High performance liquid chromatography columns, as the core consumables of HPLC systems, have a direct relationship between their lifespan and detection accuracy. The maintenance and upkeep focus on "preventing pollution, damage, and aging", reducing problems such as loss of stationary phase and column blockage through standardized operation. The specific method is to disassemble the entire process of "before use, during use, after use, and long-term idle", taking into account practicality and professionalism:
1、 Before use: Prepare well and protect the chromatographic column from the source
Column activation and equilibrium: For new columns or chromatography columns that have been idle for more than one week, mobile phase equilibrium should be maintained for 30-60 minutes (flow rate 1.0 mL/min) before use to ensure sufficient infiltration of the stationary phase; Reverse phase columns (such as C18) can be washed with methanol/water (90:10) for 20 column volumes before switching to the sample mobile phase to avoid performance degradation caused by drying of the stationary phase. If the solvent stored in the column is incompatible with the mobile phase (such as using n-hexane to store the normal phase column and methanol as the mobile phase), a transition solvent gradient should be used to rinse to prevent solvent solubility from generating bubbles or stationary phase collapse.
Sample and mobile phase purification: The sample must be filtered through a 0.22 μ m membrane to remove particulate matter and suspended solids, avoiding clogging of the column sieve plate; Samples containing high boiling point impurities, proteins, and oils need to be purified in advance through solid-phase extraction (SPE) and other methods to prevent impurities from adsorbing on the stationary phase. The mobile phase requires ultrasonic degassing for 15-20 minutes to remove bubbles (which can cause column pressure fluctuations and abnormal peak shapes); When using a buffer salt mobile phase, high-purity water (such as ultrapure water) should be prepared and filtered before use to avoid salt crystallization blocking the chromatographic column.
Instrument status check: Before installing the chromatographic column, clean the injection port liner and replace the aging gasket to avoid gasket debris and sample residue entering the column; Check for leaks or blockages in the pipeline to ensure stable pressure in front of the column; Confirm that the column joint is well sealed and select a matching graphite pad to avoid column damage caused by carrier gas leakage or uneven pressure.
2、 In use: Standardized operation to avoid column damage
Temperature and pressure control: Strictly follow the maximum operating temperature of the chromatographic column (usually ≤ 60 ℃ for reverse phase columns and ≤ 80 ℃ for normal phase columns) to avoid accelerated loss of the stationary phase due to high temperatures; The column pressure should be controlled within the recommended range at the factory (usually ≤ 40MPa). If the pressure suddenly increases by more than 30%, the machine should be stopped immediately for troubleshooting (such as filtering the mobile phase and cleaning the injection port) to avoid high pressure causing fixed phase compaction and column bed collapse. The recommended heating rate is ≤ 10 ℃/min to avoid sudden temperature rise and drop that may damage the column structure.
Guidelines for using mobile phase: Avoid using highly corrosive solvents such as concentrated hydrochloric acid and sodium hydroxide. The pH range of the mobile phase in reverse phase columns should be controlled between 2-8 (except for special acid and alkali resistant columns). Exceeding this range can cause dissolution of the silica gel matrix and hydrolysis of the stationary phase. During gradient elution, the proportion of organic phase should not change too quickly (such as a change of ≤ 10% per minute) to avoid rapid contraction or expansion of the stationary phase; After using the mobile phase containing buffer salts, it is necessary to rinse it with a high proportion of aqueous phase in a timely manner to prevent salt crystallization.
Injection operation requirements: The injection volume should match the column capacity (conventional C18 column injection volume ≤ 20 μ L) to avoid peak tailing and stationary phase contamination caused by overload; The temperature setting of the injection port is reasonable, 10-20 ℃ higher than the highest boiling point of the sample, but not exceeding the maximum operating temperature of the column, to prevent impurities from contaminating the chromatographic column due to sample decomposition. To avoid continuous injection of high concentration and highly contaminated samples, it is recommended to rinse 10-15 column volumes with blank mobile phase after every 10-20 injections.
3、 After use: Clean in a timely manner to extend the lifespan of the column
Conventional cleaning process: After the experiment is completed, rinse the chromatography column with a mobile phase gradient to remove residual samples and impurities. Reverse phase column: first rinse 20 column volumes with methanol/water (50:50), then rinse 30 column volumes with pure methanol or acetonitrile to remove strongly adsorptive impurities; Normal phase column: Rinse 20 column volumes with n-hexane/isopropanol (90:10) and store with pure hexane. If the sample contains difficult to wash impurities such as protein and oil, 5-10% tetrahydrofuran (THF) can be added during the cleaning process to enhance the washing effect, but attention should be paid to the compatibility of THF with some stationary phases.
Special pollution treatment: If the column pressure increases and the peak shape tail is severe, it may be contamination inside the column, and deep cleaning can be carried out. Reverse phase column: Wash with a gradient of methanol → methanol/THF (80:20) → methanol → acetonitrile, with 20 column volumes per step; Normal phase column: Rinse with n-hexane → n-hexane/ethyl acetate (50:50) → n-hexane. Do not rinse the normal phase column with strong polar solvents (such as acetone, dichloromethane) to avoid loss of the stationary phase.
Storage method: Short term storage (within 1 month): The reverse phase column is sealed with pure methanol or acetonitrile, and the normal phase column is stored with n-hexane to ensure that there are no bubbles inside the column; Long term storage (over 1 month): The reverse phase column is stored in methanol/water (90:10), and the normal phase column is stored in n-hexane/isopropanol (95:5) to prevent drying and aging of the stationary phase. When storing, seal both ends of the chromatography column with plugs and place it in a cool and dry place (temperature 5-30 ℃), avoiding direct sunlight.
Through the above standardized maintenance, the service life of high-performance liquid chromatography columns can be extended to 1000-2000 analyses, while ensuring the accuracy and repeatability of detection data and reducing usage costs. The maintenance methods for different types of chromatography columns (such as ion exchange columns and chiral columns) need to be adjusted according to the manufacturer's instructions, with a focus on mobile phase compatibility and stationary phase characteristics.