Quartz Furnace Atomic Absorption Spectrometry Research Articles

Determination of selenium in food and environmental samples by hydride generation high-resolution continuum source quartz furnace atomic absorption spectrometry

The paper presents a method for Se determination in a wide variety of food and environmental samples by hydride generation high-resolution continuum source quartz furnace atomic absorption spectrometry.

UV-photochemical vapor generation with quartz furnace atomic absorption spectrometry for simple and sensitive determination of selenium in dietary supplements

This study describes the optimization and quantification of UV-photochemical vapor generation using the Se(IV) standard, together with application of the proposed technique for practical purposes. The generation process was performed in continuous mode and was combined with atomic absorption spectrometry utilizing an externally heated quartz furnace as an atomizer. Formic acid with a concentration of 0.5molL−1 acted as the photochemical agent during the UV-assisted conversion of Se(IV) from the condensed to the gaseous phase; no further chemicals were needed. A very low limit of detection (LOD) 40ngL−1 was achieved under the optimum experimental conditions and the repeatability expressed as % RSD was 1.8% at 5μgL−1 Se(IV). Analysis of the certified reference NIST SRM 1643e was performed to demonstrate the accuracy of the method with good correlation between the certified and experimentally achieved value. The effect of various coexisting ions on the selenium signal was also investigated. Finally, commercially available dietary supplements containing selenium in the form of inorganic Se(IV) and Se(VI) were analyzed. The yields attained using only simple ultrasonic-assisted extraction of Se compounds from the samples by deionized water did not differ by more than 15% compared to the producers of declared contents of selenium for four of the five samples tested.

Underestimation of total arsenic concentration in groundwater samples determined by hydride generation quartz furnace atomic absorption spectrometry due to sample characteristics

Total arsenic concentrations in groundwater samples determined by hydride generation quartz furnace atomic absorption spectrometry may underestimated due to a loss of quartz cell surface “conditioning.” This loss of quartz cell surface “conditioning” is due to the analysis of many samples that do not contain measurable quantities of the analyte. This process is further accelerated by the use of high concentrations of sodium tetrahydroborate and hydrochloric acid. Analysis of the highest calibration standard in between the samples and the use of low concentrations of sodium tetrahydroborate and hydrochloric acid could minimize the error arising from this source.

Cloud point extraction–thermospray flame quartz furnace atomic absorption spectrometry for determination of ultratrace cadmium in water and urine

A simple, low cost and highly sensitive method based on cloud point extraction (CPE) for separation/preconcentration and thermospray flame quartz furnace atomic absorption spectrometry was proposed for the determination of ultratrace cadmium in water and urine samples. The analytical procedure involved the formation of analyte-entrapped surfactant micelles by mixing the analyte solution with an ammonium pyrrolidinedithiocarbamate (APDC) solution and a Triton X-114 solution. When the temperature of the system was higher than the cloud point of Triton X-114, the complex of cadmium-PDC entered the surfactant-rich phase and thus separation of the analyte from the matrix was achieved. Under optimal chemical and instrumental conditions, the limit of detection was 0.04 μg/L for cadmium with a sample volume of 10 mL. The analytical results of cadmium in water and urine samples agreed well with those by ICP-MS.

On-line photoassisted vapour generation implemented in an automated flow-injection/stopped-flow manifold coupled to an atomic detector for determination of selenium

A flow-through UV reactor has been implemented in an automated flow-injection/stopped-flow manifold, and used for on-line generation of Se volatile derivatives prior to detection by quartz furnace atomic absorption spectrometry. The presence of a low molecular weight organic acid (formic or acetic) in the carrier was a necessary requirement so that efficient vapour generation was achieved. Stopped-flow conditions were employed with the aim of increasing the time for which the sample zone was subjected to UV irradiation while it was transported to the detector. The simultaneous formation of H2 during the photochemical decomposition of formic acid facilitated the atomization of the Se derivatives in the quartz furnace, and therefore the addition of H2 to the carrier gas, which is necessary for efficient atomisation, could be eliminated. Nevertheless, the presence of H2 in the carrier gas (Ar) was required for efficient atomisation when using acetic acid as carrier. This manifold allowed a sample throughput of 26 h−1 with a detection limit of 0.5 ng mL−1 Se and a repeatability, expressed as relative standard deviation, of 4%. Effect of concomitants in the online generation of Se vapours with the new manifold was investigated. Chloride salts of alkaline and alkaline-earth elements did not interfere at concentrations up to 10 000 mg L−1, but nitrate salts caused a positive effect. Tolerance of typical hydride-forming elements such as As and Sn was much higher with UV vapour generation as compared to chemical hydride generation. The presence of Cu(II) was critical since interference effects are observed from 0.05 mg L−1, but tolerance of Ni(II) was greater with UV vapour generation.

Determination of butyltin species in natural waters using aqueous phase ethylation and off-line room temperature trapping

Monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) were determined in natural water samples by aqueous phase ethylation with sodium tetraethylborate (STEB), room temperature trapping of the resulting volatile derivatives on Tenax TA ®, followed by gas chromatography–quartz furnace atomic absorption spectrometry (GC–QFAAS). Recoveries of butyltin spikes from natural water samples were 90–109% at concentrations of ∼100 ng Sn/l. The method precision at ∼100 ng Sn/l was ≤6% RSD for butyltins spiked into natural waters. The detection limits for 1 l water samples were <1 ng Sn/l for all butyltin species. Sample throughput of the method is high (greater than three samples per hour) due to the two-stage nature of the procedure, which allows derivatisation/trapping and GC–QFAAS quantitation to be performed separately. Off-line trapping is also advantageous as it extends the life of the GC column and quartz furnace to at least 12 months due to minimisation of carry-over of co-purged material.

Adsorption of aqueous inorganic mercury and methylmercury on suspended kaolin: influence of sodium chloride, fulvic acid and particle content

The main tendencies in the adsorption of dissolved inorganic mercury (Hg2+) and methylmercury (MeHg+) on suspended kaolin particles have been investigated in synthetic aqueous solutions. The influence of NaCl, fulvic acid (FA) and suspended particulate matter (SPM) in the system has been studied at a constant pH of 7.2. The experiments were arranged according to a full factorial design with three factors (NaCl, FA SPM) at low (−) and high (+) levels. A central point (0) was repeated four times to estimate the reproducibility of the results. The low and high levels investigated were 0–35 g l−1, 0–10 mg l−1 and 0.5–5 g l−1 for the concentrations of NaCl, FA and kaolin respectively. In order to match the linear range of the analytical technique the total concentration of mercury (as Hg2+ or MeHg+) in the synthetic suspensions was 25 ng ml−1. After chemical stabilization of each suspension, the Hg2+ or MeHg+ content in the clear filtrate was determined by an automated hyphenated technique combining the following steps: (i) derivatization by hydride generation, (ii) preconcentration by cryogenic trapping, (iii) separation by packed column gas chromatography and (iv) detection by quartz furnace atomic absorption spectrometry. The removal of Hg2+ and MeHg+ from the solution via adsorption on particles ranged, respectively, from 12.4 to 94.9% and from 1.7 to 45.6% of the total mercury compound concentration. High concentrations of NaCl led to lower adsorption rates of both mercury species. The adsorption of MeHg+ was enhanced in the presence of FA, whereas that of Hg2+ was clearly diminished. High levels of SPM promoted the adsorption of both Hg2+ and MeHg+ on kaolin particles. Several experiments were also conducted to check the adsorption rate of Hg2+ and MeHg+ on natural particles collected in the Gironde estuary. The results confirmed the general trends observed when using reference kaolin particles. The results presented here will be helpful for groups modelling the physico-chemical behaviour of mercury in estuary conditions. Copyright © 2001 John Wiley & Sons, Ltd.

Adsorption of aqueous inorganic mercury and methylmercury on suspended kaolin: influence of sodium chloride, fulvic acid and particle content

AbstractThe main tendencies in the adsorption of dissolved inorganic mercury (Hg2+) and methylmercury (MeHg+) on suspended kaolin particles have been investigated in synthetic aqueous solutions. The influence of NaCl, fulvic acid (FA) and suspended particulate matter (SPM) in the system has been studied at a constant pH of 7.2. The experiments were arranged according to a full factorial design with three factors (NaCl, FA SPM) at low (−) and high (+) levels. A central point (0) was repeated four times to estimate the reproducibility of the results. The low and high levels investigated were 0–35 g l−1, 0–10 mg l−1 and 0.5–5 g l−1 for the concentrations of NaCl, FA and kaolin respectively. In order to match the linear range of the analytical technique the total concentration of mercury (as Hg2+ or MeHg+) in the synthetic suspensions was 25 ng ml−1. After chemical stabilization of each suspension, the Hg2+ or MeHg+ content in the clear filtrate was determined by an automated hyphenated technique combining the following steps: (i) derivatization by hydride generation, (ii) preconcentration by cryogenic trapping, (iii) separation by packed column gas chromatography and (iv) detection by quartz furnace atomic absorption spectrometry. The removal of Hg2+ and MeHg+ from the solution via adsorption on particles ranged, respectively, from 12.4 to 94.9% and from 1.7 to 45.6% of the total mercury compound concentration. High concentrations of NaCl led to lower adsorption rates of both mercury species. The adsorption of MeHg+ was enhanced in the presence of FA, whereas that of Hg2+ was clearly diminished. High levels of SPM promoted the adsorption of both Hg2+ and MeHg+ on kaolin particles. Several experiments were also conducted to check the adsorption rate of Hg2+ and MeHg+ on natural particles collected in the Gironde estuary. The results confirmed the general trends observed when using reference kaolin particles. The results presented here will be helpful for groups modelling the physico‐chemical behaviour of mercury in estuary conditions. Copyright © 2001 John Wiley &amp; Sons, Ltd.

Determination of methylcyclopentadienyl-manganese tricarbonyl by solid phase microextraction-direct thermal desorption-quartz furnace atomic absorption spectrometry

A new procedure that uses a pre-concentration system based on solid phase microextraction (SPME) and detection by quartz furnace-atomic absorption spectrometry after thermal desorption from the microextraction fiber has been proposed for the determination of methylcyclopentadienylmanganese tricarbonyl (MMT) in gasoline and water. Working MMT solutions were prepared in 40 ml amber vials, and sampling was performed by exposing the SPME fiber to the headspace over vigorously stirred samples for 15 min. The analytical performance characteristics of the proposed procedure were as follows: the detection limit for MMT was 0.71 ng ml −1 (as Mn), with a relative standard deviation of 4% for MMT determination of 25 ng ml −1 (as Mn, n=6) while the calibration curve was linear up to 100 ng ml −1 range. The proposed procedure was finally applied to the determination of MMT in gasoline and water samples and non significant differences (Student's t-test) were found between obtained values (using direct calibration and standard additions) and those expected values.

Determination of tetraethyllead by solid phase microextraction–thermal desorption–quartz furnace atomic absorption spectrometry

A new procedure that uses a preconcentration system based on solid phase microextraction (SPME) and detection by quartz furnace atomic absorption spectrometry after thermal desorption from the microextraction fiber has been proposed for the determination of tetraethyllead in gasoline (leaded and unleaded) and water. Three different volatilizators were designed and their influence in the thermal desorption of tetraethyllead was studied. Working tetraethyllead solutions were prepared in 40 ml amber vials and sampling was performed by exposing the SPME fiber to the headspace over vigorously stirred samples for 10 min. The analytical performance characteristics of the proposed procedure were as follows: the detection limit for tetraethyllead was 0.43 ng ml−1, with a relative standard deviation of 6% for determination of 10 ng ml−1 of tetraethyllead (n = 5) while the calibration curve was linear up to 50 ng ml−1 range. The proposed procedure was finally applied to the determination of tetraethyllead in gasoline and water samples obtaining a good agreement with those values obtained by an alternative method that included the direct injection of tetraethyllead, via a septum, in the heated volatilizator with a gas chromatographic syringe, the tetraethyllead volatilisation and its transport by the gas carrier to the quartz furnace, where the analytical signal was observed. This procedure could be easily adapted for the speciation of ionic lead and tetraethyllead.

Arsenic speciation in some environmental samples: a comparative study of HG-GC-QFAAS and HPLC-ICP-MS methods

Some water and soil extracts polluted with arsenic, and a sewage sludge certified for total arsenic have been analysed by high-performance liquid chromatography–inductively coupled plasma–mass spectrometry (HPLC–ICP–MS) and hydride generation–gas chromatography– quartz furnace atomic absorption spectrometry (HG–GC–QFAAS techniques.) Detection limits in the range of 200–400 and 2–10 ng l−1 respectively allowed the determination of inorganic [As(III), As(V)] and methylated (DMA, MMA, TMAO) arsenic species present in these samples. Results obtained by both methods are well correlated overall, whatever the arsenic chemical form and concentration range (8–10 000 μg l−1). Comparison of these results enabled us to point out features and disadvantages of each analytical method and to reach a conclusion that they are suitable for arsenic speciation in these environmental matrices. Copyright © 2000 John Wiley & Sons, Ltd.

Analysis of organomercuric species in soils from orchards and wheat fields by capillary gas chromatography on-line coupled with atomic absorption spectrometry after in situ hydride generation and headspace solid phase microextraction

A convenient procedure for the determination of organomercuric compounds in soils from orchards and wheat fields is described based on the aqueous derivatization of the polar organomercuric halides in 0.1 M HAc-NaAc (pH 4) buffer into their hydrides by addition of 1 mL of 6% KBH4 with subsequent headspace solid phase microextraction (SPME) of the volatile derivatives. The volatile derivatives are separated by gas chromatography (GC) with a Supelco SPB-1 capillary column and on-line detected by electric heated quartz furnace atomic absorption spectrometry (AAS). The relative standard deviations for ten replicate measurements are 2.1%, 2.8% and 3.5% for methyl-, ethyl- and phenylmercury with absolute detection limits of 16 ng, 12 ng and 7 ng, respectively. This method is applied to the analysis of organomercuric compounds in soil samples and 0.04–0.64 μg/g of organomercuric species are detected in soils from different sites. The recoveries after standard addition are between 93–106%.

An analytical method for the detection of methylantimony species in environmental matrices: methylantimony levels in some UK plant material

We report, using sodium borohydride (NaBH4) derivatizing agent with purge and trap quartz furnace atomic absorption spectrometry (QF-AAS), a method for the detection of methylantimony compounds from environmental matrices and samples. The generation of trimethylantimony as a standard compound has also been examined using (CH3)3SbCl2. This method has been reported previously to produce not only (CH3)3Sb but mixtures of (CH3)2SbH, CH3SbH2 and SbH3 when solutions of (CH3)3SbCl2 were derivatized. Rigorous exclusion of oxygen combined with rapid purging of reduced analytes into a cold trap has reduced these by-products to undetectable levels. These results are of importance in view of the increasing importance of the role of organoantimony species in the natural environment, which depends on the reliability of speciation produced by the hydride generation method. Levels of methylantimony found in some UK plant samples are in the 100–200 ng g–1 range. This is the first report of methylantimony species from the UK natural environment.

Cryofocusing coupled to atomic absorption spectrometry for rapid and simple mercury speciation in environmental matrices

A fully automated on-line hyphenated system for mercury speciation analysis in environmental samples is presented. It provides derivatization by hydride generation or ethylation, preconcentration by cryotrapping, separation by packed column gas chromatography and detection by quartz furnace atomic absorption spectrometry. Automation of the hyphenation results in improved reproducibility of the analysis. The system has been specifically optimised for analysis of mercury compounds, but it is also potentially operative for other hydride- or ethylated derivative-forming elements, after the corresponding optimisation. Main advantages and potential limitations of the system are discussed. General procedures for the analysis of both solid (sediments, biotissues, suspended particulate matter) and liquid (sea and fresh water) samples are proposed and validated by analysis of certified reference materials. The obtained methylmercury and inorganic mercury concentrations are in agreement with the certified values. Detection limits of the method have been estimated as 0.5 ng g–1 , 3 ng g–1 , 0.1 ng l–1 for both mercury species in dry sediments, biological tissues and aqueous samples, respectively. Analysis of one sample only requires 10 min (hydride generation) or 20 min (ethylation), so that a sample throughout of 6 or 3 samples h–1, respectively, may be achieved. Results from the analysis of real samples collected in the Gironde and Scheldt estuaries (sediments, suspended particulate matter, water and biological tissues) are also provided.

Microwave-accelerated speciation analysis for butyltin compounds in sediments and biomaterials by large volume injection capillary gas chromatography quartz furnace atomic absorption spectrometry

A method for speciation analysis of butyltins in sediments and biomaterials by capillary GC with atomic absorption spectrometric detection was developed. Mono-, di- and tributyltin in sediments were quantitatively leached with 50% acetic acid, whereas biomaterials were dissolved in a 25% tetramethyl ammonium hydroxide (TMAH) solution; both processes were completed under the action of a low-power focused microwave field within 1–5 min which is 20–100 times faster than with conventional procedures. The butyltins were derivatized with sodium tetraethylborate (NaBEt 4) in the aqueous phase, and simultaneously extracted into hexane (5 min). On-line preconcentration in the injector liner by solvent venting enabled to obtain a detection limit of 5 ng g −1 for 0.2 g of dry sample. A sample throughput of 5 samples h −1 was achieved. The method developed was validated by analyzing three certified reference materials: PACS-1, CRM 462 and NIES 11.

Optimization of atomization parameters in the speciation of organotin compounds by hydride generation–gas chromatography–electrothermal atomic absorption spectrometry

The detection of organotin hydrides by electrothermal (quartz furnace) atomic absorption spectrometry coupled on-line with hydride generation is closely dependent on several parameters such as the geometry of the quartz cell and the flow rates of additive gases. The influence of the design of the atomizer and the effects of the gas flow rates were evaluated in this study. The design of the quartz cell atomizer is not critical provided that a few rules are followed: the helium flow carrying organotin hydrides should be mixed with hydrogen in as small as possible dead volume (no mixing chamber) and oxygen introduction should be made as close as possible to the light path. The ratios of gas flow rates must be optimized for each cell design, the most important being the H2:O2 ratio chosen to produce highly reducing working conditions. Detection limits obtained after optimization ranged from 30 to 130 pg depending on the conditions and species.

Quality control in the speciation analysis of butyltin compounds in marine biological samples by hydride generation–cold trapping and on‐line quartz furnace atomic absorption spectrometry

AbstractThe determination of tributyltin (TBT) in sea food (mussel, oyster, fish) by a hydride generation–cold trapping–quartz furnace atomic absorption spectrometry procedure has been studied with emphasis on quality control. Large amounts of spiked materials have been prepared and stored either frozen, or frozen after freeze‐drying. Extraction of TBT by 0.1 M hydrochloric acid in methanolic solution is efficient (88–96%) for wet samples or freeze‐dried samples. It is also efficient with freshly spiked materials. Consumption of sodium borohydride by the matrix makes it necessary to use quite large amounts of reagent to obtain optimal sensitivity. Analysis of a fish‐tissue Certified Reference Material seems to indicate a partial debutylation of TBT during transport and/or storage of this material.

Pentylated organotin standards: Guidelines for their synthesis, purity control and quantification

AbstractPentylated derivatives of six environmentally important organotin compounds were obtained by using a Grignard derivatization. The purity of these pentylated calibrants was checked by gas chromatography–quartz furnace atomic absorption spectrometry (GC QFAA) and gas chromatography–mass spectrometry ion‐trap detection (GC MS‐ITD). Through combination of the total tin contents of every pentylated organotin standard, obtained after wet acid destruction of 0.5 ml of the respective calibrant, and the species composition or impurities present in the same standard, a well‐defined pentylated organotin standard was obtained which could be used to calibrate GC QFAA and GC atomic emission detection (AED) systems.In a similar way aqueous organotin standards can be obtained, which can be used in spiking experiments to verify the recovery efficiency of a developed analytical extraction procedure for organotins.

Speciation of butyltin compounds in sediments using gas chromatography interfaced with quartz furnace atomic absorption spectrometry

A method is presented for the determination of tri- and dibutyltin in sediments by gas chromatography—quartz furnace atomic absorption spectrometry. The compounds are released from the matrix by the action of acetic acid and extracted into hexane after formation of an extractable complex with diethyldithiocarbamic acid (DDTC). Pentylmagnesium bromide is used to derivatize the non-volatile organotin—carbamate complexes. A detection limit of 2.5 ng/g (as Sn) can be achieved. The optimization of the different parameters is discussed and the accuracy of the method was validated by the analysis of two certified reference materials. A first approach was made to determine tri- and dimethyltin compounds forming extractable complexes with NaDDTC under pH controlled conditions.

Extraction and determination of butylin compounds in shellfish by hydride generation—gas chromatography—quartz furnace atomic absorption spectrometry

The method described involves the conversion of butyltin compounds extracted from shellfish into volatile hydrides by sodium tetrahydroborate, cryogenic trapping and selective volatilization followed by on-line quartz furnace atomic absorption spectrometric detection. Several sample pretreatment procedures were compared with emphasis on their accuracy, reproducibility and respect for the speciation of tin. Digestion with 0.083 M HCl in 16.7% methanol under sonication for 1 h is proposed. The recoveries of mono-, di- and tributyltin compounds from spiked mussel and oyster samples ranged from 96 to 99% with low degradation of butyltins (< 9%). Detection limits were in the 2–3 ng Sn g −1 (wet weight) range. The method was applied to wild and commercial samples of oysters. mussels and scallops and fairly high concentrations of butyltin compounds were measured.