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Sunday, December 29, 2019

What are the causes of peak tailing and fronting

The gas chromatography and high-performance liquid chromatography aim to achieve good separation and symmetrical peak shape. Peak tailing and fronting are the most regular chromatographic peak shape issues in method development. Every chromatographer needs to find out how to fix these issues but first, let's identify what are the causes of peak tailing and fronting.
The common reasons for peak fronting are given below.
  • Overloading of sample or column fouling:
Peaks fronting shows if the analytical column exceeds the sampling capacity, which can occur in both GC and HPLC separations.
  • Poor sample/peak capacity:
If the analyte does not have sufficient retention on the HPLC column, resulting in no proper separation taking place.
  • Saturation of the detector:
Just as the shape of the peak may change with overloading the column, overloading the measurement range of the detector can also result in loss of signal saturation and accuracy.
Poorly packed column, channeling in a packed column, dead volume inflow path and mobile phase too weak are also causes of peak fronting
The common reasons for Peak tailing are given below
  • Flow path diffusion:
Poorly fitted connectors/fittings, a column with a wrongly sized capillary connection line can all cause peak tailing.
  • pH dependence for ionizable molecules:
If there is a difference of 2 pH units between the pKa of the sample and the mobile phase, and when the sample is easily ionized, the peak tailing may result.
  • Overloading of sample or column fouling:
If the column is not washed properly after each analysis, it can form over time and change the surface chemistry of the stationary phase.

There can be many reasons for tailing and fronting. Some possible causes are:
  • Extra column effects such as overloading of column 
  • The flow rate of the mobile phase is too low
  • The void at the column inlet
  • If the concentration of buffer is too low
  • Change in the mobile phase composition
  • Blocked frit
  • Contaminated column
  • Sample reacting with active sites
  • Incorrect pH of the mobile phase /buffer

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