Quenching of lanthanides luminescence of a novel long live Tb(III)- Ethyl 1-allyl-1,2-dihydro-4-hydroxy-2-
oxoquinoline-3-carboxylate (EADHOC) as a ligand to form a complex with molar ratio 1:3 in solution has been studied
in ethanol in presence of organophosphorus pesticides both Di-chlorvos (P1) and paraoxon-Ethyl (P2). The intensity of
luminescence of Tb(III) –(EADHOC) decrease as the concentration of pesticides increase. The quenching effect was
observed with both pesticides. Direct methods of determination of pesticides under investigated have been developed by
using luminescence of Tb(III) –(EADHOC) probe in a solution. The linear range for determination of the selected
pesticides P1(Di-chlorovos) and P2(Paraoxon-Ethyl) is 7 and 1 μM. the detection limits were 1.9 and 9.8 μM for P1(Dichlorovos)
and P2 (Paraoxon-Ethyl) respectively. The Thermodynamic parameters and binding constant (K) of OPs
with Tb(III) – (EADHOC) were evaluated. Including the value of enthalpy (ΔH ) and entropy( ΔS ) changes for Probe
interaction with pesticides. As the natural water sample in this study don't contain the above mentioned OPs over the
limit detected by the methods, a recovery study was carried out after the addition of the adequate amount of
organophosphorus pesticides under investigation.