“…However such materials are not available in abundance, which has made the development of ISE a slightly difficult job. Nevertheless in recent years some new groups of compounds such as Schiff bases [27][28][29], porphyrins [30,31], calixaranes [32,33], macrocyclic compounds [34,35] and other group of compounds [36,37] have been developed which have a coordinating cavity and due to which they tend to show high affinity for some particular metals and poor for others. Among these groups, Schiff bases are the item of choice, because it is easy to form them with varying cavity size.…”