Advantages Of Gas Chromatography Analysis

Advantages of Gas Chromatography Analysis

Gas Chromatography is known for its high level of accuracy and sensitivity in detecting very small amounts of sample components. It is an effective method of analytical chemistry that helps us reveal the secrets of the sample ingredients, quantifying impurities and unknown substances. In this blog, we have covered the details of the GC procedure and how the method works in analysing samples.

What is Gas Chromatography GC?

Gas Chromatography (GC) is an analytical technique used to quantify and analyze gas, liquid, and solid samples. The method is used to separate and detect the chemical components of a sample mixture to determine the presence or absence and/or quantities. GC is widely used in various industries for quality control, research purposes, and determining the safety of edible items.

How Does Gas Chromatography Work?

Let us take a look at how the GC testing lab carries out the analysis to quantify the samples.

Basic Principle:

The method is based on the principle that when the solution sample is injected into the GC system, the solvent components are heated and vapourized within the sample injection unit.

The carrier gas passes from the sample injection unit to the column and then to the detector. Next, the vapourized components are transported by the carrier gas to the column from where the sensor measures the amount of each element. The presence of each compound is sent by an electrical signal by the detector, enabling the scientists to detect the presence of certain compounds in the sample.

How does GC work?

First, the sample is injected into the gas chromatograph with a syringe or autosampler. The injection is done through the septum, thereby preventing the loss of the mobile phase of the mixture.
The inlet is connected to an analytical column that is 10-150 m long and 0.1 to 0.53 mm in diameter. The column is a fused silica or metal tube which contains the stationary phase coated on the inside walls.
Next, the analytical column is held in the oven which is heated during the analysis to evaporate less volatile compounds.
The column outlet is then inserted into the detector, which produces a signal marking the evaporation of chemical compounds from the column.
The acquisition software records that sound to produce a chromatogram.

Once the injection is over, the chemical compounds get vapourized first. For low-concentration samples, the GC testing lab transfers the entire vapour cloud into the analytical column. For high-concentration samples, only a portion of the sample is transferred to the analytical column in split mode. The remaining components are flushed out from the system to prevent overloading of the analytical column.

GCHS Testing Services lab selects the type of column depending on the volatility and functional groups of the analytes. Liquid stationary phases can be categorized into two types: polyethylene glycol (PEG) or polydimethylsiloxane (PDMS) based, the latter with varying percentages of dimethyl, diphenyl or mid-polar functional groups.

Molecules that can undergo n-n interactions can be separated on stationary phases consisting of phenyl groups. On the other hand, molecules that are capable of hydrogen bonding like acids and alcohols can be best separated with PEG column.

Compounds suitable for GC analysis:

Solutions with a boiling point up to 400 °C
Compounds that are not decomposed at their vaporization temperature
Compounds that decompose at their vaporization temperature, but always by the same amount.

Compounds not suitable for GC analysis:

Solutions that do not vaporize (inorganic metals, ions, and salts)
Highly reactive compounds and chemically unstable compounds like hydrofluoric acid and other strong acids, ozone, NOx and other highly reactive compounds
Highly adsorptive compounds like compounds containing a carboxyl group, hydroxyl group, amino group, or sulfur
Compounds for which standard samples are difficult to obtain