Teflon injector

FIGURE 6.9 Horizontal chamber for fully online HPTLC by Nyiredy 1 — evaporator, 2 — diode-array detector, 3 — quartz glass cover plate, 4 — septum, 5 — injector block, 6 — mobile phase, 7 — filter paper, 8 — Teflon chamber, 9 — chromatoplate. (Modified from Nyiredy, Sz., J. Planar Chromatogr. 15, 454-457, 2002.)... 

The samples were placed in headspace vials. When saponification was performed, a few milliliters of NaOH solution were added to the sample. The vial was sealed with a headspace aluminum cap furnished with a Teflon-faced septum, immersed in a water bath maintained at 100 °C, and let equilibrate for 6 min before HSSPME. Afterward, the fiber was exposed to the headspace over the sample for 5-240 min, depending on the experiment. The sample was magnetically agitated during sampling. Once the exposition period was finished, the fiber was immediately inserted into the GC injector and the chromatographic analysis was carried out. Desorption time was set at 5 min. 

The continuous-stream flow-injection system (Figure 2) consisted of a gravity-feed electrolyte reservoir, a sample injection valve (Rheodyne, Model 50) fitted with a 30 /xL-sample loop, and a flow-through electrochemical detector cell. The channel diameter of the Teflon tubing for the stream was 0.8 mm. The tubing length from injector to detector was 10 cm. 

A sample must be introduced onto the column in an efficient and reproducible manner. One of the most popular injectors is the syringe injector. The sample, in a microliter syringe, is injected through a neoprene/Teflon septum. This type of injection can be used at pressures up to 3000 psi. 

Connect one end of your column blank to the tubing from the injector outlet the other end is connected to the line leading to the detector flow cell. We have one more fluid line to connect to complete our fluidics. A piece of 0.02-in tubing can be fitted to the detector flow cell outlet port to carry waste to a container. In some systems, this line will be replaced with small-diameter Teflon tubing. 

We have already discussed the use of a saturation column between the pump and injector to protect the main column against column degradation caused by high pH buffers. Another function of this column is to provide filters (the column inlet and the outlet frits) before the injector. I have seen unusual pumps that flaked Teflon off the pump seal this ended up plugging the injector. An in-line filter would have prevented the problem, which required tearing down the injector to remove the plugging. 

Pumps are basically devices for pulling in solvent, pressurizing it, and driving it out through the injector, column, and detector. As described earlier, it does this with a plunger driven through a Teflon seal into a pumping chamber (Fig. 9.2). 

The injector s wetted surfaces are stainless steel and acid-washed tubing, except for the rotor seal. The seal is a block of beryl or carbon liber-impregnated Teflon , like the pump seal, drilled for the loop and bypass pathways. Movement from inject to load is sealed and lubricated by the Teflon face plate. The injector outlet is drilled to 0.01 in and equipped with a compression fitting carrying tubing of the same diameter. 

Spare parts that are needed are compression fittings and ferrules, plunger and injector rotor seals, an extra plunger and seals, column filters, and injector needle port seals. If you do not use pacification, you might want to keep a set of check valves on hand. I always have one coil each of 0.01- and 0.02-in tubing in addition to my column blank. A replacement solvent inlet line with a porous stone is useful in case of corrosion. If you filter solvents, you need cellulose, nylon, and Teflon filters. You also need a back-up lamp for your detector. 

Pacification is a technique for removing organics and buffers from HPLC metal and Teflon surfaces and protecting them from salt corrosion with 6 N nitric acid (see Chapter 4). First, remove the HPLC column and replace it with a column bridge. Do not flush this wash into the mass spectrometer. Wash the system with water. Remove the column and replace it with a column blank. Flush with 6 N nitric acid for at least 30min, then overnight with water. Ensure the effluent pH is back to that of lab water. Replace the column and flush with mobile phase. This should be done at least once a month to clean check valves, line, and injectors. Under no circumstances should this wash be done with an HPLC column in place or into the mass spectrometer ... 

The work described by Jeannot and Cantwell implied utilizing two different apparatuses for two different steps a Teflon rod supporting the drop (for extraction) and a microsyringe (for injection of the extract into the analytical instrument). The work was further developed by incorporating only a microsyringe for extraction (as solvent drop holder) and extract injection (as sample injector) into the analytical instrument.7... 

Figure 13 Scheme of coupling of the gas chromatograph (GC) with the inductively coupled plasma mass spectrometry (ICP-MS) instrument (1) torch (2) injector supply (3) Teflon piece + Teflon Swagelok adapter (4) Swagelok T-joint (5) commercial transfer line (6) stainless steel transfer tube (7) transfer capillary. (From Ref. 91.)... 

Figure 22.2. Example of a GC-ICP-MS instrumental set-up [76], 1, torch 2, torch box 3, injector supply 4, teflon adapter 5, electrical contact point 6, thermal isolation 7, T-joint 8, transfer capillary 9, effluent splitter 10, Ar gas heating coil 11, female Swage-lok adapter 12, variable AC supply 13, earthing 14, Teflon coupling piece 15, device attaching screw to torch 16, stainless steel transfer tube and 17, transfer capillary.

The vials are closed with a teflon coated butyl rabber septum, vigorously shaken, and thermostatted for 4. 5 min. at 80°C. Pressurization time and injection time were 30 s en 15 s respectively. The injector bloc was kept at 120°C, the GC-ovenat 150°C. 

Sample volumes of 5 to 50 pL are normal. One way of injeeting a sample is shown in Figure 19-25. This injector allows sample introduction without interrupting the solvent flow. All of the parts are either stainless steel or Teflon. 

Next, we replaced the injector loops, tubing from the injectors to the mixing tee, and reactor with Teflon tubing of equivalent volumes. The flat top experiment was then repeated, with the results from this experiment plotted in Fig. 13.11. 

Figure 7 Degassing apparatus. A, reflux chamber-, B, cold flnger C, liquid storage bulb-, D, vacuum stopcock-, E, Teflon needle valve-, F, port to piston-injector [Reproduced by permission from Ind. and Eng. Chem. Fundamentals), 1972, 11, 410]...

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