Polarographic detectors

Polarographic detectors find application in monitoring the effluent from chromatography columns, including those used in HPLC. Applications of polarography are discussed in Refs 46-48 (Section 16.38). 

An electrical output for a polarographic detector is produced according the above reactions. Again, various electrolytes can be used for this type of detector, but they are usually based on KC1 or AgCl with additional high molecular mass compounds, which are added to prevent the loss of electrolyte during sterilisation. 

This basic polarographic detector has been improved over many years and the main objective has been to improve the measurement sensivity as well as to faciliate the use of the electrode in everyday laboratory practice. Reference gives a very good revision of the efforts of many researches in this field. 

When the new techniques such as ac, sw and pulse polarography were been developed, the polarographic detector in its conventional form appears to come back to everyday practice. These techniques allow measurements in which the capacity current is significantly depressed. 

A polarographic detector was used with the method of Funk [1]. For electrochemical detection it is necessary to use an electrolyte as eluent. A new separation method was developed for this reason. The reduction of O2, which could not be completely excluded, at the detector potential of -1400 mV led to distortion of the chromatogram. Because of this problem, the detection limit was 1 ppm. In the later research, this problem could be solved partially with a method which allowed the degassing of the sample. Detection limits were improved by a factor of 2. 

At polarographic detectors the best S/N ratio was obtained with small mercury drops at a fast drop rate (facilitated by the use of a horizontally placed capillary),... 

Fig- 3- Polarographic detector- 1 - DME, 2 - channel for placement of the third electrode, 3 - pool reference electrode. 

A Model 310 polarographic detector controlled by a Model 174 polaro-graphic analyzer (EG G, Princeton Applied Research Corp.,... 

Princeton Applied Research Ltd., Princeton, N.J., U.S.A. Princeton Applied Research, Model 310 Polarographic Detector. 

Fig. 12.20 Typej of amperomctric electrochemica] detector used in high-pressure liquid chromatography, (a) Tubular electrode, (b) Thin-layer channel cell, (c) Disc electrodes, (d) Rotating-disc electrode, (e) Wall jet. (f) Polarographic detector mercury Aow parallel to and in same direction as, electrolyte flow, (g) Mercury flow parallel to, and in opposite direction to, electrolyte flow, (h) Mercury flow perpendicular to electrolyte flow, (i) Porous electrode.

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