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High performance capillary chromatography columns

Product Description The capillary column is the key separation element of a gas chromatograph. It is made primarily of fused silica, and its inner wall is coated with a stationary phase. Due to their high separation ability and speed of operation, capillary coll...

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Product Description

The capillary column is the key separation element of a gas chromatograph. It is made primarily of fused silica, and its inner wall is coated with a stationary phase. Due to their high separation power and fast response time, capillary columns are widely used for the analysis of complex mixtures in areas such as ecology, food processing and petrochemicals.

Basic design and operating principle

At its core, a capillary column is a hollow tube with a very small internal diameter (0.1–0.53 mm) and a significant length (10–100 m). The sample is carried by a flow of carrier gas through the column, where the components are separated due to differences in the distribution coefficients between the stationary and mobile phases.

Materials and geometric parameters:

Material: As a rule, fused quartz is used, which is characterized by flexibility, heat resistance and chemical inertness.

Dimensions: the most common internal diameters are 0.25 mm and 0.32 mm; standard length is 30 m, however, custom-made versions are possible.

Main types of capillary columns

‌Wall Coated Column (WCOT)‌: Fixed phase is deposited directly onto the inner wall; most widely used, highly effective.

‌Porous layer column (PLOT)‌: a porous substance is applied to the inner wall; Suitable for separation of permanent gases and light hydrocarbons.

‌Carrier coated column (SCOT)‌: the carrier is deposited onto the inner wall first, followed by a fixed phase; has a large capacity.‌‌

Recommendations for choosing a column depending on the analysis parameters:

When choosing a capillary column, it is necessary to take into account the polarity of the sample to select the stationary phase, as well as optimize the dimensional parameters in accordance with the analysis tasks.

Selection of stationary phase:

Non-polar samples - It is recommended to use a non-polar phase (for example, 100% dimethylpolysiloxane), which is durable and resistant to oxidation.

Polar samples (acids, alcohols, amines) require the use of a phase with increased polarity (for example, polyethylene glycol).

For unknown samples, it is advisable to start with a column with a weakly polar phase and, if necessary, adjust the choice.

Selection of dimensional parameters:

Inner diameter: 0.25 mm - for standard analyzes and for working with mass spectrometers; 0.53 mm - for large volumes of injected sample (can serve as an alternative to packed columns).

Length: 30 m - a universal choice for most samples containing 10-50 components; For more complex mixtures, 60 m is recommended to increase separation power.

Film thickness: for high-boiling compounds, a thin film (0.1–0.25 µm) is preferred; for low-boiling ones - thick (1.0–5.0 µm).

Differences from packed columns and applications

Compared to traditional packed columns, capillary columns have significantly higher separation power and analysis speed, but their sample capacity is lower.

Separation efficiency: The number of theoretical plates for capillary columns can reach 10⁶, which significantly exceeds the performance of packed columns and allows the separation of complex multicomponent mixtures.

Applications

Environmental monitoring - determination of microquantities of organic pollutants in water and atmospheric air.

Food safety - analysis of pesticide residues, food additives and trace solvents (eg in accordance with the national standard GB 31604.60-2024).

Petrochemicals - hydrocarbon composition analysis and simulated distillation.

Maintenance Recommendations: Avoid operating above the permissible temperature, perform regular aging, and make sure there is no dead volume in the connections during installation to ensure column efficiency.

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