Food additive analysis column, chromatographic column

Chromatography columns can be divided into two categories based on their purpose: analytical and preparative, with different size specifications

① Conventional analysis column (constant quantity column), inner diameter 2-5mm (commonly 4.6mm, there are 4mm and 5mm in China), column length 10-30cm;

② Narrow bore, also known as narrow bore or semi micro column, with an inner diameter of 1-2mm and a column length of 10-20cm;

③ Capillary column (also known as micro column) with an inner diameter of 0.2~0.5mm;

④ Semi prepared column, inner diameter>5mm;

⑤ Laboratory preparation column, inner diameter 20-40mm, column length 10-30cm;

⑥ The inner diameter of the production preparation column can reach several tens of centimeters. The inner diameter of the column is generally determined based on the column length, packing particle size, and equivalent flow rate, in order to avoid pipe wall effects.

Food additive analysis column, chromatographic column

install

1. Firstly, it should be confirmed whether the joints between the column and the instrument, as well as the pipelines, match. To reduce dead volume, the inner diameter of the connecting pipeline between the injection valve, column, and detector should be as small as possible, while controlling the length of the connecting pipeline between the injector, chromatography column, and detector. Before installing the chromatography column, confirm whether the solvent in the flow path system is normal. It is recommended to install protective columns for samples with complex analysis.

2. In order to achieve the connection effect between the chromatographic column and the instrument system, nuts and tapered joints that match the interface of the chromatographic column should be used as much as possible. If the original joint is matched with other types of chromatographic columns for a long time, it is recommended to check the matching situation before connecting a new chromatographic column to avoid damage to the chromatographic column or leakage caused by mismatched chromatographic columns.

3. Universal joints made of PEEK material can be tightened by hand without the need for a specific wrench, with a pressure of 5000psi; The operating temperature should not exceed 100 ℃.

mobile phase

1. Before conducting sample testing, use 20 times less column volume of mobile phase to fully equilibrate the chromatographic column. The mobile phase must use chromatographic solvents. If using aqueous buffer, it should be prepared on the same day to maintain freshness and avoid bacterial growth.

2. Before using the mobile phase, it is necessary to filter it with a microporous membrane to eliminate the damage of particles in the mobile phase to the chromatographic system and column. After mixing with other mobile phases, the buffer solution should be re filtered to avoid changes in solubility that may cause the formation of new precipitates. Pure water should not be used as the mobile phase to rinse C18 chromatography columns to avoid column performance damage (adding 5% organic solvent to rinse the chromatography column can also achieve buffer salt cleaning and make the chromatography column easier to equilibrate).

3. The mobile phase needs to be degassed before use to avoid abnormal operation of the pump and detector caused by bubbles. If there is a significant difference between the mobile phase used during testing and the mobile phase used for chromatographic column storage, an over distribution form should be used for equilibrium. Avoid damage to the chromatography column and instrument system caused by sudden changes in the mobile phase resulting in excessive increase in column pressure or crystallization of buffer salts in the mobile phase. A normal phase chromatography column requires a longer equilibrium time than a reverse phase chromatography column.