Electrocatalytic Reduction and Determination of Iodate and Periodate at Silicomolybdate‐Incorporated‐Glutaraldehyde‐ Cross‐Linked Poly‐L‐lysine Film Electrodes

The present work describes reduction of iodate (IO₃^?), and periodate (IO₄^?) at silicomolybdate‐doped‐glutaraldehyde‐cross‐linked poly‐L ‐lysine (PLL‐GA‐SiMo) film coated glassy carbon electrode in 0.1 M H₂SO₄. In our previous study, we were able to prepare the PLL‐GA‐SiMo film modified electrode by means of electrostatically trapping SiMo₁₂O₄₀^4? mediator in the cationic film of PLL‐GA, and the voltammetric investigation in pure supporting indicated that the charge transport through the film was fast. Here, the electrocatalytic activity of PLL‐GA‐SiMo film electrode towards iodate and periodate was tested and subsequently used for analytical determination of these analytes by amperometry. The two electron reduced species of SiMo₁₂O₄₀^4? anion was responsible for the electrocatalytic reduction of IO₃^? at PLL‐GA‐SiMo film electrode while two and six electron reduced species were showed electrocatalytic activity towards IO₄^? reduction. Under optimized experimental conditions of amperometry, the linear concentration range and sensitivity are 2.5×10^?6 to 1.1×10^?2 M and 18.47 μA mM^?1 for iodate, and 5×10^?6 to 1.43×10^?4 M and 1014.7 μA mM^?1 for periodate, respectively.     

Selective photometric redox determination of periodate and iodate ions in bottled drinking water

method has been developed for the selective photometric redox determination of periodate and iodate ions in bottled drinking water based on redox reactions of analytes with Methylene Blue with different duration of processes, products of which form the analytical signal. The limits of detection for periodate and iodate ions are 0.5 and 0.2 µg/L, respectively. The allowable weight ratios for concomitant ions for (at the analyte concentration 2 µg/L) are as follows: I^–, Br^–, IO₃^–, BrO₃^–, ClO^–, CIO^–, CIO₂^–, CIO₃^– and CIO₄^–(1: 100); and for IO₃^– (1 µg/L) are: BrO₃^–₂^–, NO (1: 60), CIO^–, CIO₂^–, (1: 100), and I^–, Br^–, IO₄^–, CIO₃^–, and CIO₄^– (1: 200). The HCIO₃^–, Cl^–, and SO₄^2- anions and Ca²⁺, Mg²⁺, Na⁺, K²⁺, and NH₄⁺ cations are macrocomponents of drinking water and at total concentrations up to 10 g/L do not affect the results of analysis. In the concentration range 1–10 µg/L of IO₄^– andIO₃^–, the total error of determination is 5–7%.     

Oxidation of tris(1, 10-phenanthroline)iron(II) ion by iodate and periodate ions in neutral medium

The reactions of iodate and periodate with Fe(phen)₃²⁺ have been studied in neutral medium iodate ion is unreactive with ferroin in aqueous solution. The reaction is autocatalytic in the case of IO₄⁻. The autocatalysis disappears in an excess of IO₃⁻. The rate constants of both processes were determined and a reaction mechanism has been proposed. © 1996 John Wiley & Sons, Inc.     

Study of some phenolic-iodine redox polymeric products by thermal analyses and mass spectrometry

Summary This paper describes the use of the mass spectrometry (MS), thermal analyses (TA) and other physico-chemical methods to investigate the structure of two newly synthesized phenolic-iodine derivative polymeric products. These two products are formed as a result of redox-interaction of adrenaline hydrogen tartrate (AHT, I) with iodate (IO^-₃) and periodate (IO^-₄). The characterization of the two products were achieved satisfactorily by using the above tools and their proposed general formulae, were found to be C₅₂H₆₇O₃₆N₄I (AHT- IO^-₃, II) and C₂₆H₃₄O₁₈N₂I₂(AHT- IO^-₄, III). The fragmentation behavior of the main compound (AHT) in MS and TA (TG and DTA) techniques was investigated and compared. The results obtained were used to explain the fragmentation of the products AHT- IO^-₃and AHT- IO^-₄in mass spectrometry and thermal analyses techniques. The stabilities of different fragments were discussed. The results indicate that the two techniques are supporting each other in which the mass spectrometry provides the structural information in gas phase while the thermal analyses provides the quantitative fragmentation in the solid-state.     

Determination of Metals by Photochemical Precipitation

Abstract

The technique of precipitation from homogeneous solution by photochemical action has been successfully applied to the determination of La, Ba, and In. Precipitation is accomplished through the photoreduction of IO₄ ^? to produce the insoluble iodates. In the case of Zr and Ti, the more soluble periodate is coprecipitated with the iodate and the method is not successful. Cu and Ni cannot be estimated by this method.     

PVC membrane sensor based on periodate—Cetylpyridinium ion pair for the potentiometric determination of periodate

A new plasticized membrane sensor has been proposed for the determination of periodate based on periodate-cetylpyridinium ion pair complex. The electrode shows a linear, reproducible and stable potentiometric response with anionic Nernstian slope of 58.1 ± 0.5 mV/decade over a wide range of concentrations 10⁻⁵–10⁻² M and a detection limit of 2.0 × 10⁻⁶ M of IO₄⁻. The membrane exhibits a fast response time of 30–40 s which is independent of pH in the range 2.0–9.0. The selectivity coefficients indicate excellent selectivity for periodate over a large number of anions, e.g. iodide, bromide, chloride, iodate, bromate, nitrate, sulfate, phosphate, thiocyanate, chromate, thiosulfate, sulfite, perchlorate, citrate, acetate, oxalate, and nitrate. The prepared sensor has been successfully used for the determination of periodate (IO₄⁻) and iodate (IO₃⁻) ions with an average recovery of 99.84 ± 0.34% and 98.22 ± 0.43%, respectively. It is also applied to the determination of hydrazine compounds and aminophenol derivatives with an average recovery of 98.66 ± 0.53% and 98.40 ± 0.56%, respectively. Also, the proposed sensor was used for the determination of potassium iodate in iodized table salt and hydrazine in steam boiler feed water and p-aminophenol. The results obtained are in good agreement with those obtained by standard methods.     

Kinetics of Oxidation of L-Valine by a Copper(III) Periodate Complex in Alkaline Medium

The kinetics of oxidation of L-valine by a copper(III) periodate complex was studied spectrophotometrically. The inverse second-order dependency on [OH⁻] was due to the formation of the protonated diperiodatocuprate(III) complex ([Cu(H₃IO₆)₂]⁻) from [Cu(H₂IO₆)₂]³⁻. The retarding effect of initially added periodate suggests that the dissociation of copper(III) periodate complex occurs in a pre-equilibrium step in which it loses one periodate ligand. Among the various forms of copper(III) periodate complex occurring in alkaline solutions, the monoperiodatocuprate(III) appears to be the active form of copper(III) periodate complex. The observed second-order dependency of [L-valine] on the rate of reaction appears to result from formation of a complex with monoperiodatocuprate(III) followed by oxidation in a slow step. A suitable mechanism consistent with experimental results was proposed. The rate law was derived as:

Highly sensitive and selective amperometric sensors for nanomolar detection of iodate and periodate based on glassy carbon electrode modified with iridium oxide nanoparticles

Iridium oxide nanoparticles are grown on a glassy carbon electrode by electrodepositing method. The electrochemical behavior and electrocatalytic activity of modified electrode towards reduction of iodate and periodate are studied. The reductions of both ions occur at the unusual positive peak potential of 0.7 V vs. reference electrode. The modified electrode is employed successfully for iodate and periodates detection using cyclic voltammetry, hydrodynamic amperometry and flow injection analysis (FIA). In the performed experiments, flow injection amperometric determination of iodate and periodate yielded calibration curves with the following characteristics: linear dynamic range up to 100 and 80 μM, sensitivity of 140.9 and 150.6 nA μM⁻¹ and detection limits of 5 and 36 nM, respectively. The repeatability of the modified electrode for 21 injections of 1.5 μM of iodate solution is 1.5%. The interference effects of NO₂⁻, NO₃⁻, ClO₃⁻, BrO₃⁻, ClO₄⁻, SO₄²⁻, Cu²⁺, Zn²⁺, Mn²⁺, Mg²⁺, Cd²⁺, Ca²⁺, Na⁺, K⁺, NH₄⁺ and K⁺, CH₃COO⁻ and glucose were negligible at the concentration ratio of more than 1000. The obtained attractive analytical performance together with high selectivity and simplicity of the proposed method provide an effective and e novel modified electrode to develop an iodate and periodate sensor. Sensitivity, selectivity, the liner concentration range and the detection limit of the developed sensor are all much better than all known similar sensors in the literature for iodate and periodate determination.     

Selective photometric determination of low conentrations of selenium(IV) and selenium(VI) in bottled drinking water

A procedure is developed for the selective photometric determination of selenium(IV) in bottled drinking water by the oxidation of Methylene Blue in 1 M HCl to colorless decomposition products and of selenium(VI) by its interaction with the specified reagent at pH 5–6 with the formation of a colored ion pair. The limits of detection are 1 and 0.8 µg/L, respectively. At the concentration of selenium(IV) 2 µg/L, the admissible weight ratios are: SeO₄^2-, Br₃^- (1: 20); Br^– (1: 60); I^–, IO₃^- and IO₄^- (1: 100). At equal concentration of selenium(VI), the following species: SeO₄^2-(1: 20); Br₃^-, Br^–, I^–, IO₃^-, and IO₄^- (1: 100) do not interfere with the determination. Other anions and cations present in highly mineralized waters do not interfere with the determination. The relative error of determination is 8–10% in the concentration range 2–10 µg/L of selenium(IV) and selenium(VI) and does not exceed 5% in their concentration range of 10–100 µg/L.     

Effect of Ammonium Ions on the Electroreduction of Anions at a Mercury Electrode

The effect of ammonium ions on the electroreduction of peroxodisulfate (S₂O^2- ₈) and perbromate (BrO^- ₄) anions is found to be commensurate with that of potassium ions. Ammonium ions accelerate the reduction of iodate (IO^- ₃), bromate (BrO^- ₃), and chromate (CrO^2- ₄) anions in nonbuffered solutions and does not, in buffered ones. In the former case, the effect is connected with the pH change in the near-electrode layer during the reaction and with the participation of ammonium ions in hydrolytic equilibriums, rather than with a simultaneous transfer of ammonium ions and electrons in an elementary act. The conclusions in the literature in favor of a simultaneous transfer of the proton and electron in the proton-consuming reactions of reduction of anions is shown to be ambiguous.     

Kinetic Determination of Iodide Based on its Effect on the Hydrogen Peroxide Oxidation of Triflupromazine

Summary.  A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of iodide. The method is based on the catalytic effect of iodide on the reaction of triflupromazine (TFP) with H₂O₂. The reaction is followed spectrophotometrically by tracing the oxidation product at 498 nm within 1 min after addition of H₂O₂. The optimum reaction conditions are TFP (0.4 × 10⁻³ M), H₂SO₄ (1.0M), H₃PO₄ (2.0M), and H₂O₂ (1.6M) at 30°C. Following this procedure, iodide can be determined with a linear calibration graph up to 4.5 ng ċ cm⁻³ and a detection limit of 0.04 ng ċ cm⁻³, based on the 3 S_b criterion. The method can also be applied to the determination of iodate and periodate ions. Determination of as little as 0.2, 1.0, 2.0, and 4.0 ng ċ cm⁻³ of I⁻, IO₃ ^-, or IO₄ ^- in aqueous solutions gave an average recovery of 98% with relative standard deviations below 1.6% (n = 5). The method was applied to the determination of iodide in Nile river water and ground waters as well as in various food samples after alkaline ashing treatment. The method is compared with other catalytic spectrophotometric procedures for iodide determination. Received January 19, 2001. Accepted (revised) March 12, 2001     

Hydrothermal Synthesis of Rare Earth Iodates from the Corresponding Periodates: Structures of Sc(IO3)3, Y(IO3)3 · 2 H2O,La(IO3)3 · 1/2 H2O and Lu(IO3)3 · 2 H2O

Hydrothermal syntheses of single crystals of rare earth iodates, by decomposition of the corresponding periodate, are presented. This appears to be a generic method for making rare earth iodate crystals in a short period of time. Single crystal X‐ray diffraction structures of the four title compounds are presented. Sc(IO₃)₃: Space group R3, Z = 6, lattice dimensions at 100 K; a = b = 9.738(1), c = 13.938(1) Å; R₁ = 0.0383. Y(IO₃)₃ · 2 H₂O: Space group P1, Z = 2, lattice dimensions at 100 K: a = 7.3529(2), b = 10.5112(4), c = 7.0282(2) Å, α = 105.177(1)°, β = 109.814(1)°, γ = 95.179(1)°; R₁ = 0.0421. La(IO₃)₃ · ? H₂O: Space group Pn, Z = 2, lattice dimensions at 100 K: a = 7.219(2), b = 11.139(4), c = 10.708(3) Å, β = 91.86(1)°; R₁ = 0.0733. Lu(IO₃)₃ · 2 H₂O: Space group P1, Z = 2, lattice dimensions at 120 K: a = 7.2652(9), b = 7.4458(2), c = 9.3030(3) Å, α = 79.504(1)°, β = 84.755(1)°, γ = 71.676(2)°; R₁ = 0.0349.     

Determination of iodate and periodate at the microgram level by a kinetic method

A procedure is reported for the kinetic determination of iodate/periodate mixtures based on the reduction of these anions by the iron(II)/dipyridylglyoxal dithiosemicarbazone complex in an acidic medium. The reaction is monitored spectrophotometrically at 410 nm (absorption maximum of the iron(III) complex formed). Mixtures of these anions at μg ml^?1 levels for iodate/periodate ratios from 5:1 to 1:4 can be determined with a r.s.d, of ca. 3%. Molybdate is used to mask periodate to allow iodate to be determined alone. The sum of both anions is obtained in the absence of molybdate. Chromate, hypochlorite and hexacyanoferrate(III) interfere seriously.     

Synthesis and structure of In(IO3)3 and vibrational spectroscopy of M(IO3)3 (M=Al, Ga, In)

The reaction of Al, Ga, or In metals and H₅IO₆ in aqueous media at 180 °C leads to the formation of Al(IO₃)₃, Ga(IO₃)_3, or In(IO₃)₃, respectively. Single-crystal X-ray diffraction experiments have shown In(IO₃)₃ contains the Te₄O₉-type structure, while both Al(IO₃)₃ and Ga(IO₃)₃ are known to exhibit the polar Fe(IO₃)₃-type structure. Crystallographic data for In(IO₃)₃, trigonal, space group , a=9.7482(4) Å, c=14.1374(6) Å, V=1163.45(8) Z=6, R(F)=1.38% for 41 parameters with 644 reflections with I>2σ(I). All three iodate structures contain group 13 metal cations in a distorted octahedral coordination environment. M(IO₃)₃ (M=Al, Ga) contain a three-dimensional network formed by the bridging of Al³⁺ or Ga³⁺ cations by iodate anions. With In(IO₃)₃, iodate anions bridge In³⁺ cations in two-dimensional layers. Both materials contain distorted octahedral holes in their structures formed by terminal oxygen atoms from the iodate anions. The Raman spectra have been collected for these metal iodates; In(IO₃)₃ was found to display a distinctively different vibrational profile than Al(IO₃)₃ or Ga(IO₃)₃. Hence, the Raman profile can be used as a rapid diagnostic tool to discern between the different structural motifs.     

In[IO3](OH)2 – New member of hydrous and anhydrous iodate family with indium

A new indium iodate hydrate In[IO₃](OH)₂ was synthesized by the hydrothermal methods. Single crystal X-ray diffraction revealed centrosymmetric Pnma space group. [IO₃]-groups have typical umbrella-like configuration: iodine atom and three oxygens with I–O distances ∼1.8 Å. In-octahedra have 4 equatorial OH-groups and 2 apical O-atoms of 2 [IO₃]-groups and are connected into the layers via OH-groups. It is found that indium iodate family without any other metals is a regular row of compounds: anhydrous In[IO₃]₃, one hydrated In[IO₃]₂(OH)·H₂O, new two hydrated In[IO₃](OH)₂ and “end member” represented by three hydrated hydroxide In(OH)₃. Chemical relations are parallel to the structural: In-octahedral framework in In-hydroxide, In-octahedral layer as a fragment of the framework, In-octahedral chain as a fragment of the layer, isolated In-octahedra as a fragment of the chain with no In-octahedral condensation via vertices but only via [IO₃]-groups in anhydrous In-iodate. If alkali metals are introduced in anhydrous In-iodates, their influence is different. Large metals as K, Rb, Cs hinder condensation of {In[IO₃]₆}³⁻ blocks which are isolated in the structures whereas smaller Li, Na metals allows condensation up to bands {In[IO₃]₄}¹⁻_∞. Octahedral chains selected in hydrated In-iodates are similar to chains in nonlinear optical compound TiO[IO₃]₂. The reasons of polarity or non-polarity and possible elements substitutions promising for properties are discussed.     

罗丹明6G缔合微粒荧光猝灭法测定痕量碘酸根

研究发现在0.01mol/LHCl-8.0×10-4mol/LKI介质中,罗丹明6G(RhG)在550nm处有1个荧光峰.当有IO-3,I-3与RhG形成缔合微粒,550nm处荧光峰猝灭,在320、400、6103存在时,IO-3与过量的I-反应生成I-nm处有3个共振散射峰,在470nm处有1个同步散射峰.碘酸根浓度在2.0～100×10-7mol/L范围内与荧光猝灭强度成线性关系.据此建立了一个测定食盐中IO-3的荧光猝灭分析法.光谱研究结果表明,(RhG-I3)n缔合微粒和界面的形成是导致体系荧光猝灭的根本原因.     

Bi2(IO3)(IO6): First combination of [IO3]− and [IO6]5− anions in three-dimensional framework

A new bismuth (III) iodate periodate, Bi₂(IO₃)(IO₆) was obtained from hydrothermal reactions using Bi(NO₃)₃·5H₂O, and H₅IO₆ as starting materials. Bi₂(IO₃)(IO₆) crystallizes in the monoclinic space group P2₁/c (No. 14) with lattice parameters ɑ = 8.1119(6), b = 5.4746(4), c = 16.357(1) Å, β = 99.187(2)°, V = 717.07(9) ų, Z = 4. The structure of Bi₂(IO₃)(IO₆) features a three-dimensional framework which is a combination of [Bi(1)O₅] tetragonal pyramids, [Bi(2)O₈] bicapped trigonal prisms and [IO₃]⁻ and [IO₆]⁵⁻ anions. Thermal analysis shows that the compound is thermally stable up to about 350 °C. The solid state UV-vis-NIR diffuse reflectance spectrum indicates that Bi₂(IO₃)(IO₆) is a semiconductor with a band gap of 2.76 eV.     

Kinetics and mechanism of the oxidation of nitrilotris(methylenephosphonato)chromium(III) by periodate

The kinetics of oxidation of nitrilotris(methylenephosphonato)chromium(III), Cr^IIINTMP, by periodate to yield Cr^VI have been studied spectrophotometrically over the 5.80–6.85 pH range at 22–33 °C. The reaction rate, which is first-order with respect to [Cr^IIINTMP] and [IO^– ₄] and inversely dependent on [H⁺], obeys the rate law:-d[Cr^IIINTMP/dt=kKK_h[IO^- ₄] [Cr^III]_T/K_h+ [H⁺] +KK_h[IO^- ₄] The values of the intramolecular electron transfer, k, and the formation constant of the intermediate complex, K, were determined at various temperatures. The hydrolysis constant for Cr^IIINTMP, K _h , was determined spectrophotometrically and is in agreement with the value estimated from the kinetic data. The activation parameters were calculated from the temperature dependence of the specific rate constants. A mechanism is proposed in which the hydroxo complex, [CrHNTMP(OH)]^3–, is the reactive species. The results support a mechanism where intramolecular electron transfer is the rate-determining step.     

Kinetics and mechanism of oxidation of bis(2,4,6-tripyridyl 1,3,5-triazine)iron(II) by vanadium(V), periodate and iodate ions in acetate buffers

The kinetics of oxidation of bis(2,4,6-tripyridyl 1,3,5-s-triazine)iron(II) by vanadium(V), periodate and iodate has been studied in acetate buffers by stopped-flow and spectrophotometric methods. The oxidation reaction of bis(2,4,6-tripyridyl 1,3,5-s-triazine)iron(II) by vanadium(V), periodate and iodate follows first order kinetics for the substrate and oxidant. Hydrogen ion has no significant effect on the rate. A generalized mechanism was proposed for these reactions and these reactions follow the rate law: Rate = k [oxidant] [Fe(tptz)₂ ²⁺].     

Kinetic Determination of Iodide Based on its Effect on the Hydrogen Peroxide Oxidation of Triflupromazine

 A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of iodide. The method is based on the catalytic effect of iodide on the reaction of triflupromazine (TFP) with H₂O₂. The reaction is followed spectrophotometrically by tracing the oxidation product at 498 nm within 1 min after addition of H₂O₂. The optimum reaction conditions are TFP (0.4 × 10⁻³ M), H₂SO₄ (1.0M), H₃PO₄ (2.0M), and H₂O₂ (1.6M) at 30°C. Following this procedure, iodide can be determined with a linear calibration graph up to 4.5 ng ċ cm⁻³ and a detection limit of 0.04 ng ċ cm⁻³, based on the 3 S_b criterion. The method can also be applied to the determination of iodate and periodate ions. Determination of as little as 0.2, 1.0, 2.0, and 4.0 ng ċ cm⁻³ of I⁻, IO₃ ^-, or IO₄ ^- in aqueous solutions gave an average recovery of 98% with relative standard deviations below 1.6% (n = 5). The method was applied to the determination of iodide in Nile river water and ground waters as well as in various food samples after alkaline ashing treatment. The method is compared with other catalytic spectrophotometric procedures for iodide determination.