Renewable column on-line magnetic preconcentration of Cd(II) using Fe3O4 nanoparticles functionalized with l-glutamine for determination by flame atomic absorption spectrometry

Bifunctional magnetic nanoparticles with ion imprinting for improving the flow through determination of ultratraces of Cd(II) using magnetic preconcentration

A novel bifunctional magnetic sorbent with mercapto and amino groups and ion imprinting (MBII) was synthesized using a one-step aqueous sol-gel process for preconcentration and determination of Cd(II) ions. MBII was employed as a microcolumn (MC) filler in a flow-through system coupled to GFAAS. The magnetic properties of the solid allowed microcolumn magnetic solid-phase extraction (MCMSPE) to be performed by simply including a single circular magnet around the MC. This assembly enabled complete attachment of the solid to the MC wall leaving a central void to facilitate higher sample flow rates without blockage or material loss. For comparison, a bifunctional magnetic solid without imprinting (MBNI) was also synthesized and evaluated. Both MBII and MBNI were characterized by FTIR, SEM, EDX, BET and magnetization measurements. The results showed the preservation of the magnetic core, its superparamagnetism and the functional groups in the solid. Batch studies revealed a maximum adsorption capacity for both materials at pH around 6 with equilibrium reached within 5 minutes. The advantages were reflected in the maximum adsorption capacity of MBII, which was found to be 2.5 times greater than that of MBNI. Both adsorbents were compared as MC fillers for dynamic preconcentration in MCMSPE systems. Under optimized conditions, MBNI showed a PCF of 125 and MBII of 250. The higher selectivity of MBII was corroborated by interfering ion studies. The analytical performance parameters for the proposed method using MBII as an adsorbent showed a detection limit of 0.05 ng L-1, a linear range of 2.0-80 ng L-1, an RSD% of 2.2 (n = 7; 20 ng L-1) and a lifetime of more than 300 preconcentration-elution cycles without loss of sensitivity or need for refilling. The method was successfully applied to the determination of trace Cd(II) in osmosis, lake and tap water with recoveries ranging from 98 to 105%. Comparison of these results with those of similar reported methods showed a considerable improvement primarily attributed to the combined effect of MBII's higher retention capacity and its magnetic properties that allowed higher sample flow rates and, thus, enhanced figures of merit.

A novel "off-on" fluorescent probe for the detection of nickel ions and its clinical application

Nickel serves as an essential micronutrient for the human body, playing a vital role in various enzymatic processes. However, excessive nickel entering the environment can cause pollution and pose serious risks to animals, plants, and human health. High concentrations of nickel ions in the human body increase the risk of various diseases, highlighting the need for accurate measurement of nickel ions levels. In this study, we designed a sequence-specific cleavage probe for nickel (II) ion called SSC-Ni. Similar to the TaqMan probe, SSC-Ni is an off-on fluorescent probe with an exceptionally low background fluorescence signal. It exhibits high detection specificity, making it highly selective for nickel ions, and the detection limit of the probe towards Ni2+ is as low as 82 nM. The SSC-Ni probe can be utilized for convenient and cost-effective high-throughput quantitative detection of nickel ions in serum. Its user-friendly operation and affordability make it a practical solution. By addressing the lack of simple and effective nickel ion detection methods, this probe has the potential to contribute significantly to environmental monitoring and the protection of human health.

A novel ratiometric fluorescent probe for the detection of nickel ions in the environment and living organisms

Nickel resources are abundant in the world, and the application of nickel in production and life is more and more extensive. However, excessive nickel entering the environment will not only cause environmental pollution but also seriously endanger plants, animals and human health. Nickel compounds are carcinogenic and have been classified as a class 1 carcinogen. Nickel mainly exists in the form of divalent ions in the environment. However, there are few simple and effective methods for the detection of nickel ions, and these methods still have certain limitations. At present, the mechanisms of nickel influence in organisms are also unclear. Therefore, we constructed a ratiometric fluorescent probe Ra-Ni, which can achieve its own self-calibration and avoid the interference of other factors, thereby realizing the specific identification of nickel ions. The probe can detect nickel ions sensitively with a detection limit as low as 26.2 nM and can respond in a short time (< 2 min), which proves the great potential of the probe in the detection of nickel ions. At the same time, Ra-Ni has also been successfully used for imaging nickel ions in living cells and zebrafish, providing an effective tool for the study of physiological and pathological processes. The detection effect of nickel ions in actual water sample is also satisfactory, which further demonstrates the practicability of Ra-Ni in environmental applications.

An ion imprinted magnetic organosilica nanocomposite for the selective determination of traces of Cd(II) in a minicolumn flow-through preconcentration system coupled with graphite furnace atomic absorption spectroscopy

In this paper we present the determination of ultratraces of cadmium ions in water by means of a minicolumn (MC) flow-through preconcentration system coupled with graphite furnace atomic absorption spectrometry. The core of the system is a lab-made ion imprinted magnetic organosilica nanocomposite which is employed as filler of the MC for the selective retention of the analyte. In this case superparamagnetic magnetite nanoparticles were coated with an amine-functionalized shell and ion imprinted with Cd(II) by a simple sol-gel co-condensation method. The setup was completed with the inclusion of a magnet fixed around the packed MC. This assembly - which is studied with an MII material for the first time here - allowed a homogeneous distribution of the solid on the walls of the MC, leaving a hole in the center and enabling the absence of material bleeding or obstructions to the free movement of fluids. Ion imprinted (MII) and non-imprinted (MNI) materials were studied for comparison purposes. Both were characterized and compared by DRX, FTIR, and SEM and their magnetic behavior by magnetization curves. Batch experiments showed an equilibration time of less than 10 minutes and a maximum adsorption pH of around 7 for both solids. The maximum capacity for MII was greater than that of MNI (200 mg g^-1 and 30 mg g^-1 respectively) and thus, the former was chosen for analytical purposes. Under MC dynamic conditions, sample and elution flow rates, volumes of the sample and eluant, and type and concentration of the most suitable eluant have been thoroughly investigated and optimized. Under the optimal experimental conditions, the MII filler showed a preconcentration factor of 200, a limit of detection of 0.64 ng L^-1, a linear range of 2.5-100 ng L^-1, RSD% of 1.9 (n = 6; 10 ng L^-1) and a lifetime of more than 800 cycles of concentration-elution with no loss of sensitivity or need for refilling. The effect of potentially interfering ions on the percent recovery of cadmium was also studied. The proposed method was successfully applied to the determination of traces of Cd(II) in osmosis and tap water with recoveries of 98.0-101.3%. A comparison with similar methods is also provided.

Flow-Injection Methods in Water Analysis-Recent Developments

Widespread demand for the analysis and control of water quality and supply for human activity and ecosystem sustainability has necessitated the continuous improvement of water analysis methods in terms of their reliability, efficiency, and costs. To satisfy these requirements, flow-injection analysis using different detection methods has successfully been developed in recent decades. This review, based on about 100 original research papers, presents the achievements in this field over the past ten years. Various methodologies for establishing flow-injection measurements are reviewed, together with microfluidics and portable systems. The developed applications mostly concern not only the determination of inorganic analytes but also the speciation analysis of different elements, and the determination of several total indices of water quality. Examples of the determination of organic residues (e.g., pesticides, phenolic compounds, and surfactants) in natural surface waters, seawater, groundwater, and drinking water have also been identified. Usually, changes in the format of manual procedures for flow-injection determination results in the improvement of various operational parameters, such as the limits of detection, the sampling rate, or selectivity in different matrices.

Cationic microcrystalline cellulose - Montmorillonite composite aerogel for preconcentration of inorganic anions from dairy wastewater

Development of efficient adsorbents to inorganic anions as a solid phase extraction (SPE) material is highly desirable for chromatographic analysis and pollution control. In this work we developed a new hybrid cationic microcrystalline cellulose aerogel composite. Cationic cetylpyridinium imbedded montmorillonite (CPC-MT) was uniformly entrapped in microcrystalline cellulose (MCC) to enhance anionic adsorption efficiency and mechanical stability. The developed CPC-MT@MCC aerogel was used as an SPE adsorbent for anions from dairy wastewater by coupling with ion-column chromatography. Further quaternized CPC-MT@MCC aerogel (CPC-MT@QMCC) showed unique low density (10.6 mg cm^-3), large specific surface area (320 m² g^-1), porosity 70%, 800 mg g^-1 nitrate adsorption capacity within 60 min and ease of elution in alkaline solutions. The CPC-MT@QMCC aerogel showed efficient regeneration and reuse performances for up to 10 cycles. More importantly, a dynamic binding efficiency of 710 mg g^-1 highlights its excellent performance for practical applications. 96% of nitrate anion from environmental manure wastewater samples were adsorbed with 98.7% recovery. A good linear relationship was obtained in the range of 0.01-10 mg L^-1 and the limits of detection was 0.5 mg L^-1 using CPC-MT@QMCC aerogel as a preconcentration column. The successful synthesis of such intriguing and economic CPC-MT@QMCC aerogel may provide a promising matrix for high-performance and high efficiency chromatographic media.