Split Peaks

Split Peaks

Ideally all the peaks in the chromatogram will have a symmetrical shape. However, when the sample does not get transferred efficiently from the inlet to the column, the peak can split.

The commonest cause is poor manual injection, whereby the sample isn’t being injected in one smooth, rapid operation – perhaps because the syringe is providing some resistance. This wouldn’t be expected with an autosampler, which routinely provide better reproducibility.

The solvent used for the sample extraction and/or washing the syringe will affect the ability to focus the analytes on the column if there is a mismatch between the polarity of the solvent and the stationary phase. Remember like dissolves like and adjust the solvent or stationary phase to match the polarity of your target analytes.

Incomplete sample vaporisation is another cause of split peaks, and this is easily fixed by optimising the inlet temperature based on the volatility of the target analytes. 250°C is a good starting point for most applications but if the analytes are in the semi volatile range, increase the temperature to 300°C.

Vaporisation can also be enhanced by increasing the surface area in the inlet by using glass wool or using a baffled liner design.

It is also a possibility that the sample is being introduced too quickly onto the column. In this case try using a slower injection speed, especially when injecting into an open liner or if possible, use a liner containing glass wool.

Related Resources