Automatic titrators computer-controlled

Derivative methods work well only when sufficient data are recorded during the sharp rise in plT occurring near the equivalence point. This is usually not a problem when the titration is conducted with an automatic titrator, particularly when operated under computer control. Manual titrations, however, often contain only a few data points in the equivalence point region, due to the limited range of volumes over which the transition in plT occurs. Manual titrations are, however, information-rich during the more gently rising portions of the titration curve before and after the equivalence point. 

Avdeef, A. Bucher, J. J., Accurate measurements of the concentration of hydrogen ions with a glass electrode Calibrations using the Prideaux and other universal buffer solutions and a computer-controlled automatic titrator, Anal. Chem. 50, 2137-2142 (1978). 

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. 

A typical laboratory preparation recipe for this coprecipitation route is provided hereafter. The experimental setup consists of a computer-controlled automatic titrator, a syringe pump, and a reactor, heated by a thermostat. 

The third method for automatic monitoring of the gel phase synthesis has long been known [ 196] - the perchloric acid titration on polymer — and recently was built into a computer-controlled peptide synthesizer [134]. Here, the results of the analytical determinations are fed back into the monitor system, which is programmed to optimize the course of the synthesis based on the titration data. This example of best realized automatization to date, however, is restricted to acid-tolerant synthesis strategies. The limiting chemical conditions of the analytical principle in use were already discussed on p. 43—44. 

All titrations were performed using an auto titrator Model AT-97 manufactured by Mayura Analytical Pvt. Ltd., Bangalore, India. This auto titration system consists of a motor-driven titrant dispenser, a mechanical stirrer and electrodes coupled to a pH/ion analyzer and controlled by a personal computer for automatic titration and data acquisition and processing. The titrant was added from weight burette. The e.m.f. readings were recorded with an autotitrator using platinum as indicator electrode and saturated calomel electrode as reference electrode. 

Automatic titrators that are electronically equipped to compute the first and second derivative of pH with respect to time, and hence reagent flow, can automatically locate the equivalence point. The first derivative, which is the slope of the titration curve, reaches a maximum at the equivalence points. The second derivative changes sign at the equivalence points. A plot of first derivative helps in the control system design because it is indicative of the pH process sensitivity. Figure 3-2a shows a plot of the first derivatives for the weak acid and weak base titration curv e in Figure 3-le. For more information on automatic titrators, consult Reference 3.3. 

Sets of parameters such as burette volume, reagent strength, increment size and time interval, end-point potential, format of results, etc., can be stored and recalled from memory as standard methods for routine analyses. An alphanumeric keyboard is used to enter or change the parameters, to take individual pX or mV readings and to control the rinsing and the refilling of the automatic burette. Raw titration data and computed analytical results can be printed out as a permanent record, and titration curves can be produced on a chart recorder or VDU. 

As a final illustration of the use of computers in coulometric titrations, a method of automatic dilution of samples developed by Ruzicka, Christian, and co-workers is discussed. Flow injection (FI) involves the injection of a solution of analyte into a flowing carrier stream contained in narrow-bore tubing (e.g., 0.5 mm diameter) where controlled dispersion of the injected solution takes place... 

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 use of modern temperature detection methods in thermal titration has increased considerably in recent years, with several commercial instruments now available. Marini and Martin have recently reviewed this field (Marini and Martin, 1979) extensively so that only a brief discussion will be given here. We have developed a combined pH—thermal differential titration apparatus that is modelled after our earlier single-cell system (Berger et al., 1974 Marini et al., 1980). Figure 14 shows the essentials of the instrument. The unique part of this device is that it is under microprocessor control. The computer starts the titration, records the data, and speeds up or slows down the titration automatically if the curve is changing too rapidly. Data-correction programs adjust for response time and... 

Automatic oxygen titration units are commercially available, e.g., the Metrohm 665 Dosi-mat Oxygen Trtrator, which consists of a remote controlled burette and a UV detector for customer designed bottles. An analog-to-digital interface is required to connect the unit to a computer. 

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