班氏试剂

本尼迪特试剂，也称班氏试剂、本尼迪克试剂、本尼迪克试液或班乃德试剂，是一种蓝色化学试剂,为斐林试剂的改良试剂。

反应原理：柠檬酸钠和Cu2+生成络合离子，此络合离子与葡萄糖中的醛基反应生成红黄色沉淀。

首先，将需测试的样本溶解于水中，加入少量的班氏试剂，摇匀后将此混合物在沸水中加热。反应时间约为3分钟。如果测试样本是还原糖，混合物中会形成红黄色的沉淀物。这是因为还原糖会将硫酸铜中的二价铜离子(Cu2+)还原成一价亚铜离子(Cu+)，并以氧化亚铜(Cu2O)的形式沉淀出来。如果溶液中还原糖含量较低，产生的氧化亚铜便会相应减少，因此试验后可能只会出现绿色、混浊的黄色或橙色沉淀物。
鉴定还原性糖过程

1 取一支试管，注入2mL待测样品
2 向试管内注入2mL本尼迪克试剂
3 将这支试管放进盛有开水的大烧杯中，用酒精灯加热煮沸2分钟左右。
4 观察溶液颜色

结果
非还原性糖如蔗糖，淀粉，纤维素等呈阴性
还原性糖如葡萄糖，果糖，半乳糖等呈阳性
 

常温保存，有效期12个月

Benedict's reagent (often called Benedict's qualitative solution or Benedict's solution) is a chemical reagent named after American chemist Stanley Rossiter Benedict.


Benedict's solution is a deep-blue solution used to test for the presence of the aldehyde functional group, - CHO. It is an aqueous alkaline mixture of CuSO4 and sodium citrate. Here sodium citrate is the complexing agent that keeps Cu2+ in solution, which would otherwise precipitate as cupric carbonate. The substance to be tested is heated up to 95 °C (for example, in a water bath) with Benedict's solution; formation of a brick-red precipitate indicates presence of the aldehyde group in relatively high concentrations. Since simple sugars (e.g., glucose) give a positive test, the solution is used to test for the presence of glucose in urine, a sign of diabetes. One litre of Benedict's solution contains 173 grammes sodium citrate, 100 grammes sodium carbonate, and 17.3 grammes cupric sulphate pentahydrate. It reacts chemically similarly to Fehling's solution; the cupric ion (complexed with citrate ions) is reduced to cuprous ion by the aldehyde group (which is oxidised), and precipitates as cuprous oxide, Cu2O.