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  • Difference between HPLC and GC Technique

    HPLC (high-performance liquid chromatography) and GC (gas chromatography) are widely used separation techniques in pharmaceutical industries, industrial laboratories, and academia. High-performance liquid chromatography has applications in the field of pharmaceuticals, polymers; life sciences, etc. Gas chromatography has applications in pharmaceuticals, petroleum, petrochemical industry, etc.

    HPLC and GC operate on the same principle but with different results. In general, chromatography is the process of separating parts of a mixture by passing it through a gaseous column or liquid solution and generating data for the scientist to analyze.

    HPLC and GC are used in analytical chemistry to analyze samples and determine what the sample contains, its techniques are effective for the separation of analytes and it is a multipurpose and very well-accepted chromatographic technique utilized for the separation of complex mixtures. HPLC and GC are chromatography techniques based on the physical state of the mobile phase. HPLC uses liquid as the carrier and GC uses gas as the carrier.

    HPLC and GC techniques are used for identification and quantification purposes but for different intents as their functions and applications are different further HPLC and GC are based on the principle where the compound is subjected to the surface or within a solid or liquid stationary phase by isolating it with the help of the mobile phase. The selection of instruments is purely based on the nature of the sample and the requirement of the sample.

    The following table summarizes the differences between HPLC and GC techniques:

      HPLC GC
    PrincipalSeparation of the sample is accomplished by the solid stationary phase and liquid mobile phase.Separation of the sample is accomplished by liquid or solid stationary phase and gaseous mobile phase.
    Temperature ControlTemp. the control approach is not necessary or required. Generally ambient temp. is required.Temp. control is much more important as the column is placed inside the oven with a control temperature program. Generally, higher temperatures are required for analysis.
    Sample StateSeparation of the liquid state of any soluble samples usually with higher molecular weight. Separation of volatile and thermally stable samples with low molecular weight.
    ColumnColumns are generally shorter and broader in diameter.Columns are long, normally 10 to 60 meters in length, and narrow in diameter.
    Column TypesOctadecylsilane, Octyl silane, Hexyl, Trimethyl Silyl, Amino, Cyano, TMS, Silica, Hillic, Diol, Ion exchange, Chiral, Phenyl, Gel permeation & Size exclusion chromatographyWCOT, SCOT, PLOT, Carbowax, Polyethylene glycol, Dimethylpolysiloxane, Phenyl methyl polysiloxane, High molecular mass esters, Amides, Hydrocarbons, Polyaromatic compound, Cyanopropyl polysiloxane
    SeparationSeparation is based on the interaction of samples with mobile and stationary phases.Separation is based on the boiling point of the sample.
    Resolution IssuesSamples with identical polaritySamples with a similar molecular weight
    Mobile PhaseLiquids, e.g. Polar solvents like water, acetonitrile, methanol, etc. Nonpolar solvents like Hexane, Heptane, isopropyl alcohol, dichloromethane, etc. Gases, e.g. Nitrogen, Helium, Argon, Hydrogen, Oxygen
    SpeedAnalysis speed is slow.Analysis speed is fast
    Peak shapeGenerally, detect bigger or wider peaks that affect lower resolution.Relatively sharp peaks were observed with good resolution.
    DetectorsUV-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.
    CostLess costlyHigh cost

    For further information on HPLC and GC techniques feel free to contact us here.

    FAQ’s

    Define HPLC and its principle?

    HPLC is a technique in analytical chemistry used to identify, separate, and quantify each component present in the mixture. The liquid solvent contains the sample mixture which passes through the columns filled with a solid adsorbent material. The component present in the sample interacts marginally differently with the adsorbent material, causing different flow rates for different components which leads to the separation of components as they flow out of the column.

    What are the common mobile phases used in HPLC?

    The common mobile phases which are used, include any miscible combination of water with various organic solvents (the most common are Acetonitrile and methanol).

    Define Gas chromatography (GC).

    Gas chromatography is the technique used in separating compounds in a mixture by injecting a gaseous or liquid sample into the mobile phase which is called the carrier gas and passing the gas through a stationary phase.

    What is the operating principle of GC?

    In GC there is a column through which the sample passes in the vaporized phase carried along with the flow of continuous gases like inert or non-reactive gas. The components of the sample pass through the column (enclosed within a temperature-controlled oven) at different rates called the stationary phase. As the chemical exists from the column it is detected and identified electronically.

    What are the advantages of using GC?

    GC is an analytical technique and has several advantages like ease of operation, speed of analysis, separation of volatile compounds, relatively sharp peaks observed with good resolution, quantitative results, and separation of complex mixture components in a reasonable time.

    What are the advantages of using HPLC?

    HPLC is an analytical technique and has advantages like the accurate process of separation of analytes, simple data analysis, robust methods, retention time, and area of samples are precise and can be used for a wide range of compounds.

    References:

    1. Blumberg LM. Theory of Gas Chromatography. In: Poole CF, editor. Gas Chromatography, First Edition. Elsevier,
    2. Laird CK. Chemical Analysis: Gas Analysis. In: Walt Boyes, editor. Instrumentation Reference Book. Butterworth-Heinemann,
    3. High-Performance Liquid Chromatography.” Wikipedia, Wikimedia Foundation, “Gas Chromatography.” Wikipedia, Wikimedia Foundation.
    4. Ahuja S (1976) Derivatization in gas chromatography. J Pharm Science,
    5. Hartmann CH (1971) Gas chromatography detectors. Analytical Chemistry,
    6. La Course WR (2002) Column liquid chromatography: equipment and instrumentation, Analytical Chemistry.