Dyeing processes sensor

Dyeing-process behaviour with and without sensor system... 

The optical sensors are composed of ion-selective carriers (ionophores), pH indicator dyes (chromoionophores), and lipophilic ionic additives dissolved in thin layers of plasticized PVC. Ionophores extract the analyte from the sample solution into the polymer membrane. The extraction process is combined with co-extraction or exchange of a proton in order to maintain electroneutrality within the unpolar polymer membrane. This is optically transduced by a pH indicator dye (chromoionophore)10. 

Thus as in the titration curves in the solution, the response range of the pH indicators for a signal protonation process is about 2-3 pH units for absorbance-based measurements. Long-range pH sensing has to be achieved by using mixed dyes doped in solid support. While fluorescence sensors have a wider linearity because it is only related to one form of the indicator. 

Urea in kidney dialysate can be determined by immobilizing urease (via silylation or with glutaraldehyde as binder) on commercially available acid-base cellulose pads the process has to be modified slightly in order not to alter the dye contained in the pads [57]. The stopped-flow technique assures the required sensitivity for the enzymatic reaction, which takes 30-60 s. Synchronization of the peristaltic pumps PI and P2 in the valveless impulse-response flow injection manifold depicted in Fig. 5.19.B by means of a timer enables kinetic measurements [62]. Following a comprehensive study of the effect of hydrodynamic and (bio)chemical variables, the sensor was optimized for monitoring urea in real biological samples. A similar system was used for the determination of penicillin by penicillinase-catalysed hydrolysis. The enzyme was immobilized on acid-base cellulose strips via bovine serum albumin similarly as in enzyme electrodes [63], even though the above-described procedure would have been equally effective. 

Figure 3.13 Two-step grafting process in order to construct a sensor for the detection of volatile organic compounds based on the well-known solvatochromic fluorescent phenoxazinone dyes. Hydrophobizing of the surface of MCM-41 with silazanes leads to better performance of this sensor.

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