Problem: HPLC systems are forced to their pressure limits under fast HPLC and high resolution HPLC conditions. System back pressure issues can arise from efforts to increase efficiency and resolution such as increasing flow rates and column lengths, as well as reducing particle size. PEEK is the traditional tubing material of choice for most applications but it is no longer suitable for high performance HPLC. The PEEK tubing can slip or become distorted under high pressures, causing poor resolution, diminished efficiency and system failures. High performance HPLC requires a more advanced type of fitting—one which can handle the higher pressures without failing, while still eliminating dead volume that contributes to band broadening and decreased resolution.
Solution: One such option is a line of high performance fittings from Supelco that maintains the integrity of HPLC systems up to 15,000 psi with finger tightening. In particular, the Supel-Connect High Performance Fittings and Interconnects are made of 316 stainless steel and use a sliding ferrule design to allow for installation into any port. A design like this allows the user two degrees of freedom in compressing the ferrule. Partial separation of radial and axial tightening forces allow the fitting to withstand pressures greater than 15,000 psi, while providing strong elimination of dead volume. Figure 1 shows the HPLC column efficiency as a function of system backpressure. The system equipped with PEEK fittings illustrates gradual loss of efficiency starting at 3,000 psi with an eventual catastrophic failure at 5,500 psi. However, the Supelco high performance fittings show no performance loss as a function of pressure.
High performance interconnects can be used on most HPLC systems. They are available in various configurations, with either flexible or rigid stainless tubing. With the right configuration of fittings and nuts, they can also be used with PEEK, PEEKsil™, or the stainless steel tubing of the user’s choice to extend the pressure limits of standard tubing.
For more information and to see a video demonstrating the Supel-Connect high performance fittings, visit www.sigmaaldrich. com/hplc or check out the product specs at www. sigmaaldrich.com/analytical-chromatography/analyticalproducts. html?TablePage=19820794
