Interface Flow

For microbore HPLC, with a flow of less than lOOpLmin-1, off-line LC-FT1R has been developed using matrix isolation techniques. The solutes are deposited on a moving IR salt window [504] or on a rotating plated disc [486], and are measured afterwards with the aid of a FITR microscope or a reflectance accessory. FTIR detection was first applied to the analysis of microbore HPLC eluent by Teramae and Tanaka [505]. In microbore HPLC-FTIR the amount of mobile phase required for separation is much less than for conventional scale HPLC. This simplifies both flow-cell and mobile-phase elimination interfaces. Flow-cell... 

The most common LC-MS interface. Flow rates up to 1 ml/min but best at 200 pl/min or below. A charged aerosol is generated at atmospheric pressure and the solvent is largely stripped away with a flow of N gas. The charged molecules are drawn into the MS by eiectrostaticaiiy charged plates. 

In this section, the peak ultrasound echo intensity is used to locate the position of the gas-liquid interface flowing in a horizontal pipe. The accurate detection of the gas-liquid interface in pipe flow has important implications in engineering. 

Chromatographic columns with an inner diameter of 2 mm are frequently used for LC-MS applications. We have found that columns with a 3 mm inner diameter are more robust and ideally suited for use with a particle beam interface. Flow rates around 0.5mL/min can be used with conventional HPLC systems as well as LC-MS systems having a particle beam interface. Using this size column and flow rate, no adaptation of the separation method is necessary. 

Poor interface control allows the main liquid-liquid interface to leave the extractor. This may result from inadequate size of interface flow control valves, or operation with internals that provide inverse control responses such as those observed with sieve tray extractors. (See Process-Control Considerations. )... 

C.I.C. Silvestre, J.L.M. Santos, J.L.F.C. Lima, E.A.G. Zagatto, Single reaction interface flow system for chemiluminescent monitoring of mannitol based on its hydroxyl radical scavenger activity, Talanta 77 (2008) 518. 

Microscale fluidic systems use small volumes so sensitivity of detection can be a challenge. Any detector for chip-based LC needs to be small and ideally have low power consumption. It is generally a problem of interfacing. Flow cell geometry is also a big factor, e.g. a U cell instead of linear flow cell can give a ten-fold increase in sensitivity for absorbance measurements. Electrochemical detection is very common, mainly ampero-metric and potentiometric, and very amenable to detection on chip. Fluorescence is more sensitive than UV-Vis absorbance and chemiluminescence is sensitive down to a single molecule, similar to LIF. 

Silvestre, C.I.C., Frigerio, C., Santos, J.L.M., and Lima, J.LF.C (2011) Quantum dots assisted photocatalysis for the chemiluminometric determination of chemical oxygen demand using a single interface flow system. Anal. Chim. Acta, 699, 193-197. 

Intermittent flow (or deformed interface flow), where the dispersed phase flows to a certain distance either in the form of parallel or annular flow and then produces irregular droplets (Fig. 2.Id). 

F. 2.1 Flow configurations obtained in miciochannels a Drop flow, b Plug (slug) flow, c Plug-drop flow, d Deformed interface flow, e Aimular flow, f Parallel flow, g Plug-dispersed flow, h Dispersed flow (Kashid et al. 2011)... 

Electroosmotic multiphase flows. Multiphase flows driven by electrical force have attracted increasing levels of interest and potential applications in biomedical techniques. Such flows include unchanging-interface suspension flows, such as blood cell or DNA molecule suspension, and multiphase interface flows, such droplet movement in a microchannel driven by an electric held. No good solutions by conventional CED have been found for such flows. Since much progress has been made in solving the multiphase interface problems by LBM, the LPBM is very promising to provide full simulations and analysis of electroosmotic multiphase flows. 

Table 7.8 Mass transfer literature on slug-drop and deformed interface flow. ...

In the mid-90s, J. Walton and collaborators carried out permeameter tests to clarify the importance of overburden on the geomembrane (Walton et al. 1997). Sand with a permeability of 10 " m/s was used as the geomembrane subgrade. These tests have shown that the results for overburdens greater than 20 kPa could easily be interpreted with the help of Model II and the associated numerical solution for the boundary condition of the permeameter test. Clear indications of interface flow emerged only below 10 kPa. The authors recommend an earth cover of the geomembrane of at least 0.5 m. Under this condition, Eq. 7.45 can be used for the calculation... 

M.F. Gine, A.P.G. Gervasio, A.F. Lavorante, C.E.S. Miranda, E. Carrilho, Interfacing flow injection with capillary electrophoresis and inductively coupled plasma mass spectrometry for Cr speciation in water samples, J. Anal. Atom. Spectrom. 17 (2002) 736—738. 

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