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1 引言 食品添加剂中的酸味剂主要是柠檬酸,酒石酸、苹果酸等有机酸,有增进食欲、促进消化吸收等作用。饮料中的总酸量常用酸碱滴定法测定,由于共存色素的干扰和酸浓度较低,滴定误差较大。原子吸收法(AAS)已用于有机物的测定,但对总酸度的测定尚未见报道,本文用CaCO_3悬浮液同有机酸作用,离心沉降未反应的试剂,用AAS测定上清液中的Ca,可间接测定有机酸总量,用本法测定了饮料样品中的总酸度,测定结果与酸碱滴定法的结果符合。 2 实验部分 2.1 仪器与试剂 原子吸收分光光度计,岛津AA-650,仪器参数选择最大的信噪比;CaCO_3悬浮液:将1.26g Na_2CO_3和1.07gcaCl_2溶液混合后,用倾滗法制备;有机酸(柠檬酸、酒石酸、苹果酸、乙酸、琥珀酸、乳酸、富马酸)标准溶液:0.1000mol/L;所用试剂均为分析纯。
1 Introduction Food additive sour agent is mainly citric acid, tartaric acid, malic acid and other organic acids, have increased appetite, promote digestion and absorption and so on. The total amount of acid in beverages is often measured by acid-base titration. Due to the interference of coexisting pigments and the lower acid concentration, the titration error is larger. Atomic Absorption Spectrometry (AAS) has been applied to the determination of organic compounds, but the determination of total acidity has not been reported yet. In this paper, CaCO_3 suspension was treated with organic acid to centrifuge the unreacted reagents. AAS was used to determine Ca, The total amount of organic acids can be determined indirectly. The total acidity of beverage samples was determined by this method. The results of the determination were consistent with the results of acid-base titration. 2 Experimental 2.1 Instruments and reagents Atomic absorption spectrophotometer, Shimadzu AA-650, the instrument parameters to choose the maximum signal to noise ratio; CaCO_3 suspension: 1.26g Na_2CO_3 and 1.07gcaCl_2 solution prepared by decantation method; organic Acid (citric acid, tartaric acid, malic acid, acetic acid, succinic acid, lactic acid, fumaric acid) Standard solution: 0.1000mol / L; All reagents are of analytical grade.