1, 3-Xylyl and 2-bromo-1, 3-xylyl crown ethers have been tested as Ion-selective electrodes In poly (viny1 chloride)(PVC) membranes. The pattern of relectivlty appears to be essentlalty Independent of rlng dre and probably reflects the ease wllh wMch wbswutkn ol watw mokculesfrom the Inner hydratlon sphere of the lon can be effected. The ionophores have proved to be good K+ neutral carrlers showlng near-" stIan mporms to this bn, In the range ...