Hydride Generation Electrothermal Atomic Absorption Research Articles

Interface of on line coupling capillary electrophoresis with hydride generation electrothermal atomic absorption spectrometry and its application to arsenic speciation in sediment

A novel interface for on line coupling capillary electrophoresis with hydride generation electrothermal atomic absorption spectrometry (CE–HG–ETAAS) has been developed. The interface performance was examined in detail. The technique could be used to convert arsenic compounds from CE separation to corresponding volatile hydrides determined by HG–ETAAS. This paper aims to explore the best condition in the speciation analysis of inorganic arsenic by using CE–HG–ETAAS. The application of the developed CE–HG–ETAAS to inorganic arsenic speciation in sediment was investigated. The detection limits of As(III) and As(V) were 135ng/g and 160ng/g, respectively. Relative standard deviations of arsenic speciation were better than 2%. The recoveries of As(III) and As(V) in the sample with spiking concentration of 2500ng/g As(III) and 5000ng/g As(V) were 97.6% and 96.7%, respectively.

Flow injection on-line solid phase extraction for ultra-trace lead determination with hydride generation electrothermal atomic absorption spectrometry

The efficiencies of two types of chelating resins were evaluated and optimized for the extraction and determination of lead by flow injection graphite furnace and hydride generation atomic absorption spectrometry (FI-HG-ETAAS) in environmental water samples. The optimum analytical conditions were examined and the analytical features of each method were revealed and compared in terms of sensitivity, selectivity and accuracy. Lead determination by FI-HG-ETAAS using [1,5-bis(2-pyridyl)-3-sulphophenyl methylene] thiocarbonohydrazide immobilised on aminopropyl-controlled pore glass (PSTH-cpg, 55 nm) provides a detection limit of 3.0 ng l−1 lead with a relative standard deviation (R.S.D.) of 2.5% at the 50 ng l−1 level (n = 10) compared to silica gel funtionalized with methylthiosalicylate (TS-gel) which provides a detection limit of 82 ng l−1. Under the optimal experimental conditions, with the use of PSTH-cpg and a tungsten–rhodium coated graphite furnace, an enhancement factor of 20 was obtained with a sample consumption of 6.4 ml, while an enhancement factor of 3.5 was obtained with the use of TS-gel. Both methods have been applied to the determination of low levels of lead in environmental water samples. The results obtained show good agreement with certified or expected values.

Method development and optimization for the determination of selenium in bean and soil samples using hydride generation electrothermal atomic absorption spectrometry

The present investigation is the first part of an initiative to prepare a regional map of the natural abundance of selenium in various areas of Brazil, based on the analysis of bean and soil samples. Continuous-flow hydride generation electrothermal atomic absorption spectrometry (HG-ET AAS) with in situ trapping on an iridium-coated graphite tube has been chosen because of the high sensitivity and relative simplicity. The microwave-assisted acid digestion for bean and soil samples was tested for complete recovery of inorganic and organic selenium compounds (selenomethionine). The reduction of Se(VI) to Se(IV) was optimized in order to guarantee that there is no back-oxidation, which is of importance when digested samples are not analyzed immediately after the reduction step. The limits of detection and quantification of the method were 30ngL−1 Se and 101ngL−1 Se, respectively, corresponding to about 3ngg−1 and 10ngg−1, respectively, in the solid samples, considering a typical dilution factor of 100 for the digestion process. The results obtained for two certified food reference materials (CRM), soybean and rice, and for a soil and sediment CRM confirmed the validity of the investigated method. The selenium content found in a number of selected bean samples varied between 5.5±0.4ngg−1 and 1726±55ngg−1, and that in soil samples varied between 113±6.5ngg−1 and 1692±21ngg−1.

Hydride generation atomic absorption spectrometry with different flow systems and in-atomizer trapping for determination of cadmium in water and urine—overview of existing data on cadmium vapour generation and evaluation of critical parameters

An overview of literature data on vapour generation techniques for cadmium and comparison with own experiments by means of several different types of hydride generation–electrothermal atomic absorption spectrometric systems (HG–ETAAS) (batch, semi-batch (SB), continuous-flow (CF) and flow-injection (FI) as well as different gas–liquid separators (GLS) exhibits apparent variations and inconsistency. However, if data for optimal chemical conditions are re-plotted in another coordinates: C HCl (mol l −1) vs. the ratio of reductant-to-acid molar input rates (i.e. millimoles per minute), [BH 4 −]:[H +], much better consistency of data is revealed: more than half of data are clustered around 0.2–0.3 mol l −1 HCl which appears an optimal acidity at moderate BH 4 − concentrations; the tetrahydroborate molar input rates should always be in excess versus the H + molar input rates (1.1 to tenfold); relatively high flow rates of argon purge gas are required (≥120 ml min −1); special attention to the blank control at ng l −1 levels as well as to the construction of gas–liquid separator and vapour transfer lines should be paid. ‘Milder’ conditions for HG could be provided with some of the examined systems and GLSs, thus minimizing reagent consumption, blanks, vigorous reactions, foaming, aerosol production and drift in measurements: e.g. 0.4 mol l −1 HCl—3% m/v NaBH 4 with the semi-batch system and 0.25 mol l −1 HCl—2% m/v NaBH 4 in continuous flow mode. Experimental system is based on the Transversely Heated Graphite Atomizer coupled with flow injection system FIAS 400. Integrated platforms are treated for permanent modification with Zr (110 μg) or W (240 μg) and then with Ir (8 μg). Temperatures of trapping, pyrolysis and atomization are 350, 500 and 1300 °C, respectively. The best overall efficiency of HG, transportation and trapping is 41%. The characteristic mass for peak area measurements is m o=2.8 pg and the limit of detection is 0.002 μg l −1. The long-term stability of characteristic mass (within-day, 8 h) is m o=2.8±0.1 pg (R.S.D. 4.0%, n=8), whereas the corresponding between-day figures (1 mo) are m o=2.8±0.2 pg (R.S.D. 6.6%, n=6). The linear range is 0.002–0.12 μg l −1 with a sample loop of 1.8 ml, being strongly impaired with smaller sample volumes in FI mode. The sample throughput rate is 10 h −1 with the semi-batch system. Applications to real human and bovine urine samples and CRMs of sea water (CASS-3), river water (SLRS-1 and SLRS-3) and urine (SRM 2670) are presented.

Bismuth determination in environmental samples by hydride generation–electrothermal atomic absorption spectrometry

A hydride generation procedure, via flow injection, coupled to electrothermal atomic absorption spectrometry was optimised for Bi determination in sea water and hot-spring water and acid extracts from coal, coal fly ash and slag samples. The effects of several variables such as hydrochloric acid and sodium tetrahydroborate concentrations, hydrochloric acid and sodium tetrahydroborate flow rates, reaction coil length, trapping and atomisation temperatures, trapping time and the Ar flow rate have been investigated by using a 2 9*3/128 Plackett–Burman design. From these studies, certain variables (sodium tetrahydroborate concentration and trapping time) showed up as significant, and they were optimised by a 2 2+star central composite design. In addition, a study of the bismuthine trapping and atomisation efficiency from graphite tubes (GTs) permanently treated with uranium, tantalum, lanthanum oxide, niobium, beryllium oxide, chromium oxide and tantalum carbide were investigated. The results obtained were compared with those achieved by iridium and zirconium-treated GTs. The best analytical performances, with characteristic mass of 35 pg and detection limit of 70 ng l −1, were achieved by using U-treated GTs. Accuracy were checked using several reference materials: 1643d (Trace Elements in Water), TM-24 (Reference Water), GBW-07401 (Soil) and 1632c (Trace Elements in Coal).

Determination of As, Bi and Se in acidified slurries of marine sediment, soil and coal samples by hydride generation electrothermal atomic absorption spectrometry

Ir-treated graphite tubes were used for preconcentration and atomisation of the As, Bi and Se hydrides generated from acidified slurries of marine sediment, soil and coal samples. A batch mode generation system was used for the hydride generation. The variables affecting the acidified slurry preparation procedure (assisted by ultrasonic energy) and the hydride generation/trapping/atomisation processes were studied by using a Plackett–Burman design. The sensitivity (characteristic masses of 65, 75 and 100 pg, for As, Bi and Se, respectively) and precision (RSD% lower than 10%) obtained were adequate for As, Bi and Se determination in slurry samples. The accuracy of the method was verified by analysing PACS-1 (Marine Sediment), GBW-07401 (Soil) and NIST SRM 1632c (Coal) certified reference materials.

Microwave-assisted digestion of organoarsenic compounds for the determination of total arsenic in aqueous, biological, and sediment samples using flow injection hydride generation electrothermal atomic absorption spectrometry

A microwave assisted wet digestion method for organoarsenic compounds and subsequent determination of total arsenic in aqueous, biological and sediment samples by means of flow injection hydride generation electrothermal atomic absorption spectrometry (FI-HG-ETAAS) is described. Sodium persulfate, sodium fluoride and nitric acid serve as digestion reagents, which allow a quantitative transformation of organoarsenic compounds to hydride forming species in a commercial microwave sample preparation system. The maximum operating pressures of the applied tetrafluorometoxil (TFM) liners are 75 bar (high pressure vessels) and 30 bar (medium pressure vessels), corresponding to maximum solution temperatures of 300 and 260 °C. For the investigated samples, digestion temperatures of 210–230 °C (medium pressure vessels) and 240–280 °C (high pressure vessels) were obtained. In medium pressure vessels, arsenic recovery from aqueous testing solutions of dimethylarsinic acid (DMA), phenylarsonic acid (PAA) and tetraphenylarsonium chloride (TPA) at initial concentrations of 100 and 10 μg l −1 is complete, even in the presence of an excess of organic carbon (potassium hydrogen phthalate, 2000 mg l −1) or fatty acids (linolenic acid 70%; linoleic acid ≈20–25%; Oleic acid ≈3%, 900–4500 mg l −1). Arsenic recovery from aqueous arsenobetaine (ASB) solutions with the same initial concentrations is also complete if high pressure vessels and a higher concentration of fluoride ions are used, whereas the addition of organic carbon (potassium hydrogen phthalate, 2000 mg l −1, fatty acids, 900–4500 mg l −1) leads to a decrease in arsenic recovery of about 2–5%. In all cases, residual carbon contents are close to the limit of detection for the applied analytical method (15 mg l −1). Results of arsenic analysis in reference standard materials revealed a significant dependence on the material’s nature (sediment samples, plant materials and seafood samples). Sediment samples and plant materials show recoveries for arsenic around 100% after a single-step digestion in medium pressure TFM liners. Seafood (fish/lobster/mussel samples) usually require either the use of high pressure vessels or a second digestion step, if medium pressure vessels are used.

Flow injection hydride generation electrothermal atomic absorption spectrometry with in-atomizer trapping for the determination of lead in calcium supplements

Lead hydride was generated from acid solution, containing potassium ferricyanide as an oxidizing agent, by the reaction with alkaline borohydride solution. The effects of reaction conditions (hydrochloric acid, ferricyanide and borohydride concentrations), and the lengths of reaction and stripping coils were studied. The effects of trapping temperature and argon flow rate were also investigated. Under the conditions giving the best peak area sensitivity, the detection limit (concentration giving a signal equal to three S.D. of the blank signal) was 0.12 μg l −1 for a 1000 μl injection volume. The detection limit was improved to 0.03 μg l −1 when the ferricyanide was purified by passage through a cation-exchange resin. Two calcium supplement materials were analyzed by the flow injection (FI)-hydride generation (HG)-electrothermal atomization atomic absorption spectrometry (ETAAS) method, giving values of 0.55 and 0.66 μg g −1, in agreement with results obtained by previously validated methods. For a 500-mg sample the limits of detection and quantification were 0.006 and 0.02 μg g −1, respectively.

Electrolytic hydride generation electrothermal atomic absorption spectrometry - in situ trapping of As on different pre-conditioned end-heated graphite tubes

An automated analytical system for the determination of As combining an electrolytic hydride generator and a graphite furnace atomic absorption spectrometer has been developed. To investigate the trapping efficiency of permanent modifiers, the end-heated graphite tubes have been impregnated with Ir and mixed Pd/Ir pre-reduced modifiers, respectively, or pre-coated with Ir by electron beam evaporation under high vacuum. Furthermore, the influence of the modifier mass on the shape of the absorption signal has been studied and the performance of the modifier has been discussed. Using the pre-coated graphite tube the calculated detection limit (3s criteria ) for As was 3 pg and 15 ng/L (200 μL sample volume, two preconcentration steps) for the absolute mass and the concentration, respectively. The long-term stability of the permanent modifiers and their physical and or chemical changes during the lifetime of the tube have been observed.

Effect of high salt concentrations on the determination of arsenic and selenium by flow injection hydride generation electrothermal atomic absorption spectrometry

Download options Please wait... Article information DOI https://doi.org/10.1039/A802944J Article type Paper Download Citation Analyst, 1998,123, 1697-1701 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Effect of high salt concentrations on the determination of arsenic and selenium by flow injection hydride generation electrothermal atomic absorption spectrometry R. I. Ellis, N. G. Sundin, J. F. Tyson, S. A. McIntosh, C. P. Hanna and G. Carnrick, Analyst, 1998, 123, 1697 DOI: 10.1039/A802944J To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Robert I. Ellis Nils G. Sundin Julian F. Tyson Susan A. McIntosh Christopher P. Hanna Glen Carnrick

Effect of sample volume on the limit of detection in flow injection hydride generation electrothermal atomic absorption spectrometry

The analytical performance of methods for the determination of hydride forming elements has been improved recently by the development of procedures in which the hydride is trapped on the interior surface of a graphite furnace atomizer. The signal for a given concentration increases with increase in sample volume and it is often implied that a decrease in the limit of detection may also be achieved by increasing the sample volume. To evaluate this claim, a simple equation was derived which predicts the relationship between detection limit and sample volume when all the contributions to the blank are proportional to sample volume. A time-based approach to the variation of sample volume was developed to ensure that the analyte introduced from reagent contamination was, in fact, proportional to sample volume. Detection limits were measured for a series of sample volumes between 156 and 1560 µl. As the sample volume was increased, the detection limit improved significantly from 0.3 to around 0.05 µg l–1 up to a volume of about 500 µl. Between 500 and 1000 µl, a further improvement, to around 0.02 µg l–1, was obtained, but for volumes larger than 1000 µl no further significant improvement was obtained. Good agreement between the predicted and experimentally determined variations in detection limit with sample volume was obtained and thus the underlying inverse proportionality of the relationship between detection limit and sample volume was confirmed. This rectangular hyperbolic relationship has practical consequences for the extent to which detection limits can be improved by increasing the sample volume, even when the blank is very low or zero.

Determination of Se in urine by flow injection hydride generation electrothermal atomic absorption spectrometry with in-atomizer trapping

Following digestion of the sample in a mixture of bromate and hydrobromic acid, the inorganic selenium produced was quantified by trapping hydrogen selenide, formed when a 500 μl sample volume injected into a hydrochloric acid carrier stream merged with a stream of sodium borohydride solution, on the iridium-pretreated interior of a graphite furnace atomizer. A number of parameters relating to the digestion, flow injection manifold and trapping in the atomizer were investigated, including a study of factors affecting the detection limit. It was found necessary to heat the digest under reflux at a temperature of 150°C for 2 h. Quantitative recoveries, from a human urine matrix, of selenite, selenate, trimethylselenium, selenocystine, selenopurine and selenomethionine spikes were obtained. The efficiency of hydride generation, transport and trapping was 75%. The major factors affecting the detection limit were the reagent purity and the volume injected. For high-purity hydrobromic acid and borohydride free of caking agent, the detection limit, based on three times the standard deviation of the blank, was 0.06 μg l −1 for a 1000 μl injection volume corresponding to a detection limit of 3 μg l −1 for a urine sample. The method was validated by the accurate analyses of Standard Reference Material 2670 from the National Institute of Standards and Technology, and urine samples from an interlaboratory comparison program. The procedure avoids the need for perchloric acid and produces selenium in the +4 oxidation state and thus no reduction is needed prior to generation of the hydrogen selenide. The use of a graphite furnace atomizer avoids the need for frequent reconditioning of the atomizer surface and the need for the standard additions method, both of which are drawbacks of procedures which make use of the quartz tube atomizer. All sample handling procedures following the digestion were automated by the use of flow injection technology.

Investigations Into the Role of Modifiers for Entrapment of Hydrides in Flow Injection Hydride Generation Electrothermal Atomic Absorption Spectrometry as Exemplified by the Determination of Germanium

Pd-conditioned graphite tubes, placed in the furnace of an AAS instrument, were used for entrapment of germane as generated in an associated flow-injection system. Two different approaches were tested with the ultimate aim of allowing multiple determinations, i.e. , introduction of the modifier as a Pd salt solution, and use of electrolytically Pd pre-coated tubes. While the former treatment resulted in satisfactory analytical performance, although requiring separate regeneration of the tubes prior to each sampling sequence, the electrolytically pre-coated tubes did not function satisfactorily. This in turn led to a closer investigation as to the function of Pd in entrapping hydrides and releasing the analyte. Based on an evaluation of the behaviour of the two types of tubes, supplemented by scanning tunnelling microscopy studies of tubes with and without modifier and treated in different ways, it is shown that heating at 2600 °C results in a physical–chemical change of the modifier in the electrolytically coated tubes; however, this change leads only to a loss of the ability of the modifier to entrap the hydrides, while the stabilizing effect is maintained.

Determination of germanium in environmental samples by electrothermal atomic absorption spectrometry with continuous flow hydride generation in dilute perchloric acid solution

A method has been developed for the sensitive determination of germanium by continuous flow hydride generation electrothermal atomic absorption spectrometry with trapping in a graphite atomizer pretreated with palladium. The optimal acidities using different acids for the generation of germanium hydride were studied. Germanium was found to give a sharp analytical signal in 0.05 mol l–1 H2SO4, 0.15 mol l–1 HNO3, and 0.10–0.15 mol l–1 HCl. Beyond these optimal acidities, significant loss of sensitivity resulted. Among the acids investigated only perchloric acid provided a wider range of acidity (0.15–0.6 mol l–1) giving maximum efficiency for the production of germanium hydride. Interferences from Ni, Cu, Fe, Mn and Sn on the generation of the hydride from 0.5 mol l–1 HClO4 were minimized by the addition of 0.1% EDTA. The characteristic mass which gave an integrated absorbance of 0.0044 s was found to be 46 pg. An absolute detection limit (3s) of 36 pg was obtained. The method was applied successfully in the determination of germanium in coal fly ash, soil and river sediments following the decomposition of the samples by heating in a mixture of acids using a pressure bomb.

Speciation of arsenic by ion chromatography and off-line hydride generation electrothermal atomic absorption spectrometry

Download options Please wait... Article information DOI https://doi.org/10.1039/JA9930801085 Article type Paper Download Citation J. Anal. At. Spectrom., 1993,8, 1085-1090 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Speciation of arsenic by ion chromatography and off-line hydride generation electrothermal atomic absorption spectrometry H. Heng-bin, L. Yan-bing, M. Shi-fen and N. Zhe-ming, J. Anal. At. Spectrom., 1993, 8, 1085 DOI: 10.1039/JA9930801085 To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Social activity Tweet Share Search articles by author Han Heng-bin Liu Yan-bing Mou Shi-fen Ni Zhe-ming

Determination of tributyltin and inorganic tin in sea-water by solvent extraction and hydride generation electrothermal atomic absorption spectrometry

An ultrasensitive method for the determination of tributyltin and inorganic tin has been developed by in situ concentration of tin hydrides on a zirconium coated graphite tube with subsequent detection by electrothermal atomic absorption spectrometry (ETAAS). Characteristic mass values of 20 and 14 pg were obtained for tributyltin and inorganic tin, respectively, where characteristic mass is defined as that mass of analyte which provides a defined peak absorbance of 0.0044 A. The relative standard deviations for ten replicate measurements were 5.6% for tributyltin and 3.4% for inorganic tin. For speciation studies, tributyltin was extracted in dichloromethane and determined by ETAAS. The sensitivity of tin in organic solution was about the same as that for inorganic tin in aqueous solution. The method proposed was applied to the analysis of water and satisfactory results were obtained.