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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