Complexation-association-extraction-spectrophotometric determination of Pt cation based on multi-reagent analytical system with I- anion and 2-[2-[4-[(2- cyanoethyl)methylamino]phenyl]vinyl]-1,3,3-trimethyl-3H-indolium cation
A new multi-reagent analytical system with the core of 2-[2-[4-[(2-cyanoethyl)methylamino]phenyl]vinyl]-1,3,3-trimethyl-3H-indolium Chloride (CPVTI), a styryl hemicyanine cationic dye with better photostability and high molar absorption coefficient, is firstly established and utilized successfully to determine the content of Pt ion by spectrophotometric method. It involves two step treatments: adding CPVTI and I solutions into Pt solutions to be detected, and then using butyl acetate to do vortex liquid-liquid extraction. Pt cation can be incorporated by CPVTI cation with the help of I- anion, initially converting Pt cation to exist as [PtI6]2- complex anion. After forming [PtI62-•2CPVTI+](aq) ion associate in aqueous phase, it is the only one that can be extracted by butyl acetate with maximum extraction efficiency, and exists as [PtI62-•2CPVTI+](org) in extract phase. During the processes to form iodo-complex of Pt and ion associate with CPVTI, as well as to be extracted by butyl acetate, Pt is selectively chosen into the extractant of butyl acetate step by step with better interference resistance. In the CPVTI-Pt-I analytical system that the charge state of CPVTI is retained by adjusting H2SO4, it is monovalent CPVTI+ to present a strong and long-term stable spectrophotometric signal of 530 nm absorbance to determine Pt content. The system shows that a higher molar absorption coefficient is 6.52×104 L•mol-1•cm-1 at 530 nm, a lower limit of detection is 0.07 mg•L-1, and a better Sandell’s sensitivity is 0.0030 μg•cm-2. The mechanism analysis about the system establishment, concentration optimization, standard working curve, system sensitivity and stability, interference resistance against diverse metal ions, as well as practice applications are investigated and discussed.