Most high-performance liquid chromatography columns are made of stainless steel. However, when choosing pipe material, the first thing to consider is whether it is chemically compatible with the sample and mobile phase. Selection of fittings for liquid runners is often the source of problems in separation and sampling. This is usually due to the chemical incompatibility between the fittings and the sample and/or mobile phase. Some samples will "stick" on the surface of stainless steel tubes, resulting in sample loss, reduced production and residual. However, if it is determined that stainless steel is the best "material" compatible with the sample, no impurities such as oil, grease and other foreign matter from the manufacturing process should be included in the inner diameter range of the pipe. Foreign bodies may cause cross-contamination and sample reading errors. Therefore, in this industry, the cleanliness of pipe fittings is very important, and traditional pipe fittings usually need to be cleaned on site before installation.
When determining the chemical compatibility of stainless steel with the sample, we must consider the three main characteristics of the capillary provided by stainless steel:
1. Inner Diameter Smoothness
This ensures maximum permissible laminar flow, thereby reducing turbulence and improving system resolution.
The highly concentric inner diameter will reduce the fluid disturbance at the junction and help to reduce the band broadening.
3. Volume consistency
If the volume control is better, it can help to reduce the residence time and diffusion effect, thereby improving the overall peak resolution.
Choosing the right fittings ensures the integrity of the sample and provides consistent results. It can also improve the measurement speed and accuracy. Clean inner holes in the ss capillary tube
will restrict Newtonian fluid passing through the sample ring. All these characteristics will lead to better sample readings.