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91.
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Three types of monocrystalline diamond: natural diamond 1 μm, synthetic diamond 50 μm (synthetic-1), and synthetic diamond 1 μm (synthetic-2) were used for electrodes’ construction. The linear concentration ranges recorded for Pb(II), when natural diamond, synthetic-1 and synthetic-2 based electrodes were used were between 10−9 and 10−6; 10−10 and 10−7; and between 10−10 and 10−8 mol l−1, respectively. Low detection limits which lie between 10 and 100 pmol l−1 proves the sensitivity of the electrodes. It was found that Pb(II) yielded a peak at about +0.3±0.02 V (versus Ag/AgCl) for all the electrodes. Lead was determine with high reliability from water and tea samples at trace concentration levels using the proposed diamond paste based electrodes. 相似文献
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Surface-enhanced Raman scattering(SERS) is applied to detect the concentration of carbendzim(CBZ) in tea leaves. Au colloid is selected and used for active surfaces, and the extraction conditions are optimized in the experiment. The linearity range for the SERS intensity and the concentration of CBZ is found to be0.5 to 8 mg kgà1. The detection limit for CBZ is 0.1 mg kgà1and its recovery in tea samples is 72.3%. The detection results for CBZ using this method are compared with those of HPLC, and no obvious difference can be found. In addition, by dripping the condensed Au colloid on the tea leaves, the proposed SERS approach could be used to the in-situ determination of the half life period of CBZ on tea leaves. 相似文献
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Koichi Inoue Nuntawat Prayoonhan Haruhito Tsutsui Tasuku Sakamoto Maiko Nishimura Toshimasa Toyo'oka 《Journal of separation science》2013,36(8):1356-1361
Dichlorprop is available for agricultural use as a chiral pesticide. In this study, the stereoselective determination of dichlorprop enantiomers in tea samples such as green, black, jasmine, and oolong was developed by ultra performance LC with fluorescence spectrometry after covalent chiral derivatization. The separation was achieved on an Acquity BEH C18 column with the mobile phase consisting of 0.1% formic acid in acetonitrile/water at a flow rate of 0.4 mL/min. In the covalent chiral derivatization using (S)‐(+)‐4‐(N,N‐dimethylaminosulfonyl)‐7‐(3‐aminopyrrolidin‐1‐yl)‐2,1,3‐benzoxadiazole, the peak resolution between the S and R‐dichlorprop enantiomers was 2.6. LODs and LOQs values were 10 and 50 ng/mL standard solution. The linearity of the calibration curves yielded the coefficients (r2 > 0.99, ranging from 0.05 to 5 μg/mL) of determination of each of the dichlorprop enantiomers. SPE extraction was used for the sample preparation of dichlorprop in various tea samples. Recoveries were in the range of 82.4–97.6% with associated precision values (within‐day: 82.4–95.8%, n = 6, and between‐day: 83.7–97.6% for 3 days) for repeatability and reproducibility. Based on this result, our method has been proven to be highly efficient and suitable for the routine assay of dichlorprop enantiomers in various tea samples. We propose that the ultra performance LC assay after covalent chiral derivatization would be the renewed tools in the era of chiral stationary platform for chiral pesticide residues in foods. 相似文献
98.
应用柱前衍生-高效液相色谱法测定茶叶中黄曲霉毒素B1的含量。样品采用乙腈(85+15)溶液提取,滤液用MycoSepTM226柱净化,加入正己烷和三氟乙酸衍生,经C18色谱柱分离,荧光检测器检测。黄曲霉毒素B1的质量浓度在0.20~10.0μg·L-1范围内与其峰面积呈线性关系,检出限(3S/N)为0.1μg·kg-1。在0.5,1.0,5.0μg·L-1等3个浓度水平进行加标回收试验,回收率在91.9%~102%之间,测定值的相对标准偏差(n=6)在1.5%~6.9%之间。 相似文献
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A novel ehromogenic reaction involving copper(Ⅱ) and bromosulphonazo Ⅲ (Br-SAZⅢ) in hexamethylenetetramine-hydrochloric buffer solution was investigated. The results showed that a blue complex of copper(Ⅱ) and bromosulphonazo Ⅲwas formed with a molar ratio of 1:1. The apparent molar absorptivity was 3.3 × 105Lmol-1cm-1 and themaximum absorption peak was at 616.8 nm. The proposed procedure was used for quantitative estimation of Cu(Ⅱ) inthe concentration range of 0-1.024 μg/mL with the detection limit (3σ) of 7.03 × 10-4 μg/mL (n = 20). The relativestandard deviations (RSDs) were 0.56-4,68%. Under the optimized conditions, total copper in the vegetables and tea wassuccessfully determined. 相似文献
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