Question

Terminology

1. suppressor

2. Self- Regenrating (suppressor)

3. TOC

4.EOF vs Migration

5. Coulometry

6. Voltammentry

7. Amperometry

8. Potentionmetry

9. Combination Electorde

10. Alkaline Error

Answer 1

1. Suppressor and Self regenerating Suppressor

Suppression plays a key role in ion-exchange chromatography and conductivity detection. It is widely used, e.g., for the analysis of anions and organic acids.Suppression as a practical solution for ion chromatography decreases the background conductivity of the eluent minimizes baseline noise optimizes the signal-to-noise ratio increases the sensitivity of the measuring system.

TOC

Total organic carbon (TOC) is the amount of carbon found in an organic compound and is often used as a non-specific indicator of water quality or cleanliness of pharmaceutical manufacturing equipment.  A typical analysis for TOC measures both the total carbon present and the so-called "inorganic carbon" (IC), the latter representing the content of dissolved carbon dioxide and carbonic acid salts. Subtracting the inorganic carbon from the total carbon yields TOC.

Coulometry is based on an exhaustive electrolysis of the analyte. By exhaustive we mean that the analyte is completely oxidized or reduced at the working electrode or that it reacts completely with a reagent generated at the working electrode. There are two forms of coulometry: controlled-potential coulometry, in which we apply a constant potential to the electrochemical cell, and controlled-current coulometry, in which we pass a constant current through the electrochemical cell.In coulometry, we monitor current as a function of time.Knowing the total charge,determine the moles of analyte

Voltammentry

In voltammetry we apply a time-dependent potential to an electrochemical cell and measure the resulting current as a function of that potential. We call the resulting plot of current versus applied potential a voltammogram, and it is the electrochemical equivalent of a spectrum in spectroscopy, providing quantitative and qualitative information about the species involved in the oxidation or reduction reaction

Amperometry

The term amperometry describes the technique in which a fixed potential (again measured with respect to a reference electrode) is applied to a working electrode and the current resulting from oxidation or reduction reactions occurring at the working 292 Chapter 10 electrode is measured. In the case of chromatographic detection. the working electrode is located in a suitable flow-cell, through which the eluent stream passes. The analyte to be detected undergoes a Faradaic reaction if the applied potential has appropriate polarity and magnitude.

Potentiometry

In potentiometry we measure the potential of an electrochemical cell under static conditions. Because no current—or only a negligible current—flows through the electrochemical cell, its composition remains unchanged. This a benefit of potentiometry.

Twolectrodes are required in this process

1) Indicator Electrode – potential responds to activity of species of interest

2) Reference Electrode – chosen so that its potential is independent of solution composition

Alkaline error

Alkaline Error or Sodium Error occurs when pH is very high (e.g., 12) because Na + concentration is high (from NaOH used to raise pH) and H + is very low. Electrode responds slightly to Na + & gives a lower reading than actual pH. This is related to the concept of selectivity coefficients where the electrode responds to many ions but is most selective for H +. Problem occurs because Na + is 10 orders of magnitude higher than H + in the solution.