The presence of Cr (VI) in drinking water is mainly caused by leaching of chromium-containing aquifer material into groundwater. In contrast to Cr (III), it has been classified as highly toxic. For this reason, the WHO recommends the implementation of separate guideline values, instead of the so far used limit value of total chromium. The separate evaluation of Cr (VI) in raw water and during removal processes requires the Cr (VI) concentration to remain stable after sampling. In the presence of Fe (II), a stabilization of the samples is necessary to inhibit further reduction of Cr (VI) by Fe (II). In this study, two methods of Cr (VI) stabilization in Fe-(II)-containing water samples are investigated: Fe (II) oxidation by oxygen at high pH values in the presence of buffers and Fe (II) complexation by chelating agents. When adding hydrogen carbonate buffer, Cr (VI) recovery reached 100% at pH values of 10 to 12 in the presence of up to 3 mg L–1 Fe (II). Using hydrogen phosphate buffer, Cr (VI) recovery reached 100% only at pH 12 but for a Fe (II) concentration up to 6 mg L–1. Ammonium buffer was found to be less suitable for Cr (VI) stabilization. The addition of EDTA and citrate resulted in low recovery of Cr (VI), whereas citrate was found to accelerate the Cr (VI) reduction.

中文翻译：

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铁 (II) 中铬 (VI) 的稳定性：方法开发和验证

饮用水中 Cr (VI) 的存在主要是由含铬含水层材料浸出到地下水中引起的。与 Cr (III) 相比，它被归类为剧毒。为此，WHO 建议实施单独的指导值，而不是迄今为止使用的总铬限值。对原水中和去除过程中的 Cr (VI) 进行单独评估，要求 Cr (VI) 浓度在取样后保持稳定。在 Fe (II) 存在下，样品的稳定化对于抑制 Fe (II) 对 Cr (VI) 的进一步还原是必要的。在这项研究中，研究了两种在含 Fe-(II) 的水样中稳定 Cr (VI) 的方法：Fe (II) 在高 pH 值下在缓冲液存在下被氧气氧化和 Fe (II) 通过螯合剂络合. 当添加碳酸氢盐缓冲液时，在 10 到 12 的 pH 值下，在高达 3 mg L–1 Fe (II) 的存在下，Cr (VI) 的回收率达到 100%。使用磷酸氢缓冲液，Cr (VI) 回收率仅在 pH 12 时达到 100%，但 Fe (II) 浓度高达 6 mg L–1。发现铵缓冲剂不太适合稳定 Cr (VI)。添加 EDTA 和柠檬酸盐导致 Cr (VI) 的回收率低，而发现柠檬酸盐会加速 Cr (VI) 的还原。