Detection Of Trace Metals Research Articles

Concentrations of trace metals, phthalates, bisphenol A and flame-retardants in toys and other children's products in Israel

Trace metals and synthetic chemicals including phthalates, bisphenol A and flame retardants, are widely used in toys and childcare products, and may pose acute or chronic adverse health effects in children. In Israel, certain chemicals are regulated in childcare products, but there are still regulatory gaps. We tested regulated and unregulated contaminants in 174 item parts from 70 childcare items with potentially high oral or dermal exposure, including 22 children's jewelry items, 14 toys, 7 diaper-changing mats, 6 baby mattresses, 7 baby textiles and 14 feeding and bathing items. In children's jewelry, an unregulated product in Israel, 23% of samples exceeded the US standard for lead. In toys, a regulated product, we did not detect trace metals above the Israeli standard. In textiles, baby mattresses and diaper-changing mats, phthalates exceeded the European Union standard in 14–45% of tests with a mean of 6.74% by mass for diisononyl phthalate, and 1.32% by mass for di(2-ethylhexyl) phthalate. BPA migration exceeded the EU standard in 14–45% of tests with a mean of 1.03 ppm. The flame retardants polybrominated biphenyls, pentabromodiphenyl, octabromodiphenyl ether, tris(2,3-dibromopropyl) phosphate and tris-(aziridinyl)-phosphine oxide were not detected. For products regulated in Israel, our findings suggest general compliance with mandatory standards. However, a lack of comprehensive chemical regulation means that there are regulatory gaps, and products not regulated in Israel may contain high levels of chemical contamination, exceeding US or EU regulations. The results of this study have prompted the development of an Israeli safety standard for children's jewelry.

Portable detection of trace metals in airborne particulates and sediments via μPADs and smartphone.

Particulate matter (PM), a key indicator of air pollution by natural and anthropogenic activities, contributes to a wide spectrum of diseases that lead to a shortening of life expectancy. It has been recognized that trace metals in airborne PM are highly toxic and can be correlated with lesion in respiratory, gastrointestinal, immunological, and hematological systems. Traditional methods for trace metal assay require sophisticated instrumentations and highly trained operators in centralized laboratories. In this work, by integrating the technologies of microfluidic paper-based analytical devices, additive manufacturing, smartphone, and colorimetric sensing, we developed the first smartphone based paper microfluidic platform for portable, disposable, and quantitative measurements of cobalt (Co), copper (Cu), and iron (Fe) in ambient air and street sediments. On a single A4-sized paper, 48 devices were fabricated in under 30 s with a total cost of ∼$1.9. On each device, 12 reaction units were patterned and used for colorimetric tests. Particulate samples from urban ambient air and street sediments were collected, processed, and analyzed. Signals of the on-chip complexation product were recorded using a smartphone camera and processed by a self-developed app on an iOS system. For precisely controlling the object distance, chip position, and luminance, a hand-held 3D cellphone housing was designed and printed. The detection limits of Co, Cu, and Fe were determined to be 8.2, 45.8, and 186.0 ng, while the linear dynamic ranges were calculated to be 8.2-81.6, 45.8-4.58 × 102, and 1.86 × 102-1.86 × 103 ng, representing a practically relevant device performance with a significant reduction in the detection cost and time consumption. Trace metals in ambient air and sediments of two cities in China have been quantified portably, thus demonstrating the utility of our system in improving strategies for air pollution control in low-resource settings.

Multi-pulse galvanostatic preparation of nanostructured bismuth film electrode for trace metal detection

The preparation of nanostructured bismuth film electrode (nsBiFE) via ex-situ multi-pulse galvanostatic deposition protocol is presented. The nsBiFE was prepared on a glassy carbon substrate electrode and studied for anodic stripping voltammetric detection of trace metal ions. Several important parameters were examined and optimized, such as the composition of plating solution, pulse deposition current, pulse duration (pulse deposition time and relaxation time) etc. The nsBiFE exhibited excellent sensitivity associated with well-defined and reproducible signals of both test analytes, i.e. Cd(II) and Pb(II), accompanied with low background contribution. It revealed good linear behaviour in the examined concentration range of 20 − 100μgL−1 along with remarkable low limits of detection, i.e. 0.4μgL−1 for Cd(II) and 0.1μgL−1 for Pb(II) after 300s accumulation, and good repeatability with RSDs of 5.1% and 3.8% for Cd(II) and Pb(II), respectively.

Spectrophotometric Determination of the Amount of Zinc on the Imprint Left on Hands by Zinc Coatings with 5-Br-PADAP as the Chromogenic Reagent

Spectrophotometric determination of the amount of zinc on the imprint left on hands by zinc coatings with 2-(5-Bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP) as a chromogenic reagent has been studied in this paper. The effect of reaction conditions including volume and pH of buffer solution as well as the volume of chromogenic reagent on the determination has also been studied. On the optimized condition, the standard curve of zinc has been established and the amount of zinc on the imprint left on hands by zinc coatings with different contact time and time elapse has been determined separately. As the results shown, the optimized reaction condition is 4 mL of boric acid and borax buffer solution(pH 8.0), 0.2 mL of 5-Br-PADAP with the concentration of 1 g·L(-1) and 1 mL of Triton-X-100 with volume fraction of 10%. Under this circumstance, high linearity of zinc is followed between 0 and 14 μg and the regression equation of zinc is y=1.851 34x+0.002 29. The amount of zinc on the imprint left on hands by zinc coatings, ranging from 0.425 to 2.377 μg·cm(-2), increases with contact time from 10 second to 5 min and varies insignificantly from 5 to 10 min. The amount of zinc left on hands declines sharply with time elapse from 0 h to 2 h, and then slowly from 2 to 7 h. The amount of zinc within 7 h is only 0.188 μg·cm(-2), which is 90% lower than that of 0 h. Therefore, it is suggested that the trace metal detection should be conducted as soon as possible. Besides, the amount of zinc on the imprint left on hands by zinc coatings with different time elapse is not entirely comply with the intensity of imprint left by zinc coatings. This demonstrates that the amount of zinc on hands is not the only factor influencing the intensity of imprint on hands with different time elapse. Additionally, it also proves the hypothesis that zinc in the complex of zinc and protein can be captured and bonded by 5-Br-PADAP resorting to a stronger chelating capacity in the experiment for the first time. The application of the combined methods in a macro and micro view is useful for study in mechanism of influencing factors in trace metal detection, which lays foundations l for further researches.

Investigation of the Matrix Effect on the Accuracy of Quantitative Analysis of Trace Metals in Liquids Using Laser-Induced Breakdown Spectroscopy with Solid Substrates.

The detection limit of trace metals in liquids has been improved greatly by laser-induced breakdown spectroscopy (LIBS) using solid substrate. A paper substrate and a metallic substrate were used as a solid substrate for the detection of trace metals in aqueous solutions and viscous liquids (lubricating oils) respectively. The matrix effect on quantitative analysis of trace metals in two types of liquids was investigated. For trace metals in aqueous solutions using paper substrate, the calibration curves established for pure solutions and mixed solutions samples presented large variation on both the slope and the intercept for the Cu, Cd, and Cr. The matrix effects among the different elements in mixed solutions were observed. However, good agreement was obtained between the measured and known values in real wastewater. For trace metals in lubricating oils, the matrix effect between the different oils is relatively small and reasonably negligible under the conditions of our experiment. A universal calibration curve can be established for trace metals in different types of oils. The two approaches are verified that it is possible to develop a feasible and sensitive method with accuracy results for rapid detection of trace metals in industrial wastewater and viscous liquids by laser-induced breakdown spectroscopy.

Neodymium in the oceans: a global database, a regional comparison and implications for palaeoceanographic research.

The neodymium (Nd) isotopic composition of seawater has been used extensively to reconstruct ocean circulation on a variety of time scales. However, dissolved neodymium concentrations and isotopes do not always behave conservatively, and quantitative deconvolution of this non-conservative component can be used to detect trace metal inputs and isotopic exchange at ocean–sediment interfaces. In order to facilitate such comparisons for historical datasets, we here provide an extended global database for Nd isotopes and concentrations in the context of hydrography and nutrients. Since 2010, combined datasets for a large range of trace elements and isotopes are collected on international GEOTRACES section cruises, alongside classical nutrient and hydrography measurements. Here, we take a first step towards exploiting these datasets by comparing high-resolution Nd sections for the western and eastern North Atlantic in the context of hydrography, nutrients and aluminium (Al) concentrations. Evaluating those data in tracer–tracer space reveals that North Atlantic seawater Nd isotopes and concentrations generally follow the patterns of advection, as do Al concentrations. Deviations from water mass mixing are observed locally, associated with the addition or removal of trace metals in benthic nepheloid layers, exchange with ocean margins (i.e. boundary exchange) and/or exchange with particulate phases (i.e. reversible scavenging). We emphasize that the complexity of some of the new datasets cautions against a quantitative interpretation of individual palaeo Nd isotope records, and indicates the importance of spatial reconstructions for a more balanced approach to deciphering past ocean changes.This article is part of the themed issue ‘Biological and climatic impacts of ocean trace element chemistry’.

Three-Electrode on-Chip Sensors for Voltammetric Detection of Trace Metals in Natural Waters

This paper reports on the fabrication and electrochemical characterization of newly designed three-electrode on-chip devices for in situ voltammetric detection of trace metals in marine environment. Sensitivity values higher than those previously reported in literature were obtained for cadmium (Cd(II)), lead (Pb(II)), copper (Cu(II)), zinc (Zn(II)) [1] and arsenite (As(III)) [2]. The key novelty of these devices is the on-chip integration of a reference electrode (RE) towards the miniaturization of the voltammetric in situ profiling system [3].Compared to the microdisc arrays reported by Belmont et al. [1], [4], our sensors also differ in number of iridium (Ir) microdiscs (190 vs. 100), center to center distance of the microdiscs, as well as deposition/patterning techniques used during the fabrication. The sensors were fabricated on silicon wafers passivated with silicon nitride (Si3N4). Ir deposited by sputtering was patterned by Ion Beam Etching, followed by a Si3N4layer deposited by Plasma-Enhanced Chemical Vapor Deposition and subsequently patterned by Deep Reactive-Ion Etching to define the microelectrodes and bonding pads. Ir electrodes were used as either counter electrode (CE) without further modification or as a seed layer for the fabrication of the working and reference electrode (WE, RE). The WE was obtained by plating Ir microdisc array with mercury or gold nanoparticles for direct quantification of respectively cadmium, lead, copper , zinc [5] and arsenite [2], the RE was realized by plating the Ir with silver (Ag) by galvanostatic electrodeposition and chloridizing Ag to silver chloride (AgCl). A schematic view of the sensor is shown in Figure 1 as well as a picture of the microfabricated device. The electrode surface topography and cleanness were analyzed by Scanning Electron Microscopy (SEM) showing an excellent quality of the Si3N4 layer patterning in terms of geometry definition and absence of fabrication residue (as seen in Figure 2). The material properties and the electrochemical behavior of the Ir-based electrodes were characterized by cyclic voltammetry: the integrity of the thin-film Ir layer was assessed in degassed 1 M H2SO4(Figure 3a) and the absence of shielding effect was demonstrated in 1 mM potassium ferricyanide at different scan rates from 1 mV/s to 50 mV/s, as shown by the S-shaped current response in Figure 3b. The measured diffusion controlled steady-state current (118.9±2.24 nA) was found to be in good agreement with the theoretical value calculated for a recessed geometry (119.5 nA). Afterwards SU-8 was patterned by photolithography around the WE and RE to serve as containment ring for an antifouling agarose gel membrane. The pseudo-reference Ag/AgCl RE was tested in seawater showing a potential of about 37 mV against an Ag/AgCl/3 M KCl RE stable over more than 2 months as shown in Figure 4, and in synthetic solutions with different chloride concentrations giving a potential slope of 50.1 mV/decade at 25 °C. The use of an Ionic Liquid (IL) poly(vinyl chloride) (PVC) membrane [6] is currently under investigation in order to develop an all-solid-state RE towards a versatile use in brackish water as well. The first Square Wave Anodic Stripping Voltammetry (SWASV) measurements were carried out in synthetic solutions of Pb(II), Cu(II) and Cd(II) or As(III) against an external RE. Figure 5 shows the SWASV measurements obtained for different concentrations of Pb(II), Cd(II) and Cu(II) in 0.1 M NaNO3 background electrolyte for 600 s deposition time. Registered sensitivity values were 2.73 nAnM-1 min-1, 1.23 nAnM-1 min-1, 1.29 nAnM-1 min-1 and 0.6 nAnM-1 min-1for Pb(II), Cu(II), Cd(II) and As(III), respectively. SWASV measurements against on-chip RE are currently under investigation.

Three-Electrode on-Chip Sensors for Voltammetric Detection of Trace Metals in Natural Waters

Newly designed three-electrode on-chip sensors for voltammetric detection of trace metals in the nanomolar range are presented. The iridium electrodes are used without further modification as the counter electrode (CE) and as a seed layer for post-processing in case of the working and reference electrode (WE, RE). The microdisc array WE is plated with Hg and the RE is realized by plating the electrode with Ag followed by a chloridation step and deposition of PVC/IL. The characterization of the on-chip three electrodes was performed using cyclic voltammetry and chronoamperometry and their performance for trace metal detection evaluated using square wave stripping voltammetry in synthetic and seawater samples. The results demonstrated the applicability of the newly designed interconnected arrays and the on-chip CE to highly sensitive detection of trace metals. They also revealed that the analytical approach proposed for the on-chip RE is promising, but further improvements are still required.

A New Radio Frequency Plasma Oxygen Primary Ion Source on Nano Secondary Ion Mass Spectrometry for Improved Lateral Resolution and Detection of Electropositive Elements at Single Cell Level.

An important application field of secondary ion mass spectrometry at the nanometer scale (NanoSIMS) is the detection of chemical elements and, in particular, metals at the subcellular level in biological samples. The detection of many trace metals requires an oxygen primary ion source to allow the generation of positive secondary ions with high yield in the NanoSIMS. The duoplasmatron oxygen source is commonly used in this ion microprobe but cannot achieve the same quality of images as the cesium primary ion source used to produce negative secondary ions (C(-), CN(-), S(-), P(-)) due to a larger primary ion beam size. In this paper, a new type of an oxygen ion source using a rf plasma is fitted and characterized on a NanoSIMS50L. The performances of this primary ion source in terms of current density and achievable lateral resolution have been characterized and compared to the conventional duoplasmatron and cesium sources. The new rf plasma oxygen source offered a net improvement in terms of primary beam current density compared to the commonly used duoplasmatron source, which resulted in higher ultimate lateral resolutions down to 37 nm and which provided a 5-45 times higher apparent sensitivity for electropositive elements. Other advantages include a better long-term stability and reduced maintenance. This new rf plasma oxygen primary ion source has been applied to the localization of essential macroelements and trace metals at basal levels in two biological models, cells of Chlamydomonas reinhardtii and Arabidopsis thaliana.

Investigation of trace metals distribution in water, sediments and wetland plants of Kızılırmak Delta, Turkey

In this study, accumulation and distribution of Pb, Cu, Zn, Co, Ni, Mn and Fe in water, bottom sediments and four plant species (Myriophyllum verticillatum, Hydrocharis morsus-ranae, Nymphaea alba and Typha latifolia) were investigated in Çernek Lake of Kızılırmak Delta. The Kızılırmak Delta is one of the largest natural wetlands of Turkey and it is protected by the Ramsar convention since 1993. Selected physico–chemical parameters such as pH, conductivity and dissolved oxygen and also trace metal concentrations were monitored in water. All the parameters obtained were found higher than that of the national standards for the protected lakes and reserves. The accumulated amounts of various trace metals in bottom sediments and wetland plants were found in the following order of Fe>Mn>Zn>Ni>Co>Cu>Pb and Fe>Mn>Zn>Ni>Co respectively. The historical trace metal intake of Myriophyllum verticillatum, Hydrocharis morsus-ranae, Typha latifolia and Nymphaea alba were obtained higher than that of the toxic metal levels and these plants may be accepted as accumulators for the detected trace metals and also bio-indicators in the historically polluted natural areas.

Rapid amperometric detection of trace metals by inhibition of an ultrathin polypyrrole-based glucose biosensor

A sensitive and reliable inhibitive amperometric glucose biosensor is described for rapid trace metal determination. The biosensor utilises a conductive ultrathin (55nm thick) polypyrrole (PPy) film for entrapment of glucose oxidase (GOx) to permit rapid inhibition of GOx activity in the ultrathin film upon exposure to trace metals, resulting in reduced glucose amperometric response. The biosensor demonstrates a relatively fast response time of 20s and does not require incubation. Furthermore, a complete recovery of GOx activity in the ultrathin PPy-GOx biosensor is quickly achieved by washing in 2mM EDTA for only 10s. The minimum detectable concentrations achieved with the biosensor for Hg2+, Cu2+, Pb2+ and Cd2+ by inhibitive amperometric detection are 0.48, 1.5, 1.6 and 4.0µM, respectively. Also, suitable linear concentration ranges were achieved from 0.48–3.3µM for Hg2+, 1.5–10µM for Cu2+, 1.6–7.7µM for Pb2+ and 4–26µM for Cd2+. The use of Dixon and Cornish-Bowden plots revealed that the suppressive effects observed with Hg2+ and Cu2+ were via non-competitive inhibition, while those of Pb2+ and Cd2+ were due to mixed and competitive inhibition. The stronger inhibition exhibited by the trace metals on GOx activity in the ultrathin PPy-GOx film was also confirmed by the low inhibition constant obtained from this analysis. The biosensor was successfully applied to the determination of trace metals in tap water samples.

Dehydrated Carbon Coupled with Laser-Induced Breakdown Spectrometry (LIBS) for the Determination of Heavy Metals in Solutions.

In this article, a novel and alternative method of laser-induced breakdown spectroscopy (LIBS) analysis for liquid sample is proposed, which involves the removal of metal ions from a liquid to a solid substrate using a cost-efficient adsorbent, dehydrated carbon, obtained using a dehydration reaction. Using this new technique, researchers can detect trace metal ions in solutions qualitatively and quantitatively, and the drawbacks of performing liquid analysis using LIBS can be avoided because the analysis is performed on a solid surface. To achieve better performance using this technique, we considered parameters potentially influencing both adsorption performance and LIBS analysis. The calibration curves were evaluated, and the limits of detection obtained for Cu(2+), Pb(2+), and Cr(3+) were 0.77, 0.065, and 0.46 mg/L, respectively, which are better than those in the previous studies. In addition, compared to other absorbents, the adsorbent used in this technique is much cheaper in cost, easier to obtain, and has fewer or no other elements other than C, H, and O that could result in spectral interference during analysis. We also used the recommended method to analyze spiked samples, obtaining satisfactory results. Thus, this new technique is helpful and promising for use in wastewater analysis and management.

Sparked-bismuth oxide screen-printed electrodes for the determination of riboflavin in the sub-nanomolar range in non-deoxygenated solutions

Despite their outstanding performance for the stripping voltammetric detection of trace metals, bismuth electrodes show poor sensitivity for the cathodic detection of organic compounds. Moreover, oxygen removal from samples is recommended to lower the background signal, which limits their application to on-site analysis. Herein, we propose recently introduced sparked-bismuth oxide screen printed electrodes for the cathodic detection of riboflavin, a reducible organic compound. The ultra-sensitive determination of riboflavin in the sub-nanomolar range in the presence of dissolved oxygen is demonstrated. After electroless preconcentration for 60s, electrodes showed a linear response over the concentration range 1–100nmolL−1 riboflavin, while the limit of detection (S/N=3) was found to be 0.7nmolL−1 riboflavin, ca. 140-fold lower than that has been achieved with electroplated bismuth electrodes. Excellent interelectrode reproducibility and application to a pharmaceutical sample are also demonstrated.

Inhibitive potentiometric detection of trace metals with ultrathin polypyrrole glucose oxidase biosensor

A method, based on the inhibition of an ultrathin polypyrrole–glucose oxidase (PPy–GOx) potentiometric biosensor response, is described for the detection of Cu2+, Hg2+, Cd2+ and Pb2+ ions. Based on experimental conditions (0.2M pyrrole, 500UmL−1 GOx, and an applied current density of 0.05mAcm−2 and a polymerization period of 500s) previously published by us, PPy–GOx films of approximately 55nm thick were used to demonstrate the inhibitive potentiometric detection of selected trace metals down to 0.079μM Cu2+, 0.025μM Hg2+, 0.024μM Pb2+ and 0.044μM Cd2+. Furthermore, good linear concentration ranges were achieved for Cu2+ (0.079–16μM), Hg2+ (0.025–5μM), Pb2+ (0.10–15μM) and Cd2+ (0.04–62μM). The analysis of the nature of the inhibition of glucose oxidase in the PPy–GOx biosensor by these metals was achieved by Dixon and Cornish-Bowden plots. The shapes of the curves (exponential decay, parabolic and linear) obtained for the inhibitors suggest that the inhibition by the metal ions may not be exclusively directed at the essential –SH group, but involve additional binding sites of the enzyme. Dixon and Cornish-Bowden plots suggest that the inhibition is competitive for Cd2+, while non-competitive inhibition was observed for other metal ions. The ultra-thin PPy–GOx film enabled improved permeability to the metal inhibitors than possible with conventional biosensors with thicker films and, hence, better reflects the actual inhibition effect of the trace metals on the enzyme activity. The use of the ultra-thin film also eliminated the usual need for incubation of the enzyme electrode for a long period in the presence of the inhibitors. Furthermore, a rapid recovery of the enzyme activity was achieved by simply washing the electrode with water and storing in phosphate buffer for 10–15min. The proposed biosensing approach was successfully used for the detection of individual trace metals in tap water, achieving a 98–101% recovery.

XRF scanners as a quick screening tool for detecting toxic pollutant elements in sediments from Marín harbour in the Ría de Pontevedra (NW Spain)

X-ray fluorescence scanners, such as the Itrax™ Core Scanner (Itrax) (Cox Analytical Systems, Mölndal, Sweden), provide high-resolution geochemical data within several hours. However, the semi-quantitative nature of these analysers has hampered their use to study pollution. This study explores Itrax’s capabilities to detect trace metals, such as Hg and Cd, in the Ría de Pontevedra harbour (NW Spain). A set of Itrax detection levels were proposed for each metal after comparison with quantitative measurements obtained from Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Vapour Atomic Absorption Spectrometry (CVAAS) analyses. These quantitative data obtained after a sequential extraction were used to evaluate pollutant bioavailability and to determine metal pollution levels exhibiting Hg pollution. The reliability of inc/coh and Br/Cl ratios to assess the total organic matter variability was also evaluated. The results indicated that the Itrax is an efficient and fast option to monitor contamination, thereby avoiding laborious discrete analyses and reducing analytical cost and time.

Detection of copper, lead, cadmium and iron in wine using electronic tongue sensor system

An array of 10 potentiometric chemical sensors has been applied to the detection of total Fe, Cu, Pb and Cd content in digested wine. As digestion of organic matter of wine is necessary prior to the trace metal detection using potentiometric sensors, sample preparation procedures have been optimized. Different variants of wet and microwave digestion and dry ashing, 14 conditions in total, have been tested. Decomposition of organic matter was assessed using Fourier transform mid-infrared spectroscopy and total phenolic content. Dry ashing was found to be the most effective method of wine digestion. Measurements with sensors in individual solutions of Fe(III), Cu(II), Pb(II) and Cd(II) prepared on different backgrounds have shown that their detection limits were below typical concentration levels of these metals in wines and, in the case of Cu, Pb and Cd below maximum allowed concentrations. Detection of Fe in digested wine samples was possible using discrete iron-sensitive sensors with chalcogenide glass membranes with RMSEP of 0.05mmolL−1 in the concentration range from 0.0786 to 0.472mmolL−1. Low concentration levels of Cu, Pb and Cd in wine and cross-sensitivity of respective sensors resulted in the non-linearity of their responses, requiring back-propagation neural network for the calibration. Calibration models have been calculated using measurements in the model mixed solutions containing all three metals and a set of digested wine sample. RMSEP values for Cu, Pb and Cd were 3.9, 39 and 1.2μmolL−1 in model solutions and 2, 150 and 1μmolL−1 in digested wine samples.

Anodic Stripping Voltammetry Using Nanoelectrodes

Anodic stripping voltammetry is an important technique for the detection of trace metals. The technique is very sensitive but requires careful control of a range of parameters including the conditioning of the working electrode, the temperature and the hydrodyanamics. In theory nanoelectrodes are immune to stirring and thus this parameter ought to be of far less consequence in the analysis protocol. In this paper we report of preliminary studies of trace metal analysis using a commercial nanoelectrode structure and examine the robustness of the overall analytical technique.

Electrochemical determination of lead and cadmium in rice by a disposable bismuth/electrochemically reduced graphene/ionic liquid composite modified screen-printed electrode

In this study, a disposable graphene/ionic liquid composite modified screen-printed electrode was prepared by electrochemically reduction of graphene oxide onto the ionic liquid doped screen-printed electrode (IL-SPE). Then a bismuth film was in situ deposited on the surface of electrode to receive an electrochemical sensor, which was used for sensitive determination of trace lead and cadmium ions by square wave anodic stripping voltammetry (SWASV). The physicochemical and electrochemical characterizations of obtained sensor were investigated in detail. It was found that the prepared electrode possessed many attractive properties, such as large surface area, good ionic and electronic conductivity, wide electrochemical window as well as high stability and sensitivity. Under optimized conditions, the linear range of electrode was from 1.0 to 80.0μgL−1 for both metal ions with a detection limit of 0.08μgL−1 for cadmium and 0.10μgL−1 for lead (S/N=3). Finally, the proposed analytical procedure was applied to detect trace metal ions in rice samples with satisfactory results.

A BIOPHYSIOCHEMICAL ANALYSIS OF SETTLED LIVESTOCK AND POULTRY HOUSING DUSTS

The levels and composition of agricultural dusts ar e influenced by animal species, production strategy , housing type and ventilation efficiency. Agricultural dust within animal houses is complex and consists of fee d particles, microbes and their products, dander, fecal matter, gases, metals and other organic and inorganic components. Livestock and poultry production facilities may be categorized as confinement, semi-confinement or pasturebased. Characterization of animal husbandry buildin g dust will provide insight into understanding expo sures experienced by animals, workers and farm visitors. The goal was to characterize biophysiochemical feat ures of livestock dusts from swine, small ruminant, equine, poultry and cattle husbandry units. Settled dust s amples were collected from livestock and poultry housing units at the University Farm and other livestock farms ac ross the state. Morphological features were determined by el ectron microscopy and gravimetry. Biochemical evaluation consisted of pH determination and trace metal detec tion via mass spectrometry. Biological assessment c entered on bacterial characterization via selective media, DNA analysis and endotoxin quantitation. Morphological analyses revealed higher levels of respirable and t horacic particles in poultry, swine, small ruminant and equine units compared to the dairy unit (p<0.01). Dusts we re slightly acidic with the exception of the NCAT s mall ruminant unit (p<0.05). Dust endotoxin levels were consistent and bacterial species detected include Listeria and Escherichia coli . These findings suggest animal husbandry buildings harbor higher levels of smaller respirable and thoracic dust particles compared to inhalable p articles. This information may be helpful in unders tanding dust exposures experienced by animals, farmers and agricultural workers.

Trace Metal Detection Technology Based on Axis Rotation Algorithm

The staple principle of the quadrature electromagnetic method in the geophysics is researched, on this basis, a trace metal detection technology is developed, and the hardware consists of a \double-D, an instrument host. An process algorithm that eliminates the primary eld and soil background eld with axis rotation in the adaptive learning of the soil background process is advanced, which enhances the soil adaptive ability and trace metal detection sensitivity for variety of soils. The instrument is tested in three typical background environments (air, sand and magnetic soil) in which only 1g iron is contained, and each test includes prole curve and detection performance. The consequences indicate that its performance is close to the international mainstream apparatuses that have similar functions, so the design is proved to be feasible.