Preconcentration and Determination of Metal Ions Using Fluorescein-Modified Silica Gel and Inductively Coupled Plasma-Optical Emission Spectrometry

A nanozyme-catalysis-based ratiometric electrochemical sensor for general detection of Cd2+

AuPt–rGO showed good peroxidase-like activity for the oxidation of OPD to DAP (a novel internal reference) and achieved sensitive and reliable detection of Cd2+ based on a ratiometric strategy.

Multi-ion imprinted polymers (MIIPs) for simultaneous extraction and preconcentration of Sb(III), Te(IV), Pb(II) and Cd(II) ions from drinking water sources

Simultaneous extraction and preconcentration of several potentially toxic metal ions have received great attention because of their toxicological effects on aquatic life and human beings. Multi-ion imprinted polymers (MIIP) have proved to be promising adsorbents with excellent specific recognition performance than single-ion imprinted polymer. Therefore, in this study, the MIIP strategy was employed for simultaneous extraction and enrichment of Sb(III), Cd(II), Pb(II) and Te(IV) ions from drinking water sources. MIIPs was used as a sorbent material in ultrasound-assisted dispersive solid phase extraction combined with inductively coupled plasma optical emission spectrometry (UA-DSPE/ICP-OES). The experimental parameters that affect the extraction efficiency and recovery of Sb(III), Cd(II), Pb(II) and Te(IV) were investigated using response surface methodology. Under optimum conditions, the enhancement factors, linear range, limit of detection (LOD) and limit of quantification (LOQ) were 37.7-51.1, 0.04-100 µg L^-1, 0.011-0.28 µg L^-1, 0.037-093 µg L^-1, respectively. The intra-day (n = 10) and inter-day (n = 5) precision expressed as relative standard deviations (%RSDs,) were 3% and 5%, respectively. The proposed UA-DSPE/ICP-OES method was applied for preconcentration and determination of the trace metal ions in environmental samples. Furthermore, the accuracy of the method was evaluated using spiked recovery experiments and the percentage recoveries ranged from 95% to 99.3%.

Rapid ratiometric detection of Cd2+ based on the formation of ZnSe/CdS quantum dots

Developing simple and sensitive non-aggregation strategy for detecting Cd²⁺ is necessary for improving the selectivity and sensitivity of probe. Here, we establish a simple, rapid and ratiometric strategy for the recognition of Cd²⁺ based on the formation of core-shell ZnSe/CdS structure using ZnSe quantum dots (QDs). The transformation from binary ZnSe QDs to core-shell ZnSe/CdS QDs both change the elemental composition and structure of ZnSe QDs, leading to the changes in band gap of ZnSe QDs, which could be observed in the UV-vis spectra. In the detection process, ZnSe QDs only possess absorption peak at 343 nm, the formation of ZnSe/CdS after the addition of Cd²⁺ leads to the appearance of the new peak at 397 nm, while other heavy metal ions could not cause the appearance of new absorption peak. Therefore, this strategy shows good selectivity for Cd²⁺ detection. Based on this strategy, the limit of detection (LOD) for Cd²⁺ is 11 nM by UV-vis spectroscopy with a desirable relation of linearity (R² = 0.999) between A₃₉₇/A₃₄₃ and Cd²⁺ contents, which is superior to the LOD of most reported nanomaterials. The response time for Cd²⁺ detection is as short as 60 s, which is suitable for rapid detection. This ratiometric probe has also been applied to the detection of Cd²⁺ in tap water samples, the recovery of Cd²⁺ was between 94.9% and 105.6% for tap water samples, indicating the high accuracy of our ratiometric assay. Our strategy not only provided a new method for detecting Cd²⁺, but also put forward an implication that the band energy changes of QDs caused by heavy metal ions can be applied in the selective and sensitive detection of heavy metal ions.