Explanation of Chromatographic Peaks

When a sample containing salts of various anions, M A , etc. is 

After the sample plus has passed, the baseline is quickly restored to that obtained with the eluent alone. The solute anions gradually move down the column with the eluent. The total ion concentration in solution in the column is fixed by the eluent anion concentration because solute anion can only enter the solution phase by uptake of an equivalent number of eluent anions. The change in conductance when a sample solute band passes through the detector results from replacement of some of the eluent anions by solute anions, although the total ion concentration remains constant. 

This change is directly proportional to the sample concentration and the difference in equivalent conductance of the eluent anion and the sample anion. Conductivity detector response is discussed in greater detail in Section 6.3.6. 

---