Victrex PAEK Used to Make One-Piece Fitting for Ultra-High Pressure Liquid Chromatography Systems

Switzerland’s VICI AG International, Schenkon, a leading manufacturer of valves and fittings for analytical, biomedical and biocompatible precision instruments, is the first company to offer a new one-piece fitting using Victrex PAEK from Victrex, West Conshohocken Penn. According to VICI, the cost-effective injection molded carbon-fiber-reinforced VICTREX HT fitting can withstand the high pressures inherent in liquid chromatography systems and is, in fact, capable of withstanding pressures of up to 1,000 bar (14,500 psi), enabling more flexibility and easier handling.

The pressures required in liquid chromatography have been rising steadily for over five years, given that the particles of the separation materials (usually modified silica gels) now frequently have a grain size of two micrometers or less. Consequently, substances within mixtures can be separated more quickly, with identical efficiency.

VICI aimed to meet these demands with the new one-piece fitting made from Victrex HT which is capable of withstanding pressures when tightened by hand of up to 500 bar (7,250 psi). By way of comparison, 350 bar (5,000 psi) was the limit for conventional PEEK fittings. Provided the carbon-fiber-reinforced VICTREX HT fittings are tightened with an appropriate tool, they are suitable for significantly higher pressures of up to 1,000 bar (14,500 psi), confirmed VICI product manager Dr Andre Hütz, based upon testing the company has performed. Such higher pressures occur between pump and column in ultra-high performance liquid chromatography systems (UHPLC) and require that the stainless steel connecting capillaries used for the high-pressure range are fastened with appropriate fittings. Many UHPLC applications are carried out in a pressure range of approx. 600-800 bar (8700-11,600 psi), which means that the steel capillaries used between pump and column must use this type of fittings to provide a pressure tight connection between system components.

The greater strength of VICTREX HT polymer compared to unreinforced PEEK prevents the fitting from breaking apart when it is being tightened, since the carbon fibers are aligned in parallel by the injection process; this extra strength extends the service life of the fitting and allows several cycles of tightening and loosening of the fitting. In the past, this has only been possible in the high-pressure range using conventional two-piece ‘nut and ferrule’ fittings or complicated one-piece fittings. The design of such one-piece fittings often means they are only suitable for a specific connection and usually just for single use.