Retention factors with complexing eluents

The approach is to measure retention times of metal cations on columns containing low-capacity resins with eluents containing perchloric acid or various perchlorate salt.s. The perchlorate anion is used to eliminate any possible complexing of a metal ion by the eluent anion. Retention factors (k) are calculated from the retention data. 

As discussed in the early part of this chapter, macro-cyclic complexes are generally more stable in nonaqueous solvents than in aqueous solution. Therefore, it is expected that adding 18-crown-6 to a nonaqueous mobile phase would increase the retention time of cations to be separated. Fritz s group added 18-crown-6 to a nonaqueous IC mobile phase to study the retention of alkali metal cations and ammonium ion on a sulfonic acid cation-exchange resin. The retention factors of all the ions increased with increasing concentration of 18-crown-6 in acetonitrile eluent containing 1 mM methanesulfonic acid. Most notably. 

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