A robust method for speciation, separation and photometric characterization of all [PtCl6-nBrn]2- (n=0-6) and [PtCl4-nBrn]2- (n=0-4) complex anions by means of ion-pairing RP-HPLC coupled to ICP-MS/OES, validated by high resolution 195Pt NMR spectroscopy

van Wyk P.-H. ; Gerber W.J. ; Koch K.R. (2011)


A robust reversed phase ion-pairing RP-HPLC method has been developed for the unambiguous speciation and quantification of all possible homoleptic and heteroleptic octahedral platinumIV [PtCl6-nBrn]2- (n=0-6) as well as the corresponding platinumII [PtCl4-nBrn]2- (n=0-4) complex anions using UV/Vis detection. High resolution 195Pt NMR in more concentrated solutions of these PtII/IV complexes (≥50mM) served to validate the chromatographic peak assignments, particularly in the case of the possible stereoisomers of PtII/IV complex anions. By means of IP-RP-HPLC coupled to ICP-MS or ICP-OES it is possible to accurately determine the relative concentrations of all possible PtII/IV species in these solutions, which allows for the accurate determination of the photometric characteristics (λmax and e{open}) of all the species in this series, by recording of the UV/Vis absorption spectra of all eluted species, using photo-diode array, and quantification with ICP-MS or ICP-OES. With this method it is readily possible to separate and estimate the concentrations of the various stereoisomers which are present in these solutions at sub-millimolar concentrations, such as cis- and trans-[PtCl4Br2]2-, fac- and mer-[PtCl3Br3]2- and cis- and trans-[PtCl2Br4]2- for PtIV, and cis- and trans-[PtCl2Br2]2- in the case of PtII. All mixed halide PtII and PtIV species can be separated and quantified in a single IP-RP-HPLC experiment, using the newly obtained photometric molar absorptivities, e{open}, determined herein at given wavelengths. © 2011 Elsevier B.V.

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