Determination of Heavy Metal Content in Wild-Edible Mushroom from Jordan

The heavy metal content was investigated for six mushroom species native to Jordan. Metal (Cu, Pb, Cd, Fe, Zn, Mn, Ni, and Co) content in soil substrate and their relation to metal concentrations in mushroom and underlying soil were determined by flame and graphite furnace atomic absorption spectrometry. Mushroom species and soil were collected from different places in Jordan. The highest Cu level was 51.84 µg g^?1 for the species Lepista nuda; whereas, the lowest Cu level was found to be 18.51 µg g^?1 in Calvatia utriformis. Among the wild mushrooms, the highest Pb level was found as 4.81 µg g^?1 in Bovista plumbea, whereas the lowest Pb concentration was 2.01 µg g^?1 in Calvatia utriformis. The highest Cd level was determined as 1.9 µg g^?1 for Lepista nuda, whereas the lowest Cd level was 0.58 µg g^?1 for the species of Polyporus frondosus. The highest Zn level was 58.77 µg g^?1 for the species of Lepista nuda and the lowest Zn concentration was found 35.98 µg g^?1 in Calvatia utriformis. The highest Fe level was found as 317 µg g^?1 in Lepista nuda, whereas the lowest Fe concentration was 211.7 µg g^?1 in Calvatia utriformis. The highest Mn content was 36.55 µg g^?1 for Russula delica, whereas the lowest Mn level was 24.5 µg g^?1 for the species Bovista plumbea. The highest Ni content was found as 12.65 µg g^?1 for Russula delica, whereas the lowest Ni level was 0.17 µg g^?1 for Bovista plumbea. The highest Co content in the tested mushrooms was found as 3.5 µg g^?1 for the species of Agaricus bisporus, whereas the lowest Co level was 0.85 µg g^?1 for Polyporus frondosus. The results indicated that, in general, heavy metal contents in all mushroom species were lower than the underlying soil substrates except for some mushroom species.     

Pressurised fluid extraction of polycyclic aromatic hydrocarbons and their polar oxidation products from atmospheric particles

An effective method utilising pressurised fluid extraction (PFE) to simultaneously extract polycyclic aromatic hydrocarbons (PAHs) and their polar oxidation products from atmospheric particulate matter (PM) is presented. The PFE method is advantageous over the traditional Soxhlet extraction due to its lower solvent consumption (9 mL compared to 90 mL) and shorter extraction time (15 min versus 18 h). Seventy compounds including PAHs and polar PAH oxidation products containing carbonyl (oxy-PAHs), hydroxyl (hydroxy-PAHs), and carboxylic acid (carboxy-PAHs) groups were targeted in the extraction of two different PM matrices: wood smoke (WS) and diesel exhaust (DE) PM. The PFE method was optimised and then compared to Soxhlet extraction for both PM matrices. The overall amounts of PAHs and their derivatives extracted from WS PM were slightly higher for the optimised PFE method (1849 ± 21 and 1863 ± 25 µg g^?1 with dichloromethane (DCM) and methanol (MeOH), respectively) than those obtained with Soxhlet extraction (1726 ± 33 and 1769 ± 22 µg g^?1 with DCM and MeOH, respectively). For DE PM (standard reference material (SRM) 2975) the overall amounts extracted by both methods were similar (average of 165 ± 6 µg g^?1), agreeing with previously published values. The detailed evaluation of extraction efficiencies for WS PM showed similar amounts for unfunctionalised PAHs (1100 µg g^?1) for both methods and solvents. For DE PM the mass yields for PAHs using PFE with DCM (62 ± 1 µg g^?1) were the highest and nearly 20% higher than those obtained with MeOH (53 ± 2 µg g^?1). The total mass yields of carboxy and hydroxy-PAHs from WS PM were also similar (412 ± 18 and 407 ± 11 µg g^?1) for PFE and Soxhlet with MeOH, and higher than when DCM was used (371 ± 5 and 379 ± 12 µg g^?1 for PFE and Soxhlet, respectively). For both matrices, the PFE yields for oxy-PAHs were higher than those obtained with Soxhlet.     

Square-Wave Anodic Stripping Voltammetry (SWASV) for the Determination of Ecotoxic Metals,Using a Bismuth-Film Electrode

This article reviews the use of square wave anodic stripping voltammetry for the simultaneous determination of ecotoxic metals (Pb, Cd, Cu, and Zn) on a bismuth-film (BiFE) electrode. The BiFE was prepared in situ on a glassy-carbon electrode (GCE) from the 0.1 mol L^?1 acetate buffer solution (pH 4.5) containing 200 µg L^?1 of bismuth (III). The addition of hydrogen peroxide to the electroanalytical cell proved beneficial for the interference-free determination of Cu (II) together with zinc, lead, and cadmium, using the BiFE. The experimental variables were investigated and optimized with the view to apply this type of voltammetric sensor to real samples containing traces of these metals. The performance characteristics, such as reproducibility, decision limit (CC_a), detection capability (CC_β), sensitivity, and accuracy indicated that the method holds promise for trace Cu²⁺, Pb²⁺, Cd²⁺, and Zn²⁺ levels by employment of Hg-free GCE with SWASV. CCa, and CCβ were calculated according to the Commission Decision of 12 August 2002 (2002/657/EC). Linearity was observed in the range 20–280 µg L^?1 for zinc, 10–100 µg L^?1 for lead, 10–80 µg L^?1 for copper, and 5–50 µg L^?1 for cadmium. Using the optimized conditions, the stripping performance of the BiFE was characterized by low limits of detection (LOD). Finally, the method was successfully applied in real as well as in certified reference water samples.     

Determination of Rare Earth Elements in Navel Oranges from Different Geographical Regions of China by Inductively Coupled Plasma-Mass Spectrometry

There are three major production bases of navel oranges in China, including Southern Jiangxi Province, Southern Hunan Province, and the Three Gorges District of the Yangtze River. Southern Jiangxi and Southern Hunan are also famous for rare earth elements that are ionic, making them easily passed from soil to plants and fruits. To test the relative enrichment of rare earth elements in navel oranges from these production sites, ICP-MS analysis was performed following a microwave digestion procedure. The concentrations of La, Ce, Pr, and Nd in navel orange peels from Southern Jiangxi and Southern Hunan (1.26–1.86 µg g^?1) were much higher than results from the Three Gorges (0.23–0.46 µg g^?1). Moreover, yttrium is relatively enriched (0.25–0.29 µg g^?1) in navel orange peels from Southern Jiangxi at concentrations almost twice that from Southern Hunan (0.15 µg g^?1). The various concentrations and distribution of rare earth elements offers the possibility of traceability and authentication of navel oranges. Meanwhile, navel orange peels from Southern Jiangxi posed no risk in consumption, based on the maximum limit level (≤0.7 µg g^?1, wet weight) of rare earth elements in food issued in China (GB 2762-2005).     

Determination of traces of As,Cd, Cr,Hg, Mn,Ni, Sb,Se, Sn and Pb in human hair by triple quadrupole ICP-MS

With the wide range of metallic contaminants discharged in the environment, studying the human health requires a growing number of elements to be monitored in biological samples. Hair analysis has been suggested as a suitable tool for biomonitoring environmental and occupational exposure to toxic elements. This study describes a method for the determination of 10 trace elements in hair samples using ICP-QQQ-MS. Combining the power of the MS/MS high-energy Helium mode with the MS/MS O₂ mass-shift mode, the method offers great analytical performances with detection limits reaching 0.0014 µg g^?1 for As, 0.0016 µg g^?1 for Cd, 0.012 µg g^?1 for Cr, 0.0035 µg g^?1 for Hg, 0.0055 µg g^?1 for Mn, 0.10 µg g^?1 for Ni, 0.0012 µg g^?1 for Sb, 0.0083 µg g^?1 for Sn, 0.011 µg g^?1 for Se and Pb. The accuracy of the method was tested on a human hair ERM® certified reference material. Percent recoveries varied from 91.3% and 106.9% being always in the acceptance range of 90–110%. For all analysed elements, RSD% of repeatability ranged between 0.6% and 9.0% and those of intermediate precision did not exceed the limit of 20% being always lower than 10% (except for As). The proposed method was applied for the determination of trace elements in hair samples from 20 unexposed subjects. The geometric mean levels were as follows: Cr 0.28 µg g^?1, Mn 0.30 µg g^?1, Sn 1.04µg g^?1, Sb 0.07 µg g^?1, Hg 0.42 µg g^?1, As 0.02 µg g^?1, Cd 0.03 µg g^?1, Ni 0.51 µg g^?1, Se 0.45 µg g^?1 and Pb 1.83 µg g^?1. Element concentrations were in the same range with the reported data. The reported results may be useful for environmental exposure assessment or comparisons studies when establishing reference values of trace elements in exposed population.     

Determination of reference interval values for inorganic elements in whole blood samples of humans and laboratory animals by X-ray fluorescence spectrometry

Inorganic elements are responsible for essential bodily functions, such as osmotic regulation, cardiac frequency and contractibility, blood clotting and neuromuscular excitability. The determination of inorganic elements in corporeal fluids such as blood, serum, plasma and urine is used as a monitor for a part or the whole organism; their values, then, are compared with reference interval values. In this study, the energy dispersive X-ray fluorescence spectrometry (EDXRF), applying the Fundamental Parameters method, for the determination of inorganic elements in whole blood samples from humans and laboratory animals, was used. Peripheral blood samples were collected and, before coagulation, 100 μL of sample were deposited onto Whatman No. 41 filter paper and dried, using infrared spotlight. The reference interval values for healthy Brazilian population of Na were found to be 1,788–1,826 μg g^?1, of Mg 63–75 μg g^?1, of P 602–676 μg g^?1, of S 1,519–1,718 μg g^?1, of Cl 2,743–2,867 μg g^?1, of K 1,508–1,630 μg g^?1, of Ca 214–228 μg g^?1, of Fe 170–184 μg g^?1, of Cu 4–6 μg g^?1 and of Zn 1–3 μg g^?1. The reference interval values for golden hamster (Mesocricetus auratus) of Na were found to be 1,714–1,819 μg g^?1, Mg 51–79 μg g^?1, P 970–1,080 μg g^?1, S 1,231–1,739 μg g^?1, Cl 2,775–2,865 μg g^?1, of K 1,968–2,248 μg g^?1, of Ca 209–257 μg g^?1, of Fe 145–267 μg g^?1, of Cu 4–6 μg g^?1 and of Zn 3–5 μg g^?1. A comparative study between EDXRF and instrumental neutron activation analysis data was carried out and the results for both techniques are statistically equal (α = 0.05). The results contribute for the establishment of reference interval values for Na, Mg, P, S, Cl, K, Ca, Cu and Zn in the healthy Brazilian population and the referred laboratory animal species.     

First Systematic Voltammetric Measurements of Cd,Pb, and Cu in Hydrofluoric Acid-Dissolved Siliceous Spicules of Marine Sponges: Application to Antarctic Specimens

Ultrasensitive Square Wave Anodic Stripping Voltammetry is used for the first time for the systematic determination of Cd, Pb, and Cu in siliceous spicules of marine sponges; the procedure is performed directly in hydrofluoric acid solution, according to a procedure previously established in our laboratory, with the aim of demonstrating the feasibility of such measurements and to improve knowledge of heavy metal distribution in Porifera. The following Demospongiae species are considered: Sphaerotylus antarcticus, Haliclona sp., Kirkpatrickia coulmani, and Inflatella belli from the Ross Sea, Antarctica, and Petrosia ficiformis from the Mediterranean Sea, Italy. The method shows a good accuracy; the analytical variability is approximately ±10% for all the metals studied and for all the measurements performed, showing a good repeatability of the method in consideration of low metal concentrations (order of tenths of µg g^?1 dry weight, i.e., of hundreds of ng L^?1 in the HF solution). In particular, the concentrations of heavy metals in the body of the sponge vary in the range 0.038–0.93 µg g^?1 dry weight (d.w.) for Cd, 0.024–0.52 µg g^?1 d.w. for Pb, and 0.32–1.3 µg g^?1 d.w. for Cu. Similar ranges of concentration were recorded in the oscula of S. antarcticus and I. belli. Heavy metal concentration in the spicules can vary within and between specimens and, in particular, siliceous spicules of Antarctic sponges show higher concentrations of Cd and Pb and lower concentrations of Cu than those from the Mediterranean.     

Transfer of Metals from Soil to Crops in an Area near a Coal Gangue Pile in the Guqiao Coal Mine,China

A field survey was conducted to investigate the metal contamination in coal gangue, soils, and crops (rice and soybeans), and to evaluate the possible health risks to the local population through food chain transfer near a coal gangue pile in the Guqiao Coal Mine, China. Contamination levels of zinc, lead, cadmium, and copper in coal gangue, soils, and crops were measured, and bio-accumulation factors from soil to crops were determined; the health risks were calculated accordingly. Results showed that both coal gangue and soil contained high levels of cadmium (0.15 mg kg^?1and 0.20 mg kg^?1) exceeding the background value of the soil. The lead soil concentration was low (9.99 mg kg^?1), but lead in rice (0.38 mg kg^?1) exceeded the maximal permissible limit of 0.2 mg kg^?1. For some tissues of crops studied, there was a significant correlation between the bio-accumulation factor values and the corresponding soil metal concentrations that were best described by a power equation. Oral intake of zinc, cadmium, and copper through crops posed no health risk to local residents, although hazard indices for rice (0.87–2.88) and soybeans (0.06–0.09) suggested that ingestion of rice grains was unsafe for human health. Therefore, rice was inappropriate to be planted in the soil surrounding this coal mine.     

A New Spectrophotometric Method for the Determination of Arsenic in Environmental and Biological Samples

Abstract

A simple and selective spectrophotometric method has been developed for the determination of trace amounts of arsenic using azure B as a chromogenic reagent. The proposed method is based on the reaction of arsenic(III) with potassium iodate in acid medium to liberate iodine. The liberated iodine bleaches the violet color of azure B and is measured at 644 nm. This decrease in absorbance is directly proportional to the As(III) concentration, and Beer's law is obeyed in the range 0.2–10 µg ml^?1 of As(III). The molar absorptivity, Sandell's sensitivity, detection limit, and quantitation limit of the method were found to be 1.12×10⁴ l mol^?1cm^?1, 6.71×10^?3 µg cm^?2, 0.02 µg ml^?1 and 0.08 µg ml^?1, respectively. The optimum reaction conditions and other analytical parameters were evaluated. The proposed method has been successfully applied for the determination of arsenic in various environmental and biological samples.     

Temporal variation of 7Be fallout and its inventory in purple soil in the Three Gorges Reservoir region, China

The deposition flux of ⁷Be was measured in the range from 0.4 to 5.2 Bq m^?2 d^?1, with a mean value of 2.6 Bq m^?2 d^?1, during the period of May 31, 2009?CMay 31, 2010 in the Three Gorges Reservoir region, China. The low annual deposition flux of ⁷Be was probably due to the adsorption of ⁷Be within high altitude clouds and the Qinling-Daba Mountain??s barrier and blocking effects on the cold air during winter months. There was a seasonal trend for ⁷Be deposition, showing a spring maximum and winter minimum, which may be attributed to the seasonal folding of tropopause in spring and little rainfall amount in winter. A strong positive correlation (R ² = 0.67) between ⁷Be deposition flux and rainfall was observed. The depth distribution of ⁷Be in undisturbed purple soil profiles suggested that the nuclide was mainly distributed within the top 20.0 kg m^?2 (~1.5 cm) of soil in depth and the maximum concentration occurred at a depth of 3.0 kg m^?2 (~0.2 cm), then the concentration declined quickly and exponentially with depth. The seasonal inventories of ⁷Be in soils were consistent with the values calculated from the atmospheric fluxes, which shows a great potential for using ⁷Be as a tracer to assess soil redistribution in purple soil areas of China.     

Determination of Arsenic,Mercury and Barium in Herbarium Mount Paper Using Dynamic Ultrasound-Assisted Extraction Prior to Atomic Fluorescence and Absorption Spectrometry

A dynamic ultrasound-assisted extraction method using Atomic Absorption and Atomic Fluorescence spectrometers as detectors was developed to analyze mercury, arsenic, and barium from herbarium mount paper originating from the herbarium collection of the National Museum of Wales. The variables influencing extraction were optimized by a multivariate approach. The optimal conditions were found to be 1% HNO₃ extractant solution used at a flow rate of 1 mL min^?1. The duty cycle and amplitude of the ultrasonic probe was found to be 50% in both cases with an ultrasound power of 400 W. The optimal distance between the probe and the top face of the extraction chamber was found to be 0 cm. Under these conditions the time required for complete extraction of the three analytes was 25 min. Cold vapor and hydride generation coupled to atomic fluorescence spectrometry was utilized to determine mercury and arsenic, respectively. The chemical and instrumental conditions were optimized to provide detection limits of 0.01 ng g^?1 and 1.25 ng g^?1 for mercury and arsenic, respectively. Barium was determined by graphite-furnace atomic absorption spectrometry, with a detection limit of 25 ng g^?1. By using 0.5 g of sample, the concentrations of the target analytes varied for the different types of paper and ranged between 0.4–2.55 µg g^?1 for Ba, 0.035–10.47 µg g^?1 for As, and 0.0046–2.37 µg g^?1 for Hg.     

Determination of the Mineral Composition of Watercress and Data Evaluation Using Multivariate Analysis

This paper reports the determination of the mineral composition of watercress (Nasturtium officinale Cruciferae, Brassicaceae), grown in soils from three cities in the Bahia State of Brazil, and in a fourth city where plants were grown in a hydroponic system. The sampling was carried out during the summer and winter. Analyses were performed with inductively coupled plasma optical emission spectrometry (ICP OES), and the accuracy was confirmed with a certified reference material of apple leaves.

Principal component analysis (PCA) and hierarchical cluster analysis (HCA) revealed different mineral compositions of the samples collected in the summer and winter.

Samples collected in the summer had a higher concentration of the nutrients iron, calcium, and magnesium, and the samples collected in the winter had a higher concentration of manganese and copper. The average contents of the samples (expressed as wet weight) were 2.50 and 3.03 mg g^?1 for calcium, 0.37 and 0.86 mg g^?1 for magnesium, 8.68 and 10.84 µg g^?1 for iron, 8.42 and 8.47 µg g^?1 for zinc, 0.61 and 0.47 µg g^?1 for copper, and 7.78 and 5.03 µg g^?1 for manganese for summer and winter, respectively. These results are in agreement with values previously reported in the literature. Samples collected from the hydroponic system in the winter had a lower concentration of all nutrients.     

Use of ionic liquid based chitosan as sorbent for preconcentration of fluoroquinolones in milk,egg, fish,bovine, and chicken meat samples by solid phase extraction prior to HPLC determination

The possibility of using ionic liquid based chitosan sorbent for the separation and preconcentration of fluoroquinolone antibiotics (marbofloxacin, enoxacin, ofloxacin, ciprofloxacin, and enrofloxacin) has been studied. For this reason, different ionic liquids were prepared and coated on the chitosan sorbent. The conditions of the preconcentration of fluoroquinolones on a microcolumn have been optimized and the extraction efficiencies of the prepared sorbents have been compared. The compounds were eluted with 5 mL of 20% NH₃ (v/v, MeOH) solution and determined by HPLC with diode array and fluorescence detector. The limits of detection were found as 4.23 µ g L^?1 for marbofloxacin, and 1.09 µg L^?1 for enoxacin; 3.23 × 10^?3 µg L^?1 for ofloxacin; 8.39 × 10^?3 µg L^?1 for ciprofloxacin; and 19.50 × 10^?3 µg L^?1 for enrofloxacin. The developed method was applied for the analysis of fluoroquinolone in milk, egg, fish, bovine, and chicken samples and the recoveries were obtained in the range 70–100%.     

Identification and Quantification of Heterologous Compounds Parthenin and Organic Acids in Parthenium Hysterophorus L. Using HPLC-PDA-MS-MS

Parthenium hysterophorus L., is an obnoxious weed known for its environmental health hazards and medicinal uses. These characteristics are due to presence of sesquiterpene lactones and organic acids; therefore a rapid and sensitive analytical procedure using HPLC-PDA-MS-MS was developed and optimized for separation, identification, and quantification of parthenin and six organic acids. Separation and characterization of compounds was achieved on a RP-C18 column with 1% acetic acid in water (A) and acetonitrile (B) as a mobile phase at a flow rate of 0.6 mL min^?1 and by matching their UV and mass spectra with reference compounds. Six organic acids (ferulic acid, 0.1 mg g^?1 to coumaric acid, 13.6 mg g^?1) and parthenin (27.4 mg g^?1) were characterized within 26 minutes of chromatographic separation in plant extract. The calibration curves are linear with correlation coefficients from 0.985 to 0.998, limit of detection and quantification ranged between 1.0 µg mL^?1 (anisic acid) to 2.2 µg mL^?1 (parthenin) and 2.5 µg mL^?1 (coumaric acid) to 5.2 µ g mL^?1 (parthenin) and recovery ranged between 90.9% to 97.3%. To the best of our knowledge this is the first report for the simultaneous separation of parthenin and organic acids. The method is applicable for screening of commercial crops, medicinal plants, and their products which might be mixed with P. hysterophorus during harvesting period.     

Multivariate Analysis for the Classification Differentiation of Brazilian Sugarcane Spirits by Analysis of Organic and Inorganic Compounds

Abstract

Brazilian sugarcane spirits were analyzed to elucidate similarities and dissimilarities by principal component analysis. Nine aldehydes, six alcohols, and six metal cations were identified and quantified. Isobutanol (LD 202.9 µg L^?1), butiraldehyde (0.08–0.5 µg L^?1), ethanol (39–47% v/v), and copper (371–6068 µg L^?1) showed marked similarities, but the concentration levels of n-butanol (1.6–7.3 µg L^?1), sec-butanol (LD 89 µg L^?1), formaldehyde (0.1–0.74 µg L^?1), valeraldehyde (0.04–0.31 µg L^?1), iron (8.6–139.1 µg L^?1), and magnesium (LD 1149 µg L^?1) exhibited differences from samples.     

On-Line Two-Dimension Liquid Chromatography for the Analysis of Ingredients in the Medicinal Preparation of Coptis Chinensis Franch

An on-line two-dimension microflow liquid chromatography was developed for better separation and analysis of the highly complex ingredients of medicinal preparation of traditional Chinese medicine Coptis Chinensis Franch. A two-valve switching system was utilized for two-dimension chromatography with strong cation exchange and reverse-phase capillary columns separation. The components were separated well by this system and yielded over 420 peaks. Under the optimal condition, 4 compounds were detected quantitatively. A good linear relationship was obtained from 0.2 µg mL^?1 to 24 µg mL^?1with detection limits (S/N = 3) ranging from 0.05 µg mL^?1 to 0.2 µg mL^?1for the compounds. We demonstrated that the method can be successfully applied to the analysis of a natural complex sample, with satisfactory results.     

Colorimetric Determination of Lead Using Gold Nanoparticles

A combined homogeneous assay and colorimetric determination method using gold nanoparticles was developed for rapid determination of lead(II) in contaminated natural waters. The presence of lead(II) in the colloidal gold suspension causes a change in the absorbance of the suspension. An increase in the absorption property at 595 nm is accompanied by a change in the size of the gold nanoparticles. High concentrations of lead cause aggregation of the gold colloids. Colloidal gold nanoparticles were synthesized using tannic acid as the reducing agent; this reagent allowed selective determination of lead in 10 µL of water, with a detection limit of 310 ng mL^?1 with an analysis time of 5 min. The coefficient of variation for lead(II) within the working range of the assay (520 ng mL^?1–13 µg mL^?1) varied from 1.3% to 9.2%. The limit of detection using this method with a sample volume of 50 µL was 60 ng mL^?1. The coefficient of variation for lead over the working range of the determined concentrations (80 ng mL^?1–25 µg mL^?1) varied from 0.2% to 9.3%, while the values for the inter-day assay (n = 8) were less than 10%. The method was employed for the analysis of river, lake, marsh, and spring water; the recovery of lead was determined to be 72.5%–130% for 10 µL of water and 93.6%–114.7% for 50 µL.     

Determination of Gold(III) by Simplified Room-Temperature Ionic Liquid Extraction with Flame Atomic Absorption Spectrometry

A new simplified extraction of gold(III) using a room-temperature ionic liquid prior to determination by flame atomic absorption spectrometry has been developed. The extraction method uses 1-butyl-3-methylimidazolium hexafluorophosphate without a chelating agent. The parameters of the extraction system were investigated in detail. Under the optimized conditions, a linear range of 0.19 to 38.20 µg · mL^?1, a limit of detection of 0.072 µg · mL^?1, an enrichment factor of 10.0, and an extraction capacity of 6.6 mg · g^?1 were obtained. The extraction mechanism and the selectivity of 1-butyl-3-methylimidazolium hexafluorophosphate for gold(III) were also investigated. The method was applied for the determination of gold(III) in water samples with satisfactory results.     

Multi‐Walled Carbon Nanotubes as Sorbent for Flow Injection On‐Line Microcolumn Preconcentration Coupled with Flame Atomic Absorption Spectrometry for Determination of Cadmium and Copper

Abstract

Multi‐walled carbon nanotubes (MWNTs) were used as sorbent for flow injection (FI) on‐line microcolumn preconcentration coupled with flame atomic absorption spectrometry (FAAS) for determination of trace cadmium and copper in environmental and biological samples. Effective preconcentration of trace cadmium and copper was achieved in a pH range of 4.5–6.5 and 5.0–7.5, respectively. The retained cadmium and copper were efficiently eluted with 0.5 mol L^?1 HCl for on‐line FAAS determination. The MWNTs packed microcolumn exhibited fairly fast kinetics for the adsorption of cadmium and copper, permitting the use of high sample flow rates up to at least 7.8 mL min^?1 for the FI on‐line microcolumn preconcentration system without loss of the retention efficiency. With a preconcentration time of 60 sec at a sample loading flow rate of 4.3 mL min^?1, the enhancement factor was 24 for cadmium and 25 for copper at a sample throughput of 45 h^?1. The detection limits (3σ) were 0.30 and 0.11 µg L^?1 for Cd and Cu, respectively. The precision (RSD) for 11 replicate measurements was 2.1% at the 10‐µg L^?1 Cd level and 2.4% at the 10‐µg L^?1 Cu level. The developed method was successfully applied to the determination of trace Cd and Cu in a variety of environmental and biological samples.     

Removal of lead from aqueous solutions by adsorption with surface precipitation

An activated carbon from Coconut (Cocos nucifera) shells was prepared by physical activation with carbon dioxide and water vapor. The activated carbon obtained has a surface area of 1058 m² g^?1 and such a high micropore volume of 0.49 cm³ g^?1. This carbon was studied for the removal of lead from water. Sorption studies were performed at 30 °C, at different pH and adsorbent doses, in batch mode. Lead precipitation was observed on the surface of the activated carbon. Maximum adsorption occurred at pH 9 for an adsorbent dose of 2 g L^?1. Kinetic studies, at the initial concentration of 150 mg L^?1 of lead, pH 5 and an adsorbent dose of 1 g L^?1, yielded an equilibrium time of 50 h for this activated carbon. The kinetic data were modeled with the pseudo first order, the pseudo second order and the Bangham models. The pseudo second order model fitted the data well. The sorption rate constant (7 × 10^?4 mol^?1 Kg s^?1) and the maximum amount of lead adsorbed (0.23 mol kg^?1) are quite good compared to the data found in literature. Sorption equilibrium studies were conducted in a concentration range of lead from 0 to 150 mg L^?1. In an aqueous lead solution with an initial concentration of 30 mg L^?1, at pH 5, adsorbent dose 1 g L^?1, activated Coconut shell carbon removed at equilibrium 100 % of the heavy metal. The equilibrium data were modeled with the Langmuir and Freundlich equations, of which the former gave the best fit. The Langmuir constants Q_{max eq} (0.23 mol kg^?1) and K_L (487667 L mol^?1) are in good agreement with literature. XPS studies identified adsorbed species as lead carbonates and/or lead oxalates and precipitates as lead oxide and/or lead hydroxide on the activated carbon surface. The Coconut shell activated carbon is a very efficient carbon due to its high surface area, to the presence of many micropores on its surface and to the presence surface groups like hydroxyls promoting adsorption in the porous system and lead crystal precipitation on the activated carbon surface.