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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.

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Mn(II)-based electron spin resonance (ESR) spectroscopy was used for detecting butyrylcholinesterase (BChE) and organophosphorus pesticides (OPs). MnO2 nanosheets were synthesized with manganese chloride and hydrogen peroxide. With the catalysis of BChE, S-butyrylthiocholine iodide (BTCh) was hydrolyzed into thiocholine which has a reducing −SH group. In the presence of thiocholine, MnO2 nanosheets were broken down and Mn(IV) in MnO2 nanosheets was reduced into Mn(II). Mn2+ is a paramagnetic ion and gives a good ESR signal. In contrast, MnO2 nanosheets have no ESR signal and need not be separated from Mn2+. Mn2+ can be determined directly by ESR spectroscopy, and no further sensing probe is needed. ESR spectroscopy based on directly detecting Mn2+ is much simpler than those using other probes besides MnO2. The ESR signal of Mn2+ is proportional to the catalytic activity of BChE. OPs which inhibit the activity of BChE can also be detected by probing the ESR signal of Mn2+. Since there is no ESR signal of MnO2 nanosheets, the background signal in the absence of BChE was close to zero. The limit of detection (LOD) of BChE was as low as 0.042 U L–1. The standard curve for determining the OP paraoxon was established by measuring the inhibition of BChE by paraoxon, and the LOD of paraoxon was found to be 0.076 ng mL–1. The spiked Chinese cabbage extract samples were analyzed, and the experimental results indicated that the recoveries were from 96.5 to 102.8%. The planted Chinese cabbage was sprayed with the paraoxon solution, and the residue amount of paraoxon in the extract was estimated by the method. The result obtained by the present method was consistent with that obtained by HPLC, which proved the practicability of this new method.

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.

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The phenolic compound contents, antioxidant capacities, and α‐amylase and tyrosinase inhibitory activities of 10 wild and 19 cultivated blueberries grown in northeast China were evaluated. The results showed that the α‐amylase inhibitory activities of the blueberries represented, by 1/IC50, correlated with their total phenolic contents (TPCs). Moreover, the tyrosinase inhibitory activities correlated with the total anthocyanin contents (TACs). High‐performance liquid chromatography and electrospray mass spectrometry were conducted to determine and identify seven phenolic acids. The average caffeic acid contents of the cultivated and wild blueberries were 277.37 and 17.71 μg/g, respectively. The total phenolic, anthocyanin, and flavonoid contents were determined. Wild blueberries have higher TPCs, α‐amylase inhibitory activities, and antioxidant capacities. Cultivated blueberries have higher TACs and exhibit tyrosinase inhibitory activities similar to those of the wild ones. Practical applications This study revealed that wild blueberries have high α‐amylase inhibitory activities and are effective as natural α‐amylase inhibitors for the treatment of diabetes. In addition, wild blueberries were found to be rich in phenolics and have high antioxidant capacities. Thus, because of these properties, wild blueberry products with antidiabetic and antioxidant potential can be developed for use in biomedical and pharmaceutical industries.