The present invention relates to the synthesis of lipophilic or immobilized monobasic phosphate (H
2
PO
4
) ionophores (7, 8a, 8b and 11) to be used as ion recognition molecules for monobasic phosphate (H2PO
4
″) in the cocktail preparation of hydrophobic polymer membranes in ion selective electrode (ISE) or ion-sensitive field effect transistor (ISFET) chemical sensors for detection of monobasic phosphate (H
2
PO
4
) ionic species in soil, synthetic media, hydrophonic liquid, tree sap, ground water and rivers.