High-performance
liquid chromatography and Gas chromatography both are the separation techniques
for the components in analytical chemistry and they are well established from
overtime. Each technique has many advantages and some disadvantages over each other.
Here
are mentioned some advantages of HPLC over GC.
Mobile Carrier Phase:
Gas
chromatography evaporates the sample and it is taken with the system by an
inert gas like nitrogen or helium. The use of hydrogen gas gives improved
efficiency and separation. But, due to the flammable nature of gases, many
laboratories prevent the use of these gases. While using liquid chromatography,
samples are solid or liquid forms and travel through high pressure through
solvents or mobile phases such as methanol, acetonitrile, and water, etc.
through the column. The solvent composition can be modified as per the
requirement of samples / complex mixture of components gives better separation,
but in GC a gas passes through the column at constant proportion.
Column Types:
The
gas chromatography column has an extremely small internal diameter and 10 to 45
meters in length. These are silica-based columns and it can be heated up to 150
C. Columns of HPLC are also made up of silica-based covered with stainless
steel outer surface and are up to 50 to 250 cm in length, These columns are
used under ambient temperate on high pressure.
Compound
Stability:
In gas
chromatography, the sample is introduced into the injector and vaporizes it at
a specific temperature and travels through the column. Thus, the compound
should be capable of withstanding the heat at high temperatures without
degradation. On the contrary, in the high-performance liquid chromatography
system, you allow the analysis of stable or less stable compounds because the
heating to sample is not necessary.
Sample
Requirement:
Samples
by GC required volatile compounds but in HPLC both volatile and nonvolatile
samples are analyzed.
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