Slurry analysis after lead collection on a sorbent and its determination by electrothermal atomic absorption spectrometry

In this study, in order to eliminate the drawbacks of elution step and to reach higher enrichment factors, a novel preconcentration/separation technique for the slurry analysis of sorbent loaded with lead prior to its determination by electrothermal atomic absorption spectrometry was described. For this purpose, at first, lead was collected on ethylene glycol dimethacrylate methacrylic acid copolymer (EGDMA-MA) treated with ammonium pyrolidine dithiocarbamate (APDC) by conventional batch technique. After separation of liquid phase, slurry of the sorbent was prepared and directly pipetted into graphite furnace of atomic absorption spectrophotometer. Optimum conditions for quantitative sorption and preparation of the slurry were investigated. A 100-fold enrichment factor could be easily reached.

The analyte element in certified sea-water and Bovine-liver samples was determined in the range of 95% confidence level. The proposed technique was fast and simple and the risks of contamination and analyte loss were low. Detection limit (3δ) for Pb was 1.67 μg l⁻¹.     

The use of slurry sampling for the determination of manganese and copper in various samples by electrothermal atomic absorption spectrometry

Manganese and copper in multivitamin-mineral supplements and standard reference materials were determined by slurry sampling electrothermal atomic absorption spectrometry. Slurries were prepared in an aqueous solution containing Triton X-100. The effects of different parameters such as ratio of solid to liquid phase volume, total slurry volume and addition of Triton X-100 as a dispersant on the analytical results were investigated. The graphite furnace programs were optimized for slurry sampling depending on the analytes and their concentrations in the samples. The linear calibration method with aqueous standard solutions was used for the quantification. At optimum experimental conditions, R.S.D. values were below 5%. The analytes were determined in the limits of 95% confidence level with respect to certified values in coal and soil standard reference materials and to those found by wet-digestion in multivitamin-mineral supplements. Detection limits (3delta) for Mn and Cu were 0.10 microg L(-1) and 1.82 microg L(-1) for 10 microL coal standard reference material slurry, respectively.     

Gadolinium hydroxide coprecipitation system for the separation-preconcentration of some heavy metals

A simple and new procedure for the determination of trace amounts of lead(II), cobalt(II), manganese(II) and copper(II) is described, that combines atomic absorption spectrometry-gadolinium hydroxide coprecipitation. One milliliter of 1% gadolinium(III) solution was added to each sample; the pH was then adjusted to 11 in order to collect trace heavy metals on gadolinium(III) hydroxide. The precipitate was separated by centrifugation and dissolved in 1 mL of 1 mol L(-1) HNO3. The influences of analytical parameters including amount of gadolinium(III), sample volume, etc. were investigated on the recoveries of analyte ions. The effects of concomitant ions were also examined. The recoveries of the analyte ions were greater than 95. The detection limits for the analyte elements based on 3 sigma (n=20) were in the range of 0.52-12.0 microg L(-1). The method was applied to the determination of analytes in real samples and good results were obtained (relative standard deviations <10%, recoveries >95%).     

Slurry analysis of cadmium and copper collected on 11-mercaptoundecanoic acid modified TiO2 core-Au shell nanoparticles by flame atomic absorption spectrometry

Separation/preconcentration of copper and cadmium using TiO(2) core-Au shell nanoparticles modified with 11-mercaptoundecanoic acid and their slurry analysis by flame atomic absorption spectrometry were described. For this purpose, at first, titanium dioxide nanoparticles were coated with gold shell by reducing the chloroauric acid with sodium borohydride and then modified with 11-mercaptoundecanoic acid. The characterization of modified nanoparticles was performed using ultra-violet spectroscopy and dynamic light scattering. Copper and cadmium were then collected on the prepared sorbent by batch method. The solid phase loaded with the analytes was separated by centrifugation and the supernatant was removed. Finally, the precipitate was slurried and directly aspirated into the flame for the determination of analytes. Thus, elution step and its all drawbacks were eliminated. The effects of pH, amount of sorbent, slurry volume, sample volume and diverse ions on the recovery were investigated. After optimization of experimental parameters, the analytes in different certified reference materials and spiked water samples were quantitatively recovered with 5% RSD. The analytes were enriched up to 20-fold. Limits of detection (N=10, 3σ) for copper and cadmium were 0.28 and 0.15 ng mL(-1), respectively.     

Coprecipitation of Ni(2+), Cd(2+) and Pb(2+) for preconcentration in environmental samples prior to flame atomic absorption spectrometric determinations

A coprecipitation procedure has been presented prior to flame atomic absorption spectrometric determination of nickel, cadmium and lead ions in environmental samples. Analyte ions were coprecipitated by using copper hydroxide precipitate. The influences of some analytical parameters like amounts of copper, sample volume, etc., on the recoveries of the analytes were investigated. The interference of other ions was negligible. Under the optimized conditions, the detection limits (3 sigma, n=15) of lead(II), nickel(II) and cadmium(II) were 7.0, 3.0 and 2.0 microg/L, respectively. The proposed method has been successfully applied for the determination of traces of Ni, Cd and Pb in environmental samples like tap water.     

Dysprosium(III) hydroxide coprecipitation system for the separation and preconcentration of heavy metal contents of table salts and natural waters

A procedure for the determination of trace amounts of Pb(II), Cu(II), Ni(II), Co(II), Cd(II) and Mn(II) is described, that combines atomic absorption spectrometry-dysprosium hydroxide coprecipitation. The influences of analytical parameters including amount of dysprosium(III), centrifugation time, sample volume, etc. were investigated on the recoveries of analyte ions. The effects of concomitant ions were also examined. The recoveries of the analyte ions were in the range of 95.00-104.00%. The detection limits corresponding to three times the standard deviation of the blank for the analytes were in the range of 14.1-25.3 microg/L. The method was applied to the determination of lead, copper, nickel, cobalt, cadmium and manganese ions in natural waters and table salts good results were obtained (relative standard deviations <10%, recoveries >95%).     

Multi-element coprecipitation for separation and enrichment of heavy metal ions for their flame atomic absorption spectrometric determinations

A preconcentration-separation technique for lead(II), cadmium(II), chromium(III), nickel(II) and manganese(II) ions has been established. The procedure is based on coprecipitation of these ions by the aid of Cu(II)-dibenzyldithiocarbamate precipitate. The precipitate was dissolved in 0.5 mL of concentrated HNO(3), and made up to 5 mL with distilled water. The heavy metals were determined by flame atomic absorption spectrometer. The effects of analytical parameters like pH, amounts of reagents, sample volume, etc. on the recoveries of heavy metals were investigated. The influences of matrix ions were also examined. The detection limits for the heavy metals based on 3 sigma (N=21) were found in the range of 0.34-0.87 microg L(-1). In order to validate the proposed method, two certified reference materials of NIST SRM 2711 Montana soil and NIST SRM 1515 Apple leaves were analyzed with satisfactory results. The proposed method was applied for the determination of lead, cadmium, chromium, nickel and manganese in environmental samples.     

Development and application of acousto-optic background correction for inductively coupled plasma atomic emission spectrometry

In two configurations, a solid-state acousto-optic (AO) deflector or modulator is mounted in a 0.5 m monochromator for background correction with inductively coupled plasma atomic emission spectrometry (ICP-AES). A fused silica acousto-optic modulator (AOM) is used in the ultraviolet (UV) spectral region applications while a glass AO deflector (AOD) is used for the visible (VIS) region. The system provides rapid sequential observation of adjacent on- and off-line wavelengths for background correction. Seventeen elements are examined using pneumatic nebulization (PN) and electrothermal vaporization (ETV) sample introduction. Calibration plots were obtained with each sample introduction technique. Potable water and vitamin tablets were analyzed. Flame atomic absorption (FAA) was used to verify the accuracy of the AO background correction system.     

Analysis of high-purity cadmium and cadmium dioxide by atomic absorption spectrometry

To ensure high-speed analytical support to the technology of cadmium tungstate single crystal growth, we have developed an electrothermal atomic absorption spectrometry technique for analysis of high-purity cadmium and cadmium oxide for the technologically important impurities Ag, Co, Cr, Cu, Fe, Mn, Ni, Pb, and Sn with detection limits from 2 × 10^–7 to 6 × 10^–6 wt %.     

Octadecyl immobilized surface for precipitate collection with a renewable microcolumn in a lab-on-valve coupled to an electrothermal atomic absorption spectrometer for ultratrace cadmium determination

Octadecyl immobilized surface was, for the first time, proved to be a superb precipitate-collecting medium. Surface charge effect was assumed to dominate the adsorption of cadmium hydroxide precipitate, facilitated by electrostatic interaction between the negatively charged C18 bead surface and positively charged cadmium hydroxide clusters. Residual silanol groups on the C18-immobilized silica surface did not contribute to precipitate adsorption. A novel procedure for ultratrace cadmium preconcentration was proposed by incorporating a renewable microcolumn in a lab-on-valve system. Cd(OH)(2) precipitate was adsorbed onto the C18 surface, which was afterward eluted with 20 microL of nitric acid (1%) and quantified with detection by electrothermal atomic absorption spectrometry. An enrichment factor of 28 and a limit of detection of 1.7 ng L(-1), along with a sampling frequency of 13 h(-1) were obtained with a sample consumption of 600 microL within the concentration range of 0.01-0.2 microg L(-1), achieving a precision of 2.1% RSD at the 0.05 microg L(-1) level. The enrichment factor was further enhanced to 44 by increasing the sample volume to 1200 microL. The procedure was validated by analyzing cadmium in three certified reference materials, that is, river sediment (CRM 320), sea lettuce (CRM 279), and frozen cattle blood (GBW 09140). Good agreement between the obtained results and the certified values was achieved.     

Study on solid phase extraction and graphite furnace atomic absorption spectrometry for the determination of nickel, silver, cobalt, copper, cadmium and lead with MCI GEL CHP 20Y as sorbent

A solid phase extraction and graphite furnace atomic absorption spectrometry (GFAAS) for the determination of nickel, silver, cobalt, copper, cadmium and lead with MCI GEL CHP 20Y as sorbent was studied. Trace amounts of chromium, nickel, silver, cobalt, copper, cadmium and lead were reacted with 2-(2-quinolinil-azo)-4-methyl-1,3-dihydroxidobenzene (QAMDHB) followed by adsorption onto MCI GEL CHP 20Y solid phase extraction column, and 1.0molL(-1) HNO(3) was used as eluent. The metal ions in 300mL solution can be concentrated to 1.0mL, representing an enrichment factor of 300 was achieved. The recoveries of analytes at pH 8.0 with 1.0g of resin were greater than 95% without interference from alkaline, earth alkaline and some metal ions. When detected with graphite furnace atomic absorption spectrometry, the detection limits in the original samples were 1.4ngL(-1) for Cr(III), 1.0ngL(-1) for Ni(II), 0.85ngL(-1) for Ag(I), 1.2ngL(-1) for Co(II), 1.0ngL(-1) for Cu(II), 1.2ngL(-1) for Cd(II) and 1.3ngL(-1) for Pb(II). The validation of the procedure was performed by the analysis of the certified standard reference materials, and the presented procedure was applied to the determination of analytes in biological, water and soil samples with good results (recoveries range from 89 to 104%, and R.S.D.% lower than 3.2%. The results agreed with the standard value or reference method).     

Celtek clay as sorbent for separation-preconcentration of metal ions from environmental samples

The sorption conditions including pH of the aqueous solution, sample volume, etc., on Celtek clay of copper(II), cadmium(II), lead(II), chromium(III), nickel(II) and cobalt(II) ions from environmental samples has been studied. The effects of electrolytes as matrix on the preconcentration were also investigated with the recoveries >95%. The 3 sigma detection limits for copper, cadmium, lead, chromium, nickel and cobalt ions were found to be 0.25, 0.32, 0.73, 0.45, 0.50 and 0.41 microg/l, respectively. The relative standard deviation was <10% for the determination of analytes. The procedure was validated by analysis of a NRCC-SLRS 4 Riverine Water, SRM 1573a Tomato leaves and IAEA 336 Lichen standard reference materials. The developed method was successively utilized for the determination of Cu(II), Cd(II), Pb(II), Cr(III), Ni(II) and Co(II) in various samples including natural waters, wheat and human hair by flame atomic absorption spectrometry (FAAS) with satisfactorily results (recoveries>95% and R.S.D.'s<10%).     

Ultra-trace determination of silver in water samples by electrothermal atomic absorption spectrometry after preconcentration with a ligand-less cloud point extraction methodology

A very simple and ligand-less cloud point extraction (CPE) methodology for the preconcentration of ultra-trace amounts of silver as a prior step to its determination by electrothermal atomic absorption spectrometry (ETAAS) has been developed. The method is based on the extraction of silver at pH 9 by using non-ionic surfactant polyethyleneglycolmono-p-nonylphenylether (PONPE 7.5) without adding any chelating agent. Several important variables that affect the CPE efficiency and ETAAS signal were investigated and optimized. The preconcentration of 15 ml sample solution allowed us to achieve an enhancement factor of 60. The calibration graph using the preconcentration system was linear in the range of 5-100 ngl(-1) with a correlation coefficient of 0.9991. The lower limit of detection (3s) obtained in the optimal conditions was 1.2 ngl(-1). The relative standard deviation (R.S.D.) for eight replicate determinations at 30 ngl(-1) Ag level was 4.2%. The proposed method was successfully applied to the ultra-trace determination of silver in water samples.     

Detection of Sodium in Highly Pure Graphite via High-Resolution Electrothermal Atomic Absorption Spectrometry with a Continuous Spectrum Source

This study is dedicated to elucidating the analytical abilities of electrothermal atomic absorption spectrometry with a continuous spectrum source (ETAAS-CSS) to detect the presence of sodium in highly pure graphite powder. In order to plot the calibration dependence for sodium detection, a special technique based on argon dilution of the atomic vapor obtained by introducing the aqueous reference solution in the atomizer is applied. The conditions for thermal pretreatment of highly pure graphite powder and atomization of sodium are established, and the sodium detection threshold is evaluated via ETAAS-CSS (2.6 × 10^–4 ng) as well. The validity of the results is confirmed via the sample variation method.     

UV vapor generation for determination of selenium by heated quartz tube atomic absorption spectrometry

A new vapor generation technique utilizing UV irradiation coupled with atomic absorption for the determination of selenium in aqueous solutions is described. In the presence of low molecular weight organic acid solutions, inorganic selenium(IV) is converted by UV irradiation to volatile selenium species, which are then rapidly transported to a heated quartz tube atomizer for detection by atomic absorption spectrometry. Optimum conditions for photochemical vapor generation and interferences from concomitant elements were investigated. Identification of the volatile products using cryotrapping GC/MS analysis revealed that inorganic selenium(IV) is converted to volatile selenium hydride, selenium carbonyl, dimethyl selenide, and diethyl selenide in the presence of formic, acetic, propionic, and malonic acids, respectively. In acetic acid solution, the efficiency of generation was estimated to be 50 +/- 10%. No interference from Ni(2+) and Co(2+) at concentrations of 500 and 100 mg L(-)(1), respectively, was evident. A detection limit of 2.5 microg L(-)(1) and a relative sensitivity of 1.2 microg L(-)(1) (1% absorption) with a precision of 1.2% (RSD, n = 11) at 50 microg L(-)(1) were obtained.     

Sample preconcentration using ion-exchange polymer film for laser ablation sampling inductively coupled plasma atomic emission spectrometry

An efficient sample pretreatment/introduction technique for the inductively coupled plasma atomic emission spectrometry (ICP-AES) using ion exchange for analyte preconcentration and matrix separation and laser ablation sampling for sample introduction has been developed. Ammonium pyrrolidine dithiocarbamate (APDC)-polystyrene films are coated on glass plates for analyte preconcentration. Repetitive laser ablation sampling of the polymer film removes the ion-exchanged metal ions from the polymer film as fine particles for sample introduction into the ICP. After immersing the sample probe in a sample solution for 5 min, the ICP emission intensity for laser ablation of the polymer film is a few times larger than that after solution nebulization. The sample probe removes only a small fraction of the sample solution and, therefore, in principle, does not disturb the original solution significantly. Single-pulse laser ablation of the polymer film shows that the ion-exchanged metal ion concentration in the film reduces exponentially with the depth of the polymer film. Ion exchange to the polymer film is probably limited by the rate of metal ion diffusion into the film. Calibration curves for Cu, Hg, Pb, and Zn show linear dynamic range of ～1-2 orders of magnitude. The linear dynamic range for Cu increases to >3 orders of magnitude when using Pb as an internal standard. RSD of the ICP emission intensity is ～8%.     

Determination of trace metals by atomic absorption spectrometry after coprecipitation with europium hydroxide

A procedure for the determination of trace amounts of chromium(III), iron(III), lead(II) and manganese(II) is described, that combines atomic absorption spectrometry-europium hydroxide coprecipitation. The influences of analytical parameters including amount of europium(III), amount of ammonia, sample volume, etc. were investigated on the recoveries of analyte ions. The effects of concomitant ions were also examined. The recoveries of the analyte ions were in the range of 95-104%. The detection limits (3 s) were in the range of 1.7-17.1 microg/L. The validation of the presented coprecipitation procedure was performed by the analysis of Bovine Liver 1577-b and BCR-144R Sewage Sludge (domestic origin) standard reference materials. The method was applied to the determination of analytes in real samples including natural waters and some food, soil and fertilizer samples, etc. and good results were obtained (relative standard deviations < 10%, recoveries > 95%).     

原子吸收法测定白酒中铅和锰的方法改进

目的:本文以简化操作步骤,改进实验方法为目的,着重研究利用原子吸收光谱法直接测定白酒中的铅和锰。方法:直接对样品进行稀释,用火焰原子吸收法测定锰。以磷酸氢二铵为基体改进剂,用石墨炉原子吸收光谱法测定铅。结果:该方法操作简单快速,减少了试剂用量,而且精密度和准确度都能满足实验要求。结论:该方法是可行的,值得推广使用。     

Evaluation of an ultrasonic acid digestion procedure for total heavy metals determination in environmental and biological samples

In this study, a sample preparation method based on ultrasonic assisted acid digestion (UAD) has been evaluated for total heavy metals (Cd, Cr, Ni and Pb) determination in different environmental (soil, sediment and sewage sludge), and biological (fish muscles, vegetables and grains) samples, using electrothermal atomic absorption spectrometry (ETAAS). The investigated parameters influencing UAD such as presonication time, sonication time, temperature of ultrasonic bath, and different acid mixtures were fully optimized, whereas power was maintained constant at 100% of nominal power of ultrasonic bath. Six different sets of above parameters were applied on six certified reference materials (CRMs) having different matrices. The accuracy of the method was also tested by comparing the results with those obtained from conventional hot plate assisted acid digestion method on same CRMs. Analytical results for HMs by both methods showed no significant difference at 95% confidence limit (p<0.05). Recoveries of HMs ranging from 96.2% to 102% and 96.3% to 98.6% were obtained from biological and environmental samples, respectively. The average relative standard deviation of UAD method varied between 3.5% and 8.2%, depending on the analyte.