Below is the chromatogram of a standard solution of acenaphthene on a 50 mm L ti

Question

Below is the chromatogram of a standard solution of acenaphthene on a 50 mm L times 2.1 mm ID C18 column eluted isocratically with 50% acetonitrile in water at a flow rate of 0.2 ml/min. This standard solution is suggested by the vendor to check the efficiency of the column periodically. A Calculate the column efficiency (N) for this column, (use two equations and avg) B. What is the theoretical plate height (H) of this column under these conditions? C. A new column should have a column efficiency of -4400 for this standard under these conditions. Would you consider this column to be in good condition?

Explanation / Answer

Ansa) Let us first write the condition given

column = acenapthalene 150mm L x 2.1mm ID C18

Phase = 50% acetonitrile in water

Flow rate = 0.2ml/min

Now from the chromatogram graph we can measure the retention time

Retention time t =760mm

and half width peak = 25mm

Now column efficiency N = 16 (t/w)2

                                     = 16(760/25)2

                                     = 14786

b) Now theoritical height H = Length of the column / number of theoritical plate

          length of the column = 150mm

number of theoritical plates= 14786

H= 0.01014473mm

c) I would not consider this column to be in good condition as columns with high number of theoritical plates will have more efficiency and will produce narrower peaks .                        

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