PEEK capillaries

Figure 2.12 Exploded (left) and assembled (right) view of a toroid cavity autoclave probe for in situ investigations under high gas pressures or in supercritical fluids. Autoclave base (A) and autoclave body (P-bronze, B) thermocouple (C) coaxial heater (D) PTFE ring (E) central conductor (Cu/Be ring, F) nonmagnetic pin from male coaxial connection (G) RF feedthrough (from Rathke [28], H) base-plate (MACOR, I) fixing screws (P-bronze, J) PEEK capillary (l<) ceramic ball (Si3N4, L) PTFE seal (M).

The ClinLab flow cell Sputnik [123] was originally developed for H PLC applications but is a separate device which in principle can be combined with every amperometric detector which is designed for three-electrode operation (Figure 4.74). Two PEEK capillaries and three electronic plugs are the only external interfaces. 

Figure 8.11 Separation of a mixture of human hormones (a) total ion current (TIC) profile (b) UV profile (254 nm). Conditions injection volume, 60 nl capillary, 25 cm x 250 /xm I.D. PEEK capillary, C18, 5 /xm flow rate, 1 /xl/min gradient, 40-80% acetonitrile in 25 min. Peaks 1, nortestosterone 2, testosterone 3, diethylstilbestrol 4, methyltestosterone 5, medroxyprogesterone , diethylstilbestrol impurity. (Reprinted from Ref. 26 with permission.)...

Teflon and peek capillaries are easily cut with a razor blade but cutting instruments are also available. Steel is difficult to cut because thin-walled mbes are prone to deformation and thick-walled ones to clogging or to a reduction of their inner diameter. It is best to use one of the special instruments which are available from the vendors of capillaries follow the instructions. Without such a device at hand, cut a score over the whole circumference of the capillary by means of a small file. It is then grasped with two smooth-jawed pliers or with a vice and one plier very close to the score and bent back and forth until it breaks. If a freshly cut capillary is built into the instrument for the first time, attach it with the new end downstream from the pump and do not connect another instrument but allow the effluent, with possible dust, to go directly to waste. 

Replace the capillaries or install them in reverse direction. Caution do not overtighten the fittings of peek capillaries. 

If the problem persists, replace your normal injection valve (very often this is the culprit ) with a PEEK valve and, if necessary, also the stainless steel capillaries with PEEK capillaries. Also replace the material of the seals. Lastly you should silanize the glassware you work with. 

Which type of oven was used Air circulating oven or aluminum block - the heat conductivities are different Also, differences can occur using stainless steel or PEEK capillaries. 

In most cases, routine problems can be solved with a polyaryl-etheretherketone (PEEK) capillary. However, PEEK is susceptible to attack by halogens and strong Brpnsted and Lewis acids as well as some halogenated compounds and aromatic hydrocarbons. A stainless steel capillary with additional protection of turbomo-lecular pump (admission of shielding gas) should be used in corrosive media (NH3, CI2, F2 etc.). Glass-lined plastic is the optimal choice when any undesirable reagent adsorption should be diminished. 

A methodology of bonding the monolith to the wall of PEEK capillary tubing... 

In RP chromatography, PEEK capillaries have good chemical stability and are largely inert. The tailing due to interactions with silanol groups seen with fused silica capillaries does not arise here [2]. They are very flexible and are available at relatively low prices, in many dimensions. The different i.d.s can easily be determined from the color coding. 

A fundamental premise is that there are robust methods in the individual dimensions. For the column switching, manifold valves with fast circuit times and a low void volume are essential. During the time of column switch the flow is completely interrupted for a moment, leading to pressure fluctuations. Therefore, steel or PEEK capillaries with a large wall thickness and especially tightened fittings are necessary. 

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