无水葡萄糖鉴别

s0365023

欧洲药典里无水葡萄糖鉴别要用到薄层色谱，具体方法如下：
Thin-layer chromatography (2.2.27).Solvent mixture: water R, methanol R (2:3 V/V).
Test solution. Dissolve 10 mg of the substance to be examined in the solvent mixture and dilute to 20 mL with the solvent mixture.
Reference solution (a). Dissolve 10 mg of glucose CRS in the solvent mixture and dilute to 20 mL with the solvent mixture.
Reference solution (b). Dissolve 10 mg each of fructose CRS, glucose CRS, lactose CRS and sucrose CRS in the solvent mixture and dilute to 20 mL with the solvent mixture.
Plate: TLC silica gel G plate R.
Mobile phase: water R, methanol R, anhydrous acetic acid R, ethylene chloride R (10:15:25:50 V/V/V/V); measure the volumes accurately since a slight excess of water produces cloudiness.
Application: 2 µL; thoroughly dry the points of application.
Development A: over a path of 15 cm.
Drying A: in a current of warm air.
Development B: immediately, over a path of 15 cm, after renewing the mobile phase.
Drying B: in a current of warm air.
Detection: spray with a solution of 0.5 g of thymol R in a mixture of 5 mL of sulfuric acid R and 95 mL of ethanol (96 per cent) R. Heat at 130 °C for 10 min.
System suitability: reference solution (b):
–  the chromatogram shows 4 clearly separated spots.
Results: the principal spot in the chromatogram obtained with the test solution is similar in position, colour and size to the principal spot in the chromatogram obtained with reference solution (a).
对于红色字体部分，我不知道该如何理解，为什么需要展开A和展开B？具体怎么操作的？
有知道的同仁，麻烦说一下，谢谢！

hongwei2000

由于葡萄糖极性非常强
在展开剂中很难展开（即比移值很低）
也很难将之与类似的化合物（一般也是糖类）分开
所以展开了两次

s0365023

hongwei2000 发表于 2015-4-23 19:28
由于葡萄糖极性非常强
在展开剂中很难展开（即比移值很低）
也很难将之与类似的化合物（一般也是糖类）分 ...

谢谢解答。。。。。。。。