Wall-jet flow cell

FIGURE 3-22 Coimnon detector configurations (a) thin-layer (channel) and (b) wall-jet flow cells. WE = working electrode. 

CdTe Wall jet flow cell growth of thin films 1999 [114]... 

Scheme 17.1. Schematic diagram of biosensor and wall-jet cell. (A) Screen-printed electrode front-view (1) silver ink acting as reference electrode, (2) graphite ink acting as working electrode successively modified with PB and (3) silver ink acting as counter electrode. (B) PB-modified screen-printed electrode side-view (1) polyester film as support for printing step, (2) graphite ink and (3) PB layer. (C) Wall-Jet flow cell side-view (1) inlet of the flow, (2) outlet, (3) cell made of Teflon and (4) glucose biosensor. (D) Wall-jet flow cell front-view (1) outlet, (2) inlet of the flow, (3) O-ring, (4) flow-cell and (5) glucose biosensor. Reprinted from Ref. [4] with permission from Elsevier.

Fig.4. Flow-injection response of PVC electrode containing in the membrane dibenzo-18-crown-6 and dioctyl adipate conditioned in potassium chloride solution. Injected 80 nmol of each species. Carrier 1 mM LiCl. Flow-rate 6.8 ml/min. Wall-jet flow-cell arrangement. 

The EDT Research wall-jet flow-cell LC03 (see Figure 1) gave a detection limit of 100 pg of 3,4-chlorofluoroaniline under similar conditions. In operation the glassy carbon electrode showed much better mechanical and chemical stability towards a wide range of solvents of interest in HPLC than the carbon-paste electrode. 

Until recently, the fast rate at which a surfactant layer forms at the solid-liquid interface has prevented accurate investigation of the adsorption process. As a result, the mechanism of surfactant adsorption has been inferred from thermodynamic data. Such explanations have been further confused by misinterpretation of the equilibrium morphology of the adsorbed surfactant as either monolayers or bilayers, rather than the discrete surface aggregates that form in many surfactant-substrate systems.2 However, the recent development of techniques with high temporal resolution has made possible studies of the adsorption, desorption,25>38,4i,48-6o exchange rates of surfactants. In this section, we describe the adsorption kinetics of C ,TAB surfactants at the silica-aqueous solution interface, elucidated by optical reflectometry in a wall-jet flow cell. The adsorption of C jTAB surfactants to silica is the most widely studied system - and hence the adsorption kinetics can be related to the adsorption process with great clarity. For a more thorough review of adsorptions isotherms, the t5q)es of surfactant structures that form at the solid-liquid interface, and the influence of these factors on adsorption, the reader is directed to Reference 24. 

Munoz, E., Palmero, S. (2004) Potentiometric stripping of arsenic(III) using a wall-jet flow cell and gold(III) solution as chemical reoxidant. Electroanalysts. Vol. 16, pp. 1956-1962... 

From an hydrodynamic point of view the behavior of an electrode in a wall-jet flow cell is similar to the most common electrochemical hydrodynamic tool, i.e.. 

Gorton et al. (1985) employed GOD adsorbed on spectral carbon for glucose determination in a wall jet flow-through cell of an FIA system. Up to 120 samples per hour have been measured with good precision. The enzyme electrode was stable for 3-7 days. Coating of the spectral carbon by a Pd/Au layer of 20 pm thickness permits H2O2 to be anodically indicated at potentials as low as +350 mV vs SCE. The enzyme activity is not affected by this modification. 

A. G. Fogg and A. M. Summan, Simple Wall-Jet Detector Cell Holding Either a Solid Electrode or a Sessile Mercury-Drop Electrode and an Illustration of Its Use in the Oxidative and Reductive Flow Injection Voltammetric Determination of Food Colouring Matters. Analyst, 109 (1984) 1029. 

The enzyme modified electrode was fitted into a Teflon holder and inserted into a flow-through wall-jet amperometric cell (28), The enzjmie electrode was used as the working electrode, an A AgCl (0.1 M KCl) electrode as reference electrode, and a platinum wire served as the auxiliary electrode. The electrodes were connected to a three-electrode potentiostat (Zata Elektronik, Lund, Sweden), controlling the applied... 

Figure 3.6 Different FIA cell configurations (a) Wall-jet type cell (b) commercial thin layer flow cell (c) Plexiglass flow cell and (d) micro flow cell. Cells (a), (c), and (d) were built in the author s laboratory.

Di Benedetto, E. T., and T. Dimitrakopoulos, 1997. Evaluation of a new wall-jet flowthrough cell for commercial ion-selective electrodes in flow injection potentiometry. Electroanalysis 9 179-182. 

The most widely used amperometric detectors are based on the thin-layer and wall-jet configurations (Figure 3-22). The thin-layer cell relies on a thin layer of solution that flows parallel to the planar electrode surface, which is imbedded in a... 

Tubular Planar (parallel flow) Thin-layer cell Planar (perpendicular) Wall-jet detector 1= 1.61 nFC(DA/r)2/3U123 i = 0.68 nFCD2l3v- 6(A/b)V2UV1 i = 1.47 nFC(DA/b)2/3U123 i = 0.903nFCD2f3v- 6A3/4u 2 i = 0. mnFCD2/3v-5/ua-V2A3/tU3/4... 

Fig. 10. Flow-through electrochemical cell designs. I, Planar geometries, thin-layer (A) and wall-jet (B) flow cell designs. II, Cylindrical geometries, open tubular (A), wire in a capillary (B), and packed-bed (C) flow cell designs...

FIGURE 13.3 Hydrodynamic voltammograms of Prussian blue-modified electrodes in a wall-jet cell with continuous flow of 0.8ml/min ( ) background in air saturated solution (0.1 M KC1 + 0.01 M phosphate, pH 6.0), ( ) 0.1 mM H2O2. 

The analytical performance of Prussian blue-modified electrodes in hydrogen peroxide detection were investigated in a flow-injection system equipped with a wall-jet cell. Nano-structured Prussian blue-modified electrodes demonstrate a significantly decreased background, which results in improved signal-to-noise ratio. 

Substrate orientation should be examined to determine if some planes are preferentially etched. If there is preferential etching taking place, what is its dependence on the etching cycle conditions The hardware being used for these studies should also be investigated. Very little has been done to optimize the flow cell. It is anticipated that a hydrodynamic electrode system such as a rotating disk or wall jet should work as well. 

Flow Cells, Channel Electrodes and Wall-Jet Electrodes... 

Figure 7.8 Schematic representation of a typical wall-jet electrode used for electroanalytical measurements (a) contact to Pt disc electrode (the shaded portion at the centre of the figure) (b) contact to ring electrode (c) AgCl Ag reference electrode (d) Pt tube counter electrode (e) cell inlet (f) cell body (made of an insulator such as Teflon), (b) A typical pattern of solution flow over the face of a wall-jet electrode, showing why splash back does not occur. Part (a) reproduced from Brett, C. M. A. and Brett, A. M. O., Electroanalysis, 1998, 1998, by permission of Oxford University Press.

Convection-based systems fall into two fundamental classes, namely those using a moving electrode in a fixed bulk solution (such as the rotated disc electrode (RDE)) and fixed electrodes with a moving solution (such as flow cells and channel electrodes, and the wall-jet electrode). These convective systems can only be usefully employed if the movement of the analyte solution is reproducible over the face of the electrode. In practice, we define reproducible by ensuring that the flow is laminar. Turbulent flow leads to irreproducible conditions such as the production of eddy currents and vortices and should be avoided whenever possible. 

Figure 4.11 — (A) High-volume wall-jet cell. (B) Bubble-through flow-cell. (1) Cell body (2) membrane (3) ion-selective electrode (4) steel spring (5) inner reference solution (6) sample guide.

Cobben et al. [151] designed and tested a wall-jet and a flow-through cell of this type. The wall-jet cell (Fig. 4.19.A) consisted of two parts, A and B. Part A was a Perspex block of 24 x 24 x 20 mm (1) furnished with two resilient hooks (3) for electrical contact. The hooks were pressed on the surface of the contact pads of the CHEMFET (4), the back of which lay on the Perspex surface. In this way, the sensor gate was positioned in the centre of the Perspex block, which was marked by an engraved cross. Part B was... 

The flow-through cell developed by Cobben et al. (Fig. 4.19.B) also consisted of two Perspex blocks, A and B. Part A was identical with that used in the previous wall-jet cell, whereas part B (2) was a knotted block (24 X 24 X 15 mm ) into which two holes were drilled towards the centre... 

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