Detection and Evaluation of Metals in Tea and Soils of Tea Gardens in Mingshan

[ Objective] The study aimed to detect and assess metal ions in tea and soil of tea gardens in Mingshan County. [ Method] Seven metals （ including Pb, Cr, Cu, Ca, Mn, Mg and Zn） in soil and tea samples of tea gardens in Mingshan were determined by atomic absorption spectrometry, and the pollution situation of the soil and tea by Pb, Cr and Cu were evaluated using the single factor pollution index and Nemerow pollu- tion index, finally the accumulation of heavy metals in different soils were analyzed by the enrichment factor. I-Result] There was little difference for the same heavy metals in various soils, but different heavy metals had very significant difference. The enrichment factors of metals needed by tea growing, such as Ca, Mn, Mg and Zn, were higher than heavy metals like Pb and Cr. In addition, soils and tea of the six tea gardens were not polluted by Pb, Cr and Cu, and both single factor pollution index and Nemerow pollution index were below 0.7. [ Condusion] The research could provide scientific references for preventing tea from being polluted by heavy metals.

Novel colorimetric,photothermal and up-conversion fluorescence triple-signal sensor for rosmarinic acid detection

Rosmarinic acid(RA)is promising as a natural and nontoxic food additive.However,many analysis methods for RA generally depend on large instruments and single signals for quantitative detection.A new upconversion fluorescence,colorimetric and photothermal multi-modal sensing strategy is developed for the quantification of RA.β-cyclodextrin(CD)modified citric acid(Cit)wrapped NaYF_(4):Yb/Er-Cit-CD(Y:Yb/Er-Cit-CD)up-conversion nanocomposite has been synthesized,which emits green fluorescence at 550nm under 980nm near-infrared(NIR)excitation.In the presence of oxidized 3,3',5,5'-tetramethylbenzidine(oxTMB),the green fluorescence is significantly quenched attributed to the fluorescence inner filter effect(IFE)between oxTMB and Y:Yb/Er-Cit-CD.When RA is intervened,blue oxTMB is reduced to colorless 3,3',5,5'-tetramethylbenzidine(TMB)inducing the recovery of up-conversion fluorescence.At the same time,colorimetric and photothermal signals readout can be easily achieved thanks to the color indication and photothermal effect of the oxTMB.The constructed Y:Yb/Er-Cit-CD/oxTMB sensor displays high sensitivity,visibility and simplicity for RA,and the limits of detection(LOD)for fluorescence,colorimetric and photothermal were 0.004μmol/L,0.036μmol/L and 0.043μmol/L,respectively.This sensing system is successfully performed for the detection of RA in food samples.