Zsófia Fehér

Injection techniques in dynamic flow-through analysis with electroanalytical sensors

Abstract The theoretical and practical aspects of injection techniques used in flow-through systems with ion-selective electrodes and voltammetric detectors are discussed. Mathematical descriptions of the measuring systems based on the use of mixing chambers in the analytical channel are briefly outlined. The effects of different parameters on the analytical signals are described theoretically and experimentally. The methods developed for the evaluation of the analytical signals are presented in detail.

Electrochemical detection in liquid flow analytical techniques: Characterization and classification (IUPAC Technical Report)

Liquid flow analytical techniques are classified, and definitions are provided of flow-injection analysis, segmented flow analysis, flow titration, continuous monitoring, liquid chromatography, and capillary electrophoresis. Electrochemical detection and flow through detection cells are characterized with respect to the surface and bulk detection. The detector performance is discussed in terms of its principal analytical parameters, such as detection limit and dynamic concentration range, as well as its dynamic characteristics, such as the response time, sampling frequency, transport lag, and long-term stability. Moreover, different detection modes are critically evaluated, including both potentiostatic and galvano-static techniques. Factors influencing sensitivity and detection limit, which include electronic and hydrodynamic approach, are also discussed. Different detector designs are critically reviewed, and the special features of electrochemical detectors for flow analytical techniques are emphasized.

The application of electroanalytical detectors in continuous flow analysis

Abstract A survey is given of the different fields of application of flow-through techniques employing electroanalytical detectors. Emphasis is placed on recently developed titration techniques.

Evaluation of acid-base titration curves obtained by the triangle-programmed titration technique in flowing solutions.

Different evaluation techniques for triangle-programmed coulometric acid-base titration curves obtained with various detector systems are compared. In the case of potentiometric detection, hardware differentiation and linearization of the titration curves was investigated. Photometric end-point detection with single or mixed indicators was also studied. It was concluded that among the techniques studied the hardware potentiometric differentiation and the photometric detection with an indicator mixture are the most advantageous.

A polarographic and spectrophotometric routine analyzer for assaying content uniformity in pharmaceutical quality control

Abstract A serial analyzer with polarographic and spectrophotometric detection has been designed to speed up content uniformity tests in pharmaceutical quality control laboratories. The advantages of flow and discrete analysis are combined to provide the required speed and precision. Pharmaceutical preparations of diazepam, nitrazepam, spironolactone and pyridinolcarbamate have been tested satisfactorily. The system is easily constructed from commercially available hardware and a few home-made units. The problem of sample deaeration before polarographic measurements in flow systems is solved succesfully in a very simple way.

Application of flow-through techniques to drug dissolution studies

Two flow-through techniques, i.e., flow injection and triangle programmed flow titrimetry, have been used to follow the dissolution of durgs from pharmaceutical preparations. The applicability of direct ultraviolet spectrophotometry as a detection technique in flow injection was demonstrated for dissolution studies of nitrazepam- and metronidazole-containing pharmaceutical preparations. In the application of the triangle programmed titration technique, the dissolution of promethazine and ampicillin from pharmaceutical preparations was studied.

Determination of the drug content of pharmaceuticals containing phenothiazine compounds by triangle programmed flow titration

SummaryA flow-through triangle programmed coulometric titration technique is worked out for the determination of phenothiazine compounds. The oxidation reaction of phenothiazines with hypobromite ion served as titration reaction. A biamperometric detector cell has been used for following the titration process. The titration technique has been used for the determination of the drug content (average and individual) of chlorpromazine, promethazine, diethazine and trifluoperazine in pharmaceutical preparations. The relative standard deviation was in the range of 2.0 to 3.5%.

Automatic Electrochemical Analysis: Part 2

V. AUTOMATION IN TITRIMETRIC ANALYSIS A. Introduction Titrimetry is the most commonly used procedure among quantitative analytical chemical methods. Automation in titrimetry started with the development of different instrumental end-point indication techniques. Potentiometric, amperometric, and conductimetric end-point indication provides a certain objectivity in following the course of titration and in many cases enables one to perform special analytical tasks, but at the same time the analysis becomes lengthy if the points of titration curves are drawn manually.

Novel potentiometric monitoring combined with coulometric reagent generation

A potentiometric monitor incorporating a flow-through analysis channel has been developed based on the standard addition or subtraction principle. Programmed addition of standard or reagent was carried out at a given point of the flow-through system by current-programmed coulometry. A computer was used for data acquisition, for electric noise rejection, for signal recognition and for calculating the analytical results. The characteristics of the monitor system have been investigated under conditions optimised for the chloride determination, and the performance of it was checked by monitoring the chloride concentration in tap water.