Single-bead string reactor

In single bead string reactors the enzyme is bound both to the reactor wall and to a carrier within the reactor. Compared with open tubular reactors this reactor type provides a higher conversion at lower sample mixing. 

Packed bed reactors [51] incorporate beads, and the presence of these solid materials in the analytical path also has a beneficial influence on the flow pattern, reducing sample broadening and, hence, sample dispersion. However, hydrodynamic pressure tends to be increased, especially when small particles and/or particles with heterogeneous sizes are used. Single bead string reactors [5] were proposed to circumvent this drawback. These reactors utilise large (particle diameters about 70% or the tube inner... 

Analysis of Eq. 3.6 reveals that the function C =/(f) tends to be Gaussian and approaches the Taylor model when N increases. On the other hand, the validity of this equation is dubious for low N values, as the shape of the curve skews. This means that the model provides good results when applied to unsegmented-flow systems with long reactors but fails to describe sample dispersion in short reactors. This limitation of the model is not as relevant to efficient mixing devices such as the single bead string reactor [5,52],... 

J.M. Reijn, W.E. van der Linden, H. Poppe, Dispersion in open tubes and tubes packed with large glass beads. The single bead string reactor, Anal. Chim. Acta 123 (1981) 229. 

Fig. 15.11 Colorimetric phenol analyser, (a) Details of the distillation unit, condenser and heat exchanger, (b) General scheme of the instrument. A, sampler B, heating bath with heating rod C, distillation head D, condenser E, heat exchanger F, strip-chart recorder G, colorimeter H, coll J, single bead-string reactor K, peristaltic pump (1) wash water (2) sample (3), air (4) phosphoric acid (5) overhead condensate (6) 4-AAP reagent (7) Fe(III) reagent (8) air (9) level control (10) bottoms draw (11) debubbler draw. (Reproduced from [39] with permission of Elsevier).

The coiled tube has so far been the most frequent geometric form of the FIA microreactor. However, it is useful to review all channel geometries (Fig. 2.8). These are straight tube (A), coiled tube (5), mixing chamber (C), single-bead string reactor (D), 3-D or knitted reactor (E)y and imprinted meander (cf. microconduits Section 4.12) or combinations of these geometries. 

Figure 2.8. The microreactor geometries most frequently used in FIA A, straight open tube B, coiled tube C, mixing chamber D, single-bead string reactor (SBSR) and E, knitted reactor. (For an example of the imprinted meandering reactor, see Chapters 3 and 4.)...

A single-bead string reactor (SBSR)(Fig. 2.8D), originally used in postcolumn derivatization [2.3] and later introduced to FIA by Reijn et al. [146], is the most effective device to promote radial mixing in a tubular reactor. The SBSR allows symmetrical peaks to be obtained... 

Single-bead string reactor (40 cm, 0.86 mm id) filled with 0.5 mm glass beads the effective cross-sectional area is different from the nominal one. 

J. M. Reijn, H. Poppe, and W. E. van der Linden, Kinetics in a Single Bead String Reactor for Flow Injection Analysis. Anal. Chem., 56 (1984) 943. 

R. Gnanasekaran and H. A. Mottola, Flow Injection Determination of Penicillins Using Immobilized Penicillinase in a Single Bead String Reactor. Anal. Chem., 57 (1985) 1005. 

Figure 5. Comparison of single bead string reactor and jet mixer. In both reactors turbulence is created in the flowing stream by alternating wide and narrow flow paths.

Enzymes have been successfully applied in the field of continuous-flow methods, especially in immobilized-enzyme reactors such as packed column and open tabular wall and single bead string reactors. All these systems have facilitated the development of FIA methods of great interest to biochemsitry and clinical and pharmaceutical chemistry, with the aid of various detectors, notably of the potentiometric, amperomet-ric, photometric, luminescence, radiometric and colorimetric types. 

Schematic diagram of an FIA-FAAS system. PP, peristaltic pump V, six-way valve V2, selection valve iji, Triton X-100 flow rate q2, diluent flow rate q, HCl (pH 4) sample, H2O (pH 7) and NaOH flow rates SRC, solid reagent column R, R2, and R3, reactors D, detector SBSR, single-bead string reactor. (From Di Nezio, M.S., Palomeque, M.E., and Fernandez Band, B.S., Talanta, 63, 405, 2004. With permission.)...

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