Malfunction of the Apparatus

This can be diagnosed from the form of the recorded peak, either when actual chemical analysis is performed or from dispersion measurements  

Peak response is sluggish in reaching baseline (large cr value). The system has a dead volume (bad connectors, large flow cell volume, large volume of the terminals of the flow cell) that acts as one or several small mixing chambers. These dead volumes should be eliminated or minimized. 

Baseline drift [Fig. 6.10(7)]. In optical detectors this is due to deposition of material on the windows of the flow cell. Such depositions may often be removed by injecting a reagent that dissolves the material, or by washing the system with a suitable wash liquid or detergent. In potentiometric detector systems, the drift may be caused by a change in the standard cell potential (either drift in the value of the indicator electrode or the reference electrode or both) or by a change in junction potentials. 

Air bubbles. Carrier stream not deaerated gases are formed as a result of a chemical reaction (e.g., CO2 see Section 6.2) or due to a Venturi effect in the flow cell, caused by the sudden decrease of pressure in the flow cell, owing to a larger inner diameter of the flow cell terminals than of that of the tube used. This effect can be eliminated by inserting the connecting tubes all the way into the terminals, so that the orifices of the tubes are as close as possible to the actual cell chamber, and by 

Abrupt noise on peaks [Fig. 6.10(2Z )]. Small air bubbles passing through the detector. The presence of air may either be due to the reasons mentioned above, or be a result of imcomplete filling of the sample loop of the injection port (check sample valve). 

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