Metal Ions Hg Research Articles

Silver Nanoparticles for Colorimetric Detection and Discrimination of Mercury Ions in Lake Water

AbstractAs the most toxic heavy metal, mercury (Hg) has been considered as the greatest environmental threat and it reach ubiquitous in industrial waste water and extended to environment. The detection of Hg2+ in environmental water is a crucial work for both protecting the environment and human health. Colorimetric assay exhibits visual discriminating and simple readout. This work presents the selective sensing of metal ion (Hg2+) by silver particles (Ag NPs), which were functionalized by galactosamine and synthesized via simple one pot method, with the average particle diameter of 18.75±0.49 nm. The limit of detection (LOD) was calculated as low as 7.92 nM. The colorimetric probe can also be performed in real water sample with good selectivity, and recovery was found to be 95–102 %, indicating can be used for on‐line determination of Hg2+ in the complex aqueous solutions. Additionally, the good catalytic performance of Ag NPs was demonstrated by hydrogenation of p‐nitrophenol and potassium ferricyanide in water samples.

RECYCLING TECHNOLOGY OF ACTIVE MATERIALS OF THE ZINC-MANGANESE CURRENT SOURCES

It is being investigated whether it is possible to develop a low-cost method for processing used Zn-MnO2 primary chemical power sour­ces, which is focused on a closed cycle of ge­nerating zinc-manganese power sources from wasted batteries. It is proposed that chemical processing reagents be replaced with less dangerous ones for the environment and people, in accordance with «green chemi» principles. The existing hydrometallurgical method of processing of primary current sources with selective extraction of the spent part of the anode mass is modified and laboratory processed. The stage of additional extraction of arsenic is entered. The proposed technological scheme avoids heavy air loads in the form of carbon dioxide emissions by eliminating the stage of burning organic matter. The use of acetic acid allows to avoid sulfuric acid discharges and to obtain high-quality for secondary production of cathode mass of new chemical current sour­ces, as well as to obtain technical zinc powder and active zinc powder using hydrometallurgical technology for anode mass production of primary batteries. Also, the presence of stages of extraction of heavy metal ions (Hg2 +, Pb2 +, Cd2 +) and Arsenic to obtain products that can be further used in other technological processes makes this technology virtually waste-free, and in the stages of recovery of acetic acid and hypochlorite – closed. Thus, the use of the proposed technological schemes allows to make such production not only a little harmful to the environment, but also for workers, as well as to simplify the requirements for technological equipment.

Adsorpsi Logam Merkuri (Hg) dari Limbah Tanah Tercemar Menggunakan Tanaman Sawi (Brassica juncea L) pada Berbagai Waktu Tanam

Mercury (Hg) as a gold extractor can cause environmental pollution, therefore, hyperaccumulator plants are needed, such as mustard greens (Brassica juncea L). Research on the effect of planting time of mustard greens on the adsorption of mercury (Hg) metal ion on contaminated soil waste has been carried out. The purpose of this research was to determine the concentration and adsorption mechanism of Hg metal ion from contaminated soil at roots and canopy of mustard plants at various planting times. Amount of Hg metal ion adsorbed on the roots and canopy of mustard greens at 2, 4, and 6 weeks of planting times were analyzed using Atomic Absorption Spectrophotometry (AAS). The results showed that the average levels of Hg metal ion adsorption at various planting time of 2, 4, and 6 weeks at roots were 156.611 μg/g, 810.256 μg/g, and 888.711 μg/g, respectively, and at the canopy were 69.486 μg/g, 134.580 μg/g, and 60.416 μg/g, respectively. The planting time of 6 weeks resulted in the highest adsorption ability of Hg at the roots. The results of the bioconcentration factor (BCF) test showed that the adsorption of Hg in the roots and canopy of the mustard plant took place using a phytoextraction mechanism (BCF < 1).

Fluorescence enhancement of bovine serum albumin gold nanoclusters from La3+ ion: Detection of four divalent metal ions (Hg2+, Cu2+, Pb2+ and Cd2+)

The combination of La3+ ion and bovine serum albumin gold nanoclusters (La3+ ion-BSA-AuNCs)-based nanosensor creates a novel and innovative miniaturized analytical method for the detection of four divalent metal ions (Hg2+, Cu2+, Pb2+ and Cd2+) simultaneously. In this work, the fluorescence enhancement was noticed in BSA-AuNCs by the addition of La3+ ion, exhibiting emission peak at 652 nm when excited at 323 nm. The fabricated La3+ ion-BSA-AuNCs acted as a fluorescent sensor for the detection of four divalent metal ions (Hg2+, Cu2+, Pb2+ and Cd2+) via fluorescence quenching (Hg2+, Cu2+ and Pb2+) and fluorescence enhancement (Cd2+) mechanisms. The La3+ ion-BSA-AuNCs-based fluorescent nanosensor exhibited good linearity with limits of detection (LOD) of 0.02, 0.048, 0.19 and 4.93 µM for Hg2+, Cu2+, Pb2+ and Cd2+ ions, respectively. The practical application of La3+ ion-BSA-AuNCs-based fluorescence method was examined for the analysis of four divalent metal ions (Hg2+, Cu2+, Pb2+ and Cd2+) in various environmental water samples. Thus, the developed probe exhibited several merits such as miniaturization, easy of operation, which allow to use as a promising analytical platform for on-site parallel detection of four divalent metal ions in real samples.

Interaction of Folic Acid with Mn2+ Doped CdTe/ZnS Quantum Dots: In Situ Detection of Folic Acid.

To utilize the nanomaterials as an effective carrier for the drug delivery applications, it is important to study the interaction between nanomaterials and drug or biomolecules. In this study GSH functionalized Mn2+-doped CdTe/ZnS QDs has been utilized as a model nanomaterial due to its high luminescence property. Folic acid (FA) gradually quenches the FL of GSH functionalized Mn2+ - doped CdTe/ZnS QDs. The Stern-Volmer quenching constant (Ksv), binding constant (Ks) and effective quenching constant (Ka) for the FA-QDs system is calculated to be 1.32 × 105M-1, 1.92 × 105 and 0.27 × 105M-1, respectively under optimized condition (Temp. 300K, pH8.0, incubation time 40min.). The effects of temperature, pH, and incubation time on FA-QDs system have also been studied. Statistical analysis of the quenched FL intensity versus FA concentration revealed a linear range from 1 × 10-7 to 5.0 × 10-5 for FA detection. The LOD of the current nano-sensor for FA was calculated to be 0.2μM. The effect of common interfering metal ions and other relevant biomolecules on the detection of FA (12.0μM) have also been investigated. L-cysteine and glutathione displayed moderate effect on FA detection. Similarly, the common metal ions (Na+, K+, Ca2+ and Mg2+) produced minute interference while Zn2+ Cu2+ and Fe3+ exert moderate interference. Toxic metal ions (Hg2+ and Pb2+) produced severe interferences in FA detection.Graphical abstract GSH-Mn2+ CdTe/ZnS QDs based Fluorescence Nanosensor for Folic acid.

Green synthesized uncapped Ag colloidal nanoparticles for selective colorimetric sensing of divalent Hg and H2O2

The green ecofriendly approach towards crystalline Ag nanoparticles (AgNPs) synthesis using apple (Malus domestica) juice has been demonstrated. The optical properties of synthesized AgNPs were studied by ultraviolet-visible spectroscopy (UV-Vis). The X-ray diffraction (XRD) studies reveals that, the synthesized green AgNPs possess good crystalline nature with face centered cubic lattice structure. Similarly, the Emission Scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) studies reveals that AgNPs has spherical shape with diameter of 60 nm and particle size ranges from 6 to 100 nm. The EDAX studies confirms the impurity free nature of AgNPs. The green synthesized AgNPs possess the surface area of about 5.069 m2/g and cross sectional area of 16.2 Ă2/ molecule. The Ascorbic acid and different proteins of apple juice, reduced silver ions into AgNPs during the synthesis. The color of the as synthesized AgNPs was dark brown and exhibited a Surface Plasmon Resonance (SPR) peak at 527 nm. Upon treating with Hg2+/H2O2, the AgNPs became colorless and the SPR band broadened and blue shifted. AgNPs exhibited remarkable colorimetric as well as spectral changes only toward Hg2+/ H2O2. The limit of detection and sensitivity of the method were 0.2656 ppm and 0.2564 ppm for Hg2+ ions. Similarly, limit of detection and sensitivity of the method was 0.216 ppm (Much less than the Threshold limit value (1 ppm) in drinking water prescribed by WHO) and 0.215 ppm mL−1 for H2O2. The sensitivity of AgNPs towards Hg2+ ions sensing is almost pH independent. Additionally, the colorimetric and naked eye sensing the environmentally toxic metal ion Hg2+ and the biologically important H2O2 using AgNPs has been demonstrated. The present system has been applied for monitoring Hg2+ ions and H2O2 in different water samples and recovery rates in spiked samples were more than 99%.

Synthesis and characterization of a plant growth regulator based silver nanoparticles for the ultrasensitive detection of environmentally toxic Hg2+ ions in tap water

Herein, we report the synthesis and characterization of a plant growth regulator based silver nanoparticles and its application as a sensor for the ultrasensitive detection of toxic metal ions (Hg2+) in tapwater.

Highly sensitive and selective colorimetric detection of dual metal ions (Hg2+ and Sn2+) in water: an eco-friendly approach.

Application of an alliin-based precursor for the synthesis of silver nanoparticles (Ag NPs) which is an emerging, reliable and rapid sensor of heavy metal ion contaminants in water is reported here. The Ag NPs were characterized by using UV-visible spectroscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy analysis techniques. The Ag NPs simultaneously and selectively detect Hg2+ and Sn2+ ions from aqueous solution. The sensitivity and selectivity of the prepared Ag NPs towards other representative transition-metal ions, alkali metal ions and alkaline earth metal ions were also studied. For more precise evidence, a density functional theory study was carried out to understand the possible mechanism and interaction in the detection of Hg2+ and Sn2+ by Ag NPs. The limits of detection for Hg2+ and Sn2+ ions were found as 15.7 nM and 11.25 nM, respectively. This assay indicates the possible use of garlic extract-synthesized Ag NPs for sensing Hg2+ and Sn2+ in aqueous solution very significantly. So, the simple, green, eco-friendly and easy method to detect the dual metal ions may further lead to a potential sensor of heavy metal ion contaminants in water of industrial importance.

Red-fluorescent graphene quantum dots from guava leaf as a turn-off probe for sensing aqueous Hg(ii)

In this work, we have prepared red-fluorescent graphene quantum dots and utilized as a highly selective and sensitive fluorescence turn-off probe for detection of the toxic metal ion Hg2+ from guava leaf extract.

Melamine Thiourea Chemically Modified Activated Carbon Derived from Water Hyacinth  as an Efficient Adsorbent for the Removal of Hg(II), Pb(II) and Cd(II) Ions from Aqueous Solution

The purpose of this work was to incorporate amine and thiol groups onto the surface of activated carbon (MT-MAC) derived from water hyacinth through amidation reaction between the amino groups of melamine thiourea (MT) and the carboxyl groups of activated carbon (OAC) in presence of dicyclohexylcarbodiimide as a coupling agent. The prepared MT-MAC exhibited extensive potential for the extraction of toxic metal ions Hg(II), Pb(II) and Cd(II) from wastewater. The prepared MT-MAC was characterized by different techniques like BET, SEM, XPS, and FTIR analysis. The results displayed that the total pore volume and surface area of OAC were found to be 864.52 m2 g-1 and 0.5216 m3 g-1, respectively and decreased up on modification with melamine thiourea to 493.78 m2 g-1 and0.2916 m3 g-1.FTIR spectra confirmed the incorporation of amine and thiol groups on the surface of OAC by the appearance of new peaks at 1625 cm-1 and 3332 cm-1 corresponding to the C=O stretching vibration of the NHCO (amide), and N-H stretching vibration, respectively. XPS displayed two new peaks due to S2p and N1s in the MT-MAC survey scan. The MT-MAC adsorbent showed high capacities for the removal of Hg(II) ( 292.6 mg.g-1), Pb(II) (237.4 mg.-1) and Cd(II) (97.9 mg.g-1) from aqueous solution at pH 5.5, agitation time 60 min and 298 K.The experimental sorption data could be fitted well with Langmuir isotherm model suggesting a monolayer adsorption behavior. Chemisorption mechanism via melaminethiourea groups grafted on the surface of activated carbon is suggested based on the excellent agreement of the kinetic data with pseudo–second-order model. The MT-MAC exhibited high stability over three adsorption-desorption cycles. The results also revealed that MT-MAC is a promising adsorbent for the extraction of Hg(II), Pb(II) and Cd(II) ions from polluted water.

Non-specific DNAzyme-based biosensor with interfering ions for the Cd2+ determination in feed

Only parts of heavy metal ions have sensitive and selective deoxyribozymes(DNAzymes), but most of heavy metal ions do not have the specific DNAzyme that limits the development of high-precise biosensors. As for cadmium ion (Cd2+), it lacks a specific DNAzyme that can be interfered by the multiple heavy metal ions (Hg2+ and Pb2+), causing poor accuracy if only non-specific DNAzyme-based biosensor measures the Cd2+ concentration. Here, one approach to solve this problem is proposed that uses in conjunction with other biosensors and the analysis data model to explore the interference law and improve the detection accuracy. The non-specific DNAzyme-based biosensor is fabricated using a field-effect transistor(FET), single-walled carbon nanotube(SWNTs) and non-specific DNAzyme. The performances are characterized by different spectral and electronic methods, indicating excellent sensitivity, stability and repeatability. Under the optimized conditions, the non-specific DNAzyme-based biosensor can determine Cd2+ down to 3.4 × 10-2 nM, and the linear range is varying from 5.0 × 10-2 to 1.0 × 103 nM with the correlation coefficient 0.98. To qualitatively and quantitatively analyze Cd2+ in a real sample, other biosensors with high sensitivity for Hg2+ and Pb2+ are selected and optimized to form a biosensor array, and then the detecting signals are processed by a mathematical model. At last, the prepared biosensor array is applied to measure the Cd2+ in feed to evaluate the detection accuracy.

Preparation and properties of a dual-function cellulose nanofiber-based bionic biosensor for detecting silver ions and acetylcholinesterase

A dual-function cellulose nanofiber (CNF)-based bionic biosensor with good biocompatibility was developed for detecting Ag+ and acetylcholinesterase (AChE) by grafting deoxyribonucleic acid (DNA) onto CNF. The Ag+ ions captured by the biosensor acted as recognition sites for the detection of AChE. The CNF-based bionic biosensor (CNF-DNA) could detect Ag+ concentrations as low as 10−6 nM in the presence of interference metal ions (Hg2+, Ba2+, Cd2+, Mg2+, Mn2+, Pb2+, and Zn2+). DNA-template silver nanoclusters (DNA-AgNCs) were formed on the surface of CNF-DNA during the detection of Ag+ (CNF-DNA-AgNCs). This new strategy yielded CNF-DNA-AgNCs through the adsorption of Ag+ ions onto the cytosine base of the single-stranded DNA in CNF-DNA without the use of any additional reducer. Meanwhile, the CNF-DNA-AgNCs exhibited excellent sensitivity and selectivity for trace levels (0.053 mU/mL) of AChE in the presence of interference reagents. The novel strategy proposed in this paper may establish a foundation for further research on DNA-template AgNCs for developing biosensors and biomarkers for in vivo and in vitro detection.

Adsorption mechanism of toxic heavy metal ions on oxygen-passivated nanopores in graphene nanoflakes

In this work, using density functional theory, we investigate the adsorption process of toxic metal ions (Hg2+, Cd2+, and Pb2+) on graphene nanoflakes (GNF) comprised of various sized oxygen-passivated nanopores to gain molecular insights into the ability of such surfaces in effectively removing the metal ions from contaminated environments. Thermodynamically, the adsorption of these ions on the oxygen-passivated nanopores is shown to be more energetically favorable than that on the pristine surface. The dispersion corrected adsorption energy calculations indicate Hg2+ ion to have the highest and Pb2+ ion the lowest affinities for interaction with such surfaces (Hg2+ > Cd2+ > Pb2+). The highest adsorption of Hg2+ and Cd2+ ions on the surfaces is seen in the 12-crown-3…Hg2+ (− 382.9 kcal/mol) and 12-crown-3…Cd2+ (− 314.7 kcal/mol) complexes, while Pb2+ ion shows the highest adsorption energy for the 18-crown-6 surface (− 195.0 kcal/mol). Noncovalent interaction plots, Hirshfeld charge analysis and energy decomposition analysis conclude that the role of charge transfer in formation of surface…ion complexes is more important than noncovalent interactions and therefore plays a key role in the adsorption of these ions on the surfaces. The magnitude of charge transfer in the complexes follows the order: surface…Hg2+ > surface…Cd2+ > surface…Pb2+, which is consistent with the adsorption energetic order of these metal ions on the surfaces. We also found that Pb2+ ion is mainly adsorbed on the surfaces via electrostatic interactions, while Hg2+ and Cd2+ ions are adsorbed through van der Waals (vdW) interactions. This could be attributed to the presence of vacant p orbitals on Pb2+ ion, which interact with the π bonds on the GNF and oxygen atoms in the nanopores through electrostatic interactions. No such vacant orbitals are available for Hg2+ and Cd2+ ions thus resulting in such ions adsorbing via vdW interactions. The contribution of ΔEorb, induction energy component of total energy, for the surface…Hg2+ complexes is more than that for the surface…Cd2+ and surface…Pb2+ complexes, following the order: surface…Hg2+ > surface…Cd2+ > surface…Pb2+ again, consistent with the calculated adsorption energy order suggesting that charge transfer indeed plays a major role in formation of such surface…ion complexes. Finally, time-dependent density functional theory calculations show that the absorption spectra of the surfaces undergo significant changes, including peak shifts, peak quenching and appearance of new peaks, upon interaction with Hg2+, Cd2+, and Pb2+ ions, such changes being consistent with binding energetics rank order of ions on these surfaces. These complexes would have potential applications in near-infra-red photonics in addition to their service of effectively remediating of toxic heavy elements from contaminated environments.

Template‐Assisted Regioselective Identification of Metal Ions on Coumarin‐Furan Conjugated Chemosensors: AIEE Effect and Photo‐Switching pH Indicator by ICT

A coumarin‐furan conjugated Schiff base chemosensor (R1) of straightforward design showed an excellent aggregation‐induced emission enhancement effect in ACN‐H2O mixtures of different ratios, which was confirmed by field emission scanning electron microscopy (FESEM) and supported by Dynamic Light Scattering (DLS). R1 identified three metal ions (Pb2+, Hg2+ and Cu2+) in colorimetric and fluorometric techniques with an intramolecular charge transfer (ICT) off‐on mechanism. The space specificity of the metal ions (Hg2+ and Cu2+) resulted in hydrolysis of ‐CH=N‐ functionality of the sensor. The latter also exhibited excellent sensitivity in acidic conditions by blocking ICT and remained stable in neutral to basic pH. Cell viability and microscopic fluorescence experiments revealed that R1 is cytocompatible and may be used for the detection of Pb2+, Hg2+, and Cu2+ ions in living cells.

Four-in-One: Advanced Copper Nanocomposites for Multianalyte Assays and Multicoding Logic Gates

The usage of non-noble-metal nanomaterials for nanoprobes or functional modules is still a big challenge because of their poor stability, functionality, and surface plasmon resonance property. In this work, copper ion, mercaptosuccinic acid, and nanocrystalline cellulose are combined for facile one-step synthesis and self-assembly of ultrasmall copper nanoparticles to produce supercolloidal particles (NCC@MSA-Cu SPs). Cu SPs show advanced multifunctionality for fast point-of-care tests (POCTs) of four metal ions (Hg2+, Pb2+, Ag+, and Zr4+). These selective recognitions integrate four different chemical reaction mechanisms (ion etching, core-shell deposition, templated synthesis, and precipitation) to produce four distinct readout signals. The multisignal mode-guided multianalyte sensing strategy can effectively avoid interference that affects single signal mode-based sensing. Benefiting from the creative multi-input and multireadout abilities, the visual multicoding logic gates of OR, NOR, AND, and INHIBIT are built based on optical responses of Cu SPs.

Partial purification and characterisation of α-amylases from the digestive tract of the Indian major carp Labeo rohita (Hamilton, 1822)

Partial purification of α-amylases from the digestive tract of the Indian major carp Labeo rohita (Hamilton, 1822) through acetone fractionation and ion exchange chromatography (DEAE-SephadexA-50) resulted in 8-fold purification with 86% recovery. Characterisation of amylase activity revealed two pH optima at 4.5 and 6.5. Activity was stable over wide pH ranges of 3.5 to 4.5 and 7 to 12. Optimum incubation temperature was 35°C. The enzyme lost 91% activity at 60°C within 15 min and was inhibited by Amylase inhibitor Type-1 (wheat); 1, 10 Phenanthroline, Ethylene diamine tetra-acetate (EDTA) and Phenyl methyl sulphonyl fluoride (PMSF). Heavy metal ions Hg++ and Cu++ strongly inhibited the enzyme activity, while Zn++ and Bi++ inhibited to a lesser extent. Native polyacrylamide gel electrophoresis of the purified amylase fractions revealed four bands, with corresponding molecular weights of 43.59, 52.36, 55.42 and 54.01 kDa. α-Amylase activity from L. rohita exhibited linear hydrolysis of starch upto 7% concentration in 60 min.

Drift Characteristics of Metal Ions in Helium in an External Electric Field

The results of Monte Carlo calculations of the drift characteristics of metal ions (Li, Be, Al, Fe, Cu, W, Hg, and Au) in a constant uniform electric field 1 < E/N < 1000 Td in helium are presented. The dependences of the mobility, longitudinal and transverse diffusion coefficients, and mean kinetic energy of ions, as well as their longitudinal and transverse temperatures, on the electric field strength are given.

Selective Formation of S4- and T-Symmetric Supramolecular Tetrahedral Cages and Helicates in Polar Media Assembled via Cooperative Action of Coordination and Hydrogen Bonds.

We report on the synthesis and self-assembly study of novel supramolecular monomers encompassing quadruple hydrogen-bonding motifs and metal-coordinating 2,2'-bipyridine units. When mixed with metal ions such as Fe2+ or Zn2+, the tetrahedron cage complexes are formed in quantitative yields and full diastereoselectivity, even in highly polar acetonitrile or methanol solvents. The symmetry of the complexes obtained has been shown to depend critically on the flexibility of the ligand. Restriction of the rotation of the hydrogen-bonding unit with respect to the metal-coordinating site results in a T-symmetric cage, whereas introducing flexibility either through a methylene linker or rotating benzene ring allows the formation of S4-symmetric cages with self-filled interior. In addition, the possibility to select between tetrahedral cages or helicates and to control the dimensions of the aggregate has been demonstrated with a three-component assembly using external hydrogen-bonding molecular inserts or by varying the radius of the metal ion (Hg2+ vs Fe2+). Self-sorting studies of individual Fe2+ complexes with ligands of different sizes revealed their inertness toward ligand scrambling.

Good hydrolysis activity on raffinose family oligosaccharides by a novel α-galactosidase from Tremella aurantialba

An α-galactosidase designated as TAG was purified from the dried fruit bodies of Tremella aurantialba with 182.5-fold purification. The purification procedure involved ion exchange chromatography on Q-sepharose, DEAE-Cellulose, and Mono Q and gel filtration by FPLC on Superdex 75. The purified α-galactosidase was a monomeric protein with a molecular mass of 88 kDa. The optimal pH of TAG was 5.0 and more than 60% of the original enzyme activity remained at pH 2.0 and 3.0. Its optimal temperature was 54 °C with good thermo-stability, 30.8% of the original activity was retained after exposure to a temperature of 70 °C for 1 h. The metal ions Hg2+, Cu2+, Fe3+ and Mg2+ strongly inhibited the enzyme activity. The enzyme activity was found to be inhibited by N-bromosuccinimide indicating that tryptophan was essential to the catalytic activity of α-galactosidase. The enzyme completely hydrolysed stachyose and partially hydrolysed raffinose to galactose at 50 °C within 6 h as detected by thin layer chromatography and the dinitrosalicylic acid method and the content of reducing sugar reached 4.36 mg/mL.

Biotoxic trace metal ion detection by enzymatic inhibition of a glucose biosensor based on a poly(brilliant green)–deep eutectic solvent/carbon nanotube modified electrode

A highly sensitive glucose oxidase (GOx) electrochemical biosensor for the determination of the biotoxic trace metal ions Hg2+, Cd2+, Pb2+ and CrVI by enzyme inhibition has been developed. GOx was immobilized on a novel sensing platform consisting of poly(brilliant green) films formed by potential cycling electropolymerization in sulfuric acid doped ethaline deep eutectic solvent on multiwalled carbon nanotube modified glassy carbon electrodes. Polymer films produced in this medium presented more uniform morphology and better electrochemical sensing properties than those prepared in aqueous solution. The inhibitor concentration necessary to give 50% inhibition, I50, was used for the determination of the type of reversible inhibition, and the relationship between I50 and the inhibition constant Ki is discussed. The new biosensor was successfully used for the determination of biotoxic trace metal ions with a nanomolar limit of detection, lower than in the literature, very good repeatability, stability and selectivity, and was applied successfully to detection of the toxic trace metal species in milk samples.