通过高碘酸钠氧化葡聚糖,制备不同氧化度的葡聚糖,采用酸量法和碘量法测定其醛基含量,但所得结果差异大.结合葡聚糖的氧化机理,以甘油的氧化反应结果作为对照,对借助化学滴定分析的酸量法和碘量法所得数据的差异性进行了分析.结果表明这种差异是由葡聚糖氧化存在的中间反应及其分支结构造成的,当高碘酸钠与葡聚糖的糖单元的物质的量比控制在2以内,操作简单的酸量法所得结果是可靠的.

A series of oxidized dextrans were prepared by oxidation of a definite amount of dextran with different amounts of 0.097 4 mol·L-1 sodium periodate solution.And a series of oxidized products of glycerol were also prepared by oxidation of different amounts of glycerol with same amounts of 0.097 4 mol·L-1 sodium periodate solution.Aldehydic groups in each of the above mentioned oxidized products were determined by both the acidimetric and iodometric titration.Significant difference among the results found by the two methods was observed.The variance was analyzed on the base of reaction mechanism of oxidation of dextran and by comparing with the process of oxidation of glycerol.As proved by the experimental data,the discrepancy in analytical results was arisen from the difference of molecular structures of the intermediate or side products in the course of oxidation of dextran.It was concluded that when the ratio of sodium periodate and sugar unit by amount of substance was controlled at less than 2,the method of acidimetric titration was preferred for the determination of aldehydic group of oxidized dextran.