Determination of cobalt and nickel by graphite-furnace atomic absorption spectrometry after coprecipitation with scandium hydroxide.

Trace amounts of cobalt and nickel in a water sample were quantitatively coprecipitated with scandium hydroxide at pH 8.0-10.5. Because the coprecipitant could be easily dissolved with 1 mol dm(-3) nitric acid, and the presence of up to 10 mg cm(-1) of scandium did not interfere with the graphite-furnace atomic absorption spectrometric determination of cobalt and nickel, the volume of the final solution prepared for the determination could be minimized down to 0.5 cm3. The concentration factor was 400-fold and the detection limits (signal to noise = 2) were 5.0 pg cm(-3) of cobalt and 10.0 pg cm(-3) of nickel in 200 cm3 of the initial sample solution. The 27 diverse ions investigated did not interfere with the determination in at least a 500-fold mass ratio to cobalt or nickel. The proposed method was successfully applied to the determination of trace amounts of cobalt and nickel in river-water samples.     

Determination of chromium, copper and lead in river water by graphite-furnace atomic absorption spectrometry after coprecipitation with terbium hydroxide.

Coprecipitation with terbium hydroxide quantitatively recovered trace amounts of chromium(III), copper(II) and lead(II) at pH 8.4 - 10.8, 8.0 - 11.5 and 8.7 - 11.5, respectively. The precipitate was dissolved in 0.85 mol dm(-3) nitric acid, and the analytes were determined by graphite-furnace atomic absorption spectrometry (GF-AAS). The presence of terbium (up to 7 g dm(-3)) did not interfere with the determination. The detection limits were 0.3 microg dm(-3) for chromium, 0.4 microg dm(-3) for copper and 0.5 microg dm(-3) for lead, when the analytes in 200 cm3 of the sample solution were concentrated into 10 cm3. The ions added to river or seawater were quantitatively recovered. Chromium and copper in a contaminated river water were successfully determined.     

Determination of silver in sea water by coprecipitation with cobalt pyrrolidinedithiocarbamate and Zeeman graphite-furnace atomic absorption spectrometry

A preconcentration technique is described for silver, which allows the precise and accurate determination of silver in sea water at nanogram per liter levels. Silver is co-precipitated with cobalt(II) pyrrolidinedithiocarbamate from 200-ml samples. The precipitate is dissolved in concentrated nitric acid and silver is quantified by Zeeman graphite-furnace atomic absorption spectrometry, with acid phosphate matrix modification. The detection limit is 0.1 ng l^?. The method is simple and rapid, and also allows the simultaneous extraction of lead, copper, cadmium, and nickel.     

Determination of copper, cadmium and lead in seawater and mineral water by flame atomic absorption spectrometry after coprecipitation with aluminum hydroxide

An aluminum hydroxide coprecipitation method for the determination of cadmium, copper and lead by flame atomic absorption spectrometry in aqueous solutions, seawater and mineral water samples has been investigated. The coprecipitation conditions, such as the effect of the pH, the amount of carrier element, the effect of possible matrix ions and the time were examined in detail for the studied elements. It was found that cadmium, copper and lead are co-precipitated quantitatively (≥95%) with aluminum hydroxide at pH 7 with low R.S.D. values of around 2 to 3%. Detection limits (38) were 6 ng ml⁻¹ for Cd, 3 ng ml⁻¹ for Cu and 16 ng ml⁻¹ for Pb. The method proposed was validated by the analysis of HPS 312205 seawater standard reference material and spiked mineral water samples.     

Determination of cadmium in river water by electrothermal atomic absorption spectrometry after internal standardization-assisted rapid coprecipitation with lanthanum phosphate.

Cadmium ranging from 1 - 8 ng could be coprecipitated quantitatively with lanthanum phosphate at pH 5 - 6 from up to 200 mL of river water samples spiked with 5 microg of indium as an internal standard. Cadmium and indium coprecipitated were measured by using electrothermal atomic absorption spectrometry. The cadmium content in the original sample solution could be determined by internal standardization with indium. Since complete collection of the precipitate and strict adjustment of the volume of the final solution after coprecipitation are not required in this method, the precipitate could be collected by using decantation and centrifugation, and then dissolved with 1 mL of about 2.4 mol L(-1) nitric acid. The proposed method is simple and rapid, and enrichment close to 200-times can be attained; the detection limit (3sigma, n = 6) was 0.63 ng L(-1) in 200 mL of the sample solution.     

Comparison of carrier elements for coprecipitation and graphite-furnace atomic absorption spectrometry

The group IIIB elements (aluminum, gallium and indium) and iron(III) were studied from the standpoint of the advantageous combination of coprecipitation and graphite-furnace atomic absorption Spectrometry (GFAAS). Milligram quantities of four hydroxides were precipitated at different pH's from solutions containing traces of copper(II) and cadmium(II) ions, in order to examine the effect of pH on the coprecipitation. Almost similar results were obtained for gallium, indium and iron hydroxides, with which the copper and cadmium were coprecipitated nearly completely at pH>7. In case of aluminum hydroxide, the optimal pH range was narrow because of the redissolution of the precipitate in alkaline solutions. The removal of indium carrier was successfully achieved by volatilization as bromide at the pyrolysis stage in GFAAS, otherwise serious background absorption interfered with the trace determination. Volatilization loss of cadmium was eliminated by adding a small amount of miourea. Gallium carrier was mostly removed as chloride, but large background absorption still occurred in the determination of cadmium.     

Determination of some heavy metals by flame atomic absorption spectrometry before coprecipitation with neodymium hydroxide

A procedure is described for the determination of trace amounts of Cd(II), Ni(II), Cu(II), Pb(II), Fe(III), Co(II), and Mn(II) that combines flame atomic absorption spectrometry with neodymium hydroxide coprecipitation. The influences of analytical parameters (amount of neodymium, pH of the model solutions, etc.) that affect quantitative recoveries of the analyte ions were investigated. The effects of concomitant ions were also examined. The detection limits for analytes were found in the range of 0.2-3.3 microg/L. The validation of the presented procedure was controlled by analysis of certified reference materials (National Institute of Standards and Technology 1570a spinach leaves and TMDA 54.4 fortified lake water). The applications of the procedure were performed by the analysis of water, food, and herbal plants from Turkey.     

Determination of beryllium in urine by graphite-furnace atomic absorption spectrometry

A method has been developed for the determination of beryllium in urine by graphite-furnace atomic absorption spectrometry. Ammonium 12-molybdophosphate and ascorbic acid were employed as a matrix modifier. The tolerable charring temperature for beryllium in both aqueous solution and urine was raised to 1400 °C in the presence of a matrix modifier. The sensitivity for the determination of beryllium was also improved by a factor of 1.5 in comparison with that obtained by using magnesium nitrate as a matrix modifier. The mechanism of the enhancement effect of ammonium molybdophosphate was ascribed to the effectiveness of the formation of gaseous BeO, which is a precursor of free beryllium. Beryllium in urine can be determined simply by dilution with ascorbic acid solution. The relative standard deviation for seven replicate determinations of beryllium was 1.9% for a urine sample containing 0.029 μg ml^?1 of beryllium.     

Determination of indium by graphite furnace atomic absorption spectrometry after coprecipitation with chitosan.

A sensitive and simple method for the determination of trace amounts of indium in water samples by graphite furnace atomic absorption spectrometry (GFAAS) after coprecipitation with chitosan was investigated. Indium was quantitatively preconcentrated from water samples by coprecipitation with chitosan at pH 7.0-9.0. The coprecipitant was easily dissolved with acetic acid, and indium in the resulting solution was determined by GFAAS. The addition of lanthanum as a chemical modifier was more effective for the atomic absorbance of indium. The detection limit (S/N > or = 3) for indium was 0.04 microg dm(-3), and the relative standard deviations (n = 5) were 3.5-4.5% at 1.0 microg/100 cm3. The results obtained in this study indicate that the proposed method can be successfully applied to the determination of trace indium in water samples.     

Determination of some trace elements in food and soil samples by atomic absorption spectrometry after coprecipitation with holmium hydroxide

The determination of trace elements in food and soil samples by atomic absorption spectrometry was investigated. A coprecipitation procedure with holmium hydroxide was used for separation-preconcentration of trace elements. Trace amounts of copper(II), manganese(II), cobalt(II), nickel(ll), chromium(lll), iron(Ill), cadmium(ll), and lead(ll) ions were coprecipitated with holmium hydroxide in 2.0 M NaOH medium. The optimum conditions for the coprecipitation process were investigated for several commonly tested experimental parameters, such as amount of coprecipitant, effect of standing time, centrifugation rate and time, and sample volume. The precision, based on replicate analysis, was lower than 10% for the analytes. In order to verify the accuracy of the method, the certified reference materials BCR 141 R calcareous loam soil and CRM 025-050 soil were analyzed. The procedure was successfully applied for separation and preconcentration of the investigated ions in various food and soil samples. An amount of the solid samples was decomposed with 15 mL concentrated hydrochloric acid-concentrated nitric acid (3 + 1). The preconcentration procedure was then applied to the final solutions. The concentration of trace elements in samples was determined by atomic absorption spectrometry.     

Determination of lead in seawater by flow-injection on-line preconcentration-electrothermal atomic absorption spectrometry after coprecipitation with iron(III) hydroxide.

A flow-injection on-line preconcentration-electrothermal atomic absorption spectrometric (ETAAS) method coupled with a coprecipitation method has been developed for the determination of lead in seawater. The combination of two preconcentration procedures, coprecipitation with iron(II) hydroxide and solid-phase extraction with a lead-selective resin, Pb-Spec, allowed the determination of lead at the ng kg(-1) level. Lead in 250 g of a sample solution was collected by coprecipitation with 10 mg of iron. The precipitate was dissolved in 25 ml of 1 mol l(-1) nitric acid; then, a 4-ml aliquot of the sample solution was introduced into the flow-injection system to preconcentrate and separate lead from iron on a Pb.Spec microcolumn. The sorbed lead was eluted with a 1.0 x 10(-4) mol l(-1) EDTA solution. The 30-microl portion of the eluate corresponding to the highest analyte concentration zone was injected into a graphite furnace. The overall enhancement factor was about 200 for 250 g of the sample. The average and standard deviation of ten blank values obtained were 1.7 ng and 0.38 ng, respectively. The recovery was 93.7 +/- 5.0% for seawater spiked with 20 ng kg(-1) lead. The proposed method is applicable to the analysis of seawater for lead at slightly higher levels.     

Determination of some trace metals in water and sediment samples by flame atomic absorption spectrometry after coprecipitation with cerium (IV) hydroxide

A cerium(IV) hydroxide coprecipitation method was developed for the determination of some trace elements (Cu, Co, Pb, Cd, Ni) in aqueous solutions, water and sediment samples by flame atomic absorption spectrometry (AAS). Several parameters governing the efficiency of the coprecipitation method were evaluated including pH of sample solution, amount of carrier element, volume of sample solution and the effect of possible matrix ions The procedure was validated by the analysis of GBW 07309 standard reference material sediment and by use of a method based on a solid phase extraction.     

Determination of trace elements in sea water by graphite-furnace atomic absorption spectrometry after preconcentration by tetrahydroborate reductive precipitation

A method is described for the preconcentration of 16 elements from coastal and deep ocean sea water based on their reductive precipitation by sodium tetrahydroborate. The enrichment factors obtained were sufficient to permit the analysis of a near-shore sea-water reference material (11 elements) and an open ocean sea-water reference material (9 elements). Recoveries from 900 ml of sea water ranged from 80 to 107% (100-ml sample for Mn) with absolute blanks between <1.0 ng (Se) and 20 ng (Cu). Estimated detection limits varied from 0.3 ng l ^?1 (Pb) to 19 ng l^?1 (As) based on a 36-fold concentration of a 900-ml sample.     

Determination of trace metals in estuarine sediments by graphite-furnace atomic absorption spectrometry

A simple and rapid acid digestion method for the decomposition of estuarine sediments is described. Quantitative recovery of Cd, Pb, Cu, Ni, Co, Be and Co is demonstrated. Sensitive, precise and accurate determination of these trace metals by graphite-furnace atomic absorption spectrometry in combination with the L'vov Platform provides an interference-free technique that permits calibration with simple aqueous solutions of metal standards. The accuracy of the method has been confirmed by analysis of two marine sediment reference materials, MESS-1 and BCSS-1.     

Determination of copper,nickel, and cadmium in sea water by apdc chelate coprecipitation and flameless atomic absorption spectrometry

Copper, nickel, and cadmium can be determined in 100 ml of sea water by coprecipitation with cobalt pyrrolidinedithiocarbamate and graphite atomizer atomic absorption spectrometry. Concentration ranges likely to be encountered and estimated (1 σ ) analytical precisions are 1–6 nmol kg^-1 (±0.1) for copper, 3–12 nmol kg^-1 (±0.3) for nickel and 0.0–1.1 nmol kg^-1 (±0.1) for cadmium. The technique may be applied to fresh-water samples with slight modification.     

Determination of nanogram amounts of cadmium in water by electrothermal atomic absorption spectrometry after flotation separation

A method is described for the flotation an determination of ng-levels of cadmium in water. Cadmium in a 1-l sample of water is coprecipitated with hydrated zirconium oxide at pH 9.1 ± 0.1. The precipitate is floated with the aid of a surfactant solution and small air bubbles, separated and dissolved in dilute hydrochloric acid. The cadmium content is determined by electrothermal atomic absorption spectrophotometry. The method is applied to the determination of ng l^?1 levels of cadmium in fresh water. The time required for preconcentration of cadmium from a 1-l sample is 20 min per sample, after 20 min stirring.     

Determination of chromium in human milk and urine by graphite-furnace atomic absorption spectrometry

Low-temperature ashing and dry ashing at 500°C are compared for the analysis of urine and human milk. Dry ashing gives superior accuracy. The importance of contamination control, background correction and temperature control are stressed. Both urine and human milk contain about 1 ng Cr ml^-1.     

Determination of cadmium in water samples by graphite furnace atomic absorption spectrometry after cloud point extraction

The formation of a complex with 2-(5-brom-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP) and cloud point extraction have been applied to the preconcentration of cadmium followed by its determination by graphite furnace atomic absorption spectrometry (GFAAS) using octylphenoxypolyethoxyethanol (TritonX-114) as surfactant. The chemical variables affecting the separation were optimized. At pH 7.0, preconcentration of only 10 mL of sample in the presence of 0.05% TritonX-114 and 2.5 × 10⁻⁶ M 5-Br-PADAP enabled the detection of 0.04 μg/L cadmium. The enrichment factor was 21 for cadmium. The regression equation was A = 0.0439C(μg/L) + 7.2 × 10⁻³. The correlation coefficient was 0.9995. The precision for 10 replicate determinations at 10 μg/L Cd was 2.7% relative standard deviation (RSD). The proposed method has been applied to the determination of cadmium in water samples. The text was submitted by the authors in English.     

Determination of cadmium and zinc in water samples by flame atomic absorption spectrometry after cloud-point extraction

The phase-separation phenomenon of nonionic surfactants occurring in an aqueous solution was used for the extraction of Cd and Zn from water samples. After complexation with 6-(4-nitrophenyl)-2,4-diphenyl-3,5-diaza-bicyclo[3.1.0]hex-2-ene (NDDBH) in hydrochloric acid medium (pH 1), the analytes were quantitatively extracted after centrifugation into the phase rich in the nonionic surfactant octylphenoxypolyethoxyethanol (Triton X-114). Tetrahydrofuran acidified with 0.1 M HCl was added to the surfactant-rich phase prior to its analysis by flame atomic absorption spectrometry. The adopted concentrations for NDDBH, Triton X-114 and hydrochloric acid were all optimized. Detection limits (3σ) of 0.33 and 0.85 ng/mL along with enrichment factors of 157 and 118 for Cd and Zn, respectively, were achieved. The proposed method was applied to the determination of Cd and Zn in acidic solutions of certified reference materials. A comparison with certified values was performed for an evaluation of the accuracy, resulting in a good agreement according to the t-test at a 95% confidence level. The high efficiency of the cloud-point extraction to carry out the determination of the studied analytes in complex matrices was, therefore, demonstrated. The text was submitted by the authors in English.     

Determination of trace elements in gallium arsenide by graphite-furnace atomic absorption spectrometry after pretreatment in gas streams

Atomic absorption spectrometry (AAS) with a resistively-heated graphite furnace is used for the determination of chromium (0.3–1 atom/10⁶ atom) in chromium-doped gallium arsenide after pretreatment in a separate furnace in a stream of argon to remove arsenic, and of manganese and silver (0.03 and 0.04 atom/10⁶ atoms, respectively) by a similar procedure after pretreatment with argon and chlorine, the latter to remove both gallium and arsenic as volatile chlorides. Results for chromium were in agreement with those obtained by furnace AAS after dissolution and by spark-source mass spectrometry (SSMS) but AAS after dissolution is more precise. Results for manganese and silver obtained by both gas pretreatments were in good agreement, but were higher than those obtained for presparked material by SSMS, indicating that surface contamination of gallium arsenide was not completely removed by the etching methods used. The procedures established that the concentrations of bismuth, indium and lead in the gallium arsenide sample were below the limits of detection of 3 × 10^?3, 10 × 10^?3 and 1 × 10^?3 atom/10⁶ atoms, respectively. In all cases, calibration graphs were constructed from data obtained with aqueous solutions of appropriate salts.