What are the Differences between GC and HPLC?

Gas chromatography (GC) vs High-Performance Liquid Chromatography (HPLC)

  • GC stands for Gas chromatography (Refer: Gas Chromatography (GC)) and HPLC stands for High-Performance Liquid Chromatography.
  • Both are separation techniques that have added massive popularity in industrial laboratories.

Brief difference between HPLC vs GC enlisted as below,

Application:

  • HPLC (High-Performance Liquid Chromatography) has applications in pharmaceuticals, foods, life sciences and polymers
  • Gas Chromatography (GC) has imperative applications in the environmental air monitoring, petroleum and petrochemical industry, & flavours and fragrances.

Mobile phase:

  • High-Performances Liquid Chromatography as name suggested liquid used as mobile phase whereas GC (Gas chromatography) operated by gas as the carrier.
  • Liquids are mostly mixtures of solvents and buffers of compatible polarities. In gas chromatography, the mobile phase is a high purity gas carrier.

Operating temperature:

  • Operating temperature of HPLC is mostly carried out at ambient temperatures (around 25°C) while Gas Chromatography separations are operated at elevated temperatures (around 250°C) which can be maintained at a constant value (isothermal) or variable as decided by the temperature program on the requirement of analytical methods.
  • Newer packings & external column oven have extended temperature limits of HPLC at some point for operation as well.
  • Temperature programmed gas chromatography (TPGC) is the procedure of cumulative the column temperature during a run in GC.

Separation of Compounds:

  • Gas chromatography separations are mainly carried out on compounds that are volatilities and remain stable at high temperatures that may be up to a few hundred in molecular weights.
  • HPLC can be used in compounds having higher molecular weights ranging from a few hundred to several million for large polymers and biomolecules. They are mainly operated at room temperature as on elevated temperatures compounds have a tendency to degrade.

Column used in HPLC and GC & Column Packings:

  • HPLC (High Performance Liquid Chromatography) normally uses columns that are shorter with wider diameters in comparison to GC columns.
  • Because in HPLC Mobile phase having the liquid which have higher viscosity, which leads to creating more back pressure.
  • In GC columns are much longer and narrower. Enlarged column length advances resolution between closely spaced peaks..
  • C8 & C18 Column packings used in HPLC.
  • GC Chromatography uses packed and capillary columns which have a higher permeability of solid supports than liquids.
  • The retention of analyte HPLC columns mainly depends on polarity differences or molecular sizes.
  • GC Chromatography separations are built on differences in volatilities of sample.

Related: Difference between HPLC and UPLC, Handling of HPLC and GC Columns

Detector used in GC and HPLC:

  • Type of HPLC Detectors: are UV-Vis, RI, photodiode array detectors (PDA), conductivity and laser detection.
  • GC Detectors are FID, NPD and FPD.
  • Mass spectrometry detectors common to both like LCMS and GCMS.

Cost of operation:

  • HPLC solvents are more costly in contrast to gases used for GC Chromatography analysis.
  • Maintenance charge of GC and HPLC depends on use, but due to high use and requirement of solvent to operate HPLC costly than GC.
  • Tandem techniques like LC-MS-MS and GC-MS-MS have prolonged the limits of detection to new frontiers of detection and automation in machines has also donated to increased laboratory uses.
Fig.1 HPLC & Fig.2 GC

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