Determination of inorganic anions via postcolumn reaction with iodide in ion chromatography

Complexation-association-extraction spectrophotometric determination of Pt cations based on a multi-reagent analytical system with I- anions and 2-[2-[4-[(2-cyanoethyl)methylamino]phenyl]vinyl]-1,3,3-trimethyl-3H-indolium cations

A new multi-reagent analytical system with 2-[2-[4-[(2-cyanoethyl)methylamino]phenyl]vinyl]-1,3,3-trimethyl-3H-indolium chloride (CPVTI), which is a styryl hemicyanine cationic dye with good photostability and a high molar absorption coefficient, as its core is first established and utilized successfully to determine the content of Pt ions via a spectrophotometric method. The process involves two treatment steps: adding CPVTI and I solutions to the Pt solution to be detected, and then using butyl acetate for vortex liquid-liquid extraction. A Pt cation can be incorporated into the CPVTI cation with the help of an I^- anion, initially converting the Pt cation into a [PtI₆]^2- complex anion. After forming a [PtI₆^2-·2CPVTI⁺]_(aq) ion associate in the aqueous phase, the Pt cation can be extracted selectively by butyl acetate with maximum extraction efficiency, and exists as [PtI₆^2-·2CPVTI⁺]_(org) in the extract phase. Via the formation of the iodo-complex of Pt and its ion associate with CPVTI, and the extraction with butyl acetate, Pt is selectively partitioned into the butyl acetate extractant in a step-by-step manner with good interference resistance. In the CPVTI-Pt-I analytical system, the charge state of CPVTI is retained by adjustment with H₂SO₄; the monovalent CPVTI⁺ presents a strong spectrophotometric absorbance signal at 530 nm with long-term stability, which allows determination of the Pt content. The system shows a high molar absorption coefficient of 6.52 × 10⁴ L mol^-1 cm^-1 at 530 nm, a lower limit of detection of 0.07 mg L^-1, and a good Sandell's sensitivity of 0.0030 μg cm^-2. Mechanistic analysis of the establishment of the system, concentration optimization, standard working curve, system sensitivity and stability, resistance against interference from diverse metal ions, and practical applications are investigated and discussed.

Host-Guest Inclusion Complexation of α-Cyclodextrin and Triiodide Examined Using UV-Vis Spectrophotometry

The historically relevant host-guest complexation of α-cyclodextrin (α-CD) and triiodide (I3(-)) in aqueous solution was examined using a systematic UV-vis spectrophotometric approach. This particular system is experimentally challenging because of the coupled equilibria, namely, I2 + I(-) ⇌ I3(-) and α-CD + I3(-) ⇌ α-CD·I3(-). We therefore developed a unique experimental approach that allowed us to determine the concentration of all iodine species. This enabled us to unequivocally demonstrate that the large increase in the UV absorbance with added α-cyclodextrin is due to an increase in the overall triiodide concentration as α-CD essentially converts iodine to triiodide according to the coupled equilibria. Herein we report (a) the complexation stoichiometry is 1:1 (i.e., the host-guest complex is α-CD·I3(-)), (b) the binding constant is KH-G = (1.35 ± 0.05) × 10(5) M(-1) at room temperature, and

Determination of bromate in water samples using post column derivatization method with triiodide

This paper describes the application of the method of post-column derivatization with triiodide and UV detection at 352 nm for the determination of bromate in drinking water, mineral water and swimming pool water samples. Optimized analytical conditions were further validated in terms of accuracy, precision, linearity, limit of detection and limit of quantification. The method detection limit was at the level of 0.4 μg/L, and the spiked recovery for bromate was in the range of 92% - 104%. The method did not need a special sample treatment and was successfully applied to the analysis of bromate at the required value that is below 2.5 μg/L.

Optimization of post-column reactor radius in capillary high performance liquid chromatography Effect of chromatographic column diameter and particle diameter

A post-column reactor consisting of a simple open tube (Capillary Taylor Reactor) affects the performance of a capillary LC in two ways: stealing pressure from the column and adding band spreading. The former is a problem for very small radius reactors, while the latter shows itself for large reactor diameters. We derived an equation that defines the observed number of theoretical plates (N(obs)) taking into account the two effects stated above. Making some assumptions and asserting certain conditions led to a final equation with a limited number of variables, namely chromatographic column radius, reactor radius and chromatographic particle diameter. The assumptions and conditions are that the van Deemter equation applies, the mass transfer limitation is for intraparticle diffusion in spherical particles, the velocity is at the optimum, the analyte's retention factor, k', is zero, the post-column reactor is only long enough to allow complete mixing of reagents and analytes and the maximum operating pressure of the pumping system is used. Optimal ranges of the reactor radius (a(r)) are obtained by comparing the number of observed theoretical plates (and theoretical plates per time) with and without a reactor. Results show that the acceptable reactor radii depend on column diameter, particle diameter, and maximum available pressure. Optimal ranges of a(r) become narrower as column diameter increases, particle diameter decreases or the maximum pressure is decreased. When the available pressure is 4000 psi, a Capillary Taylor Reactor with 12 microm radius is suitable for all columns smaller than 150 microm (radius) packed with 2-5 microm particles. For 1 microm packing particles, only columns smaller than 42.5 microm (radius) can be used and the reactor radius needs to be 5 microm.

Cyclodextrin-Aided Determination of Iodate and Bromate in Drinking Water by Microcolumn Ion Chromatography with Precolumn Enrichment

A selective and simple method for the determination of iodate (IO3-) and bromate (BrO3-) by microcolumn ion chromatography (IC) is presented. In this study, IO3- and BrO3- were determined as IBr2- and tribromide (Br3-), respectively, via a postcolumn reaction with bromide (Br) under acidic conditions with the aid of alpha-cyclodextrin (alpha-CD) in microcolumn IC. IO3- and BrO3- were selectively detected by the present method at a wavelength of 253 or 265 nm. The present system achieved good selectivity for IO3- and BrO3- as well as good repeatability under suitable conditions. Precolumn enrichment improved the detection limit, and allowed the determination of BrO3- in bottled water as low as sub microg L(-1) level in microcolumn IC.