Application of a new resin functionalised with 6-mercaptopurine for mercury and silver determination in environmental samples by atomic absorption spectrometry

Absorption and Resonance Rayleigh Scattering Spectra of Ag(I) and Erythrosin System and Their Analytical Application in Food Safety

In pH 4.4∼4.6 weakly acidic media, erythrosine (Ery) can react with Ag(I) to form hydrophobic ion-association complex, which can further aggregate to form nanoparticles with an average particle size of about 45 nm under the action of water phase extrusion and van der Waals force. As a result, it could lead to a decrease of absorbance, a significant enhancement of resonance Rayleigh scattering (RRS) and the appearance of a new emission spectrum. Based on these Phenomena, two new methods (spectrophotometry and RRS) were established for the determination of trace Ag(I). The detection limits for Ag(I) by spectrophotometry and RRS are 9.74 and 0.12 ng/ml, respectively. In this paper, we have investigated the formation of nanoparticles, the optimum reaction conditions, the influence factors, explored the reason for enhancement of the scattering intensity and the effect of coexisting substance. This research shows that RRS method not only has good selectivity and high sensitivity, but also is simple and rapid. Analyzing of actual samples and standard samples, the determination result of this method is consistent with that of standard methods (Flame atomic absorption spectroscopy). Thus the method had potential feasibility to analysis for Ag(I) in the environmental water samples, pharmaceutical, and food industries.

Bis-BODIPY linked-triazole based on catechol core for selective dual detection of Ag+ and Hg2

Herein, we introduced a new chemosensor, bis-BODIPY linked-triazole based on catechol (BODIPY-OO) prepared by bridging two units of BODIPY fluorophore/triazole binding group with a catechol unit. A solution of this compound displayed 4- and 2-fold enhancements in fluorescence intensity after adding a mole equivalent amount of Ag⁺ and Hg²⁺ ions in methanol media, respectively. ¹H NMR titrations of BODIPY-OO with Ag⁺ and Hg²⁺ suggested that the triazole was involved in the recognition process. BODIPY-OO showed high sensitivity toward Ag⁺ and Hg²⁺ over other metal ions with detection limits of 0.45 μM and 1 μM, respectively. It can also distinguish Hg²⁺ from Ag⁺ by addition of an EDTA. This compound can therefore be employed as practical fluorescent probe for monitoring the presence of Ag⁺ and Hg²⁺ ions.

BODIPY–triazole–catechol combination serves as a “turn-on” fluorescent probe for dual detection and differentiation of Hg²⁺ and Ag⁺ ions.

A new insight of structures, bonding and electronic properties for 6-mercaptopurine and Ag8 clusters configurations: a theoretical perspective

Background

Many reports have also shown that the silver nanoparticles can effectively increase the anticancer drug activity and intensely enhance the drug curative effect. The adsorption of 6MP on nanomaterials has received a lot of attentions because of the drug coordination to its chemotherapeutic activity. The geometrical structures, chemical bonds, molecular orbital properties as well as density of states for the configurations were analyzed to deeply understand the interactions between the 6MP and Ag₈ clusters for high effect anticancer drug production.

Results

In this work, the density functional theory B3LYP has been used to investigate the structures and properties of the configurations between 6-mercaptopurine (6MP) and Ag₈ clusters using 6-311++G** level as well as an effective pseudo potential LANL2DZ. The geometries of ten configurations were optimized with full freedom. The geometrical structures, chemical bonds, molecular orbital properties as well as density of states for partial configurations were analyzed based on the density functional calculations. Polarizable continuum solvent model (PCM) in self-consistent reaction field (SCRF) were used for the aqueous calculations. The influences of temperature and pressure on the stability of the predominant configurations in the gas phase were further considered using standard statistical thermodynamic methods from 50 to 500 K and at 1 bar or 100 bar.

Conclusion

The result shows that there are ten stable configurations in the gas phase and there is a strong chemical bond between a Ag and S atom in the most stable configuration. The analysis of density of states also shows that the Ag–S chemical bond in the most stable configuration has been formed. Moreover, the results show that the temperature and the pressure will significantly influence the stability of the configurations in the gas phase. Additionally, when the solvent effect was considered, we found that there are only seven stable configurations and the solvent have different effect on various configurations.

Electronic supplementary material

The online version of this article (10.1186/s13065-019-0573-z) contains supplementary material, which is available to authorized users.

Ultra-trace determination of methylmercuy in seafood by atomic fluorescence spectrometry coupled with electrochemical cold vapor generation

A homemade electrochemical flow cell was adopted for the determination of methylmercury. The cold vapor of mercury atoms was generated from the surface of glassycarbon cathode through the method of electrolytic reduction and detected by atomic fluorescence spectroscopy subsequently. The operating conditions were optimized with 2 ng mL(-1) methylmercury standard solution. The caliberation curve was favorably linear when the concentrations of standard HgCH3(+) solutions were in the range of 0.2-5 ng mL(-1)(as Hg). Under the optimized conditions, the limit of detection (LOD) for methylmercury was 1.88×10(-3)ng mL(-1) and the precision evaluated by relative standard deviation was 2.0% for six times 2 ng mL(-1) standard solution replicates. The terminal analytical results of seafood samples, available from local market, showed that the methylmercury content ranged within 3.7-45.8 ng g(-1). The recoveries for methylmercury spiked samples were found to be in the range of 87.6-103.6% and the relative standard deviations below 5% (n=6) were acquired, which showed this method was feasible for real sample analysis.

DNA-based biosensors for Hg(2+) determination by polythymine-methylene blue modified electrodes

In this work we have developed a new electrochemical DNA-based biosensor for the selective determination of the Hg(2+) ion by the use of different electrodes modified with polythymine, bearing methylene blue, as redox probe, in 3' position. The determination of Hg(2+) can be employed with an excellent degree of selectivity by the use of DNA biosensors through the formation of the complex Thymine-Hg-Thymine (T-Hg-T): in fact, Hg(2+) tends to bind two thymines, generating a T-Hg-T complex with a formation constant higher than that one of the coupling Adenine-Thymine, which can be employed for a selective, fast and cost-effective Hg(2+) detection. The presence of the Hg(2+) in solution leads to the formation of T-Hg-T complex thus causing the "hairpin-like" folding of oligonucleotide, leading to an improved electronic exchange of methylene blue with the electrode surface due to the reduced distance and thus to an increase of the faradic current which is detected by means of square wave voltammetry (SWV). To test the feasibility of this kind of biosensor to be applied to the analysis of Hg(2+) we have developed several biosensors configuration by modifying the electrochemical sensor transducer: (a) Au electrode; (b) Au screen-printed electrode (SPE). The proposed system, allows the determination of Hg(2+) in the range 0.2-100 nM (0.05-20 ppb), with a sensitivity 0.327 µA/nM, LOD 0.1 nM (0.02 ppb), LOQ 0.2 nM (0.05 ppb) and RSD ≤4.3% when Au electrode is used as electrochemical transducer; on the other hand, in the case of Au SPE the linear range is 0.2-50 nM (0.05-10 ppb), with a sensitivity 0.285 µA/nM, while LOD and LOQ are the same as previously and RSD is ≤3.8%. This enabled the detection of mercury in real samples (waters and fishes) with good accuracy (recoveries 92-101% on waters and 92-107% on fishes, respectively) and reproducibility (RSD ≤9.6% for measurements on waters and ≤8.8% on fishes, respectively).

Novel route for silylation of silica gel and aliphatic amines immobilization based on microwave-assisted solvent free synthesis and their applications for Cu(II) and Fe(III) removal from natural water samples

This article describes a new route for silica gel silylation and immobilization of aliphatic amines based on microwave-assisted solvent free synthesis to produce new solid phase extractors. The mode of synthesis was optimized under microwave conditions and achieved in a short time without using solvents. The produced phases named: silica gel- monoamine (SG-MA), silica gel- ethylenediamine (SG-EDA) and silica gel- diethylenetriamine (SG-DETA). The selectivity of these phases towards the uptake of Cu(II) and Fe(III) was checked using batch equilibration technique. Microwave radiation power and time of radiation were optimized to obtain the highest metal uptake values. The novel synthesized silica amine phases were characterized using Fourier transform infrared spectra and scanning electron microscope. The effects of different parameters including, hydrogen ion concentration, initial metal ion concentration, mass of the phase and shaking time on binding capacities of both Cu(II) and Fe(III) were explored. Results of sorption isotherms of the phases were better fitted with the Langmuir model (r² ≥ 0.950). In addition, the kinetics data were best fitted with the pseudo-second-order type (r² = 0.999). Application of SG-MA for removal of Cu(II)- and Fe(III)-spiked natural water samples was achieved satisfactorily using batch experiments. The results were found to refer to superior recovery percentages (90.0-97.01 ± 0.010-0.521%) with no significant matrix interferences.

Flame Atomic Absorption Spectrometric Determination of Trace Amounts of Silver after Solid-Phase Extraction with 2-Mercaptobenzothiazole Immobilized on Microcrystalline Naphthalene

A simple and sensitive solid-phase extraction (SPE) procedure combined with flame atomic absorption spectrometry (FAAS) was designed for the extraction and determination of trace amounts of silver. A column of immobilized 2-mercaptobenzothiazole (MBT) on microcrystalline naphthalene was used as the sorbent. Silver was quantitatively retained on the column in the pH range of 0.5–6.0. After extraction, the solid mass consisting of silver complex and naphthalene was dissolved out of the column with 5.0 mL of dimethylformamide, and the analyte was determined by flame atomic absorption spectrometry (FAAS). Under the optimum experimental conditions, the adsorption capacity was found to be 1.18 mg of silver per gram of the sorbent. A sample volume of 800 mL resulted in a preconcentration factor of 160. The relative standard deviation obtained for ten replicate determinations at a concentration of 0.8 µg L−1was 1.4%, and the limit of detection was 0.02 µg L−1. The method was successfully applied to the determination of silver in radiology film, waste water, and natural water samples. The accuracy was examined by recovery experiments, independent analysis by electrothermal atomic absorption spectrometry, and analysis of two certified reference materials.

Studies on the Removal of Malachite Green Dyes by Adsorption onto Activated Carbons – A Comparative Study

Malachite Green is an organic compound that is used as a dyestuff for the materials like silk, leather and paper. As a part of removal of malachite green dye from textile and leather industrial wastes, using activated carbon as adsorbents namely, commercial activated carbon (CAC), rose apple carbon (RAC), coconut shell carbon (CSC) and saw dust carbon (SDC). The percentage of malachite green adsorbed increases with decrease in initial concentration and particle size of adsorbent and increased with increase in contact time, temperature and dose of adsorbent. The pH is highly sensitive for dye adsorption process. The adsorption process followed first order kinetics and the adsorption data with Freundlich and Langmuir isotherm models. The first order kinetic equations like Natarajan Khalaf, Lagergren, Bhattacharya and Venkobhachar and intra particle diffusion were found to be applicable. A comparative account of the adsorption capacity of various carbons has been made. These activated carbons are alternative to commercial AC for the removal dyes in General and MG is particular. These results are reported highly efficient and effective and low cost adsorbent for the MG. The thermodynamics parameters are also studied and it obeys spontaneous process. The results are confirmed by before and after adsorption process with the help of the following instrumental techniques viz., FT-IR, UV-Visible Spectrophotometer and SEM photos.

Alumina physically loaded by thiosemicarbazide for selective preconcentration of mercury(II) ion from natural water samples

The multifunctional ligand, thiosemicarbazide, was physically loaded on neutral alumina. The produced alumina-modified solid phase (SP) extractor named, alumina-modified thiosemicarbazide (AM-TSC), experienced high thermal and medium stability. This new phase was identified based on surface coverage determination by thermal desorption method to be 0.437+/-0.1 mmol g(-1). The selectivity of AM-TSC phase towards the uptake of different nine metal ions was checked using simple, fast and direct batch equilibration technique. AM-TSC was found to have the highest capacity in selective extraction of Hg(II) from aqueous solutions all over the range of pH used (1.0-7.0), compared to the other eight tested metal ions. So, Hg(II) uptake was 1.82 mmol g(-1) (distribution coefficient log K(d)=5.658) at pH 1.0 or 2.0 and 1.78, 1.73, 1.48, 1.28 and 1.28 mmol g(-1) (log K(d)=4.607, 4.265, 3.634, 3.372 and 3.372), at pH 3.0, 4.0, 5.0, 6.0 and 7.0, respectively. On the other hand, the metal ions Ca(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II) showed low uptake values in range 0.009-0.720 mmol g(-1) (log K(d)<3.0) at their optimum pH values. A mechanism was suggested to explain the unique uptake of Hg(II) ions based on their binding as neutral and chloroanionic species predominate at pH values < or =3.0 of a medium rich in chloride ions. Application of the new phase for the preconcentration of ultratrace amounts of Hg(II) ions spiked natural water samples: doubly distilled water (DDW), drinking tap water (DTW) and Nile river water (NRW) using cold vapor atomic absorption spectroscopy (CV-AAS) was studied. The high recovery values obtained using AM-TSC (98.5+/-0.5, 98.0+/-0.5 and 103.0+/-1.0) for DDW, DTW and NRW samples, respectively based on excellent enrichment factor 1000, along with a good precision (R.S.D.% 0.51-0.97%, n=3) demonstrate the accuracy and validity of the new modified alumina sorbent for preconcentrating ultratrace amounts of Hg(II) with no matrix interference.

Solid-Phase Extraction and Spectrophotometric Determination of Mercury with 6-Mercaptopurine in Environmental Samples

A highly selective, sensitive and rapid method for the determination of trace amounts of inorganic mercury based on the reaction of Hg (II) with 6-mercaptopurine and the solid phase extraction of the complex on C18 membrane disks was developed. The 6-mercaptopurine selectively reacts with Hg (II) to form a complex in the pH range of 5-8. This complex was preconcentrated by solid phase extraction with C18 disks. An enrichment factor of 100 was achieved. The molar absorptivity of the complex is 0.26 x 10(-6) L. mol(-1) cm(-1) measured at 315 nm. The Beer's law is obeyed in the concentration range of 0.002-0.048 microg mL(-1). The relative standard deviation for eleven-replicated measurement of 0.04 microg mL(-1) is 1.5 %. The detection limit is 0.001 microg mL(-1) in the water samples. The advantage of the method is that the determination of Hg (II) is free from interference of almost all the cations and anions found in environment and wastewater samples. The determination of Hg (II) in water samples of different origins and marine sediment were carried out by the present method and cold vapor atomic absorption spectrometry (CVAAS). Also the method's accuracy was investigated by using SRM 2709. The obtained results by the present procedure were in good agreement with those of the CVAAS and certified value, so that the applicability of the proposed method was confirmed for the real samples.

Principais rotas de síntese de resinas complexantes de mercúrio

A recuperação de espécies contendo mercúrio utilizando resinas complexantes obtidas a partir da modificação de suportes poliméricos vem atraindo cada vez mais a atenção dos pesquisadores. São muitas as combinações de suportes e grupos complexantes para a síntese desses materiais. Assim, este trabalho apresenta uma revisão sobre os principais grupos funcionais avaliados, bem como as rotas de síntese adotadas para a imobilização desses grupos nos suportes. É abordada também a problemática da síntese de uma resina eficiente, produzida a partir de um processo limpo e acessível às indústrias que utilizam mercúrio em seus processos.

Orientation of 6-Mercaptopurine SAMs at the Silver Electrode as Studied by Raman Mapping and in Situ SERS

Self-assembled monolayers (SAMs) of 6-mercaptopurine (6MP) on a silver electrode in acid and alkaline media were investigated by a combination protocol of the SERS technique with Raman mapping, and it was found that the adsorption mode of 6MP SAMs changed with the pH value of the environment. Quantum calculations for the vibrational mode were performed by the BLYP/6-31G method. 6MP was adsorbed on the silver electrode with a tilted orientation via S, N1, and N7 atoms in acid medium, while the SAMs adopted head-on adsorption modes with the S atom and the N1 atom anchoring the silver surface in alkaline medium. However, 6MP SAMs turned to the same upright orientation on the electrode through the S and N7 atoms when either acid or basic solution was removed. Stability of 6MP SAMs was observed by in situ SERS spectroelectrochemical measurements. The results reveal that the desorption potentials of 6MP SAMs formed under acid and alkaline conditions from the Ag electrode were at ca. -1.3 V and -1.6 V vs SCE, respectively.

Removal and recovery of mercury(II) from hazardous wastes using 1-(2-thiazolylazo)-2-naphthol functionalized activated carbon as solid phase extractant

As a part of removal of toxic heavy metals from hazardous wastes, solid phase extraction (SPE) of mercury(II) at trace and ultra trace levels was studied using 1-(2-thiazolylazo)-2-naphthol (TAN) functionalized activated carbon (AC). The SPE material removes traces of mercury(II) quantitatively in the pH range 6.0 +/- 0.2. Other parameters that influence quantitative recovery of mercury(II), viz. percent concentration of TAN in AC, amount of TAN-AC, preconcentration time and volume of aqueous phase were varied and optimized. The possible means of removal of Hg(II) from other metal ions that are likely to be present in the wastes of the chloroalkali industry is discussed. The potential of TAN-functionalized AC SPE material for decontaminating mercury from the brine sludge and cell house effluent of a chloralkali plant has been evaluated.

Preconcentration of Mercury Using Duolite GT-73 in the Analysis of Water Samples by Inductively Coupled Plasma Atomic Emission Spectrometry

Duolite GT-73 resin was used for the preconcentration of Hg(II) from hydrochloric acid media as well as separation of the analyte from diversity of the co-existing metal ions (Al, Ca, Cd, Co, Cr, Cu, Fe, Mg, Mn, Ni, Pb and Zn) in off-line column operation. Due to the high affinity of the resin to the transition metals, Hg was adsorbed alongside with the foreign metals investigated. A complete release of the concomitant metals from the resin without the desorption of Hg was carried out using solutions of HCl and HNO3. A quantitative recovery of Hg was obtained by digestion of the resin using a H2SO4 and H2O2 mixture in an open-vessel system. An enrichment factor of 40 was achieved. The devised procedure was applied for the determination of Hg(II) in tap-water samples.

Solid phase extraction–spectrophotometric determination of dissolved aluminum in soil extracts and ground waters

An on-line solid-phase extraction (SPE) technique, linked to spectrophotometry, has been developed to overcome the problem of high matrix concentration, which is thought to interfere with the determination of low levels of aluminum (Al) in environmental samples. Tiron modified resin was prepared and used as a SPE absorbent, which can quantitatively adsorb Al(III) at pH 4-6 with an adsorption capacity of 5.6 mg g(-1) resin. The main advantages of this novel method are: (1) a much higher sensitivity has been obtained by SPE technology; and (2) a large amount of Na(+), K(+), Ca(2+) and Mg(2+) can be removed and the interference of Fe(III), Mn(II) and F(-) can be efficiently eliminated by eluting with 0.25 mol l(-1) NaOH. It is a highly selective and sensitive method for simple and quick determination of dissolved Al in soil extracts and ground waters, particularly suitable for the analysis of complex environmental samples.

Preconcentration and separation of copper, zinc and cadmium by the use of 6-mercapto purinylazo resin and their application in microwave digested certified biological samples followed by AAS determination of the metal ions

6-Mercapto purinylazo resin has been used as solid phase extractor. Based on solid phase extraction, the present work describes the preconcentration and determination of copper, zinc and cadmium in certified biological samples after microwave-assisted digestion. The exchange capacity of the resin, the sorption and desorption of metal ions, and the effect of diverse ions have also been determined. The results show that the resin is highly selective for determination of these biologically significant metals. The method is simple, rapid and free from interferences and can be used routinely.