A small amount (5 mg) of microcrystalline cellulose dispersed in the water sample (10 mL) at pH close to neutrality retains chromium(III) ions. To obtain a complete separation and facilitate the recovery of the solid phase, Triton X-100 was added, and the mixture was heated to achieve cloud point extraction. After centrifuging and discarding the aqueous phase, the residue was treated with 0.1 mL of an ethanol : hydrogen peroxide mixture, and chromium was measured by electrothermal atomic absorption spectrometry. Since only chromium(III) is extracted in this way, speciation is feasible at low levels. The enrichment factor was 95, which resulted in a detection limit of 6 ng L⁻¹ chromium. The relative standard deviation for the measurement in duplicate of five extractions of a 100 ngL⁻¹ chromium solution was 5.1%. The reliability of the procedure was assessed by analyzing five water samples with a certified chromium content. Data for the speciation of these certified reference materials are also given.

中文翻译：

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微晶纤维素，用于分散固相微萃取和使用电热原子吸收光谱法灵敏地测定水中的铬†

在接近中性的pH下，少量（5 mg）的微晶纤维素分散在水样品（10 mL）中，保留了铬（III）离子。为了获得完全的分离并促进固相的回收，添加了Triton X-100，并将混合物加热以实现浊点萃取。离心并丢弃水相后，将残余物用0.1mL的乙醇：过氧化氢混合物处理，并通过电热原子吸收光谱法测量铬。由于仅以这种方式提取铬（III），因此在低水平下形成物种是可行的。富集因子为95，检测限为6 ng L ^-1铬。100 ngL ^-1铬溶液的五次萃取重复测量的相对标准偏差为5.1％。该过程的可靠性是通过分析五个含铬含量合格的水样来评估的。还提供了这些认证参考材料的物种形成数据。