多波长光谱法测定红糖中总铁和亚铁的含量

国家标准采用原子吸收光谱法测定食品中铁含量，其前处理需要灰化等步骤，操作繁琐，耗时耗能，测的为总铁的含量。本文建立了一种三波长邻菲罗啉显色法测定红糖总铁和亚铁含量的方法，先将红糖直接溶解成一定浓度的红糖溶液，然后按照邻菲罗啉显色法并基于423、510和700 nm波长处的吸光度测出总铁的含量，并进行了红糖中总铁含量的回收率试验。红糖溶液在不添加还原剂的情况下按照相同方法测出亚铁的含量。该方法能够有效扣除了红糖中多种色素以及基线漂移对结果的影响，结果发现试验的红糖样品，其中总铁的含量为(13.65±0.29) mg/kg，亚铁含量为(13.29±0.18) mg/kg，以二价铁为主，占总铁含量98%以上；红糖中总铁含量的回收率约103%。本方法避免了灰化前处理时的繁琐，测定较简便，结果准确，适用于生产企业使用。
Determination of the total iron content in foods by atomic absorption spectrometry (the national standard method used) requires ashing during pretreatment, which renders the entire operation tedious and time and energy consuming. Herein, a triple-wavelength spectrophotometric method was established for determining the iron content in brown sugar. Brown sugar solutions of known concentration were mixed with phenanthroline monohydrate and then measured by triple-wavelength spectrophotometry at wavelengths of 423, 510, and 700 nm. The total iron content was then calculated from the spectral data. Using this method, the recovery rate of total iron content in brown sugar was evaluated, as well as the content of ferrous iron in brown sugar solutions lacking the reducing agent. The results showed that this method can efficiently deduce the influence of the color agent and baseline drift. The content of total iron was (3.65±0.29) mg/kg, whereas that of ferrous iron was (13.29±0.18) mg/kg. The valence state of iron in brown sugar was mainly ferrous, accounting for more than 98%. The recovery rate of the total iron content was about 103%. This simple technique, which avoids the complicated processes of the traditionally used method, is suitable for industrial applications.