Determination of Trace Mercury in Saltwaters at Screen-Printed Electrodes Modified with Sumichelate Q10R

Development of tBu-phenyl Acetamide Appended Thiacalix[4]arene as "Turn-ON" Fluorescent Probe for Selective Recognition of Hg(II) Ions

Herein, a novel N-(4-(tert-butyl)-phenyl)-2-chloroacetamide functionalized thiacalix[4]arene architecture, viz TCAN2PA has been synthesized and the sensing behaviour towards metal ions were explored. The probe, TCAN2PA displayed "turn-on" fluorescence response towards Hg(II) ions in acetonitrile over a series of competing common metal ions. A bathochromic shift in absorption band along with a significant "Turn-On" fluorescence behaviour of TCAN2PA was observed upon interaction with Hg(II) ions. The lower rim modification of thiacalixarene with N-(4-(tert-butyl)-phenyl)-2-chloroacetamide actively contributes toward the fluorescence property due to the presence of strong electron-donating aryl amido substituent. Fluorescence titration experiments were conducted to find out the limit of detection and to understand binding stoichiometry as well. The electron transfer interactions between the electron rich TCAN2PA host with Hg(II) ions have been postulated which is also supported by computational modelling insights.

A New Highly Selective Colorimetric and Fluorometric Coumarin-based Chemosensor for Hg2

A novel colorimetric and fluorometric method based on coumarin as signalling unit was developed for Hg²⁺ recognition and quantification. Initially, the alkyne functionality was incorporated into a coumarin system and the resulting molecule showed higher specificity and sensitivity for Hg²⁺ over other cations in both absorption and emission sensing assays. The Hg²⁺ recognition was detected as visible colour change from colourless to yellow and as fluorescence quenching. The colour change was assigned to the increased intramolecular charge transfer (ICT) in the signalling unit upon Hg²⁺ binding whereas a decline in the fluorescence intensity was ascribed to the heavy atom effect from Hg²⁺. In order to generate a material with high sensing performance level, alkyne-functionalized molecule was hosted into a polymeric material. The resulting functionalized polymer showed higher sensitivity and selectivity for Hg²⁺ over its corresponding coumarin molecule. The investigation of the possible binding modes for Hg²⁺ suggested both alkyne and triazole functionalities as potential binding sites for Hg²⁺. The limit of detection (LOD) and limit of quantification (LOQ) of the proposed method were evaluated and values less than a recommended maximum level of Hg²⁺contaminant in drinking water (2.00 μg/L) were obtained (LOD = 0.44 μg/L and LOQ = 1.33μg/L). The real-life application of the method was investigated using natural water samples containing Hg²⁺ levels equivalent to the maximum tolerable concentration of Hg²⁺ in drinking water. The outcomes suggested that the method could be used in the sensing and determination of Hg²⁺ level of contaminant in the environment.

A highly selective and sensitive ESIPT-based coumarin–triazole polymer for the ratiometric detection of Hg2+

A reversible ESIPT based system for the detection of Hg²⁺ was developed. The system exhibited better properties compared to that of recently developed ratiometric fluorescent systems.

A benzofuran-β-alaninamide based “turn-on” fluorescent chemosensor for selective recognition of Fe3+ ions

A benzofuran-β-alaninamide based chemosensor, 3-(3-((4-methylbenzyl)amino)propanamido)benzofuran-2-carboxamide (BAA), was designed and synthesized for selective detection of Fe³⁺ ions.

A colorimetric paper sensor for visual detection of mercury ions constructed with dual-emission carbon dots

A ratiometric fluorescence nanosensor has been developed by mixing blue fluorescent carbon dots and red fluorescent carbon dots, where the blue fluorescence can be selectively quenched by Hg²⁺, while the red fluorescence is an internal reference.

Simple and rapid chemiluminescence aptasensor for Hg2+ in contaminated samples: A new signal amplification mechanism

Detection of ultralow concentration of heavy metal ion Hg²⁺ is important for human health protection and environment monitoring because of the gradual accumulation in environmental and biological fields. Herein, we report a convenient chemiluminescence (CL) biosensing platform for ultrasensitive Hg²⁺ detection by signal amplification mechanism from positively charged gold nanoparticles ((+)AuNPs). It is based on (+)AuNPs charge effect and aptamer conformation change induced by target to stimulate the generation of CL in the presence of H₂O₂ and luminol without high salt medium. Notably particularly, the typical problem of the high salt medium from (-) AuNPs system, like influencing aptamers' bind with target and hindering CL reaction can be effectively addressed through the direct introduction of (+)AuNPs. Therefore, the proposed biosensing exhibits a high sensitivity toward target Hg²⁺ with a detection limit of 16 pM, which is far below the limit (10nM) defined by the U.S. Environmental Protection Agency in drinkable water, and is about 10-fold lower than the previously reported aptamer-based assays for Hg²⁺. This sensing platform provides a simple, rapid, and cost-effective approach for label-free sensitive detection of Hg²⁺. Moreover, it is universal for the detection of other targets. Undoubtedly, such a direct utilizing of (+)AuNPs' charge effect will provide a new signal amplification way for label-free aptamer-based CL analysis.

Highly selective and effective mercury(ii) fluorescent sensors

A novel and sulfur-free mercury specifically selective and highly sensitive fluorescent chemosensorLbased on the benzimidazole group and the quinoline group as the fluorescence signal group has been designed and synthesized.

Nanometer Materials Modified Electrodes for Detection of Heavy Metal Ions by Stripping Voltammetry

More and more heavy metal ions pollution events happen nowadays, so how to detect and remove heavy metal ions is a very important problem. Electrochemical method is relatively simple device, convenient automatic operation. Because of its high sensitivity and good selectivity, it becomes a good method to detect heavy metal ions. This paper summarized the detection of heavy metal ions by stripping voltammetry.

Vanillin-coumarin hybrid molecule as an efficient fluorescent probe for trace level determination of Hg(II) and its application in cell imaging

An efficient Hg(2+) selective fluorescent probe (vanillin azo coumarin, VAC) was synthesized by blending vanillin with coumarin. VAC and its Hg(2+) complex were well characterized by different spectroscopic techniques like (1)H NMR, QTOF-MS ES(+), FTIR and elemental analysis as well. VAC could detect up to 1.25 μM Hg(2+) in aqueous methanol solution through fluorescence enhancement. The method was linear up to 16 μM of Hg(2+). Negative interferences from Cu(2+), Ni(2+), Fe(3+), and Zn(2+) were eliminated using EDTA as a masking agent. VAC showed a strong binding to Hg(2+) ion as evident from its binding constant value (2.2×10(5)), estimated using Benesi-Hildebrand equation. Mercuration assisted restricted rotation of the vanillin moiety and inhibited photoinduced electron transfer from the O, N-donor sites to the coumarin unit are responsible for the enhancement of fluorescence upon mercuration of VAC. VAC was used for imaging the accumulation of Hg(2+) ions in Candida albicans cells.

Sol-gel derived highly selective optical sensor for sensitive determination of the mercury(II) ion in solution

We report a versatile optical sensor by incorporating the indicator dye 4-phenyl-2,6-bis(2,3,5,6-tetrahydrobenzo[b][1,4,7]trioxononin-9-yl)pyrylium perchlorate into a sol-gel layer. The proposed optical sensor that is stable, fast and highly selective to Hg(2+) ions shows a significant absorbance signal change on exposure to an aqueous solution containing mercury(II) ion. The sensing film is able to determine mercury(II) ion in aqueous solution with a high selectivity over a wide dynamic range between 1.52x10(-9) and 1.70x10(-2)M, at pH 5, and a lower detection limit of 1.11x10(-9)M. Validation of the assay method revealed excellent performance characteristics for Hg(2+) ions over a wide variety of other metal ions, including good selectivity, long-term response stability and high reproducibility. Applications, for the direct determination of mercury(II) in real samples, gave the results with good correlation with the data obtained by using cold vapor atomic absorption spectrometry.

Determination of trace amounts of mercury(II) in water samples using a novel kinetic catalytic ligand substitution reaction of hexacyanoruthenate(II)

A simple, sensitive, selective and rapid kinetic catalytic method has been developed for the determination of Hg(II) ions at micro-level. This method is based on the catalytic effect of Hg(II) ion on the rate of substitution of cyanide in hexacyanoruthenate(II) with nitroso-R-salt (NRS) in aqueous medium and provides good accuracy and precision. The concentration of Hg(II) catalyst varied from 4.0 to 10.0x10(-6)M and the progress of reaction was followed spectrophotometrically at 525nm (lambda(max) of purple-red complex [Ru(CN)(5)NRS](3-), epsilon=3.1x10(3)M(-1)s(-1)) under the optimized reaction conditions; 8.75x10(-5)M [Ru(CN)(6)(4-)], 3.50x10(-4)M [nitroso-R-salt], pH 7.00+/-0.02, ionic strength, I=0.1M (KCl), temp 45.0+/-0.1 degrees C. The linear calibration curves, i.e. calibration equations between the absorbance at fixed times (t=15, 20 and 25min) versus concentration of Hg(II) ions were established under the optimized experimental conditions. The detection limit was found to be 1.0x10(-7)M of Hg(II). The effect of various foreign ions on the proposed method has also been studied and discussed. The method has been applied to the determination of mercury(II) in aqueous solutions.

Determination of Antimony (III) in Real Samples by Anodic Stripping Voltammetry Using a Mercury Film Screen-Printed Electrode

This paper describes a procedure for the determination of antimony (III) by differential pulse anodic stripping voltammetry using a mercury film screen-printed electrode as the working electrode. The procedure has been optimized using experimental design methodology. Under these conditions, in terms of Residual Standard Deviation (RSD), the repeatability (3.81 %) and the reproducibility (5.07 %) of the constructed electrodes were both analyzed. The detection limit for Sb (III) was calculated at a value of 1.27×10(-8) M. The linear range obtained was between 0.99 × 10(-8) - 8.26 × 10(-8) M. An analysis of possible effects due to the presence of foreign ions in the solution was performed and the procedure was successfully applied to the determination of antimony levels in pharmaceutical preparations and sea water samples.

Determination of Lamotrigine in Pharmaceutical Preparations by Adsorptive Stripping Voltammetry Using Screen Printed Electrodes

This paper describes a procedure that has been optimized for the determination of lamotrigine by Differential Pulse Adsorptive Stripping Voltammetry (DPAdSV) using carbon screen-printed electrodes (CSPE) and mercury coated carbon screen-printed electrodes. Selection of the experimental parameters was made using experimental design methodology. The detection limit found was 5.0 x 10^-6 M and 2.0 x 10^-6 M for the non modified and Hg modified CSPE, respectively. In terms of reproducibility, the precision of the above mentioned methods was calculated in %RSD values at 9.83% for CSPE and 2.73% for Hg-CSPE. The Hg-coated CSPEs developed in this work were successfully applied in the determination of lamotrigine in pharmaceutical preparations.

Picogram detection of metal ions by melanin-sensitized piezoelectric sensor

A heavy metal ion sensor was constructed by cross-linking melanin onto the gold electrode of quartz crystal microbalance (QCM). A mercury ion sensitivity of 518+/-37 Hz/ppm was observed, a substantial increase in sensitivity compared to previous reports of 10-50 Hz/ppm with the limit of detection at 5 ppb. Detection of other metal ions including Sn(2+), Ge(4+), Li(+), Zn(2+), Cu(2+), Bi(3+), Co(2+), Al(3+), Ni(2+), Ag(+), and Fe(3+) were also performed. Unexpectedly, binding of Mn(7+), Pb(2+), Cd(2+), and Cr(3+) increased resonant frequencies. The surface profile of melanin thin film upon binding to metal ions was investigated by atomic force microscopy (AFM). Structural change of melanin upon binding to metal ions was characterized by circular dichroism and by infrared spectroscopy. The current study provides the first example of melanin-coated piezoelectric sensor showing high sensitivity and selectivity to metal ions.

Development of a disposable mercury ion-selective optode based on trityl-picolinamide as ionophore

A disposable ion-selective optode for mercury based on trityl-picolinamide (T-Pico) as neutral ionophore was developed. The sensing layer consist of plasticised PVC incorporating T-Pico as a selective ionophore for Hg2+, ETH 5418 as a chromoionophore, and potassium tetrakis[3,5-bis(trifluoromethyl)phenyl] borate as lipophilic salt. The measurement principle is based on an ion-exchange mechanism. When the optode membrane is introduced into a water sample for 5 min, there is a colour change from red to blue, depending on the mercury concentration (pH 4.7), making it possible to use the absorbance at 665 nm as the analytical signal. The optode membrane response to Hg2+ was not fully reversible; however, it reveals a very good selectivity to many cations including alkali, alkaline earth, transition, and heavy metal ions. The detection limit for Hg2+ is 5.0x10(-7) M at pH 4.7. The response characteristics of the sensor including dynamic range, reproducibility, response time, and lifetime are discussed in detail. This sensor was used for the determination of mercury in environmental water samples with satisfactory recovery.