The investigation on the radioactivity level of 90Sr in tea leaves in the vicinity of Ningde nuclear power plant / 中国辐射卫生

Objective To investigation the radioactivity level of 90Sr in tea leaves within and outside 30 km range of Ningde nuclear power plant. Methods The tea leaves within and outside the 30 km range of Ningde Nuclear Power Plant were collected from 2013 to 2018. According to“Radiochemical analysis of strontium-90 in water and ash of biological samples” (HJ 815—2016), the separation and analysis of 90Sr-90Y were carried outusing the method of di (2-ethylhexyl) phosphate (HDEHP) chromatography. Results During the period of 2013-2018, the radioactivity concentrations of 90Sr in the tea leaves within the range of 30 km around the Ningde nuclear power plant were 0.486～13.29 Bq/kg and that of 90Sr in the tea leaves outside the range of 30 km around the nuclear power station were 1.021～17.19 Bq/kg. Conclusion During the six years of operation in Ningde Nuclear Power Plant, there was no increase in the radioactivity level of 90Sr in the tea leaves around the nuclear power plant.

Tannase application in secondary enzymatic processing of inferior Tieguanyin oolong tea

Background: Inferior Tieguanyin oolong tea leaves were treated with tannase. The content and bioactivity of catechins in extracts from the treated tea leaves were investigated to assess the improvement in the quality of inferior Tieguanyin oolong tea. Results: Analysis showed that after treatment, the esterified catechin content decreased by 23.5%, whereas non-galloylated catechin and gallic acid contents increased by 15.3% and 182%, respectively. The extracts from tannase-treated tea leaves showed reduced ability to bind to BSA and decreased tea cream levels. The extracts also exhibited increased antioxidant ability to scavenge OH and DPPH radicals, increased ferric reducing power, and decreased inhibitory effects on pancreatic α-amylase and lipase activities. Conclusions: These results suggested that tannase treatment could improve the quality of inferior Tieguanyin oolong tea leaves.

Subcritical Butane Extraction for Effective Removalof Abamectin in Fresh Tea Leaves / 分析化学

Subcritical butane technology was employed for the separation of abamectin on the fresh tea leaves surface.Under the conditions of solid-liquid ratio of 1∶10 (m/V), the experiment was designed via the response surface methodology and conducted at different temperature, various separation time and discrepant cycle number.Besides, the activity of the polyphenol oxidase (PPO) relating to the quality of the tea was determined and compared.At the same time, scanning electron microscopy (SEM) was used to observe the surface structure of fresh tea leaves before and after treatment, and the effect on physiological characteristics of the leaves by subcritical butane treatment was analyzed.The experimental results showed that the subcritical butane extraction could effectively isolate the abamectin, making the physical structure basically remained and the polyphenol oxidase activity preserved as well.Through the analysis by Design Expert software, the optimal processing parameters of separating abamectin were as follows: 45℃, 30 min, 1 cycle, and solid-liquid ratio of 1∶10 (m/V).Under the optimal conditions, the separation efficiency was over 91% and the relative PPO activity was 25.73%.The structure of fresh tea leaves changed insignificantly before and after the butane processing.This study suggested that the subcritical butane extraction technology could effectively remove pesticide residues in tea, thus provided a certain scientific basis for application of subcritical fluid removal of pesticide residue in natural plants.

Optimization of a multi-residue method for 101 pesticides in green tea leaves using gas chromatography–tandem mass spectrometry

ABSTRACT A method for analysis of 101 pesticide residues in tea leaves was developed and validated for the first time. Pure acetonitrile was used as extraction solvent rather than acetonitrile after matrix hydration based on the amount of co-extracts and recoveries performance. During clean-up procedure, primary-secondary amine/graphitized carbon black (500 mg) was selected, which exhibited outstanding properties in clean-up capabilities and recoveries of pesticides comparing to primary-secondary amine/graphitized carbon black (250 mg), NH2-Carbon and TPT absorbents. The method was validated employing gas chromatography coupled to tandem mass spectrometry at the spiked concentration levels of 0.050 and 0.100 mg kg−1. For most of the targeted pesticides, the percent recoveries range from 70 to 120%, with relative standard deviations <20%. The linear correlation coefficients (r 2) were higher than 0.99 at concentration levels of 0.025–0.250 mg kg−1. Limits of quantification ranged from 1.1 to 25.3 µg kg−1 for all pesticides. The developed method was successfully applied to the determination of pesticides in tea leaf samples.