Acetic acid analysis by GC

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Acetic acid analysis by GC

Dear All,
I have a difficult method here and suggestions are very much appreciated.

The method is for residual solvent by GC for acetic acid by dirct injection (splitless) with n-propanol in water as internal standard.
Column : 10m x 0.53mm id x 2um film thickness CP-Sil-19CB
Injection Volume : 0.2ul
The %RSD is the method is always high and it is very difficult to get the consistant peak. Some time I got split peak and some time the peaks are tailing. I have tried to use the purge at the injector, e.g. 5ml/min for 5 min after each injection. The result I got is sometimes good (RSD is better), but sometimes with split peak.

anay susggestion on how to improve RSD and how to reduce varability of the method.

Many thanks.