No abstract

Electron spin resonance spectroscopy was applied to determining the antioxidant capacity of eight thiol-containing compounds, including reduced glutathione, N-acetyl-L-cycsteine, methimazole, captopril, and tiopronin with one thiol group, 1,4-dithioerythritol and 2,3-dimercapto-1-propanol with two thiol groups, as well as L-cystine with no free thiol group. Cu ion gives an electron spin resonance signal and is reduced to Cu ion with no electron spin resonance signal by the free thiol group in the compounds. Trolox equivalent antioxidant capacity (TEAC) was used to evaluate the reducing ability of the thiol-containing compounds and the TEAC values were found to be relevant to the number of thiol groups contained in the compounds. For the purpose of comparison, the UV-vis spectrophotometry, cupric reducing antioxidant capacity (CUPRAC) method, and Ellman assay were applied to the determination of the antioxidant capacity of the thiol-containing compounds. The TEAC values obtained by the present method were very close to those obtained by UV-vis method. However, compared with CUPRAC method, for methimazole the present method gave a more reasonable TEAC value. The present method was also applied to the quantification of N-acetyl-L-cycsteine, methimazole, captopril, and tiopronin in their pharmaceutical formulations.

No abstract

The homogeneous ionic liquid microextraction combined with magnetical hollow fiber bar collection was developed for extracting triazine herbicides from water samples. These analytes were separated and determined by high performance liquid chromatography. The triazines were quickly extracted into ionic liquid microdroplets dispersed in solution, and then these microdroplets were completely collected with magnetical hollow fiber bars; the pores of which were impregnated with hydrophobic ionic liquid, which makes the phase separation simplified with no need of centrifugation. Some experimental parameters, such as the type of ionic liquid, ultrasonic immersion time of hollow fiber, pH of sample solution, volume of hydrophilic ionic liquid, amount of ion-pairing agent NHPF, NaCl concentration, number of magnetical hollow fiber bar, stirring rate, and collection time were investigated and optimized. When the present method was applied to the analysis of real water samples, the precision and recoveries of six triazine herbicides vary from 0.1 to 9.2% and 73.4 to 118.5%, respectively. The detection limits for terbumeton, ametryn, prometryn, terbutryn, trietazine, and dimethametryn were 0.48, 0.15, 0.15, 0.14, 0.35, and 0.16 μg L, respectively.

Based on the foaming property of the honey, a rapid, simple, and effective method solvent floatation (SF) was developed and firstly applied to the extraction and separation of triazine herbicides in honey. The analytes were determined by high-performance liquid chromatography. Some parameters affecting the extraction efficiencies, such as the type and volume of extraction solvent, type of salt, amount of (NH)SO, pH value of sample solution, gas flow rate, and floatation time, were investigated and optimized. The limits of detection for analytes are in the range of 0.16-0.56 μg kg. The recoveries and relative standard deviations for determining triazines in five real honey samples are in the range of 78.2-112.9 and 0.2-9.2%, respectively.