Question

1.      Describe and explain the possible effect on your TLC results of the following experimental errors or variations:

(a)   The analyte spots are two large.

(b)   The analyte solution is too dilute.

(c)    The TLC reference line was drawn in ink.

(d)   You prepared the mobile phase by adding 5% of aqueous ammonia to the ethyl acetate instead of adding the required 5% of acetic acid.

Answer 1

1.

a). If the analyte spots are too large ,it will spread on the TLC plate, merge with the impurity spot and separation will become good. Every thing will spread as one big spot.

b). if the analyte solution is too dilute , the spots will not be visible. It will become difficult to identify the product spot and impurity spot. Here also separation is not good.

c). If the TLC reference line was drawn in ink, the ink will spread on the TLC plate as the mobile phase goes up .The ink will dissolve in the mobile phase used and will affect the good separation of spots.

d). Addition of ammonia to the ethylacetate instead of acetic acid will make the solution more polar and will affect the effectiveness of separation. If the mobile phase is more polar than the required polarity, the product spot and impurity spot will get merge and will not give a good separation.