Using cryptands to make a negatively-charged solution?
For some reason this question reminds me of Maxwell's demon paradox. You don't really separate anions and cations here; in reality the resulting metal ($\ce{M+}$) cryptand ($\ce{L}$) complex is going to be associated with anionic part ($\ce{X-}$) in organic solvent ($\ce{s}$) after it's being extracted from aqueous phase ($\ce{w}$). For the detailed process, refer to [1], for example.

There are two main processes to consider:


  $$
\begin{align}
\ce{L_\mathrm{s} + M^+_\mathrm{s} &amp;&lt;=&gt; LM^+_\mathrm{s}}\label{rxn:1}\tag{1}\\
\ce{\overline{\ce{L}} + M^+_\mathrm{w} + X^-_\mathrm{w} &amp;&lt;=&gt; \overline{\ce{LMX}}}\tag{2}
\end{align}$$


You would be correct if only \eqref{rxn:1} occurs, however, this is not the case.

Reference


Fyles, T. M. Can. J. Chem. 1987, 65 (4), 884–891. DOI 10.1139/v87-149 (Open Access).