Titrant delivery system

In all the titrator configurations examined by Hleftje st al., the precision-limiting factor seemed to be the end-point detection process rather than the titrant delivery system. 

In routine analysis, often a one-dimensional so-called end-point titration can be automatically carried out up to a pre-set pH or potential value and with a previously chosen overall titration velocity in order to avoid overshoot, the inflection point should be sufficiently sharp and the titrant delivery must automatically diminish on the approach to that point in order to maintain equilibrium, and stop in time at the pre-set value. For instance, the Metrohm 526 end-point titrator changes both the dosing pulse length and its velocity by means of a pulse regulator in accordance with the course of the titration curve in fact, the instrument follows the titration two-dimensionally, but finally reports only a one-dimensional result. The Radiometer ETS 822 end-point titration system offers similar possibilities. However, automated titrations mostly represent examples of a two-dimensional so-called eqilibrium titration, where the titration velocity is inversely proportional to the steepness of the potentiometric titration curve hence the first derivative of the curve can usually also be recorded as a more accurate means of determining the inflection... 

Buret—Any delivery system capable of measuring titrant in 0.05 mL or smaller graduations. 

For simple titrations the equipment necessary is not particularly sophisticated a thermometer, a buret, and an insulated beaker (or even two Styrofoam cups, one sitting in the other) will do. However, if one wants to measure specific heats or the heat of reaction, better control is required. Modern automated thermometric titrators consist of a constant delivery pump for the titrant, a temperature control system for the titrant, an insulated cell, cahbration circuitry, electronic temperature sensing, and a data processing system. Most modem instraments are totally computerized, so different methods can be programmed and mn unattended. 

The titrant is delivered with a motorized syringe pump. This permits the volume of titrant to be calculated from the rate of delivery. These pumps are able to deliver rates of flow down to microhters per minute with high precision. The temperature control system, usually a thermostatted bath for the titrant and a heater for the sample cell, is used to bring the titrant and the sample to exactly the same temperature. This is required for high precision measurements of heat capacity and enthalpy. Modem thermostats can maintain the temperature to within 0.001°C. 

Modem automated thermometric titrators consist of a constant delivery pump for the titrant, a temperature control system for the titrant, an insulated cell, calibration circuitry, electronic temperature sensing, and a data processing system. Most modem instruments are totally computerized, so different methods can be programmed and run unattended. 

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