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首页> 外文期刊>Journal of the Brazilian Chemical Society >Voltammetric Determination of Free and Total Manganese in Tea Infusions
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Voltammetric Determination of Free and Total Manganese in Tea Infusions

机译：伏安测定自由和茶叶输注中的总锰

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摘要

Tea infusions are a source of mineral nutrients, including manganese. Although it is classified as an essential element, the excess of manganese is toxic for humans and its toxicity depends on its bioavailability. In this context, we propose a simple procedure to determine free and total manganese in black tea infusions by square-wave voltammetry (SWV). Free manganese was directly quantified in the samples after simple sample dilution in 0.1 mol L−1 acetic acid/acetate buffer (pH = 4.5) while total manganese determination was carried out after sample digestion with oxidant mixture (HNO3 + H2O2). For comparison, cloud point extraction was performed to remove organic-bound manganese and the content of free metal (not extracted) measured by flame atomic absorption spectrometry (F AAS) agrees with the values obtained by the proposed SWV procedure. The limit of detection and quantification were estimated for manganese determination as 0.06 and 0.20 ?μg L−1, respectively, with a linear range observed between 20 and 250 ?μg L−1. The coefficient of variation was 9.7% (50 ?μg L−1, n = 10). The procedure was applied to determination of free and total manganese in black tea bags and the results were compared with literature procedures employing F AAS.
机译：茶食品是矿物质营养素的来源，包括锰。虽然它被归类为一个基本要素，但过量的锰对人类有毒，其毒性取决于其生物利用度。在这种情况下，我们提出了一种简单的程序，通过方波伏安法（SWV）来确定红茶输液中的自由和总锰。在0.1mol L-1乙酸/乙酸/乙酸盐（pH = 4.5）中简单的样品稀释后，在样品中直接定量自由锰，同时在用氧化剂混合物（HNO3 + H 2 O 2）的样品消化后进行总锰测定。为了比较，进行浊点提取以除去通过火焰原子吸收光谱法测量的有机结合的锰（未提取）的含量（f aas），同意通过所提出的SWV方法获得的值。估计检测和定量的极限分别估计为0.06和0.20Ωμg1-1，在20和250Ωμg1-1之间观察到的线性范围。变异系数为9.7％（50ΩμgL-1，n = 10）。该方法用于在黑茶袋中测定自由和总锰，并将结果与​​采用F AAS的文献方法进行比较。

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