Hardware-controlled titrators

According to the classification established by Pungor et al. [56], there are three levels of automatic tltrators defining as many degrees of automation, namely (a) hardware-controlled tltrators, (b) microprocessor-controlled titrators and (c) computer-controlled tltrators. 

The E536 differs from earlier Metrohm Instruments In that the rigid mechan- 

FIs- 13.3 Hardware-controlled Metrohm E536 titrator. (Reproduced with permission of Metrohm Herisau, AG). 

The Radiometer RTS 822 titrator Is eimiiar In performance to the Metrohm titrator described above. 

Provided the input voltage Is less than the reference level of Ci, the output 

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Fig. 13.4 Scheme of logic circuit of the hardware-controlled titrator designed by Hieftje et al. Ci and C2 are comparators Gi-Ge are gates I1 and I2 are inverters Mi and M2 denote monostables adjustable from 100 ps to 1 ms and T1 denotes a 2N3439 transistor. (Reproduced from [57] with permission of the American Chemical Society),... 

Figure 4-4 Hardware set up for NMR-controlled titrations NMR spectrometer, 2 PC, 3 burette, 4 glass electrode and potentiometer, 5 thermostat, 6 thermostated titration vessel, 7 stirrer, 8 pump, 9 NMR probe head.

Consequently the dynamic chemiceil shift is a ftmction of intrinsic ion-specific chemical shifts and molar fractions of protolytic species, where the latter depend simply on stability constants and concentrations of reagents used. Obviously the molar fi actions depend on the state of titration and the actual pH in solution. may be plotted as a ftmction of the state of titration S,r spectra) or as a ftmction of pH 8, pH spectra) as shown below. The hardware and software set-up for PC-guided NMR-controlled titrations or alternatively titration-dependent NMR spectroscopy is shown in Figure 4-4 and Figure 4-5 below. 

Figure 4-13shows the molar fractions of phenylephrine as functions of pH. Obviously in phenylephrine deprotonation of die ammonium cationic site is preferred to deprotonation of the phenolic function. Details of basic principles, hardware and software concepts and applications of NMR-controHed titrations are described in [14], [15], [16], [17], [18], [19], [20], [21], [22], Results from more laborious UVA7is [23], [24] and now the easily accessible automated NMR-controlled titrations of phenylephrine [22] are consistent The method of NMR-controlled titration is a powerful tool in analytical and structural chemistry, and was recently applied successfully to a series of biorelevant phosphorus compounds [18],[19],[20],[21],... 

Recently, an automatic color video image analysis system was developed to quantify antigen expression (androgen receptor) (Kim et al.,T999a). This system provides a linear relationship between the antigen content and mean optical density of the immunoperoxidase-substrate reaction product. Titration of antibody, concentration, and reaction duration of the substrate can be optimized with this system. The imaging hardware consists of a Zeiss microscope, a three-chip charge-coupled-device camera, a camera control board, and a Pentium-based personal computer. 

The coulometric titrator developed by Howard and Henzel consists of a titration cell, an electrochemical titrant generation system with a constant current source, an Orion 801A Ioanalyser pH-meter, a DEC PDP 8/E minicomputer, a teletype with a paper tape punch and the required Interface hardware to allow the minicomputer to control the titrant generation rate, acquire the data and output them. The titration cell is a thermostated 30-mL weighing bottle fitted with a rubber stopper modified to accommodate the electrodes and allow for purging with nitrogen. 

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