Determination of iron and nickel by flame atomic absorption spectrophotometry after preconcentration on Saccharomyces cerevisiae immobilized sepiolite

Iron and nickel have been preconcentrated on Saccharomyces cerevisiae immobilized sepiolite and determined by flame atomic absorption spectrophotometry (FAAS). Preconcentration studies were conducted by the column method. Effect of pH, amount of adsorbent, elution solution, flow rate and interfering ions on the recovery of the analytes have been investigated. Recoveries of Fe and Ni were 95+/-1 and 99.5+/-0.1%, respectively, at 95% confidence level. The breakthrough capacities of analytes were also investigated and found to be 0.042 mmol g(-1) for Fe and 0.055 mmol g(-1) for Ni. The proposed method was applied to the determination of iron and nickel in brass (NBS SRM 37e). The detection limit of iron and nickel were found as 0.065 and 0.087 mug ml(-1), respectively. The direct determination of trace metals by flame atomic absorption spectrometry (FAAS) is limited and difficult because of low concentration and/or matrix interferences. The proposed method is excellent for the determination of trace metal in matrixes, such as metal alloys.     

Determination of lead in preserved egg by flame atomic absorption spectrometry after chemically modified preconcentration

A sensitive method for the determination of lead in preserved egg by flame absorption spectrometry using ammonium pyrrolidine dithiocarbamate-polystyrene chemically modified platinum wire matrix is presented. The modified platinum wire matrix, after preconcentrating the lead, is placed in a flame burner for direct atomization and measurement. The concentration range is linear between 5 and 500 ng/ml lead in solution and the detection limit is 0.65 ng/ml. This new technique is sensitive and convenient.     

交联壳聚糖分离富集-火焰原子吸收法测定水样中痕量银

以甲醛、环硫氯丙烷为交联剂,由壳聚糖合成了一种新型的交联壳聚糖微球(FCCIS)分离树脂,研究了不同条件下FCCTS对Ag(Ⅰ)的吸附性能.在pH 3.6时FCCTS对Ag(Ⅰ)定量吸附,吸附在树脂上的Ag(Ⅰ)可用0.5 moL/L的氨水将其洗脱,用火焰原子吸收光谱测定.该法对Ag(Ⅰ)的检出限为61 ng/mL(3σ,n=8),相对标准偏差为2.2%(n=7,ρ=2μg/mL),线性范围为0.05～4μg/mL,加标回收率在98.8%～101.7%之间.该法已用于水样中痕量银测定.     

Determination of selenium in a nickel alloy by flame atomic absorption spectrometry after electrochemical preconcentration

The nickel alloy is dissolved in nitric/hydrochloric/phosphoric acid mixture, and selenium is electrodeposited onto a platinum loop at ?0.4 V (vs. Ag/AgCl). Selenium is atomized from the electrode in an argon/hydrogen flame with simultaneous electrothermal heating of the loop. For the NBS standard nickel-based high-temperature alloy (SRM 899), the mean value found was 9.7 μg g^?1 with a standard deviation of 0.4 μg g^?1 (certified value 9.5 ± 0.1).     

Determination of selenium in technical sulphuric acid by flame atomic absorption spectrometry after electrochemical preconcentration

Electrochemical preconcentration on a platinum filament, followed by atomization in an argon—hydrogen flame with simultaneous electrothermal heating of the filament, is used for the determination of selenium in technical sulphuric acid. The effect of experimental parameters such as acid concentration, deposition potential and temperature are described, and the speciation of selenium in sulphuric acid is discussed. The technical acids were found to contain selenium in the range 30–60 μg l^-1.     

负载硫杂杯芳烃树脂微柱分离富集-火焰原子吸收法测定痕量金

建立了大孔径树脂D101负载硫杂杯芳烃树脂微柱分离富集-火焰原子吸收光谱法测定痕量金的新方法。探讨了负载硫杂杯芳烃树脂对金的吸附原理与最佳条件。该法对金的检出限为0.23 ng/mL(3σ,n=11),线性范围为0.01~1μg/mL。对0.2μg/mL的Au 标液进行5次测定,RSD=2.1%,加标回收率在98.4%~103.3%之间。方法用于矿渣样中痕量金的分析。     

A novel preconcentration method for determination of iron and lead using Chromosorb-103 and flame atomic absorption spectrometry

Syringe connected-minicolumn (SCM) method for the preconcentration/separation of iron and lead prior to their determination by flame atomic absorption spectrometry (FAAS) was developed. The proposed method is substituted for classical batch and column methods. The method proposed was compared with the column method with respect to easiness, rapidness, simplicity and some analytical performance criteria such as recovery, precision, accuracy and risk of contamination. A minicolumn was filled with Chromosorb-103 as a sorbent and connected with a syringe. The experimental conditions such as pH of sample, concentration and amount of eluent, flow rates of sample and eluent, concentration of 8-hydroxyquinoline (oxine) as a complexing agent were optimized. The sample solution with or without oxine was drawn into the syringe and discharged manually passing through the resin. Analytes were retained at pH ≥5 and eluted with 1 M nitric acid in acetone quantitatively. Analyte elements could be concentrated up to 200-fold. The iron and lead in river-water samples and in certified reference Bovine Liver (NIST 1577b) were quantitatively recovered with relative standard deviation lower than 10%.     

Determination of beryllium in solid samples by flame atomic absorption spectrometry after preconcentration on activated carbon.

It is generally supposed that the preconcentration procedure is used for the determination of metal concentrations under the sensitivity of the measurement method. This study showed that preconcentration is also need for the beryllium (Be) concentration over the sensitivity of atomic absorption spectrometry. For this purpose, a simple and selective method for the determination of Be in solid samples is modified. The method is based on the preconcentration of the complexes of beryllium-acetylacetone plus morin, oxine, PAN and PAR on activated carbon at different pH values. The adsorbed beryllium was eluted with aqua regia and measured by flame atomic absorption spectrometry (FAAS). Recoveries of up to 85% were achieved. For removing chemical interferences and applying the method to Be determination in solid samples, the masking studies and reproducibility were examined. The detection limit was found to be 0.12 ng mL(-1). The relative sandard deviations (RSD) were found to be 8% for 60 mL of 10.0 ng mL(-1) using 10 replicate enrichment procedures. Beryllium concentrations in the studied solid samples were found in the range of 0.28 - 3.95 mg kg(-1).     

Lead preconcentration with flow injection for flame atomic absorption spectrometry

The flow-injecton preconcentration of lead with immobilised reagents under a variety of conditions is discussed. Timed sample loading and matrix removal without passing the matrix to the nebuliser were achieved simply with one valve. Reagent consumption and calibration time were reduced by the addition of further valves. A system design incorporating control of the timing of operations by a commercial autosample is described. The effects of pH and interferent ions were examined. Water samples were analysed against aqueous standards and as standard additions solutions. For an analysis time of about 3 min a preconcentration factor of about 40 was obtained for both peak height and area measurements. Detection limits of down to 1.4 ml^?1 were obtained.     

Determination of gold in ore by flame atomic absorption spectrometry with flow-injection on-line sorbent extraction preconcentration

Gold in ores was determined by flame atomic absorption spectrometry following on-line preconcentration by sorbent extraction in a flow-injection system. The medium polarity adsorption resin Amberlite XAD-8 packed in a 220-μl micro-column was used to collect gold(III) from hydrochloric acid sample solutions for 40 s at 7.6 ml/min. Ethanol was used to elute the adsorbed analytes into the nebulizer. Optimization studies were made on sample loading rate, elution rate and sample acidity. Some possible interferences on the determination are discussed. A 35-fold enrichment was achieved at a sampling frequency of 60 h^?1 and with an RSD of 1.4%. The detection limit (3σ) and 2 μg l^?1. Results for gold in ore samples showed good agreement with those obtained using activated carbon adsorption preconcentration. The recoveries were 97–108%.     

Determination of cadmium in biological materials by flame atomic absorption spectrometry with flow-injection on-line sorption preconcentration

A new on-line preconcentration flame atomic absorption spectrometry (FAAS) system for trace element determination was developed based on sorption of soluble metal complexes on the walls of a PTFE knotted reactor using flow injection techniques. The system was applied to the determination of cadmium in biological materials. Cadmium complexed with sodium diethyldithiocarbamate was sorbed on the inner walls of the reactor and eluted on-line by isobutyl methyl ketone. The retention efficiency was 81% at a sampling loading rate of 5.2 ml/min. The enhancement factor was 66 and the concentration efficiency was 61/min with a 50 sec preconcentration period, consuming 4.2 ml sample. A detection limit of 0.1 μg/l. Cd (3σ) was obtained with a sampling frequency of 55/hr. The precisions were 1.2% RSD for 20 μg/l. Cd (N = 11). Thiourea and ascorbic acid/phenanthroline were used to overcome interferences from copper and iron, respectively. The analytical results obtained for powdered rice and human hair standard reference materials were in good agreement with the certified values.     

Determination of cadmium and lead in high purity uranium compounds by flame atomic absorption spectrometry with on-line micro-column preconcentration by CL-7301 resin

An on-line solid phase micro-column extraction and determination system for trace Cd and Pb in nuclear fuel grade uranium compounds was established. The preconcentration of trace elements Cd and Pb from uranium compounds was achieved by adsorbing Cd and Pb on CL-7301 resin in hydroiodic acid media, while the uranyl ion passed through. The method coupled with flame atomic absorption spectrometry (FAAS) was applied to analysis trace Cd and Pb in real samples. The preconcentration factors obtained by this method were 320 and 180 each for Cd and Pb, respectively. Under the optimized conditions, the detection limits corresponding to three times the standard deviation of the blank were found to be 0.13 ng·mL⁻¹ and 0.37 ng·mL⁻¹ for Cd and Pb, respectively. The relative standard deviation (RSD) and the recoveries of standard addition (spiked with 1–5 ng of Cd and Pb) were of <5% (n = 10) and 96.2%–102.3%, respectively. Precision was also evaluated and found to be ≤4.3% (N = 11). The proposed method was successfully used for the determination of trace Cd and Pb in commercially available uranium compounds (e.g., uranyl acetate and triuranium octoxide).     

Determination of cadmium and lead at low levels by using preconcentration at fullerene coupled to thermospray flame furnace atomic absorption spectrometry

A new and sensitive method for Cd and Pb determinations, based on the coupling of thermospray flame furnace atomic absorption spectrometry and a preconcentrator system, was developed. The procedure comprised the chelating of Cd and Pb with ammonium pyrrolidinedithiocarbamate with posterior adsorption of the chelates on a mixture (40 mg) of C₆₀ and C₇₀ at a flow rate of 2.0 ml min⁻¹. These chelates were eluted from the adsorbent by passing a continuous flow of ethanol (80% v/v) at 0.9 ml min⁻¹ to a nickel tube placed in an air/acetylene flame. After sample introduction into the tube by using a ceramic capillary (0.5 mm i.d.), the analytical signals were registered as peak height. Under these conditions, improvement factors in detectability of 675 and 200 were obtained for Cd and Pb, respectively, when compared to conventional flame atomic absorption spectrometry. Spiked samples (mineral and tap waters) and drinking water containing natural concentrations of Cd were employed for evaluating accuracy by comparing the results obtained from the proposed methodology with those using electrothermal atomic absorption spectrometry. In addition, certified reference materials (rye grass, CRM 281 and pig kidney, CRM 186) were also adopted for the accuracy tests. Due to the good linearity ranges for Cd (0.5–5.0 μg l⁻¹) and Pb (10–250 μg l⁻¹), samples with different concentrations could be analyzed. Detection limits of 0.1 and 2.4 μg l⁻¹ were obtained for Cd and Pb, respectively, and RSD values <4.5% were observed (n=10). Finally, a sample throughput of 24 determinations per hour was possible.     

Determination of bioavailable iron in noncontaminated Slovak soils by flame atomic absorption spectrometry

A method for the extraction of bioavailable iron from soils from various parts of Slovakia using a buffered diethylenetriaminepentaacetic acid (DTPA) solution was utilized. The extractant consists of 0.005 mol dm⁻³ DTPA, 0.1 mol dm⁻³ CaCl₂, and 0.1 mol dm⁻³ triethanolamine with pH of 7.3. DTPA was selected as the chelating agent because it can effectively extract micronutrient metal, iron. Distribution of iron in the horizons of various types of soils with respect to bioavailable iron was evaluated. The bioavailable iron in the extracts was determined by flame atomic absorption spectrometry. The calibration standards were prepared in the same surroundings as the extracts. Comparing to the average of 2.7–3.7 % total iron contents in Slovak soils, the available amounts of iron represent in average only very small amounts, approximately 0.3 % in comparison to total amounts.     

火焰原子吸收光谱法测定冰晶石中的铁

建立了火焰原子吸收光谱法测定冰晶石中铁的分析方法。样品用高氯酸溶解后,在0.48mol/L的盐酸介质中用空气-乙炔火焰测定了样品中的铁,测定结果与有色金属行业标准方法(邻二氮杂菲光度法)的分析结果一致。检出限为0.004 11mg/L,相对标准偏差(RSD)为0.95%~4.5%,加标回收率为98.00%~101.49%。     

Determination of Cu, Zn, Fe, Ni and Cd by flame atomic absorption spectrophotometry after preconcentration by Escherichia coli immobilized on sepiolite

A method for the determination of Cu, Zn, Fe, Ni and Cd by flame atomic absorption spectrophotometry (FAAS) after preconcentrating on a column containing Escherichia coli immobilized on sepiolite has been developed. Optimum pH values, amount of adsorbent, elution solution and flow rate have been obtained for the elements studied. The effect of interfering ions on the recovery of the analytes has also been investigated. Recoveries of Cu, Zn, Fe, Ni and Cd by E. coli immobilized on sepiolite were 99.1+/-0.6, 98.2+/-0.6, 98.1+/-0.5, 97.2+/-0.8 and 98.2+/-0.4% at 95% confidence level, respectively. The adsorption capacity of E. coli immobilized on sepiolite was found as 0.148, 0.064, 0.098, 0.134 and 0.088 mmol/g for Cu, Zn, Fe, Ni and Cd, respectively. The proposed method was applied to the determination of trace metals in alloys (NBS SRM 85b). Trace metals have been determined with relative error lower than 10%.     

Determination of trace heavy metals in waters by flame atomic absorption spectrometry after preconcentration with 2,4-dinitrophenyldiazoaminoazobenzene on Amberlite XAD-2

A new column, solid-phase extraction (SPE), preconcentration method was developed for determination of Cd, Co, and Cu ions in natural water samples by flame atomic absorption spectrometry. The procedure is based on the retention of analytes in the form of 2,4-dinitrophenyldiazoaminoazobenzene (DNDAA) complex on a mini column of DNDAA-XAD-2 resin. The effects of pH, eluent type, eluent concentration, eluent volume, resin quantity, sample volume, sample flow rate, and matrix ions (Na, Ca, and Mg) were investigated on the recovery of the metals using model solutions. The detection limit for Cd, Co, and Cu was 0.062, 0.084, and 0.057 μg L⁻¹ and the quantification limit was 0.17, 0.24, and 0.12 μg L⁻¹ respectively. The method was validated by the analysis of a certified reference material with the results being in agreement with those quoted by manufactures. The developed method was applied to the determination of trace metal ions in tap water, river water samples with satisfactory results.     

Determination of cadmium and lead in table salt by sequential multi-element flame atomic absorption spectrometry

In the present paper, a simultaneous pre-concentration procedure for the sequential determination of cadmium and lead in table salt samples using flame atomic absorption spectrometry is proposed. This method is based on the liquid-liquid extraction of cadmium(II) and lead(II) ions as dithizone complexes and direct aspiration of the organic phase for the spectrometer. The sequential determination of cadmium and lead is possible using a computer program. The optimization step was performed by a two-level fractional factorial design involving the variables: pH, dithizone mass, shaking time after addition of dithizone and shaking time after addition of solvent. In the studied levels these variables are not significant. The experimental conditions established propose a sample volume of 250 mL and the extraction process using 4.0 mL of methyl isobutyl ketone. This way, the procedure allows determination of cadmium and lead in table salt samples with a pre-concentration factor higher than 80, and detection limits of 0.3 ng g⁻¹ for cadmium and 4.2 ng g⁻¹ for lead. The precision expressed as relative standard deviation (n = 10) were 5.6 and 2.6% for cadmium concentration of 2 and 20 ng g⁻¹, respectively, and of 3.2 and 1.1% for lead concentration of 20 and 200 ng g⁻¹, respectively. Recoveries of cadmium and lead in several samples, measured by standard addition technique, proved also that this procedure is not affected by the matrix and can be applied satisfactorily for the determination of cadmium and lead in saline samples. The method was applied for the evaluation of the concentration of cadmium and lead in table salt samples consumed in Salvador City, Bahia, Brazil.     

Determination of strontium at low concentration levels by flame atomic absorption spectrometry associated on-line with continuous coprecipitation preconcentration

A sensitive method for the determination of strontium has been developed. In this work strontium was determined by flame atomic absorption spectrometry using a continuous copreconcentration dissolution procedure based on the formation of lead sulfate followed by elution with hot EDTA solution. Manifold parameters and chemical conditions are described in detail. A concentration factor of up to 61 can be achieved at a sampling rate of 20-30 h(-1). The detection limit for strontium was 0.9 ng ml(-1) (3sigma) and the relative standard deviation was 3.5% (n = 8) at a concentration level of 100 ng ml(-1).