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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（９９２～１０２５）％。还测定了胭脂红和柠檬黄的酸离解常数ｐＫａ，其值分别为１１２９和９４３。
A fixed pH titration method for simultaneous determination of each pigment in a mixed food coloring is reported. The theoretical basis of the method is that the titration reaches a certain pH value, and the volume consumed by the titrant is in direct proportion to the total content of each pigment. Vj = kijni. The volume of titrant consumption at titration to several pH values can be calculated by Component content ni. There is no need to determine the stoichiometry point and it is not necessary to know the titrant concentration. The method was applied to the simultaneous determination of carmine and lemon yellow with satisfactory results and the recovery rate was between 992% and 1025%. The acid dissociation constant, pKa, for carmine and lemon yellow was also determined to be 11.29 and 9.43, respectively.