Trace measurement of lead and cadmium ions in wastewater samples using a novel dithizone immobilized metal–organic framework-based μ-dispersive solid-phase extraction

A low-cost, reliable, easy-to-perform, sensitive and environmentally friendly metal–organic framework (MOF)-based μ-dispersivesolid-phase extraction (μ-dSPE) method for extraction and graphite furnace atomic absorption spectrometry (GF-AAS) determination of lead and cadmium ions in several wastewater samples was successfully developed. Initially, a zinc-based MOF nanosorbent was prepared, immobilized with appropriate complexing agent dithizone (DTZ), characterized and eventually applied for the simultaneous extraction of the target ions. In practice, the application of the DTZ-based MOF nanosorbent led to improvements in the extraction efficiency. After the extraction of the target ions, the desorption process, which was facilitated with vigorous agitation, was performed by applying a small amount of a desorption solvent (inorganic acid, HNO₃). In the next step, concentrations of the desorbed heavy metal ions were measured using GF-AAS. The parameters influencing the adsorption and desorption efficiencies were thoroughly evaluated followed by the establishment of optimal conditions. Under the optimum conditions, the calibration curves for respective Pb(II) and Cd(II) ions were linear over the concentration ranges 0.5–5.0 and 0.05–2.0 μg l⁻¹. Relative recovery tests on spiked wastewater samples were performed with the results varying between 96% and 103%, whilst the analogous precisions were located in the range 1.8–3.1%. Finally, the μ-dSPE method in conjunction with GF-AAS was demonstrated to be fast, sensitive and cost-effective, and could be potentially used in environmental laboratories for the surveillance of lead and cadmium ions in various wastewater samples.     

GF-AAS法和HG-AFS法测定土壤中铅的分析方法比较

为验证土壤中铅的氢化物发生原子荧光光谱法(HG-AFS)的有效性,对3种土壤标准样品(GSS-2,GSS-3及GSS-7)进行测定,同时用国家标准方法GB/T 17141—1997[石墨炉原子吸收光谱法(GF-AAS)]进行比较测定。试验结果表明:两种方法的测定结果均与认定值一致。在精密度、回收率及检出限等方面,HG-AFS法均达到与GF-AAS法相当的水平。但HG-AFS法具有操作简单、分析快速等优势。     

Efficient Removal of Lead from Washing Effluent of Lead-contaminated Soil with Garlic Peel

Wastewater produced from the soil washing process contains heavy metals, which limits its reuse for washing. So it is necessary to develop an efficient and economical way to recycle it, and this study presented a biosorption method to realize this goal. A typical soil sample contaminated by lead was taken from the real field near a lead smelting factory, used for the toxic metals extraction with dilute citric acid. A leach liquor was obtained with lead ions at the level of 12.35 mg/L, Cd 1.2 mg/L, Cu 1.5 mg/L, Zn 2.6 mg/L, as well as the coexisting anions, such as sulphate, silicate, chloride at the concentration of several hundred miligram per liter. The garlic peel was modified by a simple chemical saponification process and used as the biosorbent for toxic metal removal. Firstly, the adsorption behavior of lead ions on the saponified garlic peel was systematically investigated using the synthetic solutions, and then the adsorption mechanisms were explored by detailed experiments combining with the thermodynamic calculation reuslts of the aqueous system of Pb(Ⅱ)-citrate-H₂O. It was found that in artificial solution containing 0.01 mol/L citrate, the maximum adsorption capacity of 261.0 mg/g was reached at pH near 3.0, and also at this very pH value the Pb²⁺ and Pb(H₂Cit)⁺ were the dominant lead species, which are favorable for adsorption due to its easier approaching to the -COO^- ligands in the saponified garlic peel partilces via charge attraction, and the appearance of Pb(HCit)⁰ and Pb(Cit)^- at pH above 3.0 inhibits the adsorption. Secondly, the real leach liquor was used for adsorption tests, and twice adsorption under the optimal conditons would decrease the residual concentrations of Pb, Cd, Cu and Zn to zero. After elution by using 0.1 mol/L nitric acid, the adsorbed metals can be recovered and garlic peel can be reused for at least 10 cycles effectively. This study presents a prospective biosorption method for economical and efficient removal of the lead ions from soil washing wastewater with citric acid as the leaching reagent.     

Slurry sampling for the determination of arsenic, cadmium, and lead in mainstream cigarette smoke condensate by graphite furnace–atomic absorption spectrometry and inductively coupled plasma–mass spectrometry

The slurry sampling technique has been applied for the determination of As, Cd, and Pb in mainstream cigarette smoke condensate (MS CSC) by graphite furnace-atomic absorption spectrometry (GF-AAS) and inductively coupled plasma-mass spectrometry (ICP-MS). The MS CSC of the 1R4F Reference Cigarette was collected by electrostatic precipitation and was subsequently prepared as two slurry samples with and without the dispersing agent Triton X-100. Comparison of results determined by ICP-MS analyses of the 1R4F MS CSC slurry samples with those from the conventional microwave digestion method revealed good agreement. The precision of Triton X-100 slurry sampling and of microwave-assisted digestion was better than 10% RSD, and both were superior to slurry sampling without use of Triton X-100. The accuracy of the analytical results for the Triton X-100 slurry sample was further verified by graphite furnace-atomic absorption spectrometry (GF-AAS). For GF-AAS, the method limits of detection are 1.6, 0.04, and 0.5 microg x L(-1) for As, Cd, and Pb, respectively. For ICP-MS, the method limits of detection are 0.06, 0.01, and 0.38 microg x L(-1) for As, Cd, and Pb, respectively. The MS CSC of the 1R4F Reference Cigarette was collected in accordance with the Federal Trade Commission (FTC) smoking regime (35 mL puff volume of 2-s puff duration at an interval of 60 s) and the concentrations of As, Cd and Pb were 6.0+/-0.5, 69.3+/-2.8, and 42.0+/-2.1 ng/cigarette, respectively.     

Lead post-mortem intake in human bones of ancient populations by (109)Cd-based X-ray fluorescence and EDXRF

In this work we measured the lead concentration in human bones of Middle Age by means of a portable X-ray fluorescence system based on ¹⁰⁹Cd radioactive source. The detection system consists on a Ge hyperpure detector. This system, conceived for in vivo Pb analysis in bone, is portable, non-destructive and is based on lead K lines detection.

The analysed bones are part of two collections of bones both from the end of Middle Age and submitted for some years to a lead polluted burial environment. The bones of one collection were buried initially on the soil in a convent, in Lisbon (Portugal) and further on, kept in a lead coffin for around 100 years. The second collection contains bones buried permanently on the soil around an old church on the south of Portugal. This place became a parking car for around 20 years.

In this work we studied the distribution of Pb in cortical bone, and trabecular regions from the outside surface to the inner part of the bone and the results are compared with the obtained ones by energy dispersive X-ray fluorescence (EDXRF).

The obtained values present a strong contamination of Pb in spongy bones kept in the lead coffin with concentrations ranging from 250 to 350 μg Pb/g bone mineral, and 4 to 7 μg Pb/g bone mineral for bones buried in the soil. Good agreement was observed between the results obtained by the two techniques.     

Extraction as a method for preparation of vegetable samples for the determination of trace metals by atomic absorption spectrometry

An alternative, simple and rapid technique was developed for a quantitative isolation of the group of eight elements: Al, Ca, Cd, Cu, Fe, Mg, Pb and Zn from vegetable material samples in an open system with the use of acids: conc. HCl, dil. HNO₃ and hydrofluoric acids. Equivalence of both the extractants, HCl and HNO₃, was found suitable for a quantitative isolation of Ca, Cu, Mg, Zn, Pb and Cd. For lead and cadmium, however, dil. HNO₃ proved to be more suitable because these elements are determined by the graphite furnace atomic absorption spectrometry (GF-AAS) technique. A quantitative dissolution of Al and Fe requires hydrofluoric acid as an additional extractant. The proposed method allows to obviate the organic matrix destruction stage, shorten the analyte dissolution time, reduce cost, and minimize hazards of loss and contamination. Validity and versatility of the method developed was verified by the analysis of standard reference materials.     

Concentrations of hazardous heavy metals in environmental samples collected in Xiamen, China, as determined by vapor generation non-dispersive atomic fluorescence spectrometry.

Non-dispersive atomic fluorescence spectrometry (NDAFS) coupled with vapor generation (VG) sample introduction was applied to the determination of the concentrations of hazardous heavy metals, such as arsenic, cadmium, lead and mercury, in seawater, soils and total airborne particulate matter (PM) collected around the Xiamen area in China. Almost 100% sample introduction efficiency was achieved by using thiourea and ascorbic acid for the pre-reduction of As(V) to As(III), K3Fe(CN)6 and tartaric acid for pre-oxidation of Pb(II) to Pb(IV), and masking the interferences arising from the co-existing transition metals to As, Cd, Hg and Pb during their vapor generation process. Moreover, a novel sample pretreatment device was developed to avoid the loss of mercury, lead, cadmium and arsenic during sample pretreatment. With such methods, the detection limit (DL) of arsenic, cadmium, lead and mercury was down to 0.08, 0.03, 0.05, 0.01 ng mL(-1) (3sigma), respectively. The relative standard deviations (RSD, n = 11) for arsenic, cadmium, lead and mercury at 10 ng mL(-1) were 0.9%, 1.6%, 1.3% and 2.0%, respectively. The concentrations of hazardous heavy metals in the environmental samples collected in Xiamen, China are in the range from 0.02 +/- 0.001 ng mL(-1) in seawater to 15.3 +/- 0.2 microg g(-1) in soils. Besides flame/GF-AAS and ICP-AES/MS, VG-NDAFS should be another choice for the determination of hazardous heavy metals in environmental samples.     

Solvent impregnated hollow fibre for a selective preconcentration of Pb(II) in an on-line determination by flame atomic absorption spectrometry

A solvent impregnated hollow fibre (SIHF) module has been developed for the preconcentration of lead by using bis(2-ethylhexyl) phosphoric acid (DEHPA) dissolved in kerosene as extractant. The module has been designed for an on-line determination of trace amounts of lead(II) at mg l⁻¹ (ppm) level by flame atomic absorption spectrometry (FAAS).

The SIHF system is based on the metal liquid–liquid distribution between aqueous solutions of different acidity and the mentioned organic solution. The highest enrichment factor of Pb(II) was determined at pH=4.0 using a formic acid/formiate buffer solution.

Preconcentration experiments were carried out at low lead(II) concentration (mg l⁻¹ level) by using the SIHF module. This study includes the influence of hydrodynamic and chemical conditions on the loading and elution of Pb(II) on the SIHF, i.e., flow rate through the fibres, acidity of the eluent (as nitric acid concentration) and the chemical nature of the acid used in the elution. Breakthrough curves were determined for different sampling flow rates, 0.54 ml min⁻¹ was selected to minimise the loading volume of Pb(II) sample. 0.1 M nitric acid was chosen as eluent solution, and perchloric acid also shows appropriate elution characteristics. The degree of concentration obtained for Pb(II) are of 10 fold the original concentration. The quantification limit for Pb(II) achieved with this preconcentration system is 0.17 mg l⁻¹.

The results obtained indicate that the SIHF system can be applied for on-line determination of trace amounts of lead(II) by FAAS.     

Isotopic Characterization of Lead in the Scottish Upland Environment

Abstract

Experimental plots have been set up at two Research Stations in upland areas of Scotland with the intention of characterising environmental samples using lead isotopic composition which varies according to the original source of the lead. Thermal ionisation mass spectrometry (TIMS) was used to measure lead isotope ratios with high precision. The ²⁰⁶Pb/²⁰⁷Pb ratios in rainwater were in the range from 1.101 to 1.153 over a period of two years at the two sites. Low ratios were associated with the very low ratios found in Britain in petrol additives during that period whereas higher ratios indicated a larger component derived from industrial sources at the Hartwood site. The ²⁰⁶Pb/²⁰⁷Pb ratios in the surface (0–2.5 cm) soil from a roadside plot were low (1.1126 and 1.1159 in 1989 and 1990, respectively) but the ratios in surface soils in plots distant from the road were considerably higher. Whereas the lead in roadside soil had a ²⁰⁶Pb/²⁰⁷Pb ratio indicating its source to be predominantly in recent petrol lead, there were significant components from other sources in the soils away from the road. The washing of grass samples resulted in no significant change in the lead isotope ratios. The lead isotope ratios measured in grass samples reflect the isotopic character of current atmospheric inputs but those in surface soil samples are an integrated record of atmospheric deposition over a long period of time. An undisturbed plot under a tree canopy had high concentrations of lead in the surface soil and low ²⁰⁶Pb/²⁰⁷Pb ratios. The ratios in fallen leaves on this plot were slightly but significantly lower than those in the grass grown on the plot. It would appear that the tree canopy is effective at scavenging lead carried in the atmosphere.     

Speciation of Iron in Soils and the Relation with Its Concentration in Fruits

An attempt was made to identify the iron species that is most responsible for plant-available Fe. Iron concentrations in fruit samples were determined by using flame atomic absorption spectrometry (FAAS). The soil samples related to these fruits were also analyzed for Fe by using various digestion and extraction reagents. The relation between the fruit-Fe and soil-extractable-Fe concentrations was examined to explain the Fe uptake of fruit from soil. The probable chemical forms of Fe in the soil were evaluated for the speciation of Fe.     

Direct and simultaneous voltammetric analysis of heavy metals in tap water samples at Assiut city: an approach to improve the analysis time for nickel and cobalt determination at mercury film electrode

Tap water samples (Assiut city, lie in the middle north of upper Egypt, approx. 370 km from Cairo, January-March, 2002) were taken from the eight sampling sites of different locations at Assiut city. The samples are analyzed to determine the total content of cadmium, copper, lead and zinc by differential pulse anodic stripping voltammetry (DPASV) while nickel and cobalt are determined by a new simple differential pulse adsorptive stripping voltammetry (DPAdSV), using dimethylglyoxime (DMG) as the complexing agent. This method uses sodium sulfite as the supporting electrolyte, which facilitates the removal of oxygen interference without the traditional necessity of purging with inert gas. The effect of various parameters was studied using DPASV (for Cd, Pb, Cu and Zn) and AdSV (for Ni and Co) methods. Subsequently, under the so found experimental conditions, the stability of calibration curves and the detection limits (μg/l) have been determined. The data achieved (for all metals utility) are comparable to those measured by the graphite furnace atomic absorption spectrophotometric (GF-AAS) method. The effects of the interferences between these metal ions have been investigated. Moreover, the effect of storage was discussed and the obtained results were compared favorably with standard official methods. Statistical analysis of the database exhibits applicability and the accuracy of the techniques. The results obtained from the two techniques (Voltammetry and GF-AAS) are in very good agreements in the most tap water samples.     

Chemical speciation of heavy metals in soils by use of XAFS spectroscopy and electron microscopical techniques

Pb-contaminated soil samples were investigated using XAFS spectroscopy and SEM/EDX as tools for the analysis of chemical binding forms. The soils originated from the vicinity of a battery factory in Hannover (Germany) and had Pb-contents between 50 g/kg and 140 g/kg. PbCO₃, PbSO₄, PbO and basic PbCO₃ could be identified as the main constituents in the samples by XAFS spectroscopy (EXAFS as well as XANES). This result is consistent with the results of the SEM/EDX investigations on the same soil samples, which showed, that almost all of the lead contained in the soils appears in the form of discrete particles of lead compounds. The EDX analysis of these particles consistently shows the presence of Pb, C, O and S.     

Lead isotope measurements on aerosol samples with ICP-MS

Size fractionated aerosols were collected with low pressure Berner impactors on a radio/TV tower 110 m above ground on a hill 10 km east of Bern at a total elevation of 1060 m asl. Two different wind sectors were chosen with the goal of assessing any differences in lead concentration and the 3 radiogenic lead isotopes (206,207,208) for east and west wind, respectively. A leaching technique was used to extract the lead quantitatively from the surface of the impaction foils. This method has been proven to be better suited for airborne particles than complete microwave digestion because it is less time consuming and contamination risk is smaller. Blank considerations played a major role in choosing all the chemicals, tubes, beakers and selecting the analytical method. Lead concentrations were determined with GF-AAS and lead isotopes with two different ICP-MS systems, one being a multicollector system. Precision of the simultaneous multicollector system was found to be at least a factor of 3 better than that of the sequentially operating ICP-MS. The small variations in isotope ratios from the two wind sectors can be distinctly seen with this enhanced precision. The observed relative difference in isotope ratios between east- and westwind was approximately 0.6% for 207Pb/206Pb and approximately 0.5% for 208Pb/206Pb.     

Multi-element determination in earthworms with instrumental neutron activation analysis and inductively coupled plasma mass spectrometry: A comparison

Earthworms were collected from agricultural fields in Admont, Graz, Piber and Gumpenstein, Austria. Six earthworm samples were investigated with INAA and with ICP-MS in parallel for the element concentrations of As, Ba, Cd, Co, Cr, Cu, Fe, Hg, Pb, Rb, Sb, Se and Zn. With both techniques 14 elements were analysed in a wide concentration range (ng/g to mg/g) GF-AAS and HG-AAS were used for verification of some element concentrations. A comparison of analytical results between INAA and ICP-MS was discussed. In general, good agreement between ICP-MS and INAA was obtained, the relative difference values of most of the elements are within ±20% range, however, a methodical error for the determination of Hg by ICP-MS was found.     

Effect of Lead Contamination on Soil Microbial Activity Measured by Microcalorimetry

Microcalorimetry was used to investigate the microbial activity in three types of soil (orchard soil, crop soil, forest soil) in Wuhan, China, and to evaluate the influence of different concentrations of lead (Pb²⁺) on soil microbial activity. The experimental results revealed that due to different physical and chemical characteristics of the soils, soil microbial activity in three soil samples were in a descending sequence: orchards soil, crops soil, forest soil. Six levels of Pb viz. 0, 10, 20, 40, 80, 160 μg·g⁻¹ were applied in these soils, and the results showed that an increase of the amount of Pb²⁺ is associated with a decrease in microbial activity in the soils due to the toxic effect of Pb²⁺. In order to gain further insight of the sequential change of microorganisms, determination of colony forming units (CFU) was performed to provide a negative linear correlation between the heat effect and the respective number of microorganisms in the system.     

Determination of lead in seawater by inductively coupled plasma optical emission spectrometry after separation and pre-concentration with cocrystallized naphthalene alizarin

An analytical method for separation and pre-concentration of lead in seawater for determination by inductively coupled plasma optical emission spectrometry has been investigated. Lead was retained in the solid phase (0.5 g) composed of co-precipitated naphthalene and alizarin red. The solid phase quantitatively sorbs Pb(II) at pH 8–9, and the metal was eluted using 5.0 ml of 2 mol l⁻¹ nitric acid. The effect of NaCl, KCl, BaCl₂, CaCl₂, Na₂SO₄, MgCl₂ and Na₃PO₄ on the sorption of Pb(II) in the solid phase was studied. A set of solutions containing varying amounts of electrolytes (0.5; 1.0; 3.0 and 5.0% m/v) with Pb (50 μg) was prepared and the recommended procedure applied. The Na₃PO₄ was found to interfere; the other electrolytes did not interfere up to 5% m/v. A pre-concentration factor of 40 was obtained in this analytical procedure. The limit of detection and limit of quantification for Pb(II) were 53 and 176 μg l⁻¹, respectively. Lead was determined in seawater samples collected in Salvador city, Bahia, Brazil. The precision, expressed as R.S.D., was 1.8–4.6%, and the recovery of lead added to seawater samples was 95–97%.     

Lead isotopic analysis of infant bone tissue dating from the Roman era via multicollector ICP–mass spectrometry

Archaeological samples originating from a cemetery of a Roman settlement, Pretorium Agrippinae (1st–3rd century A.D.), excavated near Valkenburg (The Netherlands) have been subjected to Pb isotopic analysis. The set of samples analysed consisted of infant bone tissue and possible sources of bone lead, such as the surrounding soil, garum, and lead objects (e.g., water pipes). After sample digestion with quantitative Pb recovery and subsequent quantitative and pure isolation of lead, the Pb isotopic composition was determined via multicollector ICP–mass spectrometry. The Pb isotope ratio results allowed distinction of three groups: bone, soil, and lead objects + garum. The ²⁰⁸Pb/²⁰⁶Pb ratio ranges were between 2.059 and 2.081 for the soils, between 2.067 and 2.085 for the bones, and between 2.087 and 2.088 for the lead objects. The garum sample is characterised by a ²⁰⁸Pb/²⁰⁶Pb ratio of 2.085. The bone group is situated on the mixing line between the soil and lead object groups, allowing the statement that diagenesis is not the main cause of the Pb found in the bones.      

Chemical speciation of heavy metals in soils by use of XAFS spectroscopy and electron microscopical techniques

Pb-contaminated soil samples were investigated using XAFS spectroscopy and SEM/EDX as tools for the analysis of chemical binding forms. The soils originated from the vicinity of a battery factory in Hannover (Germany) and had Pb-contents between 50 g/kg and 140 g/kg. PbCO₃, PbSO₄, PbO and basic PbCO₃ could be identified as the main constituents in the samples by XAFS spectroscopy (EXAFS as well as XANES). This result is consistent with the results of the SEM/EDX investigations on the same soil samples, which showed, that almost all of the lead contained in the soils appears in the form of discrete particles of lead compounds. The EDX analysis of these particles consistently shows the presence of Pb, C, O and S. Rececived: 1 September 1998 / Revised: 15 December 1998 / Accepted: 18 December 1998     

石墨炉原子吸收光谱测定加热不燃烧烟烟草材料中铅含量的不确定度评定

为评价石墨炉原子吸收光谱法(GF-AAS)测定加热不燃烧烟(HNB)烟草材料中铅含量检测方法的可靠性和检测结果的准确性,采用自下而上法(bottom-up)评定铅含量检测结果的不确定度,分析了测量不确定度的来源及各不确定度分量的影响程度.结果表明,加热不燃烧烟烟草材料中铅含量为2.02 mg/kg,扩展不确定度为0.26 mg/kg(k=2).测量不确定度主要来源于标准曲线拟合和仪器稳定性.故选择适宜的试验方案及试剂,设置合适的仪器参数,确保良好的仪器状态及性能,是获得准确检测结果的前提条件.     

污泥焚烧中铅的形态转化及脱除的热力学平衡研究

利用热力学平衡模型预测了污泥焚烧过程中铅的形态转化和迁移规律, 并采用系统吉布斯自由能最小的原理对Al₂O₃, SiO₂, TiO₂和CaO 4种吸附剂吸附污泥燃烧中铅的效果进行了模拟计算. 探讨了痕量元素Pb与S, Cl的相互作用及S和Cl的存在对吸附剂与Pb反应的影响. 研究结果表明, 污泥焚烧中Pb的形态转化受到S, Cl及矿物质的影响较大. 有S存在情况下, Pb在低温条件下主要以固态PbSO₄存在, 温度较高时以气态PbO存在; Cl较易和Pb结合形成低沸点的金属氯化物而导致Pb的挥发, 并且Cl含量的增加会加速Pb的挥发. 4种吸附剂对污泥焚烧中Pb都有一定的脱除能力, 其中Al₂O₃可以在较宽温度范围对Pb进行捕集, 而CaO对Pb的化学吸附能力较差. 由于S, Cl与Pb有更强的反应性, 因此S, Cl的存在对吸附剂与铅的反应有抑制作用, 使有效吸附的温度范围变窄, 吸附效率降低, 甚至失去脱除Pb的能力, 并且Cl的影响大于S.