Molybdenum(VI) Oxide-Modified Silica Gel as a Novel Sorbent for the Simultaneous Solid-Phase Extraction of Eight Metals with Determination by Flame Atomic Absorption Spectrometry

A silica-based inorganic sorbent was synthesized by the thermal decomposition of ammonium heptamolybdate on silica and applied for the preconcentration and simultaneous determination of Cd, Co, Cr, Cu, Fe, Mn, Ni, and Pb in river water samples using a column system with flame atomic absorption spectrometry. Attenuated total reflection-Fourier transformation infrared spectroscopy, scanning electron microscopy, and electron dispersive spectroscopy were used for sorbent characterization. The effects of pH, sample volume, eluent type, eluent concentration, eluent volume, sample flow rate, and matrix ions (Al, Bi, Ca, Mg, and Zn) on the recovery of the metals in model solutions were investigated. The adsorption capacities (µmol g^?1) of SiO₂-MoO₃ were 88.96 (Cd), 169.69 (Co), 153.85 (Cr), 188.88 (Cu), 179.05 (Fe), 163.81 (Mn), 136.31 (Ni), and 38.61 (Pb). The detection limits of the method were 9.09, 10.82, 10.77, 49.57, 31.64, 6.40, 8.86, 19.15?µg L^?1 for Cd, Co, Cr, Cu, Fe, Mn, Ni, and Pb, respectively, with a preconcentration factor of 25. The developed method was used for the determination of the target metals in real samples and the recoveries for spiked samples were found to be from 91.2% to 102.9%.     

Preparation, characterization, and application of a new thiol-functionalized ionic liquid for highly selective extraction of Cd(II)

A highly selective thiol-functionalized ionic liquid (thiol-FIL) was synthesized and characterized by FT-IR and ESI mass spectroscopy. The capability of thiol-FIL to extract Cd(II), Ni(II), Cr(III) and Pb(II) was evaluated. It is found that thiol-FIL possesses high selectivity for Cd(II), and this has led to a method for determination of Cd(II) by flame atomic absorption spectrometry that is free of interferences by up to a 1,000-fold excess of Na(I), Mg(II), Ca(II), Mn(II), Fe(III), Al(III), Cu(II), Zn(II), Ni(II), Cr(III), Co(II), As(III), Pb(II), and Hg(II). With extraction equilibrium time of 1 min, a good linearity (r = 0.9998) and a detection limit of 0.39 μg?L^?1 were obtained. The precision (RSD) for 11 replicate measurements of 10 μg?L^?1 Cd was 1.6%. The method was validated using certified reference materials. The recoveries of cadmium in spiked real samples ranged from 97% to 102%.     

Novel Chelating Resin for Solid-Phase Extraction of Metals in Certified Reference Materials and Waters

A new chelating resin, poly(diacetonitrile methacrylamide-co-divinylbenzene-co-vinylimidazole), was synthesized and characterized by infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and elemental analysis. The novel resin was used for the first time as a chelating adsorbent for the preconcentration of Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn from various samples by flame atomic absorption spectrometry. The adsorption capacities of the resin were 29.3, 31.6, 29.3, 27.3, 35.5, 31.7, 39.8, and 32.3?mg?g^?1 for Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn, respectively. The detection limits of the metal ions were from 0.42 to 3.21?µg?L^?1. A preconcentration factor of 30 for all metal ions was obtained. The precision of the method as the relative standard deviation was less than or equal to 2.6%. The described method was validated with certified reference materials and fortified real samples. The method was used for the determination of the analytes in well water and wastewater.     

Determination of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts by electrothermal atomic absorption spectrometry after preconcentration by column solid phase extraction

Methods are described for the determination of trace and ultra trace amounts of Cd, Co, Cr, Cu, Fe, Mn, Ni and Pb in natural waters, alkali and alkaline earth salts. Separation and preconcentration of trace metals is achieved by a column solid phase extraction procedure using silica gel modified with derivatives of dithiocarbamates — Na-DDTC (sodium diethyldithio-carbamate and HMDTC (ammonium hexamethylene-dithiocarbamate) as column packing material. The influence of the sorbent preparation procedure on the degree of sorption of the trace analytes is examined for different pH values of the sample solution. Isobutylmethyl ketone (IBMK) is proposed as an effective eluent for quantitative elution of retained metal ions. Optimal instrumental parameters for ETAAS determination of preconcentrated elements in organic eluate are presented. Practical application of sorbents in analysis of natural waters and alkali and alkaline earth salts is demonstrated. Proposed preconcentration procedure combined with ETAAS determination of trace analytes allows the determination of 0.04 g l^–1 Cd, 0.1 g l^–1 Cr, Cu, and Mn and 0.3 g l^–1 Co, Fe, Ni and Pb in natural waters and 1.10^–7% Cd, 3.10^–7% Cr and Mn, 7.10^–7% Co, Ni and Pb and 2.10^–6% Cu and Fe in alkali and alkaline earth salts.     

Determination of some trace metals with a new synthesized polymer resin by FAAS in various tea and herbal plants samples

In this work, a new polymer resin with a functional groups capable of holding trace metals has been synthesized. The structure of polymer resin has been examined by BET-N₂ method analyzer, IR spectrometer, scanning electron microscope (SEM) and elemental microanalyser. The synthesized polymer resin was used for the simultaneous separation and preconcentration of the trace metals from various tea and herbal plants samples. After extraction process, flame atomic absorption spectrometry (FAAS) was used to determine the trace metals. The analytical parameters and solid phase extraction (SPE) performance such as pH, sample volume, flow rates of sample, flow rates of eluent, concentration, volume and type of eluent and effect of interference ions, were investigated. The limits of detection (DL) of the SPE procedure for trace metals, were calculated to be (3s) in the range of 0.9?4.0 μg L^?1 (n = 21) and the factors of preconcentration (PF) were obtained at 200 for Cd, Co, Cu, Fe, Ni and Zn, and at 50 for Cr, Mn and Pb ions and the relative standard deviation (RSD) at ≤ 2% (n = 11).     

Solid phase extraction and preconcentration of some metal ions using Schiff base immobilised silica gel followed by ICP-OES

ABSTRACT

In this study, a simple and efficient solid phase extraction procedure was developed for simultaneous separation and preconcentration of Ba, Cd, Co, Cu, Mn and Ni. The methodology was based on preconcentration of the target analytes on N,N’-bis(4-methoxysalicylidene)-1,3-propanediamine modified silica gel prior to inductively coupled plasma optic emission spectrometry detection. The experimental conditions were as follows: pH of sample 5.00; sample and eluent flow rates 3 mL min^?1; sample volume 25 mL; eluent 0.5 mol L^?1 HNO₃; eluent volume 3.0 mL. Preconcentration factor was achieved as 33.3 for Ba, Co, Mn; 83.3 for Cd, Ni; 166.7 for Cu. Limits of detection were found as 0.33, 0.26, 0.27, 0.36, 0.27 and 0.19 µg L^?1 for Ba, Cd, Co, Cu, Mn and Ni, respectively. The relative standard deviations of 2.6–3.8% were obtained via nine parallel analyses. The suggested procedure was successfully validated by the analysis of TMDA-53.3 Lake Ontario water and ERM-CA022a soft drinking water certified reference materials and applied to various natural water samples.     

Development of a simple and fast ultrasound-assisted extraction method for trace element determination in tobacco samples using ICP-MS

The current study describes a simple and fast method for the determination of Ba, Cd, Co, Cr, Cu, Mn, Ni and Pb in tobacco samples. Commercial cigarettes obtained from local market stores were analysed by inductively coupled plasma mass spectrometry (ICP-MS) after ultrasound-assisted extraction in acidic medium, and the results were compared to those obtained following microwave-assisted digestion of the samples. The sonication time was evaluated from 0 to 60 min, and a 30 min extraction time was selected. The concentration of HNO₃ was also optimised at 0.7 mol L^?1. In order to verify the accuracy of the proposed method, a certified reference material was submitted to the same extraction protocol adopted for the samples, and good agreement with the certified values was obtained at a 95% confidence level, except for Co. The extraction of Pb was also semi-quantitative. A total of four tobacco samples were analysed, with concentrations ranging from 0.4 for Cr to 214.6 µg g^?1 for Mn. The proposed method was demonstrated to be fast, sensitive, precise and accurate for the determination of Ba, Cd, Cr, Cu, Mn an Ni and for the semi-quantitative analysis of Co and Pb in tobacco samples.     

Trace metal accumulation in tissues of sole (Solea senegalensis) and the relationships with the abiotic environment

The distribution patterns and the organ-specific accumulation trends of 10 trace metals (iron, manganese, zinc, copper, chromium, nickel, cobalt, lead, cadmium and silver) and 4 major elements (sodium, potassium, calcium and magnesium) in 10 different tissues (heart, muscle, kidney, stomach, intestine, liver, gill, gonads, white skin and dark skin) of a benthic fish species (Solea senegalensis) from a densely populated coastal area affected by anthropogenic activities, the Bay of Cadiz (SW Spain), have been investigated. High variability of metal concentrations among tissues were found for Ca, Fe, Zn, Cu, Pb and Ag. Factor analysis was applied to study this variability. Five principal components were found explaining the 92.95% of the total variance and similarities in behavioural patterns of bioaccumulation were described. They associated Mg, Cr, Ni and Mn to intestine and stomach tissues (PC1), Ag, Cu and Cd to liver (PC2), Zn, K and Co to gonads (PC3), Na, Fe and Pb to gill, heart and kidney tissues (PC4) and Ca, Pb and Mn to gill and dark skin (PC5). The metallic concentration in the sediment and water was also studied. The pollution in this area was found moderate with outstanding values of Zn, Cu and Pb (average values of 139, 50.4 and 75.6?mg?kg^?1, respectively) in sediment and dissolved Cu (average value of 2.5?µg?L^?1). Metal bioconcentration trends followed the order Zn?>?Cu?>?Cd?>?Pb for dissolved metals in seawater, Cu?>?Zn?>?Cd?>?Pb?≈?Mn?>?Fe?≈?Ni?≈?Co for metals associated to particulate matter and Zn?≈?Cu?>?Cd?>?Mn?>?Co?≈?Fe?>?Ni?≈?Pb?>?Cr for metals in the sediment. Higher values were found for copper in liver, zinc in gonads and lead in gill, showing the relationship between biotic and abiotic environment. In addition, Cd bioconcentration factors were found high in liver and gill showing the sensitivity of sole to this metal even at low concentrations.     

Solid phase extraction of heavy metal ions based on a novel functionalized magnetic multi-walled carbon nanotube composite with the aid of experimental design methodology

We report that magnetic multiwalled carbon nanotubes functionalized with 8-aminoquinoline can be applied to the preconcentration of Cd(II), Pb(II) and Ni(II) ions. The parameters affecting preconcentration were optimized by a Box-Behnken design through response surface methodology. Three variables (extraction time, magnetic sorbent amount, and pH value) were selected as the main factors affecting sorption, and four variables (type, volume and concentration of the eluent; elution time) were selected for optimizing elution. Following sorption and elution, the ions were quantified by FAAS. The LODs are 0.09, 0.72, and 1.0 ng mL^?1 for Cd(II), Ni(II), and Pb(II) ions, respectively. The relative standard deviations are <5.1 % for five separate batch determinations at 30 ng mL^?1 level of Cd(II), Ni(II), and Pb(II) ions. The sorption capacities (in mg g^?1) of this new sorbent are 201 for Cd(II), 150 for Pb(II), and 172 Ni(II). The composite was successfully applied to the rapid extraction of trace quantities of heavy metal ions in fish, sediment, soil, and water samples.

Multi-elemental analysis in biological samples by on-line preconcentration on 8-hydroxyquinoline-cellulose microcolumn coupled to simultaneous ICP-AES

Summary The analytical performance of an on-line oxine-cellulose microcolumn preconcentration system coupled to simultaneous ICP was investigated. Different factors including the pH of the sample solution, the flow rates of sample loading and eluation, the acidity of eluent and different eluents were investigated and optimized. In comparison with continuous aspiration, the signal enhancement factors of eleven elements (Zn, Cu, Ni, V, Cr, Fe, Mn, Co, Pb, Cd and Al) were in the range of 6.4 to 13.5 for peak height (0.5 s) and 3.7 to 5.8 for peak area (15 s), respectively. The influences of matrix ions, such as Ca, Mg, Fe, Cu and NaCl were studied. Performance was demonstrated by simultaneous determination of seven (Zn, Cu, Ni, V, Cr, Fe, Mn) elements in a number of CRMs. Most results were satisfactory, except for iron and chromium. The possible reasons were discussed. Co, Pb, Cd and Al were not available in the simultaneous instrument. Therefore, only the analytical performance was measured for these elements by the sequential instrument.On leave from Shanghai Institute of Metallurgy, Academia Sinica, Shanghai, China 200050     

Trace Elements in Pleurotus Ostreatus,P. Eryngii,and P. Nebrodensis Mushrooms Cultivated on Various Agricultural By-Products

Abstract

Mushrooms are efficient accumulators of essential and toxic elements. Although oyster (Pleurotus spp.) mushrooms are widely commercialized and consumed, few data exist regarding trace elements content and bioaccumulation in cultivated P. ostreatus and P. eryngii, while no data are available for P. nebrodensis. The contents of Al, As, Ba, Cd, Co, Cr, Cs, Cu, Fe, K, Mn, Na, Ni, Pb, Rb, Sr, V, and Zn were monitored using inductively coupled plasma-mass spectrometry (ICP-MS) and atomic emission spectrometry (AES) in P. ostreatus, P. eryngii, and P. nebrodensis mushrooms and their cultivation substrates that include wheat straw (WHS), grape marc (GMC), olive leaves (OLV), and two-phase olive mill wastes (OMW), separately or in mixtures. Bioaccumulation factors (BAFs) less than 0.3 were obtained for Al, Ba, Co, Cr, Fe, Mn, Ni, Pb, Sr, and V; BAFs exceeding 1 for K?>?Zn?>?Cd?>?Cr?>?Rb?>?As, while the BAFs for Na were less 0.7. Mushrooms grown on OLV and OMW presented lower BAFs than those grown on WHS and GMC for all elements except for K, Cd, and Cu. P. ostreatus was an effective accumulator for Cr, Fe, and Zn; P. eryngii for Al, Cs, Ni, and V; and P. nebrodensis for As and Cd. The estimated daily intakes (μg kg^?1 body weight) from mushroom consumption were less than 0.010 for As, Cd, Co, Cs, Pb, and V, 0.010–0.10 for Ba, Cr, Ni, and Sr, 0.10–5.0 for Al, Cu, Fe, Mn, Rb, and Zn, 65–83 for Na, and 858–1030 for K. Overall, the mushrooms studied provide significant amounts of K, adequate amounts of Mn and Zn and low amounts of Na and toxic elements.     

SPE and determination by FAAS of heavy metals using a new synthesized polymer resin in various water and dried vegetables samples

Firstly, poly[phenyl thiadiazole methacrylamide-co-divinylbenzene-co-2-acrylamido-2-methylpropane sulfonic acid] (PTMAAm-co-DVB-co-AMPS), a new polymer resin was synthesized. This polymer resin was characterized by elemental analyzer, X-ray diffractometer, scanning electron microscope (SEM) and IR spectrometer. The glass column packed with the synthesized polymer resin was used for solid phase extraction (SPE). At the same time, the analytes were separated and preconcentrated from various water, dried vegetables samples and standard reference material (CRM) with SPE and determined by flame atomic absorption spectrometer (FAAS). The experimental conditions of this method such as pH, flow rates of sample, flow rates of eluent, type / concentration / volume of eluent, sample volume and matrix ions were examined. The limits of detection (µg L^?1) were calculated (3s) 0.9 for Mn(II), 1.4 for Cd(II), Co(II) and Zn(II), 1.5 for Cr(III), 2.2. for Cu(II), 1.9 for Pb(II),1.5 for Ni(II) and 1.9 for Fe(III) (n = 21). The low relative standard deviation, ≤ 2% (n = 11) and preconcentration factor as 75 for analytes were obtained.     

Simultaneous determination of seven metal ions in water samples by solid-phase extraction on polyacrylonitrile activated carbon fibres

A new solid-phase extraction method utilising polyacrylonitrile activated carbon fibres (PAN-ACFs) as adsorbent was developed for the preconcentration of trace metal ions prior to their determination by inductively coupled plasma optical emission spectrometry (ICP-OES). The PAN-ACFs oxidised with nitric acid were characterised by FT-IR, XRD, SEM and BET analysis. Then the resulting PAN-ACFs were used as solid-phase adsorbent for simultaneously determination of trace Al(III), Be(II), Bi(III), Cr(III), Cu(II), Fe(III) and Pb(II) ions in aqueous solutions. The influences of the analytical parameters on the recoveries of the studied ions were investigated. The optimum experimental conditions of the proposed method were pH: 6.0; eluent concentration and volume: 3.0 mL of 1.5 mol L^?1 nitric acid; flow rates of sample and eluent solution: 1.5 mL min^?1. The preconcentration factors were found to be 67 for Al(III), Bi(III); 83 for Cr(III), Cu(II), Fe(III) and 50 for Be(II), Pb(II). The precision of this method was in range of 1.5%~3.5% and the detection limit of this metal ions was between 0.06~1.50 μg L^?1. The developed method was validated by the analysis of a certified reference sample and successfully applied to the determination of trace metal ions in water samples with satisfactory results.     

Schiff base-functionalised styrofoam resin for preconcentration of metal ions in wastewater and wastewater-irrigated vegetables samples

Polystyrene (PS) was extracted from styrofoam waste and functionalised with schiff base, N,N-bis(salicylidene)cyclohexanediamine (SCHD) through an azo spacer. The resin was characterised and used for preconcentration of Pb(II), Ni(II) and Cd(II) ions prior to their trace determinations by microsample injection system–coupled flame atomic absorption spectrometry (MIS-FAAS). The recoveries of studied metal ions were achieved ≥96.0% with relative standard deviation (RSD) ≤4.5 at optimum parameters: pH 8; resin amount 300 mg; flow rates 3.0 mL min^?1 of sample solution; and 2.0 mL min^?1 of eluent (2.0 mol L^?1 HNO₃). The limits of detection (LODs) and limits of quantification (LOQs) were found to be 0.32, 0.23 and 0.21 and 1.10, 0.78 and 0.69 μg L^?1, respectively, with preconcentration factors (PFs) of 500, 800 and 1000, respectively. The linear ranges of the method were 1–40, 1–25 and 1–20 μg L^?1 for Pb(II), Ni(II) and Cd(II) ions, respectively. The accuracy and validation of the method were evaluated by analysis of certified reference materials (CRMs). The method was successfully applied for preconcentration of studied metal ions in wastewater and wastewater-irrigated vegetable samples.     

Elemental Analysis of Edible Mountain Nettle (Obetia tenax) and the Influence of Soil on Its Chemical Composition

In developing countries, the dietary intake of essential elements is largely dependent on the consumption of edible fruits and leafy vegetables. The distribution of elements in the indigenous edible plant, Obetia tenax (mountain nettle), was investigated as a function of soil quality from eight sites in KwaZulu-Natal, South Africa. The results show concentrations of elements in the leaves to be in decreasing order of Ca?>?Mg?>?Fe?>?Mn?>?Zn?>?Cr?>?Cu?>?Ni?>?Pb?>?Co?>?As?>?Cd?>?Se, and in the stems and roots to be in decreasing order of Ca?>?Mg?>?Fe?>?Mn?>?Zn?>?Cu?>?Ni?>?As?>?Pb?>?Co?>?Cd?>?Cr?>?Se. The quality and pollution status of soil was evaluated by geoaccumulation indices and enrichment factors, which indicated moderate cadmium contamination at the Msinga location that was confirmed by the pollution index and ecological risk levels of single-factor pollution. An assessment of overall contamination of soil using Nemerow pollution index showed moderate pollution by cadmium, while the potential toxicity index indicated low-grade risk for all elements at all sites. Principal component and cluster analysis revealed two groups of elements with similarities, As, Cd, Co, Cr, Cu, Mn, Ni, and Fe, suggesting a lithogenic source and an anthropogenic source for Pb and Zn. Correlation analysis showed significantly positive correlations between As, Co, Cr, Cu, Fe, and Ni/Cd in the soil, confirming the elements’ common origin.     

A novel magnetic metal organic framework nanocomposite for extraction and preconcentration of heavy metal ions, and its optimization via experimental design methodology

We describe a novel magnetic metal-organic framework (MOF) prepared from dithizone-modified Fe₃O₄ nanoparticles and a copper-(benzene-1,3,5-tricarboxylate) MOF and its use in the preconcentration of Cd(II), Pb(II), Ni(II), and Zn(II) ions. The parameters affecting preconcentration were optimized by a Box-Behnken design through response surface methodology. Three variables (extraction time, amount of the magnetic sorbent, and pH value) were selected as the main factors affecting adsorption, while four variables (type, volume and concentration of the eluent; desorption time) were selected for desorption in the optimization study. Following preconcentration and elution, the ions were quantified by FAAS. The limits of detection are 0.12, 0.39, 0.98, and 1.2 ng mL^?1 for Cd(II), Zn(II), Ni(II), and Pb(II) ions, respectively. The relative standard deviations were <4.5 % for five separate batch determinations of 50 ng mL^?1 of Cd(II), Zn(II), Ni(II), and Pb(II) ions. The adsorption capacities (in mg g^?1) of this new MOF are 188 for Cd(II), 104 for Pb(II), 98 Ni(II), and 206 for Zn(II). The magnetic MOF nanocomposite has a higher capacity than the Fe₃O₄/dithizone conjugate. This magnetic MOF nanocomposite was successfully applied to the rapid extraction of trace quantities of heavy metal ions in fish, sediment, soil, and water samples.

Comparative Study of Biosorption of Heavy Metals Using Living Green Algae Scenedesmus quadricauda and Neochloris pseudoalveolaris: Equilibrium and Kinetics

The biosorption of several heavy metals such as cobalt(II), chromium(III), lead(II), cadmium(II), nickel(II), and manganese(II) from aqueous systems on living microalgae cultures, Scenedesmus quadricauda and Neochloris pseudoalveolaris were studied under laboratories conditions. The kinetic and statistical parameters were calculated by using the data obtained from batch cultivation and well fitted a pseudo-first-order rate equation. The initial metal concentrations in solution were about 5–40 mg · L^?1. According to the pseudo-second-order model, the biosorption capacities of Scenedesmus quadricauda for Co(II), Cr(III), Pb(II), Cd(II), Ni(II), and Mn(II) ions were found in the ranges of 2.14–52.48, 1.98–81.98, 8.05–4.26, 7.81–24.96, 2.17–55.71, and 3.54–75.20 mg g^?1, respectively. Kinetic studies revealed that the metal uptake capacity of each living green algae was rather fast. It was also observed that the biosorption kinetic rate decreased with increasing concentration for both microalgae. The application of diffusion-controlled models to the experimental results indicated that the contribution of intraparticle diffusion to the overall sorption kinetics was not very important. Results showed that Co(II), Cr(III), Pb(II), Cd(II), Ni(II), and Mn(II) ions could effectively be absorbed by using living microalga cultures from aqueous solutions.     

Co-precipitative pre-concentration with sodium diethyldithiocarbamate and ICP-AES determination of Se, Cu, Pb, Zn, Fe, Co, Ni, Mn, Cr and Cd in water

Sodium diethyldithiocarbamate in the presence of a weak oxidizing agent is used as a co-precipitative agent for the pre-concentration of Se, Cu, Pb, Zn, Fe, Co, Ni, Mn, Cr and Cd. A procedure was developed for ICP-AES determination of these elements after pre-concentration in river and waste water (an enrichment factor of 40). The recovery of all the elements tested for was more than 98%. The limits of determination (mg l⁻¹) (10 S.D. blank) are 0.001 (Cu, Co, Cr, Mn), 0.0007 (Zn, Cd), 0.003 (Se), 0.004 (Fe), 0.007 (Ni), and 0.01 (Pb).     

Simultaneous preconcentration and determination of nickel and cobalt using functionalised mesoporous silica spheres by ICP-OES

In this work functionalised mesoporous silica spheres have been utilised for the simultaneous preconcentration of nickel and cobalt. The silica spheres (SiSPs) prepared by the sol-gel method were functionalised with sodium diethyldithiocarbamate (DDTC-SiSPs). They were characterised by SEM, TEM, XRD, FTIR, CHN and nitrogen adsorption. The adsorption efficiency of DDTC-SiSPs was examined by batch equilibrium technique. The DDTC-SiSPs showed 100% adsorption for Ni (II) and Co (II). The effect of changing variables such as pH, shaking time, sample volume, preconcentration factor, eluent type and volume were investigated so as to obtain maximum recovery with high selectivity over interfering ions. The maximum adsorption capacity was found to be 15.15 mg g^?1 and 11.80 mg g^?1 for Ni (II) and Co (II) respectively using DDTC-SiSPs. 100% recovery was achieved with 5 mL of 2 M HNO₃. The maximum preconcentration factor was 400 and the 3σ limits of detection were 0.201 µg L^?1 and 0.198 µg L^?1 for Ni (II) and Co (II) respectively. Thermodynamic studies showed that adsorption of Ni (II) and Co (II) on DDTC-SiSPs is exothermic with enthalpy changes of –0.514 KJ mol^?1 and –0.854 KJ mol^?1 for Ni (II) and Co (II) respectively. The method was applied to the preconcentration and determination of Ni (II) and Co (II) from tap, river and sea water.     

Preparation of sinapinaldehyde modified mesoporous silica materials and their application in selective extraction of trace Pb(II)

A new solid phase extractant, sinapinaldehyde (SA) modified SBA-15 mesoporous silica, was developed for selective extraction and preconcentration of trace Pb(II) from aqueous solutions. The successful immobilization of SA on SBA-15 and the strong interaction between SA-SBA-15 and Pb(II) were characterized and confirmed by FTIR spectroscopy and scanning electron microscopy. Parameters such as solution pH, shaking time, eluent condition and sample volume were optimized so that the maximum removal of Pb(II) from solution could be achieved. At pH 4.0, the maximum adsorption capacity of the sorbent for Pb(II) was found to be 33.6?mg?g^?1 and the adsorbed Pb(II) could be completely eluted using a mixed solution of 2?M HCl and 5% CS(NH₂)₂. Some common metal ions such as K(I), Na(I), Mg(II), Ca(II), Cr(III), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) did not interfere with the adsorption of trace Pb(II). The detection limit of the present method was found to be 1.3?ng?mL^?1 and the relative standard deviation was less than 2.0% (n?=?8). These results suggested that this new sorbent is very efficient and selective for the removal of trace Pb(II) in water samples.