高级检索

    凯氏蒸馏-自动光度滴定法测定水果干制品中二氧化硫残留量

    Determination of Sulfur Dioxide Residues in Dried Fruit Products by Kjeldahl Distillation-Automatic Photometric Titration

    • 摘要: 建立了凯氏蒸馏-自动光度滴定法测定水果干制品中二氧化硫残留量的方法,并采用单因素试验和响应面Box-Behnken设计试验优化了水体积(mL)和样品质量(g)的比值(液料比)、盐酸溶液浓度、超声浸提时间、蒸汽输出量等试验条件。称取5 g粉碎后的样品,用水270 mL和7 mol·L-1盐酸溶液10 mL超声浸提15 min,在90%的蒸汽输出量下蒸馏9 min,冷凝得到的液体用25 mL吸收液(20 g·L-1乙酸铅溶液)收集。在吸收液中加入盐酸10 mL、10 g·L-1淀粉指示液1 mL,在自动光度滴定仪上滴定,设定信号漂移值为15 mV·min-1,检测波长为640 nm,利用滴定曲线的一阶导数确定滴定终点。结果显示:在最优试验条件下,所得测定值(0.367 g·kg-1)和预测值(0.365 g·kg-1)基本一致;对实际样品进行加标回收和精密度试验,回收率为94.3%~99.7%,测定值的相对标准偏差(n=7)不大于0.90%;将该方法所得结果同GB 5009.34-2016所采用的全玻璃蒸馏-人工滴定法进行比对,在95%置信水平下,2种方法无显著性差异。

       

      Abstract: A method for the determination of sulfur dioxide residues in dried fruit products was established by Kjeldahl distillation-automatic photometric titration, and test conditions, including the ratio of water volume (mL) to sample mass (g) (liquid-solid ratio), concentration of hydrochloric acid solution, ultrasonic extracting time, steam output, were optimized by single factor test and response surface Box-Behnken design test. 5 g of Crushed sample were weighted and extracted with 270 mL of water and 10 mL of 7 mol·L-1 hydrochloric acid solution for 15 min by ultrasound, and distilled for 9 min with the steam output of 90%. The condensed liquid was collected by 25 mL of absorbent (20 g·L-1 lead acetate solution), 10 mL of hydrochloric acid and 1 mL of 10 g·L-1 starch indicator solution were added into the absorption solution, and the mixed solution were titrated by automatic photometric titrator. The signal drift value was set as 15 mV·min-1, and the detection wavelength was set as 640 nm, and the titration endpoint was obtained from the first derivative of the titration curve. The results showed the determined value (0.367 g·kg-1) was in conformity with the predicted value (0.365 g·kg-1) under the optimal test conditions. Tests for recovery and precision on actual samples were made, and values of recovery were found in the range of 94.3%-99.7%, with RSDs (n=7) of the detemined values not more than 0.90%. The results obtained by the proposed method were compared with those obtained by full glass distillation-artificial titration method given by GB 5009.34-2016, and no significant difference was found between the two methods at the 95% confidence level.

       

    /

    返回文章
    返回