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 micrometres or less. Consequently, substances within mixtures can be separated more quickly, with identical efficiency.
High-quality material – high-quality fitting
To satisfy these demands, VICI has introduced a new one-piece fitting made from VICTREX HT
high-performance polymer, capable of withstanding pressures when tightened by hand of up to 500 bar (7,250 psi).
1 By way of comparison, 350 bar (5,000 psi) was the limit for conventional PEEK fittings. Provided the carbon-fibre 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 Dr Andre Hütz, Product Manager at VICI AG International, 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, which means that the steel capillaries used between pump and column must use this type of fitting 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 fibres 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.
1 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.
“Assisted by Victrex and its material and processing expertise, we have developed and commercialised a new product in this segment to offer users greater flexibility, reusability and above all easier handling compared to steel screw fittings. Also, being manufactured by
injection moulding, it is favourable in cost terms, too“, explains Dr Andre Hütz, product manager at VICI AG International. “We have performed tests showing that, when tightened by hand, the new VICTREX HT fittings can be used at 500 bar and above. When tightened with a tool, they can also be reused at least three times after first use at a test pressure of 950 bar.”
1
1) VICI has confirmed that the performance claims are based upon testing it has performed. According to VICI test documentation, results depend on the level of tightening.
Further information on VICI at www.vici-jour.com; https://www.vici.com/; https://www.vici-dbs.com
Further information on Victrex at www.victrex.com
+++
About VICI
For more than 50 years, the VICI Group has been a market leader in the design and production of standard and customised metal and polymer valves and screwed connections. These are used in chromatography and in the analytical, biochemistry and medical technology fields. The product portfolio covers a wide range of related products, such as pneumatic and electric valve drives, polymer and stainless steel tubing and capillaries, sample loops, filters, low pressure liquid pumps, gas generators, gas purifiers, gas calibrators and diffusion tubes as standards for tool calibration, GC detectors, GC columns, fast GC components, safety products, syringes and much more.
