     

Reduction of spectral interferences in inductively-coupled plasma emission spectrometry by selective spectral-line modulation

Spectral interferences in inductively-coupled plasma (i.c.p.) emission spectrometry can be significantly reduced through the use of selective spectral-line modulation. In this method, a mirrored, rotating chopper directs the emission from an i.e.p. alternately through and past a flame; selective modulation is achieved when the flame contains absorbing atoms identical to emitting atoms in the i.c.p. The ability of selective spectral-line modulation to minimize broadband, narrow line, and scattered light spectral interferences is demonstrated. Signal-to-background ratios for detection with spectral-line modulation are shown to be higher than those obtained by conventional detection. The effect of modulating conditions on working curve slope and linearity is discussed and the limitations of the proposed method are critically evaluated.     

Reduction of spectral interferences in flame emission spectrometry by selective spectral-line modulation

Spectral interferences in flame emission spectrometry can be significantly reduced through the use of selective spectral-line modulation (s.l.m.). In this method, a mirrored, rotating chopper is used to direct the emission from a sample flame alternately through and around a second (modulating) flame; selective modulation is achieved when the modulating flame contains absorbing atoms identical to emitting analyte atoms in the sample flame. The effects of optical configuration and modulating conditions on working curve slope, linearity, and signal-to-noise ratio are examined. Also, the ability of s.l.m. to minimize broad-band and narrow-line spectral interferences is demonstrated. In particular, it has been shown that the interference of the 554-nm CaOH band on barium determinations can be largely overcome. Also, interference of several palladium lines on nickel in the 350-nm region can be reduced. Finally, it is shown how the interference of flame background itself can be restricted in s.l.m. procedures.     

A multiple grating flame photometer for the simultaneous determination of five elements

A flame emission spectrometer for the simultaneous determination of five elements has been constructed. The instrument is built around a special holographic diffraction grating, built up from several smaller gratings with different ruling characteristics, each covering a different spectral range. It is provided with automatic background correction and a photon counting system. Sensitivity and precision are good. The instrument is compared with other multichannel flame emission systems. Construction of the spectrometer including electronics is described.     

Dissolution of molybdenum-silicon (-boron) alloys using a mixture of sulfuric, nitric and hydrofluoric acids and a sequential correction method for ICP-AES analysis

For the major component analysis of Mo-Si (-B) alloys by ICP-AES, an appropriate dissolution method is necessary. The general procedure using a HNO3-HF mixture cannot be applied for Mo-Si (-B) alloys due to Si volatilization followed by violent reaction and due to MoO2 precipitation in the preparation of a Mo standard solution from metallic Mo. Good results were obtained with a mixture of 10 mL H2SO4, 1 mL HNO3, 2 mL HF and 12 mL H2O for Mo-Si (-B) alloys. The samples were completely dissolved at room temperature without any losses. A sequential correction method is also suggested to correct several errors in ICP-AES analysis such as fluctuation in the emission intensities, spectral interferences, non-spectral interferences and blank values.     

A semi-automated method for the determination of arsenic in soil and vegetation by gas-phase sampling and atomic absorption spectrometry.

A study of different types of interferences has been carried out with an inductively coupled plasma source for emission spectrometry. The interferences are classified as chemical, nebulization, atomization and spectral. Chemical interferences are negligible and nebulization ones can be avoided easily. Spectral interferences can be resolved with the use of an electronic correction device. The only residual interferences are due to atomization; although these are low. they can be avoided only by precise information on the physicochemical mechanisms involved.     

Applications of fabry—pérot interferometry in multi-element flame emission analysis

A system for multi-element flame emission analysis based on a scanning Fabry–Pérot interferometer is described and evaluated. Detection limits and linearity of response for ten elements commonly determined by flame photometry compare well with conventional single-element methods. Analyses for several elements in tap water, serum, urine, standard orchard leaf and low-alloy steel demonstrate the good accuracy and precision of the technique; the resolution allows up to five elements to be determined simultaneously.     

电感耦合等离子体原子发射光谱法测定低碳高硫钢中铋的含量

采用电感耦合等离子体原子发射光谱法测定某低碳高硫钢中的铋含量。通过实验探讨了钢中基体元素及共存元素对铋元素分析谱线的光谱干扰情况,确定了合适的分析谱线和背景校正方法,铋元素的分析谱线为223．061nm。根据某低碳高硫钢中铋元素含量范围,合成系列标准溶液,建立工作曲线,工作曲线的线性范围为0．01％～0．50％,线性相关系数r=0．9998,方法检出限为0．00279％,测量结果的相对标准偏差小于2．7％,加标回收率为98．2％～101．2％。     

Molecular absorption spectrometry in flames and furnaces: A review

Molecular absorption spectrometry (MAS), originally developed in the 1970s, is a technique to determine non-metals in flames and graphite furnaces by monitoring the absorbance of diatomic molecules. Early studies employed low resolution instruments designed for line source atomic absorption, which provided a limited choice of analytical wavelengths, insufficient spectral resolution, and spectral interferences. However, the development of high-resolution continuum source atomic absorption spectrometry (HR-CS AAS) instrumentation has allowed the analysis of challenging samples for non-metals as well as some difficult elements to determine by AAS, such as aluminum and phosphorus. In this review, theory and analytical considerations for MAS are discussed. The principles and limitations of low resolution MAS are described, along with its applications. HR-CS AAS instrumentation is reviewed, emphasizing performance characteristics most relevant for MAS. Applications of flame and HR-CS GFMAS are reviewed, highlighting the most significant work to date. The paper concludes with an evaluation of the enhanced analytical capabilities provided by HR-CS MAS.     

Spectral interferences and background overcompensation in zeeman-corrected atomic absorption spectrometry : Part 1. The effect of iron on 30 elements and 49 element lines

The background compensation performance of a Zeeman corrector with the magnetic field acting on the graphite atomization cell was assessed for 30 elements and 49 element lines in an iron matrix. Two of the elements studied, gallium and zinc, are influenced by background overcompensation which introduces serious negative systematic errors. The overcompensation is due to the presence of iron lines close to the 287.4-nm gallium line and the 213.9-nm zinc line; when the magnetic field is on, the σ-components of the adjacent iron lines overlap at the position of the analyte line and a background, which is not present when the magnetic field is off, is recorded. When gallium and zinc are measured under the same conditions but with deuterium arc background correction, the adjacent iron lines cause positive systematic errors. These spectral interferences for gallium in the presence of iron can be avoided by doing the measurements at the 294.4-nm gallium line; the two lines have about the same sensitivity. When zinc is to be measured at the 213.9-nm line, with either type of background correction, the spectral interferences from iron can be avoided by careful selection of the graphite-furnace parameters. In addition to spectral interferences, iron also affects the sensitivity for both gallium and zinc.     

Laser excited atomic fluorescence of some transition elements in the nitrons oxide-acetylene flame

A pulsed, tunable dye laser, pumped with a nitrogen laser is used to excite the atomic fluorescence of Sc, V, Hf, Nb, Os, Zr, W, Rh and Ru. Except in the case of Rh, the nitrous oxide-acetylene flame has been used. The results obtained for Zr and W are due to scattering of the laser radiation from unvaporized particles in the flame. Since, for most elements, several fluorescence lines of comparable intensity have been observed after the primary excitation process, the usefulness of observing non-resonance fluorescence is stressed, particularly with regard to the possibility of minimizing spectral interferences. The experimental results demonstrate that the limits of detection obtained with the dye laser source are comparable or better than the best atomic absorption limits only when the same primary absorption line used for the atomic absorption measurements can be used for exciting the fluorescence.     

Flame spectra of sc,y and rare-earth elements

Flame spectra are presented of sandium, yttrium and the rare-earth elements, except cerium and promethium. These elements were extracted with a solution of 2-thenoyltrifluoroacetone (TTA) in 4-methyl-2-pentanone (hexone) and their spectra in the organic medium were subsequently recorded by means of a flame spectrophotometer. The precise wave length and relative spectral intensity of each line and band are tabulated. Included, also, are the 1/2-band widths and the relative spectral interferences of other elements of the group with the emission of measurement of the bands and lines listed. Operating conditions, applicability and limitations of the method in the estimation of some of the rare-earth elements are given     

用自适应滤波校正电感耦合等离子体原子发射光谱分析中的光谱干扰

本文从分析谱线与干扰的统计特性出发，将信号处理技术的自适应嗓声抵消模型用于校正ＩＣＰ－ＡＥＳ中的光谱干扰。模拟与实测光谱校正结果表明，光谱干扰自适应滤波方法是可行的、有效的。     

Dissolution of molybdenum-silicon (-boron) alloys using a mixture of sulfuric, nitric and hydrofluoric acids and a sequential correction method for ICP-AES analysis

For the major component analysis of Mo-Si (-B) alloys by ICP-AES, an appropriate dissolution method is necessary. The general procedure using a HNO₃-HF mixture cannot be applied for Mo-Si (-B) alloys due to Si volatilization followed by violent reaction and due to MoO₂ precipitation in the preparation of a Mo standard solution from metallic Mo. Good results were obtained with a mixture of 10 mL H₂SO₄, 1 mL HNO₃, 2 mL HF and 12 mL H₂O for Mo-Si (-B) alloys. The samples were completely dissolved at room temperature without any losses. A sequential correction method is also suggested to correct several errors in ICP-AES analysis such as ?uctuation in the emission intensities, spectral interferences, non-spectral interferences and blank values.     

Multi-element analysis by inductively-coupled plasma emission spectrometry in animal diets and faeces containing chromium marker

A simple fusion method is given for the dissolution of chromium(III) oxide marker in animal diets and faeces. Chromium is determined by inductively-coupled argon plasma emission spectrometry and, for comparison, by flame atomic absorption spectrometry. The feasibility of simultaneous multi-element analysis is investigated. Data on interferences and recovery are presented.     

Submicro Determination of Copper and Zinc in Needle Biopsy-Sized Cardiac and Skeletal Muscles by Atomic Absorption Spectroscopy Using Stoichiometric Air-Acetylene Flame

Abstract

A highly sensitive and rapid procedure is described for submicro quantitation of copper and zinc contents from the nitric acid extract of fat free-dry-tissue (FFDT) by a double beam atomic absorption spectrophotometer using stoichiometric air-acetylene flame. Simultaneous background correction was afforded with a deuterium lamp for Zn analysis to eliminate interferences from non-atomic absorption at 213.9 nm. Cu and Zn standards, as well as the muscle extracts, were prepared in an aqueous medium containing 0.75 M Ultrex quality HNO₃ for spectral analysis which did not quench or enhance the relevant absorbance signals. Inherent mineral constituents of muscle such as Ca, Mg, Na, K, and P, when added upto ～10-60 fold greater than the physiological concentration, did not cause either analytical or chemical interferences. Muscle specimens weighing between 0.8-12.0 mg FFDT were extracted in 5 ml of 0.75 M HNO₃ and directly aspirated into the flame. Muscle Cu and Zn contents were expressed in mg/kg FFDT. The smallest sample size confidently analyzed using this technique was ～0.4 mg FFDT which corresponds to 2.0 mg of fresh tissue and can be safely obtained from a patient by muscle needle biopsy. Recovery studies from the inherent muscle matrix revealed 100.01 ± 0.399 and 99.64 ± 0.13% precisions for Cu and Zn respectively.     

Non-linear spectral interferences in an inductively coupled plasma optimized for simultaneous multi-element analysis of plant and soil samples by atomic emission spectrometry

Summary The spectral interferences by Al, Ca, Fe, K, Mg and Na in the direct simultaneous determination of As, Cd, Co, Cu, Hg, Pb and Se in plant and soil samples by ICP-AES are investigated, and a non-linear relationship between the apparent analyte concentration for As, Cd, Co, Hg and Se is observed. A correction method for non-linear spectral interferences is discussed and non-linear spectral correction coefficients are calculated.     

Investigation of interferences in the determination of thallium in marine sediment reference materials using high-resolution continuum-source atomic absorption spectrometry and electrothermal atomization

A high-resolution continuum-source atomic absorption spectrometer with a xenon short-arc lamp as the radiation source, a compact double echelle monochromator with a focal length of 302 mm and a spectral resolution of λ/Δλ≈110 000, and a UV-sensitive charged-coupled device (CCD) array detector was used to investigate the spectral interferences found with a conventional line-source atomic absorption spectrometer in the determination of thallium in marine sediment reference materials. A transversely heated graphite furnace was used as the atomizer unit, and the samples were introduced in the form of slurries. A strong iron absorption line at 276.752 nm, which was observed at atomization temperatures >2000 °C in the vicinity of the thallium resonance line at 276.787 nm, could be responsible for some of the interferences observed with low-resolution continuum-source background correction. The outstanding feature at atomization temperatures <2000 °C was the electron excitation spectrum of the gaseous SO₂ molecule that exhibited a pronounced rotational fine structure, and is for sure the main reason for the observed spectral interferences. The molecular structures could be removed completely by subtracting a model spectrum recorded during the atomization of KHSO₄, using a least squares algorithm. The same results, within experimental error, were obtained for thallium in a variety of marine sediment reference materials using ammonium nitrate as a modifier, ruthenium as a permanent modifier in addition to ammonium nitrate, and without a modifier, using aqueous standards for calibration, demonstrating the ruggedness of the method. A characteristic mass of 15–16 pg Tl was obtained, and a limit of detection of 0.02 μg g⁻¹ Tl was calculated from the standard deviation of five repetitive determinations of HISS-1, the sediment with the lowest thallium content.