Furnace Atomic Absorption Spectrometric Determination Research Articles

Investigation of thermospray flame furnace atomic absorption spectrometric determination of cadmium combined with ultrasound-assisted dispersive liquid-liquid microextraction

ABSTRACT Ultrasound-assisted dispersive liquid-liquid microextraction (UA-DLLME) was combined with thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) for the first time to develop a highly sensitive method for the determination of cadmium. Ultrasound was used to assist the liquid phase extraction, replacing the traditional disperser solvent. A self-assembled TS-FF-AAS instrument was adopted to improve the analytical performance of traditional flame atomic absorption spectrometry (FAAS), and the characteristic of micro-injection is fully suitable to be coupled with UA-DLLME. The developed combination significantly improved the analytical performance of TS-FF-AAS and traditional FAAS, while overcoming problems of nebulisation associated with the coupling of FAAS and liquid phase extraction methods. Some environmental water samples were collected and analysed by the developed coupling with satisfactory results.

Thermoresponsive polymer-mediated extraction for graphite furnace atomic absorption spectrometric determination of trace metals in high purity iron

A thermoresponsive polymer-mediated extraction was designed for the selective separation of traces metal ions from high purity iron solutions. Traces metals were extracted into the coagulum of a thermoresponsive polymer, poly(N-isopropylacrylamide) as their dibenzyldithiocarbamate chelates, while Fe(III) matrix remained in the bulk aqueous solution as its water-soluble tartrate chelate. The coagulum was readily collected from the solution and then dissolved with a small amount of N,N-dimethylformamide for the introduction to a graphite furnace of atomic absorption spectrometer. The use of 0.5gl−1 poly(N-isopropylacrylamide), 2.0mM sodium dibenzyldithiocarbamate, and 0.6M diammonium tartrate (pH10.7) allowed nearly complete (>99.9%) collection of Co(II), Ni(II), Cu(II), Cd(II), Pb(II), and Bi(III) with reducing Fe(III) concentration from 50mgml−1 to 14±1μgml−1 being lower than the tolerance limits for the determination of traces of metals. Because of effective elimination of iron matrix, six metals at fractional μgg−1 levels were successfully determined with high reproducibility. The accuracy and precision were evaluated by analyzing certified reference materials of high purity iron.

Graphite furnace atomic absorption spectrometric determination of vanadium after cloud point extraction in the presence of graphene oxide

Vanadium (V) and vanadium (IV) in the presence of a small concentration of graphene oxide (0.05mgmL−1) are quantitatively transferred to the coacervate obtained with Triton X-114 in a cloud point microextraction process. The surfactant-rich phase is directly injected into the graphite atomizer of an atomic absorption spectrometer. Using a 10-mL aliquot sample and 150μL of a 15% Triton X-114 solution, the enrichment factor for the analyte is 103, which results in a detection limit of 0.02μgL−1 vanadium. The separation of V(V) and V(IV) using an ion-exchanger allows speciation of the element at low concentrations. Data for seven reference water samples with certified vanadium contents confirm the reliability of the procedure. Several beer samples are also analyzed, those supplied as canned drinks showing low levels of tetravalent vanadium.

Chemical vapor generation of bismuth in non-aqueous phase based on cloud point extraction coupled with thermospray flame furnace atomic absorption spectrometric determination

A novel method for the chemical vapor generation (CVG) of bismuth in non-aqueous phase based on cloud point extraction (CPE) coupled with thermospray flame furnace atomic absorption spectrometric (TS-FF-AAS) determination was developed. The method is based on the complex of bismuth with ammonium pyrrolidine dithiocarbamate (APDC). When the temperature of the system was higher than the cloud point of Triton X-100, Bi-APDC complex was extracted into Triton X-100 and separation of the analyte from the matrix was achieved. Volatile species of Bi were effectively generated through reduction of the extraction organic phase with solid KBH4 in non-aqueous phase. Some parameters that influenced CVG, extraction and subsequent determination were evaluated in detail, such as the concentrations of Triton X-100 and APDC, pH and extraction time, flow rates of carrier gas, as well as interferences. Under optimized conditions, the detection limit (LOD) for Bi was 8ngmL−1. Relative standard deviation for five replicate determinations of the standard solution containing 200ngmL−1 Bi was 3.8%. The proposed method was successfully applied to the determination of Bi in natural water samples, ore samples and certified reference materials with satisfactory results.

Enhancement effect of room temperature ionic liquids on the chemical vapor generation of lead, cadmium and bismuth for thermospray flame furnace atomic absorption spectrometric determination

A novel method was developed for the chemical vapor generation (CVG) of lead, cadmium and bismuth based on the enhancement effect of room temperature ionic liquids followed by thermospray flame furnace atomic absorption spectrometry (TS-FF-AAS) determination. Room temperature ionic liquids (RTILs) and ammonium pyrroldinedithiocarbamate (APDC) were used as enhancement reagents and chelating reagents for the CVG of lead, cadmium and bismuth, respectively. TS-FF-AAS was used for the determination of lead, cadmium and bismuth. The addition of RTILs led to an improvement of 3.5, 3.0 and 4.0 times the CVG efficiencies of Pb, Cd and Bi, respectively. The efficiencies for the CVG of Pb, Cd and Bi in the presence of RTILs and APDC were 55%, 46% and 60%, respectively. Volatile species of Pb, Cd and Bi were effectively generated through reduction of acidified analyte solutions with KBH4 in the presence of 0.02% (m/v) APDC and 0.1% (v/v) 1-butyl-3-methylimidazolium tetrafluoroborate ([C4MIM]BF4). Some parameters that influenced CVG and the subsequent determinations were evaluated in detail, such as the concentrations of RTILs, APDC, HNO3 and KBH4; the flow rates of the carrier gas, lengths of the reaction tube and transfer tube, as well as interferences. Under optimized conditions, the detection limits for Pb, Cd and Bi were 8, 1 and 5 ng mL−1, respectively. Relative standard deviations for five replicate determinations of a standard solution containing 200 ng mL−1 Pb, Cd and Bi were 4.5%, 5.5% and 5.2%, respectively. The proposed method was successfully applied in the determination of Pb, Cd and Bi in certified environmental reference materials with satisfactory results.

Cloud point extraction for the determination of trace amounts of Pt(iv) by graphite furnace atomic absorption spectrometry

A cloud point extraction (CPE) system for the graphite furnace atomic absorption spectrometric (GFAAS) determination of Pt(IV) has been developed. The procedure is based on the complexation of Pt(IV) with 4-(p-chlorophenyl)-1-(pyridin-2-yl)thiosemicarbazide (HCPTS) in the presence of Triton X-114 as a non-ionic surfactant. The optimum conditions for the procedure were investigated with respect to several experimental parameters such as pH of the solution, Triton X-114 and HCPTS concentrations, incubation time and temperature, and centrifugation rate and time. Under the optimum experimental conditions, the calibration curve was linear up to 50 ng mL−1 with a detection limit of 0.25 ng mL−1 and the enrichment factor was 47. No considerable interference was observed due to the presence of coexisting anions and cations. The accuracy of the results was verified by analyzing the spiked water from different sources (tap, river, brackish, sea and industrial waste water). The proposed method has been applied for the determination of Pt(IV) in some real samples such as food and geological samples with satisfactory results.

A novel approach in dispersive liquid–liquid microextraction based on the use of an auxiliary solvent for adjustment of density: UV–VIS spectrophotometric and graphite furnace atomic absorption spectrometric determination of gold based on ion pair formation

This paper presents a novel approach to dispersive liquid–liquid microextraction (DLLME), based on the use of an auxiliary solvent for the adjustment of density. The procedure utilises a solvent system consisting of a dispersive solvent, an extraction solvent and an auxiliary solvent, which allows for the use of solvents having a density lower than that of water as an extraction solvent while preserving simple phase separation by centrifugation. The suggested approach could be an alternative to procedures described in the literature in recent months and which have been devoted to solving the same problem. The efficiency of the suggested approach is demonstrated through the determination of gold based on the formation of the ion pair [Au(CN) 2] − anion with Astra Phloxine (R) reagent and its extraction using the DLLME procedure with subsequent UV–VIS spectrophotometric and graphite furnace atomic absorption spectrometric detection. The optimum conditions were found to be: pH 3; 0.8 mmol L −1 K 4[Fe(CN) 6]; 0.12 mmol L −1 R; dispersive solvent, methanol; extraction solvent, toluene; auxiliary solvent, tetrachloromethane. The calibration plots were linear in the ranges 0.39–4.7 mg L −1 and 0.5–39.4 μg L −1 for UV–VIS and GFAAS detection, respectively; thus enables the application of the developed method in two ranges differing from one from another by three orders of magnitude. The presented approach can be applied to the development of DLLME procedures for the determination of other compounds extractable by organic solvents with a density lower than that of water.

Graphite furnace atomic absorption spectrometric determination of cadmium after solid-liquid extraction with dithizone

A method for the determination of trace amount of cadmium ion after preconcentration by extracting its dithizone complex into molten naphthalene was developed. Several experimental conditions such as pH of the solution, stirring time, the amounts of naphthalene, standing time and volume of the solution were optimized. Trace amount of cadmium ion in aqueous solution of sample was chelated with 5 mL of 0.001 M dithizone at pH 8. After addition of 0.15 g naphthalene, the solution was heated to about 85 oC and stirred (800 rpm) for 2 min to reproduce the microcrystalline naphthalene. Cadmium ion was determined by a graphite furnace atomic absorption spectrometer. The interfering effects of diverse concomitant ions (cations and anions) were investigated. Artificial sea water and a standard reference material (SRM) were analyzed by this method. The sensitivity and detection limit of 1.2 ngL -1 and 1.5 ng L -1 were found, respectively.

Graphite furnace and hydride generation atomic absorption spectrometric determination of cadmium, lead, and tin traces in natural surface waters: Study of preconcentration technique performance

In this study three major types of preconcentration methods based upon different principles (cation exchange, physical absorption and hydrophobic extraction) were evaluated and optimized for the extraction and determination of three highly toxic heavy metals namely Cd, Pb and Sn by graphite furnace and hybrid generation atomic absorption spectrometry in real samples. The optimum analytical conditions were examined and the analytical features of each method were revealed and compared. Detection limits as low as 0.003–0.025 μg L −1 for Cd 2+, 0.05–0.10 μg L −1 for Pb 2+ and 0.1–0.25 μg L −1 for Sn 4+ depending on the extraction method were obtained with RSD values between 3.08% and 6.11%. A preliminary assessment of the pollution status of three important natural ecosystems in Epirus region (NW Greece) was performed and some early conclusions were drawn and discussed.

Biosorption of aluminum on Pseudomonas aeruginosa loaded on Chromosorb 106 prior to its graphite furnace atomic absorption spectrometric determination

A biosorption procedure for separation-enrichment of aluminum in environmental samples has been presented in this work. Pseudomonas aeruginosa loaded on Chromosorb 106 has been used as biosorbent for that purpose. P. aeruginosa is a gram-negative, aerobic rod. The influences of pH of the aqueous solution, eluent type, eluent volume, sample volume, etc. were examined on the quantitative recovery of aluminum in P. aeruginosa loaded on Chromosorb 106. The effects of concomitant ions on the recoveries of aluminum were also investigated. The detection limit based on 3 sigma for aluminum is 30 ng L −1. Three certified reference materials (LGC 6010 Hard Drinking Water, NIST-SRM 1568a Rice Flour and NRCC-DORM-2 Dogfish Muscle) were analyzed for the validation of the presented procedure. The proposed procedure was applied to the determination of aluminum in environmental samples including natural water and food samples. The concentration of aluminum in real samples was found at ppb level.

Speciation of selenium(IV) and selenium(VI) in environmental samples by the combination of graphite furnace atomic absorption spectrometric determination and solid phase extraction on Diaion HP-2MG

A simple solid phase extraction procedure for speciation of selenium(IV) and selenium(VI) in environmental samples has been proposed prior to graphite furnace atomic absorption spectrometry. The method is based on the solid phase extraction of the selenium(IV)–ammonium pyrrolidine dithiocarbamate (APDC) chelate on the Diaion HP-2MG. After reduction of Se(VI) by heating the samples in the microwave oven with 4 mol l −1 HCl, the system was applied to the total selenium. Se(VI) was calculated as the difference between the total selenium content and Se(IV) content. The experimental parameters, pH, amounts of reagents, eluent type and sample volume were optimized. The recoveries of analytes were found greater than 95%. No appreciable matrix effects were observed. The adsorption capacity of sorbent was 5.20 mg g −1 Se (IV). The detection limit of Se (IV) (3sigma, n = 11) is 0.010 μg l −1. The preconcentration factor for the presented system was 100. The proposed method was applied to the speciation of selenium(IV), selenium(VI) and determination of total selenium in natural waters and microwave digested soil, garlic, onion, rice, wheat and hazelnut samples harvested various locations in Turkey with satisfactory results. In order to verify the accuracy of the method, certified reference materials (NIST SRM 2711 Montana Soil, NIST SRM 1568a Rice Flour and NIST SRM 8418 Wheat Gluten) were analyzed and the results obtained were in good agreement with the certified values. The relative errors and relative standard deviations were below 6 and 10%, respectively.

Monitoring of V(IV) and V(V) in Etnean drinking-water distribution systems by solid phase extraction and electrothermal atomic absorption spectrometry

Monitoring activities carried out since 1994 showed the presence of significant levels of vanadium in drinking waters delivered in a lot of Etnean towns. The highest vanadium concentration was found in ground waters collected in the drainage gallery Ciapparazzo located on the Northwestern flank of Mt. Etna in Bronte's area (Catania, Italy). This drainage gallery, with a flow rate of near 500 l s − 1 , is an important water source for several towns of the Etnean province. On account of different toxicological behaviours of V(IV) and V(V), which are the only possible oxidation states in aqueous media, a research project was set up to evaluate the ratio between their concentrations before and after disinfection treatments (chlorination or UV irradiation). Data were acquired in the most representative sites of the drainage gallery and the distribution network to evaluate the effect of residence times and disinfection treatments on possible species interconversion. The average total concentration of vanadium was 165 μg l − 1 . Speciation analyses performed by solid phase extraction of both species followed by furnace atomic absorption spectrometric determination of V(IV) eluates revealed that the latter was the predominant species (90–100%) in untreated waters. Moreover, among the two disinfecting treatments applied by the water supplier, only sodium hypochlorite altered the species ratio and determined an instant increase of near 20% in V(V) relative concentration. No significant effect was observed as residence time varied in the drainage gallery or in the distribution systems. Other physico-chemical and chemical parameters (i.e. pH, E H, water temperature, electrical conductance, dissolved oxygen as well as major and minor inorganic cations and anions) were determined in the collected water samples to evaluate if they are proper or not for interconversion of the two V species. Redox potential of the water was also correlated to the percentage of V(IV).

Separation and speciation of selenium in food and water samples by the combination of magnesium hydroxide coprecipitation-graphite furnace atomic absorption spectrometric determination

A simple and economic separation and speciation procedure for selenium in food and water samples have been presented prior to its graphite furnace atomic absorption spectrometry (GFAAS). Magnesium hydroxide coprecipitation system for selenium(IV) was applied to the separation and speciation of selenium ions. The influences of the various analytical parameters for the quantitative recoveries of selenium ions like pH, amounts of magnesium ions as carrier elements, etc. on were examined. The effects of the alkaline and earth alkaline metals, some transition metals and some anions on the recoveries of selenium(IV) were also investigated. The recoveries of analytes were found greater than 95%. No appreciable matrix effects were observed. The detection limit, defined as three times the blank standard deviation (3 σ), was 0.030 μg l −1. The preconcentration factor for the presented system was 25. The proposed method was applied to the speciation of selenium(IV), selenium(VI) and determination of total selenium in natural waters and microwave digested various food samples with satisfactory results. The procedure was validated with certified reference materials. The relative errors and relative standard deviations were below 6% and 10%, respectively.

A solid phase extraction procedure for Indium prior to its graphite furnace atomic absorption spectrometric determination

A procedure based on solid phase extraction of indium ions at trace level on Chromosorb 108 resin as bathocuproinedisulfonic acid chelate is presented for its preconcentration. The optimum pH value for quantitative sorption is 8.0–9.0, and desorption can be achieved by using 10.0 ml of 2 M HNO 3. The effects of diverse ions on the sorption and recovery of indium have been studied. The capacity of sorbent was 3.78 mg In/g resin. Recoveries for indium from water samples were in the range 95–105%. The accuracy of procedure was confirmed by indium determination in certified reference materials. The method developed was applied with varying results to the analysis of real samples including metallic zinc with satisfactory results.

Graphite furnace atomic absorption spectrometric determination of Ni and Pb in diesel and gasoline samples stabilized as microemulsion using conventional and permanent modifiers

A procedure for the graphite furnace atomic absorption spectrometric determination of Ni and Pb in diesel and gasoline samples was developed. Sample stabilization was necessary because of evident analyte losses that occurred immediately after sampling. Excellent long-term sample stabilization was observed by mixing different organic solvents with propan-1-ol and 50% vol/vol HNO 3 at a 3.3:6.5:1 volume ratio. For Pb, efficient thermal stabilization was obtained using aqueous Pd–Mg modifier as well as for Ir as permanent modifier. The drying temperature and ramp rate influenced the sensitivity obtained for Ni, and had to be carefully optimized. Taking this into account, the same sensitivity was attained in all investigated organic media stabilized as microemulsion. Thus, calibration with microemulsions prepared with a single organic solvent was possible, using aqueous or organic stock solutions. Commercial gasoline and diesel samples were directly analyzed after stabilization as microemulsion and by comparative UOP procedures. n-Hexane microemulsions were used for calibration, and good agreement was obtained between the results using the proposed and comparative procedures. Typical coefficients of variation ( n = 6) ranged from 1% to 4%, and from 1% to 3% for Ni and Pb, respectively. Detection limits ( k = 3) in the original gasoline or diesel samples, derived from 10 blank measurements, were 4.5 and 3.6 μg l − 1 for Ni and Pb, respectively, comfortably below the values found in the analyzed samples.

The study of applicability of dithiocarbamate-coated fullerene C 60 for preconcentration of palladium for graphite furnace atomic absorption spectrometric determination in environmental samples

The present method comprises an off-line enrichment of Pd on the fullerene, C 60, coated with ammonium pyrrolidinedithiocarbamate (APDC), followed by the elution of formed Pd-chelate with ethanol and the subsequent determination of Pd from the eluate by graphite furnace atomic absorption spectrometry. By using fullerene loaded with 0.1% APDC, the analytical system is simplified as the sample can be directly preconcentrated on the column. The following parameters affecting the preconcentration of Pd on C 60 were optimized: amount of ligand used for the coating of fullerene, sample pH, kind of eluent, sample and eluent flow rates, volume and number of fractions of eluent used. The sorption efficiency for Pd on coated fullerene was 99.2±1.1%. The best elution efficiency for Pd from the column was obtained with 0.6 ml of ethanol at a flow rate of 0.2 ml min −1. The limit of detection was 0.044 ng ml −1. The effect of sample pretreatment procedure on the preconcentration of Pd by evaluated method is discussed. The content of Pd in road dust (179.2±17.4 ng g −1) determined by proposed method was in agreement with the results obtained with a reference method. The low recovery of analyte (64%) was obtained for geological material CRM SARM-7 (platinum ore) due to the much higher concentration of interfering elements.

Graphite Furnace Atomic Absorption Spectrometric Determination of Rhodium after Online Ion‐Exchange Preconcentration

A method for the determination of rhodium in different samples at trace levels is presented. The investigated metal is preconcentrated on a chelating resin microcolumn [1,5‐Bis(2‐pyridyl)‐3‐sulphophenyl methylene thiocarbonohydarzide (PSTH) immobilized on an anion‐exchange resin (Dowex 1x 8‐200)] placed in the autosampler arm. The modification of the autosampler in the tubing line and circuit allowed either the flow of the sample through the column or the operation of the autosampler in the normal mode, where microlitres of 4 M HNO3, which acts as the elution agent, pass through the microcolumn eluting Rh(III), which is directly deposited in the graphite tube as a drop of a precisely defined volume. The detection limit is 0.3 ng mL−1. Linearity is maintained in the concentration range 0–50 ng mL−1 for rhodium, with correlation factor of 0.999 and relative standard deviation of 1.8% for 10 ng mL−1 of Rh. The effects of various parameters such as pH, concentration and volume of eluent, sample loading time, sample flow rate, and interference of a large number of metal ions and anions on the determination of this metal was studied in detail to optimize the conditions for their determination in various samples. The method is found to be highly selective, fairly sensitive, simple, rapid and economical, and may be safely applied to their determination in different complex materials, such as environmental samples and catalysts.

Biosorption of platinum and palladium for their separation/preconcentration prior to graphite furnace atomic absorption spectrometric determination

Inexpensive baker's yeast Saccharomyces cerevisiae and green algae Chlorella vulgaris, either free or immobilized on silica gel have been shown to selectively accumulate platinum and palladium from water samples in acidic medium (pH 1.6–1.8). Optimization of conditions of metals biosorption (sample pH, algae and yeast masses, adsorption time, temperature) was performed in batch mode. The procedure of matrix separation based on biosorption of platinum and palladium on algae C. vulgaris covalently immobilized on silica gel in flow mode was developed. The use of algae in flow procedure offers several advantages compared with its use in the batch mode. The procedure shows better reproducibility (<2%), improved efficiency of platinum retention on the column (93.3±1.6%), is less laborious and less time consuming. The best recovery of biosorbed metals from column (87.7±3.3% for platinum and 96.8±1.1 for palladium) was obtained with solution of 0.3 mol l −1 thiourea in 1 mol l −1 hydrochloric acid. The influence of thiourea on analytical signals of examined metals during GFAAS determination is discussed. The procedure has been applied for separation of noble metals from tap and waste water samples spiked with platinum and palladium.

Graphite Furnace Atomic Absorption Spectrometric Determination of Lead and Cadmium Extracted from Ceramic Foodware: Collaborative Study

A modification of the official flame atomic absorption spectrometric (FAAS) method for determining lead and cadmium extracted from ceramic foodware was collaboratively studied. In the modified method, graphite furnace atomic absorption spectrometry (GFAAS) is substituted for FAAS. The modified method also includes mandatory quality control procedures to improve method performance. The extraction procedure of the official method (leaching with 4% acetic acid for 24 h at room temperature) remains unchanged. Seven laboratories analyzed blind duplicate portions of 3 ceramicware leach solutions containing Pb at concentrations of 0.0196, 0.403, and 3.73 microg/mL and Cd at concentrations of 0.00236, 0.0456, and 0.544 microg/mL. Performance of the modified method compared well with that of the official method. The repeatability relative standard deviation (RSDr) ranged from 0.87 to 6.7% for Pb and from 3.7 to 11% for Cd. The reproducibility relative standard deviation (RSDR) ranged from 4.5 to 12% for Pb and from 7.0 to 11% for Cd. Accuracy of collaborator results was 97-98% for Pb and 93-101% for Cd. Quality control results and quantitation limits were excellent. Method quantitation limits varied among laboratories from 0.005 to 0.019 microg/mL for Pb and from 0.0004 to 0.0019 microg/mL for Cd. The modified method was adopted First Action by AOAC INTERNATIONAL.

Sequential liquid–liquid extraction graphite furnace atomic absorption spectrometric (GFAAS) and spectrophotometric determination of zirconium(IV) with calixarene hydroxamic acid

A new calixarene hydroxamic acid, 25,26,27,28-tetrahydroxy-5,11,17,23-tetrakis ( N- p-chlorophenyl) calix[4]arene hydroxamic acid (CPCHA) is synthesized and used for the extraction and graphite furnace atomic absorption determination of zirconium(IV). The extract is also determined spectrophotometrically as CPCHA–SCN complex having maximum absorbance at 447 nm with molar absorptivity 9.4×10 3 l mol −1 cm −1. The Beer's law obeys in the range of 1.0–9.5 ppm of zirconium. The graphite atomic absorption (GFAAS) increases the sensitivity by about 50 folds. The method is applied to the trace determination of zirconium(IV) in standard samples.