The emission spectra of arctiin were determined under various experimental conditions. In addition, a fluorescence method was developed to obtain the binding constants and sites of the interaction between arctiin and DNA. A competitive binding experiment and melting temperature mensuration were carried out to investigate the binding mechanism of arctiin and DNA. The experimental results showed that the interaction between arctiin and DNA belongs to a groove binding mode. 相似文献
A green and simple method, ionic liquid‐based microwave‐assisted surfactant‐improved dispersive liquid–liquid microextraction and derivatization was developed for the determination of aminoglycosides in milk samples. Nonionic surfactant Triton X‐100 and ionic liquid 1‐hexyl‐3‐methylimidazolium hexafluorophosphate were used as the disperser and extraction solvent, respectively. Extraction, preconcentration, and derivatization of aminoglycosides were carried out in a single step. Several experimental parameters, including type and volume of extraction solvent, type and concentration of surfactant, microwave power and irradiation time, concentration of derivatization reagent, and pH value and volume of buffer were investigated and optimized. Under the optimum experimental conditions, the linearities for determining the analytes were in the range 0.4–10.0 ng/mL for tobramycin, 1.0–25.0 ng/mL for neomycin, and 2.0–50.0 ng/mL for gentamicin, with the correlation coefficients ranging from 0.9991 to 0.9998. The LODs for the analytes were between 0.11 and 0.50 ng/mL. The present method was applied to the analysis of different milk samples, and the recoveries of aminoglycosides obtained were in the range 96.4–105.4% with the RSDs lower than 5.5%. The results showed that the present method was a rapid, convenient, and environmentally friendly method for the determination of aminoglycosides in milk samples. 相似文献
In this work, a novel method based on ultrasonic-assisted nebulization extraction coupled with solid phase extraction (UANE-SPE) and determined by high performance liquid chromatography was developed for the determination of triterpenoids in root of Euphorbia pekinensis Rupr. The experimental conditions for the UANE-SPE, such as type of extraction solvent, sample amount, type and amount of sorbent, extraction time and volume of the elution solvent, were examined and optimized. The method was successfully applied to determine euphol and tirucallol in the dried root of E. pekinensis Rupr. The recoveries of the analytes were in the range of 89.1–102.0 %. The limits of detection were 12 μg g−1 for tirucallol and 10 μg g−1 for euphol. The extraction yields obtained by the proposed method are higher than those obtained by the conventional extraction methods, such as reflux and ultrasonic-assisted extraction. Compared with the traditional methods, the proposed method can reduce the consumption of the labor, shorten the sample preparation time and increase the efficiencies in the extraction of active constituents from plant materials.
We have synthesized silver nanoparticles (AgNPs) decorated with α-cyclodextrin (CD) by using the traditional silver mirror reaction in the presence of CD. The CD-AgNPs were used as substrate in surface-enhanced Raman spectroscopy (SERS) for determining melamine. The intensity of the Raman band of melamine at 704 cm?1 was used to determine melamine in milk and milk powder. The use of CD-AgNPs as the SERS substrate rather than classical silver nanoparticles makes the method more sensitive in giving an enhancement by a factor of up to?~?106 in scattering efficiency. The effects of the volume of solutions (of CD-AgNPs, NaCl, NaOH, melamine) and of mixing time were optimized. The standard addition method was employed for quantitative analysis. The correlation coefficient of the calibration plot is 0.9995, and the limit of detection is 3.0 μg L?1. The method was successfully applied to the determination of melamine in milk and milk powder, with relative standard deviations of <10 % and recoveries between 89 and 104 %.
Figure
Novel silver nanoparticles decorated with α-cyclodextrin (CD-AgNPs) were prepared. The melamine in milk and milk powder was determined using SERS and CD-AgNPs. The limit of detection is 3.0 μg L?1, and recoveries between 89 and 104 % 相似文献
This paper described a novel assay of enzyme based on the measurement of enhanced resonance light-scattering (RLS) signals resulting from the electrostatic and coordination interaction of functionalized CdTe nanoparticles with enzyme. The CdTe nanoparticles which were modified with 3-mercaptocarboxylic acid (MPA) have abundant carboxylic groups (COOH). So the nanoparticles are water-soluble, stable and biocompatible. At pH 8.3 phosphate buffered saline (PBS), the RLS signals of functionalized nano-CdTe are greatly enhanced by bromelain and papain in the region of 220-800 nm characterized by the peak around 318-314 nm, respectively. The optimization conditions of the reaction were also examined and selected. Under the selected conditions, the enhanced RLS intensity is linearly proportional to the concentration of bromelain and papain. The liner range is (0.09-0.9) x 10(-6)mol/L for bromelain and (0.048-0.702) x 10(-6)mol/L for papain. The influences of some foreign substances were also examined. This method can be applied to the determination of enzyme. 相似文献