Relevant knowledge and experience of liquid chromatography maintenance 1. The mixed solvent must be filtered before mixing. If it is filtered after mixing, it can only be used organically, never with Water. Because the water-based material is cellulose, the organic phase more or less dissolves a little cellulose, causing pollution. 2. It is better to dissolve standard samples or samples with mobile phase (excluding special cases), which can avoid many troubles. 3. The purpose of heating the column and increasing the temperature is partly to increase the solubility of the solute, but more important is to reduce the viscosity of the solvent, thereby improving the peak shape and resolution. Note: The increase in temperature will reduce the retention time, which also affects the resolution. The temperature change has a great influence on the band width, and the height of the tray is affected by the temperature, although it also depends on the type of chromatography used Always reduce the height of the tray. 4. The temperature of the C18 column should generally not exceed 40 degrees Celsius, otherwise the healthy phase will easily fall off. 5. For the use of the sampler, it is better to use methanol or acetonitrile repeatedly after a period of time for cleaning, except for washing with water every time. 6. When using HPLC for analysis, the retention time sometimes drifts and sometimes changes rapidly. What is the reason? How to solve it? Answer: Regarding the drift problem: 1. Poor temperature control, the solution is to use a constant temperature device to keep the column temperature constant 2. The mobile phase changes. The solution is to prevent the mobile phase from evaporating and reacting. 3. The column is not well balanced, the column needs to be equilibrated for a longer time Seven, on the issue of rapid change: 1. The flow rate changes, the solution is to reset the flow rate to keep it stable 2. There are air bubbles in the pump, which can be expelled through operations such as exhaust. 3. The mobile phase is not suitable, the solution is to change the mobile phase or make the mobile phase properly mixed in the control room 8. What is the cause of peak tailing or double peaks in liquid chromatography? 1. The sieve plate is blocked or the column is invalid. The solution is to reversely wash the column, replace the sieve plate or replace the column. 2. There is interference peak, the solution is to use a longer column, change the mobile phase or replace the column with good selectivity 9. What is the main reason for non-linear shunt during capillary chromatography split injection? 1. The temperature of the injector is too low, the sample is not completely vaporized, and the classification and shunt occurs. 2. The temperature of the injector is too high, some components may be thermally decomposed, and some samples may undergo catalytic decomposition, or the sample may be partially adsorbed on the inner surface of the injector. 3. The sample is not uniformly mixed or insufficiently mixed before the split point. 4. The system's sampling pad, column joints and other places are leaking. 10. When doing liquid chromatography analysis, the column pressure is unstable, what is the reason? How to solve it? Answer: The reasons may be: 1. There is air in the pump, the solution is to clear the air in the pump and degas the solvent; 2. If the proportional valve fails, replace the proportional valve. 3. If the pump gasket is damaged, replace the gasket. 4. The bubbles in the solvent, the solution is to degas the solvent, and change the degassing method if necessary; 5. The system checks the leak, finds the leak point, and seals it. 6. Gradient elution, the pressure fluctuation is normal at this time. 11. How to prevent tar-like pollutants from entering the capillary column when doing PGS / MS analysis? Answer: Polymers, especially some polymers containing nitrogen, sulfur and halogens, often produce tar-like substances. In order to prevent this tar-like substance from entering the capillary column and causing pollution to degrade the column performance, a protective pre-column can be used, that is, a packed pre-column is connected between the cracker and the capillary column, and the tar-like substance is retained in the pre-column temperature by controlling the temperature of the pre-column In the pre-column, the pre-injection can be placed in the GC gasification chamber, so that it is easy to control the temperature and reduce the dead volume of the system. Of course, the pre-column packing needs to be replaced frequently. 12. I recently replaced another brand of ODS column. Although the separation is still possible, the retention time cannot be reproduced. Why? Answer: This is because the analyte may have the ability to form hydrogen Jian. Liquid Chromatography Although the manufacturing technology of fillers has greatly improved in the past few years, the concentration of silanol groups on the surface of ODS fillers of different manufacturers is different. It is these silanol groups that may interact with the sample. Therefore, the relative retention time of the components of the same analyte on different brands of ODS columns may be different. Adding a small amount of competitor in the mobile phase, such as triethylamine (Tea), will saturate the bonding ability of the silanol group, thus ensuring that the relative retention time on different grade columns has good reproducibility. 13. How long is the service life of high-temperature capillary columns? Answer: In addition to the performance of the column itself, the life of the capillary column depends to a large extent on the use conditions, such as the use temperature, sample status, injection volume, etc. If the sample is clean within its use temperature range, the In the case of contamination, the column life is generally between 2-3 years.
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