Ultrasound assisted-dispersive-modification solid-phase extraction using task-specific ionic liquid immobilized on multiwall carbon nanotubes for speciation and determination mercury in water samples

Solid-Phase Microextraction Mediated Solid-Phase Dielectric Barrier Discharge Vapor Generation-Atomic Fluorescence Spectrometry for Sensitive Determination of Mercury in Seawater

A novel method coupling solid-phase microextraction (SPME) to solid-phase dielectric barrier discharge (SPDBD) vapor generation was proposed and used for the sensitive detection of trace mercury (Hg) in seawater with atomic fluorescence spectrometry (AFS) in this work. The method proposed herein offers the unique advantages of integrating desorption and chemical vapor generation into one step, eliminating the use of elution reagents, and reducing the analysis time. SPME with multiwalled carbon nanotubes (MWCNTs) coated on the glass tube was used to extract Hg2+ in seawater. The Hg2+ was then desorbed and reduced to Hg0 vapor by SPDBD, which was detected by cold vapor AFS. The parameters affecting Hg2+ extraction, desorption, and vapor generation were studied. The detection limit of Hg2+ was 0.0003 μg L-1, and the relative standard deviation at a Hg2+ concentration of 0.05 μg L-1 was 4.4%. This method also has excellent antimatrix interference ability for Hg2+ determination with recoveries between 91.8% and 101.1% in the presence of extremely high concentrations (two million times excess) of coexisting ions. The practicality of this method was also evaluated by analyzing two different certified reference materials of Hg2+ in water and several seawater samples with good spike recoveries (94.0%-107.4%). Compared with solid-phase photothermo-induced vapor generation, this method has higher extraction efficiency and higher desorption efficiency without the assistance of heating as well as a lower detection limit of Hg2+, which is capable of performing trace Hg analysis in seawater.

Reshaping Capillary Electrophoresis With State-of-the-Art Sample Preparation Materials: Exploring New Horizons

Capillary electrophoresis (CE) is a powerful analysis technique with advantages such as high separation efficiency with resolution factors above 1.5, low sample consumption of less than 10 µL, cost-effectiveness, and eco-friendliness such as reduced solvent use and lower operational costs. However, CE also faces limitations, including limited detection sensitivity for low-concentration samples and interference from complex biological matrices. Prior to performing CE, it is common to utilize sample preparation procedures such as solid-phase microextraction (SPME) and liquid-phase microextraction (LPME) in order to improve the sensitivity and selectivity of the analysis. Recently, there have been advancements in the development of novel materials that have the potential to greatly enhance the performance of SPME and LPME. This review examines various materials and their uses in microextraction when combined with CE. These materials include carbon nanotubes, covalent organic frameworks, metal-organic frameworks, graphene and its derivatives, molecularly imprinted polymers, layered double hydroxides, ionic liquids, and deep eutectic solvents. The utilization of these innovative materials in extraction methods is being examined. Analyte recoveries and detection limits attained for a range of sample matrices are used to assess their effects on extraction selectivity, sensitivity, and efficiency. Exploring new materials for use in sample preparation techniques is important as it enables researchers to address current limitations of CE. The development of novel materials has the potential to greatly enhance extraction selectivity, sensitivity, and efficiency, thereby improving CE performance for complex biological analysis.

Ultrasound-assisted dispersive solid phase extraction for promoting enrichment of ng L-1 level Hg2+ on ionic liquid coated magnetic materials

Herein, we investigated the enrichment behavior of inorganic mercury (Hg²⁺) on magnetic adsorbent with different ultrasound (US) energy field input. The enrichment rate of 0.10 μg L^-1 mercury is increased by 4.5 times after US instead of stirring as dispersion mode. The input of higher frequency and power ultrasound can accelerate the enrichment of magnetic ionic liquid adsorbent and reduce the Hg²⁺ residue, importantly, which has not been reported. The positive correlation between cavitation effect and acoustic frequency and power in imaging experiments documents that US parameters are the key factors affecting the magnetic solid phase extraction. In addition, in-situ desorption and detection of adsorbate and recovery of adsorbent can be realized by slurry vapor generation (SVG) technology. The recovery of Hg²⁺ in four cycles is more than 90%, which indicates that the structure and properties of the material are not affected by the application of US. Hence, the degradation of adsorption properties caused by agglomeration of magnetic materials can be improved by introducing dispersion methods such as US. At the same time, 95% enrichment efficiency and 0.01-1.0 μg L^-1 linear calibration range corresponding to 150 mL sample documents that magnetic ionic liquid adsorbent combined with US and sensitive spectral detector can meet the needs of ng L^-1 level Hg²⁺ analysis in natural water samples.

Ultrasound-assisted dual-cloud point extraction with high-performance liquid chromatography-hydride generation atomic fluorescence spectrometry for mercury speciation analysis in environmental water and soil samples

A method for simultaneous preconcentration and determination of mercury species in water and soil samples was established using high-performance liquid chromatography with hydride generation atomic fluorescence spectrometry after ultrasound-assisted dual-cloud point extraction. The extraction process was divided into two steps. In the first cloud point extraction, inorganic mercury and methylmercury formed chelates with sodium diethyldithiocarbamate and were extracted into Triton X-114 micelles. In the second stage, a displacement reaction between sodium diethyldithiocarbamate-inorganic mercury/methylmercury and l-cysteine occurred, and the analytes entered the l-cysteine aqueous solution under ultrasonication. This aqueous solution was directly introduced to the high-performance liquid chromatography with hydride generation atomic fluorescence spectrometry and the detection was completed within 6 min. Under the optimum experimental conditions, the linear range was 0.10-5.0 μg/L (r ≥0.9993) for inorganic mercury and methylmercury, and the enhancement factors were 15.7 for inorganic mercury and 6.35 for methylmercury. The limits of detection for inorganic mercury and methylmercury were 0.004 and 0.016 μg/L, respectively. The approach was successfully applied to the determination of trace inorganic mercury and methylmercury in water and soil samples with good recoveries (85.3-110%). This method solved the problem of peak fusion of the two analytes and was successfully applied to the speciation analysis of mercury.

Determination of Total Mercury in Solid Samples by Anodic Stripping Voltammetry

The anodic stripping voltammetry (ASV) was investigated to determine total mercury in solid samples using a gold electrode. The mercury was deposited on the gold electrode in a preconcentration step. The oxidation peak of mercury was irreversible. The optimal conditions of the procedure were found to be as follows: 0.05 mol L−1 HCl solution, deposition potential −0.5 V vs. Ag/AgCl/KCls, deposition time 40 s, and sweep rate 0.04 V s−1. Under the optimal conditions, the peak current showed a linear dependence on Hg2+ concentration in the range from 0.01 to 0.1 mg l−1. The detection limit and quantification limit were 4.28 µg L−1 and 12.98 µg L−1, respectively. The mean recovery and relative standard deviation were 91.2% and 2.4% (n = 9). The procedure was successfully applied for determining total mercury in samples collected from Hanoi light bulb warehouse—The Rang Dong Light Source and Vacuum Flask JSC. The results were compared with cold vapor atomic absorption spectrometry (CV-AAS).

DNA-Gold Nanozyme-Modified Paper Device for Enhanced Colorimetric Detection of Mercury Ions

In this work, a paper device consisted of a patterned paper chip, wicking pads, and a base was fabricated. On the paper chip, DNA–gold nanoparticles (DNA–AuNPs) were deposited and Hg²⁺ ions could be adsorbed by the DNA–AuNPs. The formed DNA–AuNP/Hg²⁺ nanozyme could catalyze the tetramethylbenzidine (TMB)–H₂O₂ chromogenic reaction. Due to the wicking pads, a larger volume of Hg²⁺ sample could be applied to the paper device for Hg²⁺ detection and therefore the color response could be enhanced. The paper device achieved a cut-off value of 50 nM by the naked eye for Hg²⁺ under optimized conditions. Moreover, quantitative measurements could be implemented by using a desktop scanner and extracting grayscale values. A linear range of 50–2000 nM Hg²⁺ was obtained with a detection limit of 10 nM. In addition, the paper device could be applied in the detection of environmental water samples with high recoveries ranging from 85.7% to 105.6%. The paper-device-based colorimetric detection was low-cost, simple, and demonstrated high potential in real-sample applications.

Photo-generation of mercury cold vapor mediated by graphene quantum dots/TiO2 nanocomposite: On line time-resolved speciation at ultra-trace levels

Mercury speciation was achieved using a nanocomposite, consisting of graphene quantum dots (GQDs) and TiO₂ nanoparticles, to mediate photo-degradation of mercurial species into the Hg cold vapor detected by atomic spectrometry. Sample solution (containing Hg²⁺, CH₃CH₂Hg, and CH₃Hg at hundreds of ng L^-1) was placed in quartz tube containing formic acid solution (2% v/v) and microliter aliquot of GQDs/TiO₂ nanocomposite dispersion (0.6 mg of nanocomposite). The tube was placed inside a photochemical reactor then, adapted to the mercury-dedicated spectrometer. Quantitative speciation was achieved taking advantage of the differences in UV photodegradation kinetics: Hg²⁺ (5 min), CH₃CH₂Hg (9 min) and CH₃Hg (13 min). Gas-chromatography cold vapor atomic fluorescence spectrometry was used to confirm the evolution of the reactions over time during photo-reaction. The limits of detection were 10 ng L^-1 for CH₃CH₂Hg and 7 ng L^-1 for Hg²⁺ and CH₃Hg.