Liquid chromatography maintenance knowledge

1. The column is not used for an extended period. When storing, it should be filled with a suitable solvent and sealed at both ends—such as acetonitrile (ACN) for reversed-phase columns or the corresponding organic phase for normal-phase columns. This helps prevent drying and contamination. 2. For manual injectors, when using buffer solutions, flush the inlet with water and move the injection valve several times per milliliter to prevent residue buildup and ensure smooth operation. 3. The mobile phase must be filtered before use. Avoid using distilled water that has been stored for a long time, as it can promote bacterial growth and lead to clogging or contamination of the system. 4. For the seal-wash function on the 1100 system, prepare a solution of 90% water and 10% isopropanol. Siphon the solution out at a rate of 2–3 drops per minute, ensuring the solvent does not dry out during the process. This helps maintain the integrity of the seals and prevents damage from salt crystallization. 5. For other maintenance-related questions, refer to the user manual or contact your field engineer for guidance. **Maintenance Knowledge: Frequently Asked Questions** 1. **Why do solvents and samples need to be filtered?** Filtration is essential to protect both the column and the instrument. It prevents blockages caused by particulate matter and ensures accurate analytical results. - **Column Protection**: The packing material in the column is very fine, and the flow path is narrow. Small particles in the sample or solvent can easily clog the column or capillary tubing. - **Instrument Protection**: Particles can cause wear and clogging in the injection valve, sapphire piston rod, and pump head, leading to reduced performance and potential failure. **Types of Sample Filters:** - **30 mm inner diameter**: Ideal for large injection volumes (up to 50 μL). Available in 0.2 μm and 0.45 μm pore sizes, made of cellulose, acetate, or PTFE. - **13 mm inner diameter**: Suitable for a wide range of applications, typically 0.2 μm or 0.45 μm, made of cellulose. - **3 mm inner diameter**: Designed for small injection volumes (up to 7 μL), also available in 0.2 μm and 0.45 μm. **Filter Types and Compatibility:** 1. **PTFE Filter**: Resistant to all solvents, acids, and salts. No leaching of substances. 2. **Cellulose Acetate Filter**: Not recommended for organic solvents but ideal for water-based solutions, especially for protein samples. 3. **Nylon 66 Filter**: Compatible with most organic solvents and aqueous solutions. Can handle strong acids and 70% ethanol, but not dimethylformamide. 4. **Regenerated Cellulose Filter**: Low protein binding, suitable for both water-soluble and organic solvent-based samples. 2. **Why is the online Seal-wash option necessary when using buffer salts in HPLC?** When buffer salts are used, they can precipitate inside the pump head due to high pressure and evaporation. These salt crystals are hard and can scratch the sapphire piston rod, damaging the seals and causing leaks. The online Seal-wash option helps remove these deposits, preventing damage. It is highly recommended to use this feature when the buffer concentration is 0.1 M or higher.

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