Sensitive Determination of Metal Ions in Drinking Water by Capillary Electrophoresis Coupled with Contactless Conductivity Detection Using 18-Crown-6 Ether and Hexadecyltrimethylammonium Bromide as Complexing Reagents

A simple, economical, and sensitive capillary electrophoresis (CE) method integrated with capacitively coupled contactless conductivity detection was developed for the determination of metal ions such as K+, Na+, Mg2+, Sr2+, Ca2+ in drinking water. 18-Crown-6 ether and Hexadecyltrimethylammonium Bromide (CTAB) were employed as complexing reagents. The effects of electrolyte additives, citric acid buffer solution, and other separation conditions of CE were comprehensively investigated and carefully optimized. The best results were obtained in a running buffer solution composed of citric acid (12 mM), 18-crown-6 ether (0.2 mM), and CTAB (0.015 mM) at pH 3.5. Under these conditions, a complete separation of five metal ions was successfully achieved in less than 12 min. The limits of detection for the optimal procedure were determined to be in the range of 0.02 - 0.2 mg·L-1. The repeatability with respect to migration times and peak areas, expressed as relative standard deviations, was better than 2.3% and 5.1%, respectively. Evaluation of the efficiency of the methodology indicated that it was reliable for the determination of metal ions in six different brands of drinking water samples.

Electrochemical Detection of Sudan I Using a Multi-Walled Carbon Nanotube/Chitosan Composite Modified Glassy Carbon Electrode

In this work, a simple and sensitive electrochemical method was developed to determine Sudan I by cyclic voltammetry and differential pulse voltammetry using a glassy carbon electrode modified with a chitosan/carbon nanotube composite. In cyclic voltammetry, Sudan I exhibited a well-defined oxidation peak located at 0.72 V at the multi-walled carbon nanotube (MWCNT)/chitosan-modified GCE. The determination conditions, including pH, scan rate, and chitosan: MWCNT mass ratio at the modified electrode, were optimized. Under the optimum experimental conditions, Sudan I could be linearly detected by differential pulse voltammetry with a detection limit of 3.0 × 10-8 mol?L-1.

Exocytosis determination of SH-SY5Y single cell stimulated by diff erent stimulants on indium tin oxide (ITO) micro-pore electrode

The human neuroblastoma SH-SY5Y cell line has been used as a model to study mechanisms of neurotransmitter release.In order to study the mechanism of SH-SY5Y single cell exocytosis stimulated by different stimulants,including high K+,3-(1-nitroso-2-pyrrolidinyl)pyridine and nicotine,a type of indium tin oxide(ITO)micro-pore electrode was used to obtain the corresponding amperometric response time.When the cell is stimulated by 0.1 M K+,almost immediate exocytosis could be detected,due to the rapid depolarization of cell membrane.However,the stimulations with 1 mM nicotine and 3-(1-nitroso-2-pyrrolidinyl)pyridine result in a short delay between stimulation and exocytosis,which can be correlated with the time needed for binding of the stimulant to the nicotinic acetylcholine(ACh)receptor and the induction of post-binding phenomena.Thus,the response time of SH-SY5Y single cell exocytosis is significantly affected by the exocytosis mechanisms.

Ultrasensitive and Signal-on Electrochemiluminescence Aptasensor Using the Multi-tris(bipyridine)ruthenium(Ⅱ)- β-cyclodextrin Complexes

An ultrasensitive and signal-on electrochemiluminescence(ECL)aptasensor to detect target protein(thrombin or lysozyme)was developed using the host-guest recognition between a metallocyclodextrin complex and single-stranded DNA(ss-DNA).The aptasensor uses both the photoactive properties of the metallocyclodextrins named multi-tris(bipyridine)ruthenium(Ⅱ)-β-cyclodextrin complexes and their specific recognition with ss-DNA,which amplified the ECL signal without luminophore labeling.After investigating the ECL performance of different multi-tris(bipyridine)ruthenium(Ⅱ)-β-cyclodextrin(multi-Ru-β-CD)complexes,tris-tris(bipyridine)-ruthenium(Ⅱ)-β-cyclodextrin(tris(bpyRu)-β-CD)was selected as a suitable host molecule to construct an atasensor.First,double-stranded DNA(ds-DNA)formed by hybridization of the aptamer and its target DNA was attached to a glassy carbon electrode via coupling interaction,which showed low ECL intensity with 2-(dibutylamino)ethanol(DBAE)as coreactant,because of the weak recognition between ds-DNA and tris(bpyRu)-β-CD.Upon addition of the corresponding protein,the ECL intensity increased when target ss-DNA was released because of the higher stability of the aptamer-protein complex than the aptamer-DNA one.A linear relationship was observed in the range of 0.01 pmol/L to 100 pmol/L between ECL intensity and the logarithm of thrombin concentrations with a limited detection of 8.5 fmol/L(S/N=3).Meanwhile,the measured concentration of lysozyme was from 0.05 pmol/L to 500 pmol/L and the detection limit was 33 fmol/L(S/N=3).The investigations of proteins in human serum samples were also performed to demonstrate the validity of detection in real clinical samples.The simplicity,high sensitivity and specificity of this aptasensor show great promise for practical applications in protein monitoring and disease diagnosis.

Hybrid vesicles of pillar[5]arene/silica:Host-guest complexation and application in pH-triggered release

Integrating silica with organic nanoparticles can generate unique properties.Here pillar[5]arene/silica hybrid vesicles were constructed based on the amphiphilic and rigid properties of pillararenes,as well as the catalytic hydrolysis of tetraethoxysilane.Such vesicles exhibited the high strength of silica and unique molecular recognition of pillararenes,both of which could tune the pH-trigge red release behavior.Furthermore,a rhodamine B derivative with hexyl group(RhB-C6) was synthesized,which can form a complex with the pillar[5]arene.Based on the host-guest interaction and high strength of silica,the hybrid vesicles could load more RhB-C6 and the rhodamine B was released more slowly compared with the organic vesicles.

Selective fluorescence labeling and sensitive determination of Staphylococcus aureus by microchip electrophoresis with a multiple-concentration approach

The detection of Staphylococcus aureus （S. aureus） is very important as it is responsible for bacterial infectious diseases and food poisoning. In this paper we explored the application of fluorescently labelled vancomycin to specifically bind and detect S. aureus. In view of the specificity of vancomycin towards bacterial cell surfaces, we utilized Cy5 to label vancomycin （CyS-Van） for the identification of S. aureus. Our experiments were designed to examine in greater detail the specificity of the reaction between CyS- Van and S. aureus. Detection parameters such as the derivatization conditions, concentrations of buffer, pH value, response performance of CyS-Van to bacterial surface, injection time and reversed-polarity time have been investigated and optimized. To develop a simple and quick assay for the detection of S. aureus at low concentrations, we propose to use the Cy5-Van for labeling the 5. aureus coupled with an on-line multiple-concentration in microcbip electrophoresis. Under the optimized conditions, the detection orS. aureus was achieved within 150 s with limit of detection （S/N = 3） of 981 CFU/mL, and 350- fold enhancement was obtained for S. aureus as compared to using the no concentration step. It is self- evident that this approach has great potential in the future for the analysis of S. aureus.