摘要
Fe(Ⅱ)的含量及变化与土壤和沉积物的氧化还原性质关系密切。当与Fe(Ⅲ)共存时,Fe(Ⅱ)的测定往往受到干扰。本文研究了常用显色剂2,2’-联吡啶和菲洛嗪(Ferrozine)测定土壤Fe(Ⅱ)时存在的问题及解决办法。结果表明,Fe(Ⅲ)可与显色剂作用形成络合物,该络合物对Fe(Ⅱ)测定所用波段的光线具有吸收作用,从而使Fe(Ⅱ)浓度被过高估计。Fe(Ⅲ)对Fe(Ⅱ)测定的干扰程度与其浓度及所选显色剂有关。当以2,2’-联吡啶为显色剂时,单位浓度Fe(Ⅲ)(1.0 mg/L)将导致Fe(II)的测定值比实际值高0.012 mg/L;而当菲洛嗪为显色剂时,单位浓度Fe(Ⅲ)引起的Fe(Ⅱ)高估值在0.010～0.032 mg/L之间。F-能够抑制Fe(Ⅲ)-显色剂络合物的形成。当F-的加入量超过Fe(Ⅲ)的4倍时,F-能有效地消除Fe(Ⅲ)的干扰。实际样品的测定结果表明,改进的Fe(Ⅱ)分光光度法能够满足土壤及沉积物中Fe(II)的准确测定。
The amount and change of Fe（Ⅱ） is tightly related to the oxidation-reduction properties of soils and sediments. Inaccurate evaluation commonly occurs in spectrometry because of co-existed Fe（Ⅲ）. In the present work, the reliable spectrometric determination of Fe（Ⅱ） was investigated by using the alternative chromogenic reagent of 2,2＇-dipyridine and ferrozine. The results indicated that co-existed Fe（Ⅲ） resulted in the overestimation of Fe（Ⅱ） due to the formation of Fe（Ⅲ） complexes with chromogenic reagent, and the overestimation extent depended on Fe（Ⅲ） concentration and the types of chromogenic reagent. When 2,2＇-dipyridine was chosen, Fe（Ⅱ） could be overestimated by 0.012 mg/L per mg/L Fe（Ⅲ）. If ferrozine employed, the overestimation magnitude of Fe（Ⅱ） ranged from 0.010 to 0.032 mg/L per mg/L Fe（Ⅲ）, which depended on Fe（Ⅲ） concentration. Fluoride ion could efficiently inhibit the formation of Fe（Ⅲ） complexes with chromogenic reagents. While Fe（Ⅲ） was masked completely, the amount of added fluoride was estimated to be at least 4 times higher than Fe（Ⅲ）. With the modified method, Fe（Ⅱ） in extractants of soils and sediments could be determined with a satisfactory result.
出处
《土壤》
CAS
CSCD
北大核心
2011年第4期662-668,共7页
Soils
基金
国家自然科学基金项目(40730528和40873061)资助
