Electrothermal Atomization Atomic Absorption Spectrometry Research Articles

Computer aided signal analysis in electrothermal atomization-atomic absorption spectrometry—accuracy and precision: peak height vs peak area

A systematic approach to the question of the height or area calculation in electrothermal atomization-atomic absorption spectrometry (ETA-AAS) is given. Points studied are the real time sampling, power spectrum, temperature and the chemical composition of the sample. It turned out that generally the height gives somewhat more precise results for the furnace studied, the Varian CRA 90, but the difference with the area measurements was not dramatic. A far better approach is the measurement of the height multiplied by the peak time. Precision here can be as good as 1–2 % RSD on a concentration level of 0.3 μg 1 , while a characteristic mass of 0.041 μg is obtained. This shows how good ETA-AAS can be. However, with chemical more complex elements as lead, the mentioned precision will only be reached after sample destruction or matrix modification.

Furnace design in electrothermal atomization-atomic absorption spectrometry

The heating characteristics and analytical performance of conventional, longitudinally heated tubes and transverse heated ETA-AAS tubes are discussed, including the influence of the tube material on the different furnace designs. From the present study it can be concluded that the best furnace material is pyrolytically coated electrographite. Analytical results obtained with the presently available totally pyrolytic graphite tubes are at best similar to pyrolytically coated tubes, whereas glassy carbon tubes cannot successfully be used at temperatures higher than 2500°C. Transverse heated tubes of totally pyrolytic graphite and transverse heated integrated contact tubes are promising because of their spatially more homogeneous temperature distribution.

Determination of vanadium in urine by electrothermal atomisation atomic absorption spectrometry

A sensitive method for the determination of vanadium in urine by electrothermal atomisation atomic absorption spectrometry (ETA-AAS) is described. After wet ashing of the urine sample with nitric acid, vanadium is chelated with 8-hydroxyquinoline in isobutyl methyl ketone and determined by ETA-AAS with a pyrolytically coated graphite furnace atomiser. The effects of acidity and amount of reagent required for the extraction were studied. The reproducibility, precision, analytical recovery and interferences of the method were investigated. The method allows concentrations of vanadium of less than 0.5 µg l–1 to be detected. The reference interval obtained is 0.87–8.55 µg l–1 of vanadium.

Application of inductively coupled plasma mass spectrometry (ICP-MS) for trace metal determination in foods

The application of inductively coupled plasma mass spectrometry (ICP-MS) for trace and ultra-trace metal determination in foodstuffs has been investigated. The ICP-MS technique was compared with electrothermal atomisation atomic absorption spectrometry (ETA-AAS) for Cd and Pb in three biological standard materials. Results for Mo and V by ICP-MS were compared with the certified values. The ETA-AAS gave results that were closest to the certified values, with good precision. The ICP-MS results were encouraging and compared well for Cd and Pb, with both ETA-AAS and the certified results. The precision was acceptable at the higher element concentrations but degraded considerably at the lower levels. An investigation into the causes of the poor precision revealed molecular interferences and instrument hardware were partially to blame. Noticeable improvements in accuracy and dramatic improvements in precision were then obtained. Molecular ion interferences over the 51–81 a.m.u. mass range were investigated using several chemical matrices (HNO3, HCl, H2SO4, H3PO4, H2O2 and NH3) and the results confirmed that dilute HNO3 is the most suitable acid matrix. Data are presented on the problems of the determination of As and V in the presence of 51CIO+ and 75ArCl+ and the possibilities for data correction explored.

Kidney and liver levels of some major, minor and trace elements in two Ontario communities

The contents of Ag, As, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Hg, K, Mg, Mn, Mo, Na, Ni, P, Pb, Se, Sr, Th, Ti and Zn in 143 autopsied liver and kidney specimens from two Ontario communities (Kingston and Ottawa) were determined using the techniques of inductively-coupled plasma-atomic emission spectrometry, and electrothermal atomization-atomic absorption spectrometry coupled with hydride evolution (As, Se), reduction-aeration (Hg), or solvent extraction (Pb). The majority of samples came from individuals older than 50 y. In general, the data for the various elements were independent of age or sex but showed some dependence on location for elements such as Cu, Fe, K, Mg, Mn, Na, P, Se and Zn. Despite these differences the elemental values of the liver and kidney samples from both the communities were within the normal range.

Electrothermal atomisation atomic-absorption spectrometry with the direct introduction of slurries. Determination of trace metals in soil

Lead and cadmium are determined directly in soil by pipetting an aqueous slurry into a graphite furnace electrothermal atomiser. Aqueous calibration standards are used, and analyte recovery is complete provided that the soil is finely ground. The precision (relative standard deviation) at typical concentrations in soil is approximately 2–4% for cadmium and 8–9% for lead. The importance of soil particle size has been studied, and it is shown that insufficient grinding leads to poor recovery from larger particles. The major error is in the atomisation process, and analyte losses during pipetting of slurries into the atomiser are relatively small.

Direct collection of lead in the atmosphere by impaction for determination by electrothermal atomization atomic absorption spectrometry

A dry collection system has been developed for the acquisition of solids, particularly lead, suspended in air. When coupled with electrothermal atomization atomic absorption spectrometry (EAAAS), a real-time determination of the metals content of an aerosol can be made. The suspended solids are collected through inertial impaction on a graphic tube. Detailed information on the collection system is presented. 16 references, 3 figures, 1 table.

Determination of indium in geological materials by electrothermal-atomization atomic absorption spectrometry with a tungsten-impregnated graphite furance

The sample is fused with lithium metaborate and the melt is dissolved in 15% (v/v) hydrobromic acid. Iron(III) is reduced with ascorbic acid to avoid its coextraction with indium as the bromide into methyl isobutyl ketone. Impregnation of the graphite furnace with sodium tungstate, and the presence of lithium metaborate and ascorbic acid in the reaction medium improve the sensitivity and precision. The limits of determination are 0.025–16 mg kg −1 indium in the sample. For 22 geological reference samples containing more than 0.1 mg kg −1 indium, relative standard deviations ranged from 3.0 to 8.5% (average 5.7%). Recoveries of indium added to various samples ranged from 96.7 to 105.6% (average 100.2%).

A pyrometric feedback system covering the entire temperature program for electrothermal atomization-atomic absorption spectrometry

A new pyrometric temperature feedback control system 1 1 Patent pending. for ETA-AAS is introduced which controls the entire temperature range needed for analysis. The system consists of a single infrared sensitive detector and independent feedback control circuitry for the three separate heating stages of a Varian CRA 63 or CRA 90 power supply to which it was added. The temperature region covered by the system encompassed from 300 to 3300 K. The precision of the temperature control amounts to ±20 K at 330 K., ±5 K at 700 K and ±2 K at 2300 K. In order to test the performance of the system, lead in blood and cadmium in urine were determined. Substantial improvements as compared to the conventional system were obtained with respect to optimization of the temperature program, precision and sensitivity.

Some observations on direct determination of cadmium in urine by electrothermal atomization atomic absorption spectrometry

A systematic approach to the question of the height or area calculation in electrothermal atomization-atomic absorption spectrometry (ETA-AAS) is given. Points studied are the real time sampling, power spectrum, temperature and the chemical composition of the sample. It turned out that generally the height gives somewhat more precise results for the furnace studied, the Varian CRA 90, but the difference with the area measurements was not dramatic. A far better approach is the measurement of the height multiplied by the peak time. Precision here can be as good as 1–2 % RSD on a concentration level of 0.3 μg1, while a characteristic mass of 0.041 μg is obtained. This shows how good ETA-AAS can be. However, with chemical more complex elements as lead, the mentioned precision will only be reached after sample destruction or matrix modification.

Some instrumental improvements in electrothermal atomization-atomic absorption spectrometry: Application in biomedical research

Some instrumental improvements in electrothermal atomization-atomic absorption spectrometry (ETA-AAS) are described. The improvements pertain to signal response systems and temperature control of the furnace heating, all achieved at the Coronel Laboratory. The application of these systems lead to simple sample handling with the possibility of determining series of samples for biomedical research. Precision, detection limits and sensitivity have been improved whereas the risk of contamination has been reduced to a minimum. With these systems the analytical power of ETA-AAS is clearly shown: low detection limits, simple sample handling and high speed of analysis.

Temperature-controlled electrothermal atomization-atomic absorption spectrometry using a pyrometric feedback system in conjunction with a background monitoring device

The construction of a temperature-controlled feedback system for electrothermal atomization-atomic absorption spectrometry (ETA-AAS) using an optical pyrometer applied to the atomization stage is described. The system was used in conjunction with a fast-response background monitoring device. The heating rate of the furnace amounted to 1400° s −1 with a reproducibility better than 1%. The precision of the temperature control at a steady state temperature of 2000°C was 0.1%. The analytical improvements offered by the present system have been demonstrated by the determination of cadmium and lead in blood and finally by the determination of lead in serum. Both the sensitivity and the precision of the method have been improved. The accuracy of the method was checked by determining the lead content for a number of scrum samples both by ETA-AAS and differential pulse anodic stripping voltametry (DPASV) and proved to be satisfactory.

Heating characteristics of glassy carbon tubes used in electrothermal atomization-atomic absorption spectrometry

Glassy carbon tubes of standard dimensions can be heated up to 3200 K with minor modification to the power supply that is used to heat graphite tubes. Under standard conditions the heating rates of graphite and glassy carbon are about the same. An increased voltage is required to heat glassy carbon tubes lo the same furnace temperature. The power consumption of the various tubes is shown to be equal. Similar analytical sensitivity can be obtained with glassy carbon and pyrolytically coated graphite lubes, provided that the same heating rates can be realized. The glassy carbon material supplied by Tokai shows high blank signals for Al, Fe and Si and blank signals are also observed for Mn, Ti and V. The purity of the glassy carbon from Le Carbone-Lorraine is much better. However, a glassy carbon material of higher purity should be developed for use in ETA-AAS.

Direct determination of inorganic mercury in biological materials after alkali digestion and amalgamation.

A reliable method is described for the determination of inorganic mercury in biological materials in the presence of organic mercury. This is principally based on the fact that hydrogen peroxide oxidatively liberates inorganic mercury from organic substances in strong alkali and reduces it to the metallic state without decomposing organic mercurials concomitantly present. The metallic mercury, vaporised with a nitrogen stream, is trapped by gold amalgamation and then released for electrothermal atomisation atomic-absorption spectrometry. The detection limit is 1 ng of inorganic mercury and the co-efficient of variation for 40 ng of inorganic mercury is 2.8%.

On the optimization of blood lead standards in electrothermal atomization atomic absorption spectrometry

This study is concerned with the optimization of blood lead standards in ETA-AAS (electrothermal atomisation-atomic absorption spectrometry), using a direct method, i.e. the determination of lead in 15-fold diluted blood. With three bottles of whole blood containing respectively heparin, citrate and EDTA as an anticoagulant, and 14 working standard solutions, 42 calibration curves were constructed. It appeared that standards prepared in heparinised blood yield calibration curves with a less steep slope than in the case of citrate or EDTA blood. As a primary standard, lead acetate is considered best for both heparinised and citrated blood: metallic lead is advantageous for EDTA blood. In all cases a low pH of both stock standard and working standard solution is preferred. Using a reference sample the best conditions for obtaining accurate results were investigated. The use of metallic lead as a primary standard ensures a combination of low systemic error with high precision and steep slope.

A direct differential pulse anodic stripping voltammetric method for the determination of thallium in natural waters

A dual direct method for the ultratrace determination of thallium in natural waters by differential pulse anodic stripping voltamrnetry (d.p.a.s.v.) is presented. D.p.a.s.v. at the hanging mercury drop electrode and at the mercury film electrode is used in the concentration ranges 0.5–100 μg Tl l -1, and 0.01–10 μg Tl l -1, respectively. Quantification is aided by the technique of standard additions. The response of the method is optimized for typical natural surface water matrices. An intercomparison of thalium determinations performed by the two anodic stripping methods and electrothermal-atomization atomic absorption spectrometry on normal and thallium-spiked surface water samples demonstrates equivalent accuracy within the range where atomic absorption is applicable. The method appears free from serious interferences.

Elemental Trace Analysis of Biological Materials

I. INTRODUCTION A. Scope and Purpose of the Review The purpose of this paper is to evaluate the effectiveness of a number of the more popular trace element analytical techniques in meeting the needs of the life scientists. Emphasis is directed towards the determination of trace elements in biological materials using those techniques that are currently being used extensively for this purpose or show promise in the immediate future. Techniques compared include anodic-stripping voltametry (ASV), atomic absorption spectrometry (AAS), electrothermal atomization-atomic absorption spectrometry (ETA-AAS), emission spectrometry (ES), inductively coupled plasma-atomic emission spectrometry (ICP-AES), ion-selective electrodes (ISE), neutron activation analysis (NAA), spark-source mass spectrometry (SSMS), and X-ray fluorescence (XRF) spectrometry. Emphasis is placed on their actual use in clinical analyses as indicated by their appearance in the clinical chemical literature for the past 10 years, rather than convent...