Question

Give two advantages of capillary GC columns over packed GC columns. When do you think that external standardisation would be used as the quantitative method of choice in GC analysis?

Answer 1

1) Amount of be injsample to be injectede is less compared packed column.

2) Resolution power is more with caplillary columns over packed ones.

Due to this merged peaks can be separated very well.

3) Low analysis time of capillary columns due fast separation of analytes into individual components.

Unknown concentration of an analyte is determined by two standardisation methods in GC. a) Internal standarisation method and b) External standardisation method.

In internal standarisation method a known amount of anylte is added to the unknown sample under similar analytical conditions. Then based on the known analyte signal in GC the unknown concentration will be measured. Under this analytical conditions if the internal standard is reacted with the unknown sample and leads to error in the final result. This problem can be eliminated by external standardisation method. In this method a standard curve is plotted by taking known concentrations of external standard. From this plot we can find out the unknown concentration.