Preconcentration and determination of boron in milk,infant formula,and honey samples by solid phase extraction-electrothermal atomic absorption spectrometry

This work presents alternative procedures for the electrothermal atomic absorption spectrometric determination of boron in milk, infant formulas, and honey samples. Honey samples (10% m/v) were diluted in a medium containing 1% v/v HNO₃ and 50% v/v H₂O₂ and introduced in the atomizer. A mixture of 20 µg Pd and 0.5 µg Mg was used for chemical modification. Calibration was carried out using aqueous solutions prepared in the same medium, in the presence of 10% m/v sucrose. The detection limit was 2 µg g^− 1, equivalent to three times the standard error of the estimate (s_y/x) of the regression line. For both infant formulas and milk samples, due to their very low boron content, we used a procedure based on preconcentration by solid phase extraction (Amberlite IRA 743), followed by elution with 2 mol L^− 1 hydrochloric acid. Detection limits were 0.03 µg g^− 1 for 4% m/v honey, 0.04 µg g^− 1 for 5% m/v infant formula and 0.08 µg mL^− 1 for 15% v/v cow milk. We confirmed the accuracy of the procedure by comparing the obtained results with those found via a comparable independent procedure, as well by the analysis of four certified reference materials.     

One-step synthesis of agarose coated magnetic nanoparticles and their application in the solid phase extraction of Pd(II) using a new magnetic field agitation device

A magnetic solid phase extraction method based on agarose coated magnetic nanoparticles)ACMNPs(coupled to a new magnetic field agitation (MFA) device was developed and investigated for the separation, preconcentration and determination of Pd(II) in aqueous solutions. For the first time, the formation of the nanoparticles and their encapsulation in agarose micro-flakes was conducted in a single step. For this purpose, preparation of the magnetic iron oxide nanoparticles was performed in an alkaline agarose solution. The sizes of Fe₃O₄ nanoparticles and agarose micro-flakes were 10–14 nm and 90–130 μm, respectively. The nanomagnetic agarose particles were functionalized by iminodiacetic acid and subjected to magnetic field agitation in the MFA device. The influence of different analytical parameters such as pH, ionic strength, type and volume of desorption solvent and amount of the adsorbent on the preconcentration of Pd(II) were investigated. Eight replicated analysis at the optimized conditions, resulted in a recovery of 94.1% with an RSD of 5.2% for Pd(II). The detection limit of the method (3σ) was 47 ng L⁻¹ for the analyte. The method was successfully applied to the determination of Pd(II) in natural water samples.     

钯与对若丹宁偶氮苯甲酸络合物的固相萃取和光度测定

根据新试剂对若丹宁偶氮苯甲酸(RABA)与钯的显色反应及C18固相萃取小柱对显色络合物的固相萃取,建立了一种测定痕量钯的新方法,在pH为2.0～4.0的HCl-邻苯二甲酸氢钾(HCl-KHP)缓冲介质中,在CTMAB存在下,钯与RABA发生反应形成1:1的稳定络合物,该络合物可用C18固相萃取小柱富集,小柱上富集的络合物用乙醇洗脱后用光度法测定,在富集后的测定液中,络合物最大吸收波长为500 nm,摩尔吸光系数ε=1.36×105 L·mol-1·cm-1,Pd2 量在0.1～1.0 μg/mL内符合比尔定律,方法用于催化剂中钯的测定.     

Non-chromatographic determination of ultratraces of V(V) and V(IV) based on a double column solid phase extraction flow injection system coupled to electrothermal atomic absorption spectrometry

In this work, a non-chromatographic procedure for the on-line determination of ultratraces of V(V) and V(IV) is presented. The method involves a solid phase extraction-flow injection system coupled to electrothermal atomic absorption spectrometry (SPE-FI-ETAAS). The system holds two microcolumns (MC) set in parallel and filled with lab-made mesoporous silica functionalized with 3-aminopropyltriethoxy silane (APS) and mesoporous silica MCM-41, respectively. The pre-concentration of V(V) is performed by sorption onto the first MC (C1) filled with APS at pH 3, whilst that of V(IV) is performed by sorption onto the second column (C2) filled with mesoporous silica MCM-41 at pH 5. Aqueous samples containing both analytes are loaded and, after pre-concentration (pre-concentration factor PCF = 10, sorption flow rate = 1 mL min⁻¹, sorption time = 10 min), they are eluted in separate vessels with hydroxylammonium chloride (HC) 0.1 mol L⁻¹ in HCl 0.5 mol L⁻¹ (elution volume = 1 mL, elution flow rate = 0.5 mL min⁻¹). Afterwards, both analytes are determined through ETAAS with graphite furnace. Under optimized conditions, the main analytical figures of merit for V(V) and V(IV) are, respectively: detection limits (3 s): 0.5 and 0.6 μg L⁻¹, linear range: 2-100 μg L⁻¹ (both analytes), sensitivity: 0.015 and 0.013 μg⁻¹ L and sample throughput: 6 h⁻¹ (both analytes). Recoveries of both species were assayed in different water samples. Validation was performed through certified reference materials for ultratraces of total vanadium in river water.     

Preconcentration of copper on ion-selective imprinted polymer microbeads

Molecular recognition-based separation techniques have received much attention in various fields because of their high selectivity for target molecules. Molecular imprinting has been recognized as a promising technique for the preparation of such systems. In this study, we have prepared a novel molecular imprinted adsorbent to remove heavy metal ions with high selectivity. The Cu(II)-imprinted poly(ethylene glycol dimethacrylate–methacryloylamidohistidine/Cu(II)) (poly(EGDMA–MAH/Cu(II))) microbeads with an average size of 150–200 μm were prepared by dispersion polymerization. These Cu(II) imprinted microbeads were used in the adsorption–desorption of copper(II) ions from metal solutions. Adsorption equilibria was achieved in about 1 h. The maximum adsorption of Cu(II) ions onto imprinted microbeads was about 48 mg/g. The pH significantly affected the adsorption capacity of imprinted microbeads. The observed adsorption order under competitive conditions was Cu(II) > Zn(II) > Ni(II) > Co(II) in mass basis. The imprinted microbeads can be easily regenerated by 0.1 M EDTA solution with higher effectiveness. The imprinted microbeads showed excellent selectivity for the target molecule (i.e. Cu(II) ions due to molecular geometry). These features make imprinted microbeads very good candidate for selective removal of Cu(II) ions at high adsorption capacity. Detection limit was increased at least 1000-folds with the preconcentration approach using the imprinted microbeads. The method was also applied to certified reference and seawater samples.     

Silk fibroin as a sorbent for on-line extraction and preconcentration of copper with detection by electrothermal atomic absorption spectrometry

Silk fibroin is a kind of polypeptide with functional amino acids in its structure. The electric charges in its molecular chains originating from the dissociation of acidic groups, i.e., hydroxyl, phenol and carboxyl, provide vast potentials for the retention of metal species of interest. In this study, the selective retention of Cu²⁺ with silk fibroin at pH 6.0 was investigated and a novel on-line procedure for separation/preconcentration of Cu²⁺ from complex sample matrices was thus developed by using a sequential injection system with an electrothermal atomic absorption spectrometry. A novel concept of enrichment index (EI), i.e., defined as enrichment factor (EF) obtained by consuming unity of sample volume (ml), was proposed for evaluating the enrichment efficiency of a flow-based preconcentration procedure. With a sampling volume of 900 μl, an EI of 30.3 (EF = 27.3) was achieved, which was much improved as compared to that of reported procedures. A detection limit of 8.0 ng l⁻¹ was achieved within a linear range of 0.025-1.5 μg l⁻¹ along with a precision of 2.2% R.S.D. at 0.5 μg l⁻¹. The practical applicability of this procedure was validated by analyzing a certified reference material of riverine water (GBW08608) and a certified reference material of seawater (NASS-5) achieving satisfactory agreements between the certified and the obtained values. A spiking recovery was also performed by using a cave water sample.     

A rapid solid sampling method for determination of nickel and copper along human hair by ETAAS

A procedure for copper and nickel determination in scalp hair by solid sampling electrothermal atomic absorption spectrometric method was described. The hair samples (0.02 to 0.4 mg) were inserted directly on the platforms of solid sampling autosampler. The effects of pyrolysis temperature, atomization temperature, the amount of sample as well as addition of a modifier (Pd/Mg) and/or auxiliary digesting agents (hydrogen peroxide and nitric acid) and/or a surfactant (Triton X-100) on the determination of copper and nickel by solid sampling atomic absorption spectrometry were investigated. After optimization of parameters, the average recoveries of copper in two different certified reference hair samples were 105.7 and 97.6%. The recoveries of nickel in the both certified reference hair samples were in 95.2 and 96.4%. The limits of detection (3σ, N = 10) for copper and nickel were 22 ng/g and 35 ng/g, respectively. Heterogenous distribution of analyte in microscale for segmental analysis could be determined which is important to know that analyte quantity and time of poisoning of a person was exposed. For this purpose, 0.5 cm of pieces were cut along one or a few close strands and analyzed by solid sampling. This process could not be performed by wet-digestion method because 50 mg of sample is needed each time. Finally, the method was applied for the determination of copper and nickel concentrations in the hairs of different persons.     

二苄基硫醚树脂对钯的固相萃取吸附性能研究

基于二苄基硫醚树脂与钯的络合反应,建立了一种高选择性固相萃取吸附钯的方法。在0.1~6.0 mol/L的HCl介质中,钯可以被二苄基硫醚树脂吸附富集并形成1∶2稳定络合物,该络合物可用20 g/L酸性硫脲溶液洗脱,洗脱液经处理后用分光光度法测定,树脂结构不被破坏且可重新处理使用。方法用于吸附分离钯,回收率达90%以上。     

Solid phase extraction of copper (II) by sorption on octadecyl silica membrane disk modified with a new Schiff base and determination with atomic absorption spectrometry

A simple, selective and reliable method for rapid extraction and determination of trace amounts of Cu (II) ions from aqueous samples using octadecyl-bonded silica membrane disks modified with bis-(3-methoxy salicylaldehyde)-1,6-diaminohexane and flame atomic absorption spectrometry (FAAS) is presented. Extraction efficiency, the influence of pH, flow rates, amount of ligand, and type and least amount of eluant were investigated. The linear dynamic range of the proposed method for Cu (II) ions was found in a wide concentration range of 1.0 (± 0.2)–150 (± 2) μg l^− 1. The detection limit and preconcentration factor of this method were found 30.0 (± 0.7) ng l^− 1 and 100 respectively. The reproducibility of the procedure is at the most 2.0%. The effects of various cationic interferences on the percent recovery of copper ion were studied. The method was used to the recovery of copper ion from different synthetic, alloys and biological samples.     

电热原子吸收分析中的固体进样技术

本文综述了电热原子吸收分析中固体进样技术的进展,详细讨论了固体直接进样和悬浮体进样和样品制备方法、进样工具、校正曲线、基体改进技术、分析性能及其最新应用。     

Determination of Ultratrace Amounts of Copper（ Ⅱ ） in Water Samples by Electrothermal Atomic Absorption Spectrometry After Cloud Point Extraction

IntroductionIn environment, copper is usually found in traceor ultratrace levels, and its detection requires sensitiveinstrumental measuring techniques such as electrother-mal atomic absorption spectrometry(ETAAS) and ICP-AES or ICP-MS. Frequently, a prec…     

Metal speciation by coupled in situ graphite furnace electrodeposition and electrothermal atomic absorption spectrometry

The technique of coupled in situ electrodeposition–electrothermal atomic absorption spectrometry (ED–ETAAS) is applied to the analytes Bi, Pb, Ni and Cu. Bi, Pb, Ni and Cu are deposited quantitatively from their EDTA complexes at E_cell=1.75, 2.0, 3.0 and 2.5 V, respectively (E_cell=E_anode−E_cathode+iR). By varying the cell potential, selective reduction of free metal ions could be achieved in the presence of the EDTA complexes. For Bi³⁺ and Pb²⁺ this utilised the voltage windows E_cell=0.6–1.0 and 1.8–2.0 V, respectively. For Ni, deposition at E_cell=1.7–2.0 V achieved substantial, but not complete, differentiation between Ni²⁺ (ca. 90–100% deposition) and Ni(EDTA)²⁻ (ca. 12–20% deposition). An adequate voltage window was not obtained for Cu. The ability of ED–ETAAS to differentiate between electrochemically labile and inert species was demonstrated by application of both ED–ETAAS and anodic stripping voltammetry to the time-dependent speciation of Pb in freshly mixed Pb²⁺–NaCl media. Application to natural water samples is complicated by adsorption of natural organic matter to the graphite cathode.     

Determination of tellurium at ultra-trace levels in drinking water by on-line solid phase extraction coupled to graphite furnace atomic absorption spectrometer

In this paper, two time-based flow injection (FI) separation pre-concentration systems coupled to graphite furnace atomic absorption spectrometry (GFAAS) for tellurium determination are studied and compared. The first alternative involves the pre-concentration of the analyte onto Dowex 1X8 employed as packaging material of a micro-column inserted in the flow system. The second set-up is based on the co-precipitation of tellurium with La(OH)₃ followed by retention onto XAD resins. Both systems are compared in terms of limit of detection, linear range, RSD%, sample throughput, micro-columns lifetime and aptitude for fully automatic operation.     

Application of multiwalled carbon nanotubes as solid phase extraction sorbent for preconcentration of trace copper in water samples

The adsorption behavior of multiwalled carbon nanotubes (MWNTs) toward copper has been investigated systemically, and a new method has been developed for the determination of trace copper in water samples based on preconcentration with a microcolumn packed with MWNTs prior to its determination by flame atomic absorption spectrometry. The optimum experimental parameters for preconcentration of copper, such as pH of the sample, sample flow rate and volume, elution solution and interfering ions, have been investigated. Copper can be quantitatively retained by MWNTs in the pH range 5-8, and then eluted completely with 0.5 M HNO3. The detection limit of this method for Cu was 0.42 ng/mL, and the RSD was 3.5% at the 10 ng/mL Cu level. The method was validated using a certified reference material, and has been successfully applied for the determination of trace copper in water samples.     

Use of 2-(tert-butoxy)-N-(3-carbamothioylphenyl)acetamide and graphene oxide for separation and preconcentration of Fe(Ⅲ),Ni(Ⅱ),Cu(Ⅱ) and Zn(Ⅱ) ions in different samples

A simple and selective method using a column packed with graphene oxide(GO) as a solid phase extractant has been developed for the multi-element preconcentration of Fe(Ⅲ),Ni(Ⅱ),Cu(Ⅱ) and Zn(Ⅱ)ions prior to flame atomic absorption spectrometric determinations.The method is based on the sorption of mentioned ions on synthesized GO using 2-(tert-butoxy)-N-(3-carbamothioylphenyl)acetamide as a chelating agent.Several parameters on the extraction and complex formation were optimized.Under the optimized conditions(pH 6,flow rate 9 mL/min),metal ions were retained on the column,then quantitatively eluted by HNO3solution(5 mL,3.0 mol/L).The preconcentration factor was calculated as250.The detection limits for the analyte ions of interest were found in the range of 0.11 ng/mL(Ni2+) to0.63 ng/mL(Cu2+).The column packed with GO was adequate for metal ions separation in matrixes containing alkali,alkaline earth,transition and heavy metal ions.