Amperometric titrations polarographic methods

Amperometric titration is a better method than polarographic methodfor quantitative analysis. 

The entire subject of amperometric titrations has been reviewed in a number of monographs on electrochemistry 4-6 a definitive work on this subject also has been published.7 Because the amperometric titration method does not depend on one or more reversible couples associated with the titration reaction, it permits electrochemical detection of the endpoint for a number of systems that are not amenable to potentiometric detection. All that is required is that electrode conditions be adjusted such that either a titrant, a reactant, or a product from the reaction gives a polarographic diffusion current. 

Polarographic methods can be used to estimate the equivalence point of a reaction, provided that at least one of the participants or products of the titration is oxidized or reduced at the microelectrode. When the potential applied across the two electrodes is maintained at some constant value, the current may be measured and plotted against the volume of the titrant, thus, the term amperometric titration. In the case of working electrode-reference electrode pair, the potential of the indicator electrode is maintained at a constant value with respect to a reference electrode, measuring a limiting current, which is proportional to the concentration of one or more of the reactants or products of the titration. 

Several analytical methods will differentiate the "free" (hydrated) metal ions from dissolved complexed metal ions. These methods include specific ion electrodes, polarographic, and other amperometric and voltammetric methods and various types of spectroscopy (see Section 7-10). Specific ion electrodes only respond to the free metal ion for which they are "specific." To determine the relative amounts of complexed and uncomplexed metal ion in a solution, we can use a "wet chemical" method to measure the total concentration of "free + complexed" ions, and then an ion-specific electrode to determine the free metal ion concentration (activity). Care must be taken to eliminate interferences that may affect these measurements. We deduce the concentration of the "complexed ions" by the difference between these two measurements. For example, in the EDTA titration method for hardness, free and complexed calcium and magnesium ion s are measured. 

Kinetic methods of analysis Amperometric titration Coulometric titration Potentiometric titration Spectrometric analysis Fast-sweep polarographic analysis Thermal anal5reis Synthesis experiments Chromatographic experiments. 

In indirect methods, as mentioned in Chapter IV, polarographic-ally inactive substances are transformed into compounds showing waves on polarographic curves, or concentration changes of a polarographically active substance which reacts with the electro-inactive compound to be determined, are measured. Finally, polarometric (amperometric) titrations can be included in this group of analytical methods. 

Miscellaneous Procedures. Most of the other procedures for the determination of —SH groups are variants of the processes indicated above. Of particular interest are the several amperometric titration procedures which, in effect, depend on mercaptide formation. Polarographic methods have also been used. An interesting submicro method for cystine by a Cartesian diver technique has recently been developed the method depends on the catalytic effect of —SS— groups on the decomposition of azide ion to nitrogen (78,94). The method cannot be applied to the direct determination of —SH groups. 

The simplest methods of HTSC analysis are based on the determination of the products of sample dissolution in acidic media. Potentiometric, amperometric, or coulometric titrations are frequently used (mainly for YBCO ceramics [525-527] and their analogs with other rare-earth elements [528, 529], and also for BSCCO [530]). We note particularly the method of potentiostatic coulometric analysis [531], which allows one to analyze thallium cuprate samples over a wide range of the Tl/Cu ratio, and also the method of flow-through coulometry for determining the effective valence of copper [532]. The polarographic determination of Cu content in the samples obtained by dissolving HTSCs in concentrated alkaline solutions with special... 

---