Detector wall-jet

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... 

Wall-jet detector, 88, 89, 162 Whole cell sensors, 182 Working electrodes, 2, 107... 

Considering the wall-jet or impinging-jet type of detectors, there has been some confusion in the literature about the names of the different types149 Fig. 5.24 shows the difference between the free and the confined wall-jet detectors, where the flow jet is appreciably smaller than in the impinging-jet types. 

Figure 3.26 — Schematic view of large volume wall-jet detector (A) inlet (B) electrode array (C) counter-electrode (D) referaice electrode (E) outlet. Also shown (right) bottom view of the electrode array. (Reproduced from [191] with permission of the American Chemical Society).

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. 

Peak width (at half height) Workmg elechode Wall jet detector... 

H. Gunasingham, Analytical applications of the wall-jet detector. Trends Anal. Chem., 1988, 7, 217-221. 

Notes Ii(A) limiting current, cj (moIm ) bulk concentration of the reactant A, for other quantities see Table 6 R, Rj (m) radius of the disc or tubular electrode S (m ) surface of the working electrode in thin-layer, rotating disc and wall-jet system respectively b (m) dimension of the electrode perpendicular to the liquid-flow F (m s ) sample inlet rate a (m) diameter of the inlet nozzle of the wall-jet detector = laminar convection, 1 streaming perpendicular to the electrode R a is assumed. 

Detectors of the first type are called wall-jet detectors and this name is quite realistic, as can be seen in the Figure 11 where the well-known detector of Fleet and Little [17] is presented. (An analogous model has been developed by Pungor and co-workers in the sam year 1974)[35]. The solution is introduced via a nozzle and impinges normally onto the planar disk electrode. The stream is then split into two opposed channels, connecting the working electrode with two other electrodes. The distance between the nozzle tip and the electrode surface is adjustable and determines the effective cell volume. The typical cell volume (geometrical) is less than 1 jjI. 

Wall-jet detectors have several useful characteristics ... 

Fig. 11. Wall-jet detector. 1 - lead to the glassy carbon electrode.

Electrochemical detectors of the waU-jet type (Fig. 9.6, left) are simple, robust and flexible. Working and counter electrodes (if necessary, the reference electrode as well) are positioned in a large solution reservoir. The disc-shaped working electrode is in plane with one of the walls of this reservoir. In front of it, a fine nozzle is arranged. The carrier solution is ejected as a sharp jet directed towards the electrode area. The jet washes away quickly residues of older solution from the electrode surface and generates a powerful convection. Thus, a relatively high value of the diffusion-limited current is achieved with an amperometric operation, as is a fast response if operated potentiometrically. The virtual dead volume of wall-jet detectors is extraordinarily smalL It cannot be derived from the cell geometry, but must be determined experimentally by calibration. 

A multitude of cell designs, many of them interrelated, has been described. Figure 12.20 indicates some of the possible geometries. Of these, the two most common are the channel (including the thin layer type) and wall-jet detectors. 

Stojanovic RS, Bond AM, Butler ECV (1992) A comparative-study of the cylindrical wire, thin-layer, and wall-jet detector cells for the determination of inorganic arsenic by ion exclusion chromatography with constant and pulsed amperometric detection. Electroanalysis 4 453 61... 

The reaction coil is 20 cm of coiled stainless steel capillary tubing. The guard column (1.5 cm length, inside diameter) which protects the more expensive Cjg reversed-phase separating column (length = 30 cm, inside diameter = 3.9 mm) is packed with silica-based Cig material. Typical electrochemical detector cells which can be used are (i) Model TL-5 thin layer detector cell obtained from Bioanalytical Systems, (ii) Model EA 1096 wall jet detector cell obtained from Metrohm. 

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