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Determination of Promethazine Hydrochloride with Palladium(II) and Na2WO4 by Resonance Rayleigh Scattering and Resonance Nonlinear Scattering Spectra

ABSTRACT In a weak acidic medium, promethazine hydrochloride (PMZ) reacted with Pd(II) to form 2:1 cationic chelate ([Pd(PMZ)2]2+), it further reacted with Na2WO4 by virtue of electrostatic attraction and hydrophobic force to form 1:1 ternary ion-association complex ([Pd(PMZ)2] · ( )), which can result in the large-scale enhancement of the resonance Rayleigh scattering (RRS), second-order scattering (SOS) and frequency doubling scattering (FDS). The maximum RRS, SOS and FDS peaks of [Pd(PMZ)2] · were located at 310 nm, 570 nm and 391 nm, respectively, and the enhancements of scattering were proportional to the concentration of PMZ in the range of 0.0081–2.6 µg mL−1 (RRS method), 0.02–3.0 µg mL−1 (SOS method) and 0.08–2.6 µg mL−1 (FDS method). Above three methods' detection limits (3σ) were 2.1 ng mL−1, 4.4 ng mL−1 and 6.6 ng mL−1 respectively. Using Pd(II) and Na2WO4 as probe, we have developed three new, sensitive, and rapid methods for the determination of PMZ. The RRS method was applied in the determination of PMZ in the pharmaceutical form with satisfactory results. In this work, the optimal reaction conditions and the influences of coexisting substances were investigated, the composition of ion-association complex and the reaction mechanism were also discussed by the RRS method.