Frits, inlet/outlet

The last few years have seen significant developments in the Fl-FFF technique with respect to increasing its application range for organic solvents, accessible physicochemical quantities (FFF/MALLS) or instrument design (frit inlet-outlet Fl-FFF). Parallel to these developments, the application of Fl-FFF as an analysis technique has increased, possibly catalyzed by the commercial availability of S-Fl-FFF as well as A-Fl-FFF channels of different designs. For other FFF techniques, instrumentation has been more or less unmodified with the exception of El-FFF so that, in the next section, only improvements to Fl-FFF are discussed. The development of the other FFF techniques is discussed in Sect. 2. 

A gas-inlet tube of smaller diameter or a tube fitted with a fritted-glass outlet tends to become clogged during this preparation and is not recommended. 

Column Column dimension (i.d. X L) (cm X cm) Bed volume (ml) Column materials° (Tube/Frit) Column fittings (inlet/outlet) Theoretical plates (N/m) Maximum operating pressure/flow rate (kPa)/(ml/hr)... 

Figure 3.34 — Manifolds for implementation of a sensor containing a packed non-regenerable reagent and a regenerable fluorophore. (A) Flow-through sensor system 1 eluent vessel 2 pump 3 injection valve 4 TCPO reactor 5 CL cell 6 light-tight box with PMT 7 amplifier 8 recorder. (B) Design of the packed two-layer sensor 1 inlet capillary 2 inlet cap with frit 3 quartz tube 4 TCPO layer 5 frit 6 luminophore layer 7 outlet cap with frit 8 outlet capillary. (C) Manifold for implementation of the previous cell in biochemical applications (Reproduced from [240] and [241] with permission of the American Chemical Society and Elsevier Science Publishers, respectively).

From the technological point of view, the symmetrical FIFFF system has been technically bettered with a number of changes in order to improve separation performance the frit inlet and frit outlet were proposed, respectively, to quickly relax sample components to their different equilibrium distances above the accumulation wall and for on-line concentration prior to detection. This last feature addresses the dilute nature of many biological samples and compensates for some of the dilution that occurs during the separation process. 

There are three areas in a column where pressure increase can occur the inlet frit, the outlet frit, and the column bed. The most likely source of... 

Frit outlets which work in reverse to the frit inlets (see Fig. 12) have been constructed allowing a sample concentration due to the fact that the sample is compressed near the accumulation wall so that the majority of the solvent containing no sample can leave through the frit thus concentrating the sample at the outlet [52]. 

Very fast hydrodynamic relaxation as can be achieved by stream splitters or frit inlets (see Fig. 12) so that there is no need for a stop-flow or focusing period. It is important that the injection time can serve as a triggering pulse for an automated fractionator coupled to the FFF outlet. 

Zanardi-Lamardo, E., Clark, C.D., and Zika, R.G., Frit inlet/frit outlet flow field-flow fractionation Methodology for colored dissolved organic material in natural waters, Anal. Chim. Acta, 443, 171, 2001. 

Several studies involving FFF channel modifications and new experimental procedures have been aimed at increasing detectability. For example, frit-outlet flow FFF utilizes a section of the frit depletion wall near the channel outlet to remove sample-free carrier and, thus, concentrate the separated sample just prior to its reaching the detector. A 10-fold increase in the detector response of purified proteins was achieved without any effect on retention time or resolution [8]. Frit-inlet flow FFF involves a... 

Li, P. Hansen, M. Giddings, J.C. Advances in frit-inlet and frit-outlet flow field-flow fractionation. J. Microcol. Sep. 1998,10, 7-18. 

Fig. 2 The dual thin-layer flow cell for DBMS. 1 Kel-F support 2 Kalrcx gasket 3 electrode 4 Teflon gasket 5 Teflon gasket 6 porous Teflon membrane 7 stainless steel frit 8 stainless steel connection to MS 9 capillaries for Ar, 10 inlet-outlet capillaries 11 connecting ct illaries. (A) Side view of the cell (B) top view of the cell. Reprinted bom Ref. [50] with permission from Elsevier...

The catalysts were tested for their CO oxidation activity in an automated microreactor apparatus. The catalysts were tested at space velocities of 7,000 -60,000 hr . A small quantity of catalyst (typically 0.1 - 0.5 g.) was supported on a frit in a quartz microreactor. The composition of the gases to the inlet of the reactor was controlled by mass flow controllers and was CO = 50 ppm, CO2 = 0, or 7,000 ppm, HjO = 40% relative humidity (at 25°C), balance air. These conditions are typical of conditions found in spacecraft cabin atmospheres. The temperature of the catalyst bed was measured with a thermocouple placed half way into the catalyst bed, and controlled using a temperature controller. The inlet and outlet CO/CO2 concentrations were measured by non-dispersive infrared (NDIR) monitors. 

Hydrolytic Kinetic Resolution (HKR) of epichlorohydrin. The HKR reaction was performed by the standard procedure as reported by us earlier (17, 22). After the completion of the HKR reaction, all of the reaction products were removed by evacuation (epoxide was removed at room temperature ( 300 K) and diol was removed at a temperature of 323-329 K). The recovered catalyst was then recycled up to three times in the HKR reaction. For flow experiments, a mixture of racemic epichlorohydrin (600 mmol), water (0.7 eq., 7.56 ml) and chlorobenzene (7.2 ml) in isopropyl alcohol (600 mmol) as the co-solvent was pumped across a 12 cm long stainless steel fixed bed reactor containing SBA-15 Co-OAc salen catalyst (B) bed ( 297 mg) via syringe pump at a flow rate of 35 p,l/min. Approximately 10 cm of the reactor inlet was filled with glass beads and a 2 pm stainless steel frit was installed at the outlet of the reactor. Reaction products were analyzed by gas chromatography using ChiralDex GTA capillary column and an FID detector. 

The FTS experiments were conducted in a 1 L CSTR equipped with a magnetically driven stirrer with turbine impeller, a gas inlet line, and a vapor outlet line with an stainless steel (SS) fritted filter (7.0 microns) placed external to the reactor. A tube fitted with an SS fritted filter (2.0 micron opening) extends below the liquid level of the reactor for withdrawing reactor wax to maintain a nearly constant liquid level in the reactor. Another SS dip tube (1/8 inch OD) extends to... 

Sintering of the packing materials to create the inlet end-frit at a distance representing the desired packed segment length followed by the removal of the polyimide coating from the detection window close to the outlet frit. 

Chirica and Remcho first created the outlet frit, packed the column with ODS beads, and then fabricated the inlet frit. The column was filled with aqueous solution of a silicate (Kasil) and the entrapment achieved by heating the column to 160 °C [105,106]. The monolithic column afforded considerably reduced retention times compared to the packed-only counterpart most likely due to a partial blocking of the pores with the silicate solution. This approach was recently extended to the immobilization of silica beads in a porous organic polymer matrix [107]. 

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