What is a frontier peak
The leading edge is also known as the protruding peak and the tongue protruding peak. The asymmetric chromatographic peaks with a flat front and a steep trailing edge are called frontier peaks. Judgment range: when the symmetry factor of the chromatographic peak is between 0.95 and 1.05, it is a normal peak, less than 0.95 is a leading peak, and greater than 1.05 is a trailing peak. In general, chromatographic peaks of 0.9 to 1.2 are acceptable.
Causes of leading edge peaks
There are several reasons for the generation of leading edge peaks in gas chromatography:
- Column overload:
Reduce the injection volume or replace the column with a higher loading capacity.
- Co-elution of two compounds:
Sensitivity can be increased and the injection volume reduced, and the temperature can be lowered by 10-20 degrees to separate the peaks.
- Sample condensation:
Check the inlet and column temperatures and increase if necessary.
- Sample decomposition:
Deactivate the injector liner or turn down the injector temperature.
In general, pure leading peaks can be resolved by reducing the injection volume or replacing the column with a larger loading capacity.
Applications
Determination of ethylene glycol in propylene glycol
Chromatographic Condition 1
Chromatographic column: Welch WM-624 (30 m×0.32 mm, 0.25 μm) (P/N: 03908-32001).
Column temperature: the initial temperature was maintained at 120 °C for 4 min, increased to 140 °C at 8 °C/min for 10 min, and increased to 220 °C at 8 °C/min for 10 min
Inlet: 230℃
Detector: FID 250℃
Carrier gas: nitrogen
Injection volume: 1 μL
Split ratio: 10-1
Column flow rate: 1mL/min
Hydrogen-to-empty ratio: 32:200.
| Name | Retention time | Area | Height | Number of plates | Tailing factor |
| Ethylene Glycol | 3.029 | 1428438 | 436761 | 26573 | 0.758 |
Conclusion: Peak shape leading edge, high sample concentration, column overload, replace the column with a larger sample load.
Chromatographic Condition 2:
Chromatographic column: Welch WM-624 (30 m×0.53 mm, 3.0 μm) (P/N: 03908-52006).
Column temperature: the initial temperature was maintained at 120 °C for 4 min, increased to 140 °C at 8 °C/min for 10 min, and increased to 220 °C at 8 °C/min for 10 min
Inlet: 230℃
Detector: FID 250℃
Carrier gas: nitrogen
Injection volume: 1 μL
Split ratio: 10-1
Column flow rate: 4mL/min
Hydrogen to empty ratio: 32:200
| Name | Retention | Area | Height | Number of plates | Tailing factor |
| Ethylene Glycol | 3.393 | 14667 | 4195 | 22182 | 0.983 |
Conclusion: The peak shape of ethylene glycol was effectively improved by replacing the chromatographic column, and the results could meet the relevant requirements in the Chinese Pharmacopoeia 2020 Edition.
Related product information:
| P/N | Name | Specification |
| 03908-32001 | WM-624 | 30 m×0.32mm，0.25μm |
| 03908-52006 | WM-624 | 30 m×0.53mm，3.0μm |
Tailing peaks: The injection port and the chromatographic column are contaminated, and the gas injection port needs to be cleaned and maintained, such as replacing or cleaning the liner, removing the contaminants by aging the chromatographic column, or cutting 1-2% from the inlet end of the column. circle, and then reinstall.
Flat-topped peaks: Can be resolved by reducing the injection volume, increasing the carrier gas flow rate, and the column temperature. Flat-topped peaks form when the signal amplifier input is saturated and the column is overloaded.
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