Theory of Zeeman atomic absorption spectrometry

A theoretical analysis is presented of the signals observed with different systems that employ the Zeeman effect for background correction in analytical atomic absorption spectrometry.Magnetic modulation of the primary source of radiation offers basically the same possibilities as the deuterium background correction system. Correction for wavelength dependent background absorption is possible only when the magnetic field is applied to the absorbing vapour. Similar expressions are obtained for constant or variable magnetic fields directed either perpendicular or parallel to the optical axis. However, mere magnetic modulation of either the source or the atomizer cannot correct for non-absorbed lines.It is demonstrated that simultaneous correction for non-absorbed lines and background absorption can be attained with a variable magnetic field applied to the atomizer, by taking measurements at three discrete, different field strengths.     

背景吸收强度可调控与扣除干扰组分影响的红外光谱测量方法

多组分混合物的红外光谱由于特征谱带的重叠或部分重叠而给谱峰的归属辨认带来极大的困难。本研究通过扫描两个背景样品(纯KBr压片(1)和KBr+C18TCNQ压片(2))实时合成一系列背景单光束谱。每个背景单光束谱既含有背景样品1的贡献也含有背景样品2的贡献。干扰组分C18TCNQ在系列背景谱中的吸收强度随扫描次数变化而改变。当待测混合物和背景样品中干扰组分的吸收强度相等时,就可以完全扣除干扰组分的影响。本测量方法用于硬脂酸与C18TCNQ混合物中扣除硬脂酸(或者C18TCNQ)的干扰,得到令人满意的结果。合成背景样品中干扰组分的含量在测量时成为与扫描次数有关的变量,为扣除干扰组分的影响提供了直接便利的红外光谱测量方法。     

Construction and performance of an a.c. modulated magnet for Zeeman atomic absorption spectroscopy

A Zeeman atomic absorption spectroscopy system has been constructed utilizing a 50 Hz sine wave modulated magnetic field that can be directed either parallel or perpendicular to the optical axis. The amplitude of the magnetic field strength is adjustable up to 10 kG at a maximum power consumption of 0.7 kW.The readout system allows normal atomic absorption as well as d.c. and a.c. Zeeman atomic absorption measurements. Plots of experimental sensitivity vs magnetic field strength and analytical curves are in agreement with theoretical predictions.Experiments in the presence of filter simulated and real background absorbance show that the described Zeeman instrument is capable of correcting background absorption up to two absorbance units.     

Tunable thermal lens spectrometry utilizing microchannel-assisted thermal lens spectrometry

A tunable thermal lens spectrometry system was developed for microchip analysis. The system utilized a Xe lamp as an excitation source, instead of a laser. The system can measure the absorption spectrum of a turbid solution without disturbance of the light scattering background.     

A novel method for atomic absorption spectroscopy based on the analyte-Zeeman effect

A new type of atomic absorption spectrometry using the Zeeman effect of sample materials is proposed. A magnetic field was applied to the sample vapor in the direction perpendicular to the propagation of light emitted from an atomic spectral source. Absorption of radiation polarized perpendicular and parallel to the magnetic field was observed alternatively. The absorption difference was proportional to the true atomic absorption, and was not interfered with by any other molecular absorption and light scattering, i.e., background absorption. The background absorption could be monitored at exactly the same wavelength as an atomic absorption line. Suitable magnetic field strength was found for each line of the various elements.     

石墨炉原子吸收光谱中尿的背景吸收研究

本文较详细地研究了尿背景吸收的来源, 特点和消除方法, 背景吸收波长特性和在石墨管内蒸发行为的研究表明, 尿的背景吸收主要来自氯化钠, 其次是氯化铵, 其他组份的贡献很小, 时间特性研究表明, 背景吸收大小和背景吸收曲线轮廓与原子化阶段的加热方式和原子化温度有关。还研究了应用基体改进剂和其他减小背景吸收的方法。     

Progress in direct solid sampling analysis using line source and high-resolution continuum source electrothermal atomic absorption spectrometry

The literature about direct solid sample analysis of the past 10–15 years using electrothermal atomic absorption spectrometry has been reviewed. It was found that in the vast majority of publications aqueous standards were reported as having been used for calibration after careful program optimization. This means the frequently expressed claim that certified reference materials with a matrix composition and analyte content close to that of the sample have to be used for calibration in solid sample analysis is not confirmed in the more recent literature. There are obviously limitations, and there are examples in the literature where even calibration with certified reference materials did not lead to accurate results. In these cases the problem is typically associated with spectral interferences that cannot be corrected properly by the systems available for conventional line source atomic absorption spectrometry, including Zeeman-effect background correction. Using high-resolution continuum source atomic absorption spectrometry, spectral interferences become visible owing to the display of the spectral environment at both sides of the analytical line at high resolution, which makes program optimization straightforward. Any spectrally continuous background absorption is eliminated automatically, and even rapidly changing background absorption does not cause any artifacts, as measurement and correction of background absorption are truly simultaneous. Any kind of fine-structured background can be eliminated by “subtracting” reference spectra using a least-squares algorithm. Aqueous standards are used for calibration in all published applications of high-resolution continuum source atomic absorption spectrometry to direct solid sample analysis. This contribution is based on a presentation given at the Colloquium for Analytical Atomic Spectroscopy (CANAS ‘07) held March 18–21, 2007 in Constance, Germany.     

紫外吸收试剂对反相液相色谱-间接紫外检测法分析烷基磺酸盐的影响

研究了不同背景紫外吸收试剂对无紫外光吸收的烷基磺酸盐检测的影响。采用反相C18色谱柱的高效液相色谱-间接紫外检测法,以背景紫外吸收试剂-有机溶剂为流动相分离烷基磺酸盐。研究不同背景紫外吸收试剂对分离检测烷基磺酸盐的影响规律和分离机理。结果表明,不同类型的背景紫外吸收试剂测定烷基磺酸盐的色谱峰类型不同。阳离子型背景紫外吸收试剂测定烷基磺酸盐时,样品峰均为正峰;阴离子型和两性离子型背景紫外吸收试剂时,样品峰均为倒峰。比较不同的背景紫外吸收试剂,发现采用阳离子型紫外吸收试剂测定烷基磺酸盐的色谱峰更好,其中以咪唑离子液体最佳,检测响应值最高。     

Determination of Cadmium, Cobalt, Manganese, Copper, Nickel, and Chromium in Concentrated Solutions of Calcium Chloride by Electrothermal Atomic Absorption Spectrometry

A procedure is developed for the direct determination of Cd, Co, Cr, Cu, Mn, and Ni in concentrated solutions of calcium chloride by electrothermal atomic absorption spectrometry. Ascorbic and oxalic acids and magnesium nitrate were examined as chemical modifiers. Oxalic acid was found to be the best modifier. Although an atomic absorption spectrometer with a background correction system of relatively low efficiency (deuterium lamp) was used, the elements under study can be reliably determined in the presence of oxalic acid at concentrations of calcium chloride in the solution up to 6%. Because cadmium is evaporated before the major part of the given matrix, it can be determined without a modifier.     

The determination of trace elements in sulphide minerals by atomic absorption spectrophotometry with absorption tubes

A method for the determination of minor and trace elements (Zn, Cd, Pb, Cu and Ag) in sulphide minerals by atomic absorption spectrophotometry is described. For enhancing the sensitivity of the determination, the absorption tube technique is applied. Memory effects and background absorption influences on the measurement with absorption tubes are discussed.     

Correction for background absorption and stray radiation in a.c. modulated Zeeman atomic absorption spectrometry

Analytical results are presented obtained with Zeeman atomic absorption (ZAA) using a modified sine wave magnetic field. The measurement at zero field strength is lengthened to 0.5 ms for a 50 Hz magnetic field of 10 kG.The a.c. Zeeman system is extended with an additional intensity measurement performed at an intermediate field strength. The three field Zeeman system (3FZAA) permits simultaneous correction for background absorption and stray radiation at the expense of halved analytical sensitivity. The background correction capabilities of ZAA and 3FZAA are the same. However, the 3FZAA signals show increased noise in comparison to ZAA.In the three field system the roll-over problem, inherent in existing Zeeman systems, is shifted to higher concentration and to higher absorbance. The height and the position of the maximum in ZAA and 3FZAA analytical curves do not depend on the amount of background absorption.A method for the extension of analytical curves in AA is presented. Utilizing an a.c. modulated magnetic field any sensitivity between zero and ordinary AA sensitivity can be obtained.     

Indirect photometric detection in capillary zone electrophoresis

An indirect photometric detection method is described which is based on the use of an absorbing co-ion as the principal component of the background electrolyte. The zones of non-absorbing ionic species are revealed by changes in light absorption due to charge displacement of the absorbing co-ion. Theoretical considerations are given for selecting a suitable absorbing co-ion to achieve a high sensitivity of detection.The role of electromigration dispersion is illustrated by experiments and the effects of the differences in the effective mobilities of sample ions and that of the absorbing co-ion are discussed. The highest sensitivity can be achieved for sample ions having an effective mobility close to the mobility of the absorbing co-ion. In such a case, the concentration of the sample component in its migrating zone can be high while electromigration dispersion is still negligible. The useful dynamic range of the detection is then limited by the linearity and noise of the detector, the former parameter being given mostly by the shape of the on-column detection cell. The best sensitivities can be obtained in low-concentration background electrolytes containing a co-ion with high absorption at a given detection wavelength.It is shown that indirect photometric detection can be useful for detecting substances that have no optical absorption in the UV and/or visible region, provided that the composition of the background electrolyte is selected correctly.     

酶联放大安培检测基因传感器的封闭方式

在酶联放大安培检测过程中,酶和碱基链在金电极表面的非特异吸附是导致假阳性结果的主要来源.为减少非特异吸附,分别从封闭时间和封闭方式等考查巯基己醇(MCH)和牛血清白蛋白(BSA)对上述非特异性吸附因素的封闭效果.结果表明,BSA不论是对酶还是碱基链的封闭效果均优于MCH.经优化,确定BSA单一封闭剂(15min)为最佳封闭条件,并可用于急性早幼粒细胞白血病(PML-RARα)融合基因的检测.本方法可有效减少非特异吸附,缩短检测预处理时间,并使检测信号在一定程度上得到放大.     

An application of the Zeeman effect to atomic absorption spectrometry: a new method for background correction

A new Zeeman method for background correction in atomic absorption spectrometry was studied. The light source was operated in a steady magnetic field,     

The design and development of a multichannel atomic absorption spectrometer for the simultaneous determination of trace metals in hair

A multichannel atomic absorption spectrometer capable of analysing up to nine elements simultaneously in human hair has been designed. Light from an array of hollow-cathode lamps is passed through an electrically heated graphite tube into a direct reading spectrometer. The photomultiplier output is fed into a novel transient signalprocessing device which separates the absorption pulse from the continuous background and increases linear range and sensitivity. Solutions containing Ni, Co, Si, Mn, Al, Cu, Ag, Cr and Fe in nanogram and sub-nanogram amounts can be determined with reasonable precision.     

Simple mode of zeeman splitting of absorption lines in atomic absorption spectrometry

Simple equipment is described for exploiting the normal Zeeman splitting of atomic absorption lines in external alternating magnetic fields of various geometry which is suitable for flameless and flame techniques. High-level continuous or background absorption can be eliminated in this way. This is demonstrated for the determination of traces of copper and molybdenum with a carbon rod (Varian CRA 90).     

Investigation of the feasibility to use Zeeman-effect background correction for the graphite furnace determination of phosphorus using high-resolution continuum source atomic absorption spectrometry as a diagnostic tool

The determination of phosphorus by graphite furnace atomic absorption spectrometry at the non-resonance line at 213.6 nm, and the capability of Zeeman-effect background correction (Z-BC) to deal with the fine-structured background absorption due to the PO molecule have been investigated in the presence of selected chemical modifiers. Two line source atomic absorption spectrometers, one with a longitudinally heated and the other with a transversely heated graphite tube atomizer have been used in this study, as well as two prototype high-resolution continuum source atomic absorption spectrometers, one of which had a longitudinally arranged magnet at the furnace. It has been found that Z-BC is capable correcting very well the background caused by the PO molecule, and also that of the NO molecule, which has been encountered when the Pd + Ca mixed modifier was used. Both spectra exhibited some Zeeman splitting, which, however, did not cause any artifacts or correction errors. The practical significance of this study is to confirm that accurate results can be obtained for the determination of phosphorus using Z-BC.     

镥、镱基体在石墨炉原子吸收光谱中的背景吸收研究

利用镥、镱基体在石墨炉中的蒸发行为研究了背景吸收的来源 ,讨论利用基体改进剂减少氯化物背景吸收的方法 ,为镥、镱基体中超痕量元素的精确测定提供帮助。