固定pH滴定法同时测定合成食用色素胭脂红和柠檬黄

Simultaneous Determination of Ponceau 4R and Tartrazine in Mixtures by pH-fixed Titration

报道一种同时测定混合食用色素中各色素含量的固定ｐＨ滴定法。该法的理论基础是滴定到达一定ｐＨ值，滴定剂消耗体积与各色素总含量成正比关系，Ｖｊ＝ｋｉｊｎｉ，只需测定滴定至多个ｐＨ值处滴定剂消耗体积，即可用该式计算各组分含量ｎｉ。没有必要确定化学计量点，也没有必要知道滴定剂浓度。应用于胭脂红和柠檬黄的同时测定，结果满意，回收率在（９９２～１０２５）％。还测定了胭脂红和柠檬黄的酸离解常数ｐＫａ，其值分别为１１２９和９４３。

A new method for simultaneous determination of weakly acidic food pigments in mixtures by pH-fixed titration is proposed This method is based on the fact that the amount of titrant consumed to reach a certain pH value is proportional to the sum of the moles of the components Vj=k\-\{ij\}n\-i. To determine every component in the mixture, it is only needed to measure the titrant volumes consumed consumed at different fixed pH values It is not necessary to ascertain the equivalent point of titration and to know the concentration of the titrant The method has been applied to determining Ponceau 4R and Tartrazine in their mixtures simultaneously with satisfactory results, the recovery being (9921025)% The pKa values of Ponceau 4R and Tatrazine measured in this paper are 1129 and 943 respectively