Alternative thermodiffusion interface for simultaneous speciation of organic and inorganic lead and mercury species by capillary GC-ICPMS using tri-n-propyl-lead chloride as an internal standard

An alternative thermodiffusion interface (TDI) was designed and constructed for the effective online coupling of capillary gas chromatography (cGC) and inductively coupled plasma mass spectrometry (ICPMS). Pb(2+), (CH3)3Pb(+), (C2H5)3Pb(+), Hg(2+), CH3Hg(+) and C2H5Hg(+) were derived as Pb(C4H9)4, (CH3)3PbC4H9, (C2H5)3PbC4H9, (C4H9)2Hg, CH3HgC4H9, and C2H5HgC4H9 when butyl magnesium bromide was employed as a derivatization reagent for a proof-of-concept study, avoiding the loss of their species specific information. All these derivatives together with the neutral fully saturated (CH3)4Pb and (C2H5)4Pb could be quantitatively separated within 7 min using a 15 m long capillary column, allowing the determination and speciation of organic and inorganic Pb and Hg species in a single run. The method detection limits (3sigma) for Me4Pb, Et4Pb, Me3Pb(3+), Pb(2+), MeHg(+), EtHg(+), and Hg(2+) are 0.07, 0.06, 0.04, 7.0, 0.09, 0.1, and 0.2 pg g(-1), respectively. Moreover, tri-n-propyl-lead chloride was synthesized and used as an alternative internal standard for the accurate and simultaneous speciation analysis of Pb and Hg in complicated environmental and biological samples for the first time. This cGC-TDI-ICPMS method was validated by analyzing Pb and Hg species in certified reference materials and then was applied to simultaneous speciation analysis of Pb and Hg in real-life samples. It is expected that these approaches can be extended to the speciation of other organometallic compounds after suitable modifications and so will aid in monitoring the occurrence, pathways, toxicity, and/or biological effects of these compounds in the environment and in organisms.     

Chemical vapor generation atomic spectrometry using amineboranes and cyanotrihydroborate(III) reagents

Amineboranes of the type L-BH3 (L = NH3; tert-BuNH2; Me2NH; Me3N) and sodium cyanotrihydroborate(III) (NaBH3CN) have been tested as derivatization reagents in the generation of volatile hydrides and elemental mercury following aqueous phase reaction with ionic species of Hg(II), As(III), As(V), Sb(V), Sb(III), Bi(III), Se(IV), Se(VI), Te(IV), and Te(VI). Continuous flow generation atomic absorption spectrometry coupled with a flameless quartz tube atomizer (T = 25 degrees C) and a miniature argon-hydrogen diffusion flame atomizer were employed for the detection of mercury vapors and volatile hydrides, respectively. All of the reductants were able to reduce Hg(II) to the elemental state, giving sensitivities comparable to NaBH4 reduction. Under reaction conditions giving maximum sensitivity for hydride generation with NaBH4, only some amineboranes are able to produce volatile hydrides from all the elements. No evidence of hydride formation was observed from the Se(VI) and Te(VI). In general, the reducing power decreased in the order NaBH4 > H3N-BH3 > tert-BuNH2-BH3 > NaBH3CN > or = Me2HN-BH3 > Me3N-BH3. In comparison with THB, amineboranes and NaBH3CN allowed, in general, a better control of interference effects of Fe(III), Ni(II), Co(II), and Cu(II). Application to determination of mercury in certified reference material is reported. The most likely mechanism of reaction of borane complexes in chemical vapor generation is based on the direct action of hydrogen bound to boron.     

Sampling of trace volatile metal(loid) compounds in ambient air using polymer bags: a convenient method

The sampling of volatile metal(loid) compounds (VOMs) such as hydrides, methylated, and permethylated species of arsenic, antimony, and tin is described using Tedlar bags. Advantages as well as limitations and constraints are discussed and compared to other widely used sampling techniques within this area, namely, stainless steel canisters, cryotrapping, and solid adsorbent cartridges. To prove the suitability of Tedlar bags for the sampling of volatile metal(loid) compounds, series of stability tests have been run using both laboratory synthetic and real samples analyzed periodically after increasing periods of storage. The samples have been stored in the dark at 20 degrees C and at 50 degrees C. Various volatile arsenic species (AsH3, MeAsH2, Me2AsH, Me3As), tin species (SnH4, MeSnH3, Me2SnH2, Me3SnH, Me4Sn, BuSnH3), and antimony species (SbH3, MeSbH2, Me2SbH, Me3Sb) have been generated using hydride generation methodology and mixed with moisturized air. Three static gaseous atmospheres with concentrations of 0.3-18 ng/L for the various compounds have been generated in Tedlar bags, and the stability of the VOMs has been monitored over a period of 5 weeks. Sewage sludge digester gas samples have been stored only at 20 degrees C for a period of 48 h. Cryotrapping GC/ICPMS has been used for the determination of the VOMs with a relative standard deviation of 5% for 100 pg. After 8 h, the recovery rate of all the compounds in the air atmospheres was better than 95% at 20 and 50 degrees C, whereas the recovery after 24 h was found to be between 81 and 99% for all VOMs at 20 and 50 degrees C except for Me3Sb and Me3As. These species show a loss between 48 and 73% at both temperatures. After 5 weeks at 20 degrees C, a loss of only 25-50% for arsine and stibine and the above-mentioned tin compounds was determined. Only Me3Sb, Me3Bi, and Me2Te were present in the digester gas sample. After 24 h, losses of 44, 10, and 12%, respectively, could be determined. Given these results, Tedlar bags could even be used, with some limitations, for long-term sampling of air containing traces of VOMs. The loss is more pronounced at higher temperatures.     

Mechanism of generation of volatile hydrides of trace elements by aqueous tetrahydroborate(III). Mass spectrometric studies on reaction products and intermediates

The mechanism of generation of volatile metal/metalloid hydrides by derivatization with borane complexes is presented. This reaction has been employed for ultratrace element analysis since 1972 and has been the source of much controversy in regard to the reaction mechanism. Here we investigated this derivatization by using As(III), Sb(III), Bi(III), MeAsO(OH)2, and Me2AsO(OH) as model analytes and NaBH4, NaBD4, tert-BuNH2BH3, and Me2NHBH3 as borane reagents. The identification of reaction products and intermediates observed under various reaction conditions was performed by gas chromatography/mass spectrometry and electrospray ionization mass spectrometry. An alternative reaction model, based on the formation of analyte-borane complex (ABC) intermediates, is able to reconcile all the experimental evidence reported in the literature. In this study, we provide definitive evidence of the ABC hydride generation mechanism, which shows that the generation of volatile hydrides occurs via formation of ABC intermediates between hydroboron species and the analyte substrate followed by the direct transfer of hydrogen from boron to the analyte atom, and fast hydrolysis leading to the final product.     

Vapor generation by UV irradiation for sample introduction with atomic spectrometry

Volatile species of the conventional hydride-forming elements (As, Bi, Sb, Se, Sn, Pb, Cd, Te), Hg, transition metals (Ni, Co, Cu, Fe), noble metals (Ag, Au, Rh, Pd, Pt), and nonmetals (I, S) were generated following UV irradiation of their aqueous solutions to which low molecular weight carboxylic acids (formic, acetic, propionic) had been added. Free radicals arising from photodissociation of the latter provide a new and useful alternative to the common methods of chemical/electrochemical vapor generation techniques for the determination of these analytes by atomic spectrometry. Quantitative estimates of the efficiencies of these generation processes were not undertaken, although calculated signal-to-background ratios (>1500 for 5 ng/mL As, Sb, Bi, Se, and Te; 20 for 10 ng/mL Sn, Cu, Rh, Au, Pd, Pt, and Cd; 2400 for 1 ng/mL Hg; and 1000 for Co using ICP-TOF-MS detection) do provide clear evidence of the efficacy of this approach for sample introduction. In the case of Ni and Se, the tetracarbonyl and alkylated selenium compounds have been identified, respectively.     

Species-selective analysis by microcolumn multicapillary gas chromatography with inductively coupled plasma mass spectrometric detection.

A glass rod (5-20 cm long, 2 mm o.d.) containing more than 1200 parallel microchannels (< 40 microns i.d.) was converted into a high-resolution (> 100 theoretical plates cm-1) GC column by coating the inside of each channel in a way that compensated for the dispersion of the channel inner diameter. The columns were evaluated for the separation of mixtures of several organometallic (Hg, Sn, Pb) compounds prior to on-line sensitive metalselective detection by ICPMS. Chromatographic separation conditions were optimized to enable a rapid (within a maximum 30 s) multielemental speciation analysis. Absolute detection limits were 0.1 pg for Hg, 0.05 pg for Sn, and 0.03 pg for Pb using the carrier gas flows of approximately 200 mL min-1. The microcolumn multicapillary GC/ICPMS developed was applied to the analysis of a number of environmental samples. The results were validated with certified reference materials for tin (BCR477, PACS-2) and mercury (DORM-1, TORT-1).     

Quantum dot-based headspace single-drop microextraction technique for optical sensing of volatile species

Core-shell CdSe/ZnS quantum dots (QDs) dispersed in a droplet of organic solvent have been applied for the first time as luminescent probes for the selective detection of volatile species. Luminescence quenching caused by volatile species was examined after their trapping onto a drop using the headspace single-drop microextraction (HS-SDME) approach along with microvolume fluorospectrometry. The novel method is characterized by low reagent and sample consumption, especially regarding QDs, a reduction about 500-fold for each analysis being attained in comparison with luminescent probing in aqueous phase using conventional luminescence spectrometers with 1 cm quartz cells for measurement. To assess QDs as luminescent probes along with HS-SDME, 14 volatile species were tried. Strong luminescence quenching (i.e., I(0)/I > 2.5) was observed for species such as CH(3)Hg(+) and Se(IV) after hydridation with NaBH(4). Moderate luminescent quenching (I(0)/I ≈ 2) was observed for species such as Hg(II) after its conversion into Hg(0), H(2)S, and methylcyclopentadienyl-manganese tricarbonyl (MMT). Small luminescence quenching effects (i.e., 1< I(0)/I <2) were caused by other hydride forming species such as As(III), Sb(III), Te(IV), and Bi(III), as well as SnBu(4), volatile amines, and endosulfan. Detection limits of 6.3 × 10(-9) and 1.6 × 10(-7) M were obtained for Se(IV) and CH(3)Hg(+), respectively. Repeatability expressed as relative standard deviation (N = 7) was about 5%. QD-HS-SDME-μvolume-fluorospectrometry allows one to carry out matrix separation, preconcentration, and confinement of QDs, hence achieving a selective, sensitive, fast, environmentally friendly, and miniaturized luminescence assay.     

Adsorption of chromium(III), mercury(II) and lead(II) ions onto 4-aminoantipyrine immobilized bentonite

In this work, the immobilization of 4-aminoantipyrine onto bentonite was carried out and it was then used to investigate the adsorption behavior of Cr(III), Hg(II) and Pb(II) ions from aqueous solutions. The separation and preconcentration conditions of analytes were investigated, including effects of pH, the shaking time, the sample flow rate and volume, the elution condition and the interfering ions. Under optimum pH value (pH 4.0), the maximum static adsorption capacity of the sorbent was found to be 38.8, 52.9 and 55.5 mg g(-1) for Cr(III), Hg(II) and Pb(II), respectively. 2.0 mL of 2% thiourea in 1.0 M HCl solution effectively eluted the adsorbed metal ions. The detection limit (3σ) of this method defined by IUPAC was found to be 0.12, 0.09 and 0.23 ng mL(-1) for Cr(III), Hg(II) and Pb(II), respectively. The relative standard deviation (RSD) was lower 3.0% (n=8). The developed method has been validated by analyzing certified reference materials and successfully applied to the determination of trace Cr(III), Hg(II) and Pb(II) in water samples with satisfactory results.     

Simultaneous monitoring of volatile selenium and sulfur species from se accumulating plants (wild type and genetically modified) by GC/MS and GC/ICPMS using solid-phase microextraction for sample introduction

A sensitive method for determining ultratrace volatile Se species produced from Brassica juncea seedlings is described. The use of a new commercially available GC/ ICPMS interface in conjunction with solid-phase micro-extraction is a promising way to perform these studies. The addition of optional gases (O2 and N2) to the argon discharge proved to increase the sensitivity for Se and S as well as for Xe, which as a trace contaminant gas, was used for ICPMS optimization studies. However, the optimization parameters differ when an optional gas is added. In the best conditions, limits of detection ranging from 1 to 10 ppt can be obtained depending on the Se compound and 30 to 300 ppt for the volatile S species. The use of GC/MS with similar sample introduction permits the characterization of several unknown species produced as artifacts from the standards. The method allows the virtually simultaneous monitoring of S and Se species from the headspace of several plants (e.g., onions, garlic, etc.) although the present work is focused on the B. juncea seedlings grown in closed vials and treated with Se. Dimethyl selenide and dimethyl diselenide were detected as the primary volatile Se components in the headspace. Sulfur species also were present as allyl (2-propenyl) isothiocyanate and 3-butenyl isothiocyanate as characterized by GC/MS.     

Nanosemiconductor-based photocatalytic vapor generation systems for subsequent selenium determination and speciation with atomic fluorescence spectrometry and inductively coupled plasma mass spectrometry

We reported novel Ag-TiO(2)- and ZrO(2)-based photocatalytic vapor generation (PCVG) systems as effective sample introduction techniques for further improving the sensitivity of the atomic spectrometric determination of selenium for the first time, in which the conduction band electron served as a "reductant" to reduce selenium species including Se(VI) and convert them directly into volatile H(2)Se, which was easily separated from the sample matrix and underwent more effectively subsequent atomization and/or ionization. These two PCVG systems helped us to overcome the problem encountered in the most conventional KBH(4)/OH(-)-H(+) system, in that Se(VI) was hardly converted into volatile selenium species without the aid of prereduction procedures. The limits of detection (LODs) (3σ) of the four most typical Se(IV), Se(VI), selenocystine ((SeCys)(2)), and selenomethionine (SeMet) species were, respectively, down to 1.2, 1.8, 7.4, and 0.9 ng mL(-1) in UV/Ag-TiO(2)-HCOOH, and 0.7, 1.0, 4.2, and 0.5 ng mL(-1) in UV/ZrO(2)-HCOOH with the relative standard deviations (RSDs) lower than 5.1% (n = 9 at 1 μg mL(-1)) when using atomic fluorescence spectrometry (AFS) under flow injection mode. They reached 10, 14, 18, and 8 pg mL(-1) in UV/Ag-TiO(2)-HCOOH, and 6, 7, 10, and 5 pg mL(-1) in UV/ZrO(2)-HCOOH with the RSDs lower than 4.4% (n = 9 at 10 ng mL(-1)) when using inductively coupled plasma mass spectrometry (ICPMS). After the two PCVG systems were validated using certified reference materials GBW(E)080395 and SELM-1, they were applied to determine the total Se in the selenium-enriched yeast sample and used as interfaces between high-performance liquid chromatography (HPLC) and AFS or ICPMS for selenium speciation in the water- and/or enzyme-extractable fractions of the selenium-enriched yeast.     

Synthesis and characterization of metal selenide (ZnSe, CdSe, HgSe) nanoparticles

Thermolysis of [M(SeCH2CH2CH2NMe2)2] (M = Zn, Cd, Hg), prepared by the reactions of sodium salt of 3-(N,N-dimethylamino)propaneselenolate with metal acetates, afforded metal selenides (MSe). The metal selenides were characterized by XRD, EDAX, SEM, AFM, and TEM techniques. Nanoparticles of HgSe were prepared by pyrolysis in a quartz boat, solvothermal, and sonochemical methods. EDAX showed 1:1 Hg/Se ratio, while XRD and SAED patterns confirmed the formation of cubic HgSe. These particles are spherical in nature with an average diameter of 15 nm (from TEM).     

Determination of monomethylcadmium in the environment by differential pulse anodic stripping voltammetry

A differential pulse anodic stripping voltammetric (DPASV) method was used to differentiate between the cadmium species Cd(2+) and MeCd(+) (Me = methyl) in aquatic systems. These two species show peaks in the DPASV voltammogram which differ by 112 mV. In model experiments, it was demonstrated that monomethylcadmium is not stable at pH 2, but under higher pH conditions, normally found in fresh and ocean water samples, the identity of MeCd(+) was verified by different investigations, including cyclic voltammetry, selective extraction of a complex of diethyldithiocarbamate with MeCd(+) into n-hexane, and photochemical dissociation of MeCd(+) by UV irradiation. It was also shown that humic acids do not influence the voltammetric determination of monomethylcadmium. For the first time, it was possible to analyze MeCd(+) in environmental samples. During different expeditions with the German research vessel Polarstern, monomethylcadmium could be determined above the detection limit of 470 pg L(-1) in nearly all surface water samples of the South Atlantic with spot concentrations of up to about 700 pg L(-1), whereas in the North Atlantic only 15-30% of the total samples showed MeCd(+) concentrations above this limit. The existence of MeCd(+) in the remote area of the South Atlantic, as well as positive correlations with the local bioactivity in the ocean, indicates biomethylation as the most probable formation process for this methylated cadmium species. This assumption is supported by the simultaneous occurrence of other methylated heavy metal compounds, such as Me(3)Pb(+). Up to 48% of the total cadmium was found to be monomethylcadmium in some Arctic meltwater ponds.     

Species-specific isotope dilution with permeation tubes for determination of gaseous mercury species

Instrumentation and methodology for determination of the gaseous mercury species Hg0, (CH3)2Hg, and CH3Hg+ has been developed. The method is based on continuous addition of gaseous isotopically enriched Hg species (tracers) at the point of sample acquisition, in combination with reduced pressure sampling on Carbotrap adsorbent tubes. Permeation tubes are used for generation of the tracers. Collected species are thermally desorbed and purged through an aqueous sodium tetraethylborate solution for derivatization of CH3Hg+. The purged gas is dried with a Nafion membrane, and the Hg species are subsequently collected on a smaller Tenax TA adsorbent tube. Species are then thermally desorbed from the Tenax TA and introduced into a gas chromatograph connected to an inductively coupled plasma mass spectrometer for separation and detection. To be able to add tracers during field sampling, we developed a portable device, supplying the permeation tubes with a thermostated and mass flow-controlled air stream of 5.0 +/- 0.1 degrees C and 50.0 mL min(-1), respectively. Typical permeation rates obtained during a period of more than 6 weeks were 12.93 +/- 0.56, 0.42 +/- 0.01, and 0.49 +/- 0.03 (mean +/- standard deviation) pg of Hg min(-1) for a set of 199Hg0, (CH3)2 198Hg, and CH3 200Hg+ tubes, respectively. Methodological detection limits (3sigma) were determined to 700 pg of Hg m(-3) for Hg0 and 50 pg of Hg m(-3) for (CH3)2Hg and CH3Hg+. The collection efficiencies for sampled volumes of 400 L of synthetic air on the Carbotrap tubes used in this study were 13 +/- 2, 102 +/- 2, and 99 +/- 4% for Hg0, (CH3)2Hg, and CH3Hg+, respectively. Desorption efficiencies for the above species and tubes were 98 +/- 2, 98 +/- 1, and 90 +/- 4%, respectively. Fractions (20-40%) of the added (CH3)2 198Hg and CH3 200Hg+ tracers were found to be transformed during the analytical processing of collected air samples. Determined concentrations in the research laboratory air, corrected for species transformations, were 3-53, 8-11, and 1-2 ng of Hg m(-3) for Hg0, (CH3)2Hg, and CH3Hg+, respectively. Concentrations in the ambient air were determined to be 2.1-2.6 ng m(-3) for Hg0 and below the detection limit for (CH3)2Hg and CH3Hg+.     

Phase equilibria in pseudoternary systems of IV–VI compounds

Using literature data, experimental data obtained in this study, and a unified thermodynamic model, we have calculated the T-x-y phase diagrams of all the pseudoternary systems formed by the Group 14 chalcogenides: (Ge, Sn, Pb)Te, Pb(S, Se, Te), and Sn(S, Se, Te). The phase diagrams have been constructed using the known interaction parameters of the pseudobinary systems and the ternary interaction parameters derived from experimental data. The systems have small negative ternary interaction parameters, which decrease in the order β-(Ge, Sn, Pb)Te < β-Pb(S, Se, Te) < δ-Sn(S, Se, Te).     

Pervaporation as an alternative to headspace

The use of pervaporation as an alternative to headspace is proposed. The analytical system involves the speciation of organomercury compounds in solid samples using pervaporation, which has been coupled for the first time to gas chromatography. The speciation of mercury as Me(2)Hg, Et(2)Hg, and MeHgCl has been carried out without any derivatization of the analytes, which, after separation from the solid matrix, are preconcentrated on a Tenax minicolumn prior to desorption and chromatographic separation on a semicapillary column (HP-1) prior to atomic fluorescence detection. No column degradation was observed. Linear ranges and detection limits slightly better than those obtained by headspace GC were observed for mercury species in solid samples. Excellent recoveries (between 95 and 107%) for mercury species added to complex solid samples were obtained by this extremely simple and easily automated setup.     

Sensitive and selective detection of mercury (II) based on the aggregation of gold nanoparticles stabilized by riboflavin

Gold nanoparticles (AuNPs) can be stabilized by riboflavin against tris buffer-induced aggregation. However, in the presence of mercury (II) (Hg2+), riboflavin can be released from the AuNPs surface and the riboflavin-Hg2+ complex formed, leading to the aggregation of AuNPs in tris buffer. The aggregation extent depends on the concentration of Hg2+. Based on the aggregation extent, a simple and sensitive method of determining Hg2+ is developed. The method enables the detection of Hg2+ over the concentration range of 0.02-0.8 microM, with a detection limit (3sigma) of 14 nM, and shows excellent selectivity for Hg2+ over other metal ions (Cu2+, Co2+, Cd2+, Pb2+, Mg2+, Zn2+, Ag+, Ce3+, Ca2+, Al3+, K+). More importantly, the method avoids complicated surface modifications and tedious separation processes.     

Procion Green H-4G immobilized poly(hydroxyethylmethacrylate/chitosan) composite membranes for heavy metal removal

The effective removal of toxic heavy metals from environmental samples still remains a major topic of present research. Metal-chelating membranes are very promising materials as adsorbents when compared with conventional beads because they are not compressible, and they eliminate internal diffusion limitations. The purpose of this study was to evaluate the performance of a novel adsorbent, Procion Green H-4G immobilized poly(hydroxyethylmethacrylate (HEMA)/chitosan) composite membranes, for the removal of three toxic heavy metal ions, namely, Cd(II), Pb(II) and Hg(II) from aquatic systems. The Procion Green H-4G immobilized poly(hydroxyethylmethacrylate/chitosan) composite membranes were characterized by elemental analysis, scanning electron microscopy and Fourier transform infrared (FTIR) spectroscopy. The immobilized amount of the Procion Green H-4G was calculated as 0.018+/-0.003 micromol/cm(2) from the nitrogen and sulphur stoichiometry. The adsorption capacity of Procion Green H-4G immobilized poly(hydroxyethylmethacrylate/chitosan) composite membranes for selected heavy metal ions from aqueous media containing different amounts of these ions (30-400mg/l) and at different pH values (2.0-6.0) was investigated. The amount of Cd(II), Pb(II) and Hg(II) adsorbed onto the membranes measured at equilibrium, increased with time during the first 45 min and then remained unchanged toward the equilibrium adsorption. The maximum amounts of heavy metal ions adsorbed were 43.60+/-1.74, 68.81+/-2.75 and 48.22+/-1.92 mg/g for Cd(II), Pb(II) and Hg(II), respectively. The heavy metal ion adsorption on the pHEMA/chitosan membranes (carrying no dye) were relatively low, 6.31+/-0.13 mg/g for Cd(II), 18.73+/-0.37 mg/g for Pb(II) and 18.82+/-0.38 mg/g for Hg(II). Competitive adsorption of the metal ions was also studied. When the metal ions competed with each other, the adsorbed amounts were 12.74+/-0.38 mg Cd(II)/g, 28.80+/-0.86 mg Pb(II)/g and 18.41+/-0.54 mg Hg(II)/g. Procion Green H-4G immobilized poly(hydroxyethylmethacrylate/chitosan) membranes can be regenerated by washing with a solution of nitric acid (0.01 M). The percent desorption achieved was as high as 95%. These novel membranes are suitable for repeated use for more than five adsorption/desorption cycles without any considerable loss in adsorption capacity. Adsorption equilibria were well described by Langmuir equation. It can be concluded that Procion Green H-4G immobilized poly(hydroxyethylmethacrylate/chitosan) membranes may effectively be used for the removal of Cd(II), Pb(II) and Hg(II) ions from aqueous solutions.     

Phase equilibria in ternary reciprocal systems based on IV–VI compounds

Using the experimental data obtained in this study, literature data, and a unified thermodynamic model, we have calculated the T − x − y phase diagrams of all the pseudoternary reciprocal systems formed by the Group 14 metal chalcogenides: Sn, Pb ‖ S, Se; Sn, Pb ‖ S, Te; and Sn, Pb ‖ Se, Te.     

Impedimetric immobilized DNA-based sensor for simultaneous detection of Pb2+, Ag+, and Hg2+

An unlabeled immobilized DNA-based sensor was reported for simultaneous detection of Pb(2+), Ag(+), and Hg(2+) by electrochemical impedance spectroscopy (EIS) with [Fe(CN)(6)](4-/3-) as redox probe, which consisted of three interaction sections: Pb(2+) interaction with G-rich DNA strands to form G-quadruplex, Ag(+) interaction with C-C mismatch to form C-Ag(+)-C complex, and Hg(2+) interaction with T-T mismatch to form T-Hg(2+)-T complex. Circular dichroism (CD) and UV-vis spectra indicated that the interactions between DNA and Pb(2+), Ag(+), or Hg(2+) occurred. Upon DNA interaction with Pb(2+), Ag(+), and Hg(2+), respectively, a decreased charge transfer resistance (R(CT)) was obtained. Taking advantage of the R(CT) difference (ΔR(CT)), Pb(2+), Ag(+), and Hg(2+) were selectively detected with the detection limit of 10 pM, 10 nM, and 0.1 nM, respectively. To simultaneously (or parallel) detect the three metal ions coexisting in a sample, EDTA was applied to mask Pb(2+) and Hg(2+) for detecting Ag(+); cysteine was applied to mask Ag(+) and Hg(2+) for detecting Pb(2+), and the mixture of G-rich and C-rich DNA strands were applied to mask Pb(2+) and Ag(+) for detecting Hg(2+). Finally, the simple and cost-effective sensor could be successfully applied for simultaneously detecting Pb(2+), Ag(+), and Hg(2+) in calf serum and lake water.     

微波消解-电感耦合等离子体质谱(ICP-MS) 同时测定塑料包装材料中有毒有害元素

采用硝酸-过氧化氢消解体系,及高压密闭微波技术处理塑料包装材料,建立了电感耦合等离子体质谱法同时测定塑料包装材料中铅、镉、砷、铬、锑、汞、硒、钡、镍、锡、锶、铊多种有毒有害元素的方法。方法的检出限为0.02~0.20μg/L,相对标准偏差(RSD)小于10%,加标回收率为88.0%~117.0%。该方法简单、快速、灵敏、准确度好。