Theoretical Insights on the Relationship Between Detection Limit and Complex Stability of Oxine Ligand

The concept of detection limit was combined with quantum chemical calculations for trace analysis of cadmium and lead in aqueous solution using deprotonated 8-hydroxyquinoline (oxine) as ligand. The DFT study was performed using 6-31G(d), cc-pVTZ and SDD basis sets in combination with different theoretical methods such as; B3LYP, MP2 and M06L implemented in Gaussian 09 program package. The obtained results of the study in the gas and aqueous phases show that the chemical stability of the complex was found in the order Pb-oxine > Cd-oxine. Based on the calculations done, the stability order was relative to the detection limit (LOD) for the two metals Cd and Pb. Thus, a reverse relationship between LOD and binding energy has been found.