Highly sensitive trivalent copper chelate-luminol chemiluminescence system for capillary electrophoresis chiral separation and determination of ofloxacin enantiomers in urine samples

A simple,fast and sensitive capillary electrophoresis（CE） strategy combined with chemiluminescence（CL） detection for analysis of ofloxacin（OF） enantiomers was established in the present work.Sulfonated p-cyclodextrin（β-CD） was used as the chiral additive being added into the running buffer of luminol-diperiodatocuprate（Ⅲ）（K[Cu（HIO6）2],DPC） chemiluminescence system.Under the optimum conditions,the proposed method was successfully applied to separation and analysis of OF enantiomers with the detection limits（S/N=3） of 8.0 nM and 7.0 nM for levofloxacin and dextrofloxacin,respectively.The linear ranges were both 0.010-100 μM.The method was utilized for analyzing OF in urine;the results obtained were satisfactory and recoveries were 89.5-110.8%,which demonstrated the reliability of this method.This approach can also be further extended to analyze different commercial OF medicines.

The Effect of the Structure of Polychlorinated Biphenyls on their Hydroxylation, Oxidation,and Glutathionyl Conjugation Reactions

Objective To compare the nature of the metabolites formed from the phase I metabolism （hydroxylation and oxidation） and phase II metabolism （glutathionyl conjugation） of PCBs that have different chlorine substitution patterns. To discuss the structure-activity relationships and metabolic mechanisms of PCBs. Methods 4-CI-biphenyl （PCB3）, 4,4＇-CI-biphenyl （PCB15）, 3,4,3＇,4＇-Cl-biphenyl （PCB77） were used for in vitro metabolic study. LC/MS and UV-Vis studies were performed for metabolites identification. Results The cytochrome P-450 catalyzed hydroxylation rate decreased as the number of chlorine substitutions increased. In this reaction, PCB3 was fully metabolized, approximately half of the PCB15 was metabolized and PCB77 was not metabolized at all. The oxidation rate of PCB15-HQ was higher than that of PCB3-HO. under various oxidation conditions. The LC/MS and UV-Vis data suggest that in the conjugation reaction of PCB15-Q and GSH, the Michael addition reaction occurs preferentially over the displacement reaction. Conclusion The metabolic profiles of polychlorinated biphenyls （PCBs） are dramatically affected by chlorine substitution patterns. It is suggested that the metabolic profiles of PCBs are related to their chlorine substitution patterns, which may have implications for the toxicity of PCB exposure.

Resonance Light Scattering Method for Determination of Amikacin with Potassium Ferrioxalate as a Probe

In a weak acid medium, potassium ferrioxalate（PF） can react with some aminoglycoside（AGs） antibiotics, such as amikacin（AMK）, kanamycin（KANA）, tobramycin（TOB） and gentamicin（GEN）, to form ion-association complexes. It results in the enhancement of resonance light scattering（RLS） in different degrees. The maximum scattering peaks are all located at 345 nm. Among them, the relative scattering intensity（AIRLs） of AMK system is much higher than that of KANA, TOB or GEN. Therefore the method is more propitious to the determination of trace amounts of AMK. The optimum reaction conditions, influencing factors, and the relationship between scattering intensity and concentration of antibiotics were investigated by means of the proposed method. The enhancement of RLS signals is directly proportional to the concentration of antibiotics in a certain range of concentration. A new resonance light scattering method for the determination of AMK and other aminoglycoside antibiotics with [Fe（C2O4）3]^3- as a probe is thus established based on it. The method exhibits high sensitivity and good selectivity. The detection limit（3σ） for AMK is 1.8 ng/mL. The method can be applied to the determination of AMK in clinical serum samples. The reaction mechanism and the reasons for RLS enhancement are discussed in this paper.

The adsorption of silver nanoparticles on the proteins-immobilized glass slides and a visual investigation on proteins immobilization

Silver nanoparticles (AgNPs), owing to the property of plasmon resonance light scattering (PRLS), can be used as a light scattering spectral probe for visually tracing and detecting target molecules. In this study, we investigated the adsorption features of proteins immobilized on glass slides for AgNPs, and found that the scattering light of AgNPs adsorbed on the surface of glass slides could be seen by naked eyes under the irradiation of a common white light-emitting diode (LED) torch. Hereby, we established a method for visually determining the least complete quantity of immobilization of proteins on glass slides.

Investigations on the amalgamation of gold nanorods by iodine and the detection of tetracycline

The morphological transformation process of gold nanorods (Au-NRs) resulting from the reaction between tetracycline and iodine was monitored by the plasmon resonance absorption (PRA) spectra and the scanning electron microscope (SEM) images. It was found that iodine could fuse Au-NRs into sphericity with the lower aspect ratio and blue shift of the longitudinal PRA band. It was found, however, that the presence of tetracycline, since it can react with I2, decreases the effective concentration of I2 and its fusion effect on Au-NRs. As a result, the longitudinal PRA of Au-NRs shifts to longer wavelength linearly with increasing the concentration of tetracycline. With that, tetracycline can be detected in the range of 5.0×10∮5- 5.0×10−4 mol·L−1, with a limit of determination (LOD) of 2.4×10−6 mol·L−1 (3σ). Most foreign substances in the samples did not interfere in the detection, and tetracycline in the synthetic samples could be detected with the recovery in the range of 92.8%–107.2%, and RSD lower than 4.3%. The concentration of tetracycline in milk detected with standard addition method was so low that it accorded with the safety regulation.

Controllable synthesis of polyoxometalates nanocubes and their specific interactions with prion proteins

It is found that Keggin-type of polyoxometalates nanocubes could be formed in aqueous medium under the adjustment of dimethylformamide (DMF),and could be changed from solid nanocubes to hollow ones with increasing temperature. Further investigations show that this Keggin-type of polyoxometalates nanocubes can specifically interact with prion protein,and the light scattering signals are en-hanced in proportion to the content of prion in the range of 3.36―840 ng·mL-1.