Chromatographic consumables, you ask and answer me

The concept of gas chromatography: A separation technique that uses gas as the mobile phase and achieves the separation of complex samples based on the differences in forces such as adsorption and distribution between components and stationary phases. The separation object is a volatile, thermally stable sample with a boiling point generally not exceeding 500 degrees.

Gas: Carrier gas - a gas used to transport samples through the entire system. Detector gas - support gas required for certain detectors, such as FID.

Sample introduction: The process of introducing sample steam into the carrier gas. This process should have minimal impact on sample steam.

Chromatographic column: achieving the separation of sample components.

Detector: Identify and respond to the sample components exiting the column.

Data collection: Convert the signal of the detector into a chromatogram for manual or automatic qualitative and quantitative analysis.

What are the column parameters of a chromatographic column? How to select chromatographic columns for customers based on these parameters?

Chromatographic column parameters: stationary phase, column length, inner diameter, and film thickness.

Selection of fixed phase: principle of similar phase solubility.

Non/weakly polar columns - most commonly used! Medium polarity column - suitable for complex/difficult separation; Strong polarity column - commonly used for special applications.

Column length:

Rapid analysis of simple samples with a length of 10-15m, typically consisting of less than ten components

The standard column length of 25-30m meets the vast majority of applications

Analysis of 50m, 60m, 100m complex samples

Inner diameter:

0.53mm large caliber replaceable filling column can withstand large volume injection and trace analysis

0.32mm wide diameter, split/non split injection, capable of withstanding large volume injection

0.25mm narrow diameter split injection, GC/MS application, high column efficiency

0.18mm micro diameter for fast separation and high column efficiency

0.10mm fast GC, high instrument requirements for fast separation

Understand several parameters related to liquid chromatography columns and the classification and application range of Agilent chromatography columns.

Surface area - the sum of the outer surface and inner pore surfaces of particles, expressed in m2/gram;

High surface area has strong retention ability, column capacity, and resolution for the separation of multi-component samples;

Fillers with low surface area can usually quickly reach an equilibrium state, which is particularly important for gradient leaching

Aperture - The average size of a particle's pore or cavity, ranging from 60 to 10000 Å

The filler particles with large pores can prolong the retention time of solute macromolecules on the surface of the filler, achieve sufficient separation, and improve peak shape; For samples with MW ≤ 4000, choose a pore size of 80 Å, and for samples with MW>4000, choose a pore size of 300 Å

Carbon coverage - the effect on chromatographic separation, the amount of bonded phase connected to the matrix material.

High carbon coverage: improved resolution and long analysis time; Low carbon coverage: reducing operating time

Capping/Tailing - The effect on chromatographic separation, using shorter alkane chains to bond free silicon hydroxyl groups (secondary bonding)

Capping: Alleviates the chromatographic peak tailing phenomenon caused by the reaction between the tested component and the residual acidic silicone hydroxyl group on the surface of the silica gel

For polar samples, there is a significant difference in selectivity between un capped and capped chromatographic columns