Basic Difference of HPLC and GC Technique

by Rohit T. Veeprho Laboratories Pvt.Ltd

High-performance liquid chromatography (HPLC) and gas chromatography (GC) is a multipurpose and very well accepted chromatographic technique utilized for the separation of complex mixtures. HPLC and GC techniques used for identification and quantification purpose but for different intend as its function and application is different.

HPLC and GC is based on the principle where compound subjected on the surface or within a solid or liquid stationary phase by isolating it with the help of the mobile phase.

Following are the differences between HPLC and GC techniques:

	HPLC	GC
Principal	Separation of sample is accomplished by solid stationary phase and liquid mobile phase.	Separation of sample is accomplished by liquid or solid stationary phase and gaseous mobile phase.
Temperature Control	Temp. control approach is not necessary or not required. Generally ambient temp. is required.	Temp. control is much more important as the column is placed inside the oven with control temp. program. Generally higher temp. required for analysis.
Sample State	Separation of liquid state any soluble samples usually with higher molecular weight.	Separation of volatile and thermally stable samples with low molecular weight.
Column	Column are generally shorter and broader diameter.	Columns are long, normally 10 to 60 meters in length and narrow diameter.
Column Types	Octadecylsilane, Octyl silane, Hexyl, Trimethyl Silyl, Amino, Cyano, TMS, Silica, Hillic, Diol, Ion exchange, Chiral, Phenyl, Gel permeation & Size exclusion chromatography	WCOT, SCOT, PLOT, Carbowax, Polyethylene glycol, Dimethyl polysiloxane, Phenyl methyl polysiloxane, High molecular mass esters, Amides, Hydrocarbons, Polyaromatic compound, Cyanopropyl polysiloxane
Separation	Separation based on the interaction of sample with mobile and stationary phases.	Separation based on the boiling point of sample.
Resolution Issues	Samples with identical polarity	Samples with similar molecular weight
Mobile Phase	Liquids, e.g. Polar solvents like water, acetonitrile, methanol, etc. Non polar solvents like Hexane, Heptane, isopropyl alcohol, dichloromethane etc.	Gases, e.g. Nitrogen, Helium, Argon, Hydrogen, Oxygen
Speed	Analysis speed is slow.	Analysis speed is fast
Peak shape	Generally, detect bigger or wider peaks which effect lower resolution.	Relatively sharp peaks observed with good resolution.
Detectors	UV-Visible detector, Photodiode-array detection, Refractive index detector, light scattering detector, Charged aerosol detector, Conductivity detector, Fluorescence detector, Chemiluminescence detector, Optical rotation detector, Mass spectrometric, IR Detector etc.	GC detectors are sensitive and selective, e.g. Flame ionization detector (FID), Thermal conductivity detector (TCD), Electrochemical detector, Electron capture detector, Nitrogen phosphorous detector, Flame photometric detector, Electrolytic conductivity detector, Mass spectrometric, Photo Ionization detector, Reduction gas detector, Catalytic combustion detector, Helium ionization detector etc.
Cost	Less costly	High cost