Simultaneous pre-concentration procedure for the determination of cadmium and lead in drinking water employing sequential multi-element flame atomic absorption spectrometry

In this paper is proposed a simultaneous pre-concentration procedure using cloud point extraction for the determination of cadmium and lead in drinking water employing sequential multi-element flame atomic absorption spectrometry. The ligand used is 2-(2-thiazolylazo)-p-cresol (TAC) and the micellar phase is obtained using non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation.The optimization step was performed using two-level factorial design and Doehlert design. A multiple response function was established in order to get experimental conditions for simultaneous extraction of cadmium and lead.The method allows the determination of cadmium and lead with detection limits of 0.077 μg L^− 1 and 1.05 μg L^− 1 respectively, precision expressed as relative standard deviation (RSD) of 1.5 and 3.3% (n = 10) for cadmium concentrations of 30 μg L^− 1 and 50 μg L^− 1, respectively, and RSD of 1.8% and 2.7% for lead concentrations of 30 μg L^− 1 and 50 μg L^− 1, respectively. The accuracy was confirmed by analysis of a certified reference material of natural water.This method was applied for the determination of cadmium and lead in drinking water samples collected in Jaguaquara City, Brazil. Tests of addition/recovery were also performed for some samples and results varied from 95 to 104% for cadmium and 96 to 107% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by Brazilian Health Organization.     

On-line simultaneous pre-concentration procedure for the determination of cadmium and lead in drinking water employing sequential multi-element flame atomic absorption spectrometry

An on-line pre-concentration system for the sequential determination of cadmium and lead in drinking water by using fast sequential flame atomic absorption spectrometry (FS-FAAS) is proposed in this paper. Two minicolums of polyurethane foam loaded with 2-(6-methyl-2-benzothiazolylazo)-orcinol (Me-BTAO) were used as sorptive pre-concentration media for cadmium and lead. The analytical procedure involves the quantitative uptake of both analyte species by on-column chelation with Me-BTAO during sample loading followed by sequential elution of the analytes with 1.0?mol?L^?1 hydrochloric acid and determination by FS-FAAS. The optimisation of the entire analytical procedure was performed using a Box–Behnken multivariate design utilising the sampling flow rate, sample pH and buffer concentration as experimental variables.

The proposed flow-based method featured detection limits (3σ) of 0.08 and 0.51?µg?L^?1 for cadmium and lead, respectively, precision expressed as relative standard deviation (RSD) of 1.63% and 3.87% (n?=?7) for cadmium at the 2.0?µg?L^?1 and 10.0?µg?L^?1 levels, respectively, and RSD of 6.34% and 3.26% (n?=?7) for lead at the 5.0?µg?L^?1 and 30.0?µg?L^?1 levels, respectively. The enrichment factors achieved were 38.6 and 30.0 for cadmium and lead, respectively, using a sample volume of 10.0?mL. The sampling frequency was 45 samples per hour. The accuracy was confirmed by analysis of a certified reference material, namely, SRM 1643d (Trace elements in natural water). The optimised method was applied to the determination of cadmium and lead in drinking water samples collected in Santo Amaro da Purificação City, Bahia, Brazil.     

双硫腙螯合型树脂同时分离富集-火焰原子吸收光谱法测定痕量铅和镉

以大孔聚苯乙烯树脂为母体,通过-N=N-,与双硫腙键合,合成了双硫腙螯合型树脂,并将其应用于痕量铅和镉的同时分离富集,实验了酸度、流速、共存离子干扰等因素对双硫腙螯合型树脂吸附和洗脱Pb和Cd的影响,建立了双硫腙螯合型树脂同时分离富集-火焰原子吸收光度法测定食品及环境样品中痕量Pb和Cd的方法.对Pb和Cd,方法的检出限分别为0.015和0.0013μg/mL,相对标准偏差(RSD)均优于3.0%.     

The determination of lead in tapwater by resin pre-concentration followed by flame atomic absorption spectrometry

The preparation and use of a polystyrene-supported poly(maleic anhydride) resin for the preconcentration of lead from tapwater samples is described. After elution with dilute nitric acid, lead is determined by flame atomic absorption spectrometry down to levels well below the 50 ng cm^-3 E.E.C. limit.     

Ultrasound-assisted emulsification-microextraction combined with flame atomic absorption spectrometry for determination of trace cadmium in water samples

The process of ultrasound-assisted emulsification-microextraction (USAEME) was successfully applied for the first time for the extraction and pre-concentration of trace cadmium from water samples, followed by flame atomic absorption spectrometry (FAAS). In the proposed approach, sodium diethyldithiocarbamate trihydrate solution (NaDDTC·3H₂O) was used as a chelating agent and carbon tetrachloride was selected as extraction solvent. Some effective parameters on the microextraction and the complex formation were selected and optimized. These parameters included extraction solvent type as well as extraction volume, time, temperature, and pH, the amount of the chelating agent, and salt effect. Under optimum conditions, an enrichment factor of 95 was obtained from only 5.0 mL of water sample. The calibration graph was linear in the range of 10-600 μg L⁻¹ with a detection limit of 0.91 μg L⁻¹. The relative standard deviation (R.S.D) for ten replicate measurements of 50 and 500 μg L⁻¹ of cadmium were 2.56 and 1.62%. This proposed method was successfully applied in the analysis of four real environmental water samples and good spiked recoveries over the range of 96.5-101.7% were obtained.     

A pre-concentration procedure using coprecipitation for determination of lead and iron in several samples using flame atomic absorption spectrometry

The present paper proposes a pre-concentration procedure for determination of lead and iron in several samples by flame atomic absorption spectrometry. In it, lead(II) and iron(III) ions are coprecipitated using the violuric acid-copper(II) system as collector. Afterwards, the precipitate is dissolved with 1 M HNO₃ solution and the metal ions are determined. The optimization step was performed using factorial design involving the variables: pH, violuric acid mass (VA) and copper concentration (Cu).Using the optimized experimental conditions, the proposed procedure allows the determination these metals with detection limits of 0.18 μg L⁻¹ for iron and 0.16 μg L⁻¹ for lead. The effects of foreign ions on the pre-concentration procedure were also evaluated and the results demonstrated that this method could be applied for determination of iron and lead in several real samples. The proposed method was successfully applied to the analysis of seawater, urine, mineral water, soil and physiological solution samples. The concentrations of lead and iron achieved in these samples agree well with others data reported in the literature.     

A low-cost flame atomic absorption spectrometry method for determination of trace metals in aqueous samples

A simple and fast method for the extraction into xylene of sub mug l(-1) concentrations of metals using ammonium diethyldithiophosphate (DDTP) as a complexing reagent and their subsequent determination by flame atomic absorption spectrometry is described. The method was tested in sea water spiked with Au at a concentration of 3.0 mug l(-1). The extraction was carried out until the aqueous to organic phase ratio achieved a 1000-fold preconcentration of metal. Optimisation of extraction parameters and the effect of Fe interference was investigated. Sea water samples spiked with Au produced an average recovery of 95% and the detection limit (3sigma) in deionized water was 2.9 ng l(-1). High enrichment factors could be obtained due to the small final volume (mul) of organic solvent.     

浊点萃取-火焰原子吸收光谱法测定淡水鱼中痕量铅

采用以双硫腙为络合剂、Triton X-100为表面活性剂的新型浊点萃取体系富集淡水鱼中的痕量铅,并用火焰原子吸收光谱法对其进行测定。探讨了溶液pH、表面活性剂浓度、络合剂用量、平衡温度、平衡时间等对浊点萃取及测定灵敏度的影响,优化了实验条件。在最佳条件下测得铅的检出限为0.090μg/L,校准曲线相关系数为0.9999。该方法已用于淡水鱼中痕量铅的测定。     

Cloud point extraction for the determination of cadmium and lead employing sequential multi-element flame atomic absorption spectrometry

A cloud point extraction procedure for pre-concentration and determination of cadmium and lead in drinking water using sequential multi-element flame atomic absorption spectrometry is described. 4-(2-thiazolylazo)-orcinol (TAO) has been used as complexing agent and the micellar phase was obtained using the non-ionic surfactant octylphenoxypolyethoxyethanol (Triton X-114) and centrifugation. The conditions for reaction and extraction (surfactant concentration, reagent concentration, effect of incubation time, etc) were studied and the analytical characteristics of the method were determined. The method allows the determination of cadmium and lead with quantification limits of 0.30?µg?L^?1 and 2.6?µg?L^?1, respectively. A precision expressed as relative standard deviation (RSD, n?=?10) of 2.3% and 2.6% has been obtained for cadmium concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively, and RSD of 1.3% and 1.7% for lead concentrations of 10?µg?L^?1 and 30?µg?L^?1, respectively. The accuracy was confirmed by analysis of a natural water certified reference material. The method has been applied for the determination of cadmium and lead in drinking water samples collected in the cities of Ilhéus and Itabuna, Brazil. Recovery tests have also been performed for some samples, and results varied from 96 to 105% for cadmium and 97 to 106% for lead. The cadmium and lead concentrations found in these samples were always lower than the permissible maximum levels stipulated by World Health Organization and the Brazilian Government.     

Preconcentration and determination of trace metals by flow injection micelle-mediated extraction using flame atomic absorption spectrometry

Micelle-mediated extraction/preconcentration is incorporated on-line into a flow injection system used to determine low levels of Cd(II), Co(II), Cu(II), Mn(II), Ni(II), Pb(II) and Zn(II) present in various samples. The analyte is complexed with HBDAP (N,N′-bis(2-hydroxy-5-bromo-benzyl)1,2-diaminopropane). Under optimal conditions, a solution of 30% (m/v) NaCl and a sample solution containing 2.5 mL of 1% (m/v) sodium dodecyl sulfate (SDS), 0.5 mL of 1.8 × 10⁻³ M HBDAP and 2.5 mL of pH 8.5 borate buffer solution in 25 mL were pumped through the cotton filled mini-column; onto which the surfactant-rich phase containing the complex is collected. A solution of 0.5 M HNO₃ in 50% acetone is used as the eluent. The limits of detection are (ng mL⁻¹) Cd = 0.39, Cu = 3.2, Co = 7.5, Mn = 3.0, Ni = 3.4, Pb = 17.9 and Zn = 0.89 if the sample is allowed to flow for 30 s, but improved for extended preconcentration periods. Analysis of liquid and solid reference materials showed good agreement with the certified values. Complex formation constants between HBDAP and these metal ions were also determined potentiometrically.     

High performance flow flame atomic absorption spectrometry for interference-free trace determination

In High Performance Flow Atomic Spectrometry (HPF-AS), the aerosol is generated by injecting the sample solution into the gas mixing chamber with the aid of an HPLC pump (Hydraulic High Pressure Nebulization, HHPN, working pressure about 200 bar). Using an additional analytical HPLC column, between sample injection valve and nebulization nozzle, the elements under investigation can be separated from interfering elemental traces or major components (High Performance/Pressure Flow System, HPF). The elements to be determined and the interfering substances reach the flame at different times. This means, for example, that traces of Mg in solutions containing aluminum can be determined without interference. Compared to pneumatic nebulization, there is a 20 fold increase in the detection power when determining calcium in a saturated NaCl solution. HPF-AS is a rapid and sensitive method which allows separation of the calcium from the matrix with subsequent determination in less than 90 s.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday     

Use of masking agents in the determination of lead in tap water by flame atomic absorption spectrometry with flow injection pre-concentration

The selectivity of immobilised 8-hydroxyquinoline for lead is shown to be improved by the use of masking agents during pre-concentration, prior to determination by flame atomic absorption spectrometry. Interference by iron, copper, aluminium and zinc is suppressed by including triethanolamine, thiourea, fluoride, acetylacetone or cyanide in the buffer as masking agents. Species such as iron or copper can completely prevent the pre-concentration of lead. This is shown to be overcome by using a buffer consisting of 0.2 M boric acid, 2% triethanolamine, 2% thiourea and 2% acetylacetone, even when the interfering species is in a 200-fold excess over lead. Recoveries from tap water samples, to which various amounts of lead had been added, ranged from 94 to 108%. Results of analyses of tap water samples using this method were in good agreement with those obtained by electrothermal atomic absorption spectrometry.     

A rapid and simple method for the determination of trace metals in hair samples by atomic absorption spectrometry

Acid digestion procedures are described for the dissolution of human head hair in routine determinations of cadmium, chromium, mercury, lead and zinc in the same sample solution by means of atomic absorption spectrometry. The techniques employed are atomization in a Massman graphite furnace or in an air—acetylene flame; the cold-vapor cell is used for mercury. The entire analytical procedure is tested with powdered homogenized head hair samples, previously analyzed by other analytical techniques. Comparison of the results demonstrates that the proposed technique is at least as precise and accurate as the other procedures used.     

Solid phase extraction of trace cadmium and lead in food samples using modified peanut shell prior to determination by flame atomic absorption spectrometry

Microchimica Acta - Peanut shell was chemically modified with phosphoric acid and used as a solid phase extraction material for the determination of trace amounts of Pb2+ and Cd2+ in food samples...     

微波消解-原子吸收光谱法连续测定仿真饰品中铅镉镍含量

采用HNO3-HF-HCl酸体系消解样品,火焰原子吸收光谱法连续测定非金属材质仿真饰品中的铅、镉和镍。优化了仪器工作参数和消解条件,进行了共存离子的干扰试验。方法检出限分别为铅5.7 mg/kg、镉0.3 mg/kg、镍3.5 mg/kg。实际样品测定的相对标准偏差(n=6)为1.6%～5.2%,回收率为86.0%～105.8%。     

Determination of trace alkaline metals in quartz by flame atomic emission and atomic absorption spectrometry

Flame Atomic Emission Spectrometry (FAES) and Electrothermal Atomizer Atomic Absorption Spectrometry (ETA-AAS) were assessed for the determination of K and Na in quantities of less than 10 μg g⁻¹ in quartz. The advantages of the direct AAS technique (samples were atomized directly in solid form) are described as less time-consuming and do not require extensive sample preparation. The FAES technique was applied as the control method using water standard solutions for calibration. The results obtained by the two methods agree well in the concentration ranges from 0.5 to 20 μg ml⁻¹.     

The design and development of a multichannel atomic absorption spectrometer for the simultaneous determination of trace metals in hair

A multichannel atomic absorption spectrometer capable of analysing up to nine elements simultaneously in human hair has been designed. Light from an array of hollow-cathode lamps is passed through an electrically heated graphite tube into a direct reading spectrometer. The photomultiplier output is fed into a novel transient signalprocessing device which separates the absorption pulse from the continuous background and increases linear range and sensitivity. Solutions containing Ni, Co, Si, Mn, Al, Cu, Ag, Cr and Fe in nanogram and sub-nanogram amounts can be determined with reasonable precision.     

Cloud point preconcentration and flame atomic absorption spectrometric determination of Cd and Pb in human hair

Cloud point methodology has been successfully used for the preconcentration of trace amounts of Cd and Pb as a prior step to their determination by flame atomic absorption spectrometry. O,O-Diethyldithiophosphate and Triton X-114 are used as hydrophobic ligand and non-ionic surfactant, respectively. After phase separation at 40 °C based on cloud point of the mixture, the surfactant-rich phase is diluted with methanol. The enriched analyte in the final solution is determined by flame atomic absorption spectrometry using conventional nebulization. After optimization of the complexation and extraction conditions, enhancement factors of 22 and 43 were obtained for Cd and Pb, respectively. Under the experimental conditions used, preconcentration of only 10 ml of sample in the presence of 0.05% (v/v) Triton X-114 permitted the detection of 0.62 μg l⁻¹ of Cd and 2.86 μg l⁻¹of Pb. The proposed method was applied to the determination of Cd and Pb in human hair samples.     

Coprecipitation of lead and cadmium using copper(II) mercaptobenzothiazole prior to flame atomic absorption spectrometric determination

A coprecipitation method using a combination of 2-mercaptobenzothiazole (MBT) as a chelating reagent and copper as the coprecipitate carrier is described for the determination of trace lead and cadmium by flame atomic absorption spectrometry. The coprecipitation conditions, such as the effect of pH, the amount of carrier element and reagent, standing time, sample volume and matrix effects were examined in detail. It was found that lead and cadmium are coprecipitated quantitatively (≥95%) with Cu(II)-MBT at pH 9 and that the relative standard deviations (n = 7) were ≤1.6%. When using the enrichment factors of 150-fold for lead and cadmium, the detection limits (3s/b) obtained are 1.08 for lead and 0.04 μg L⁻¹ for cadmium. The method was validated with spiked sea water, stream water, well water, and vegetable samples.