Oxidimetric methods for the volumetric estimation of sulphite

1. The use of permanganate, ceric sulphate, and dichromate for the estimation of sulphite has been reinvestigated, although these reagents have heen discarded as useless by earlier investigators. By using catalysts under controlled acid concentration, we have been able to develop conditions for the quantitative oxidation of sulphite to sulphate at room temperature by any one of these oxidizing agents, avoiding the formation of dithionate. Copper sulphate and iodine monochlonde have been found useful as catalysts with potassium permanganate and dichromate; but only iodine monochloride with ceric sulphate. 2. Sodium sulphite is also oxidized quantitatively to sulphate at room temperature, when added to excess of sodium vanadate solution containing 5 to 6N hydrochloric acid and iodine monochloride as catalyst.     

Studies in bivalent chromium salts

Summary It has been shown that chromous solution can be standardised with the help of potassium dichromate, sulphatocerate, potassium iodate, bromate and periodate solutions. N-phenylanthranilic acid, ferroin and diphenylbenzidine serve as reversible indicators for the titrations of potassium dichromate and ceric sulphate against chromous solution.The authors are indebted to Dr. R. N. Singh, Professor of Chemistry, B. R. College, Agra, for his kind encouragement and for providing laboratory facilities.Part II: See Z. anal. Chem. 158, 189 (1957).     

Titrimetric determination of microgram amounts of manganese after amplification

Manganese (5-100mug) is oxidized to permanganate by periodate in 3 or 6% nitric acid. After masking of the excess ofperiodate with molybdate the permanganate and iodate formed are titrated iodimetrically.     

Utilization of ion exchangers in analytical chemistry XXVI : Application of the ion-exchange method to solutions containing oxidants

The free acid form of a cation-exchange resin of the sulfonated hydrocarbon type (Dowex 50) can be used for a quantitative liberation of the corresponding acids from salt solutions containing oxidants that are reduced by phenolic resins. Positive results have been obtained with solutions containing bromate, iodate, periodate, molybdate, and chromate. With permanganate a partial reduction occurs which prevents the application of the ion-exchange method for quantitative separation of solutions containing permanganate.     

Volumetric studies in oxidation-reduction reactions: Reduction with ferrous ethylenediamine sulphate indirect determinations

Ferrous ethylenediamine sulphate has been. used as a reducing agent in acid medium for the indirect volumetric estimations of potassium chlorate, potassium bromate, potassium metaperiodate, potassium, dichromate, potassium ferricyanide, potassium permanganate, potassium persulphate, hydrogen peroxide and ceric sulphate. The excess of ferrous ethylenediamine sulphate added to each of the substances was titrated with standard potassium permanganate and also with. standard potassium dichromate solution. In case of potassium bromate or potassium metaperiodate the end-point was not sharp in potassium dichromate titrations; while accurate volumetric observations were made with standard potassium permanganate solution.     

Iodometric microdetermination of hydrazines by amplification reactions

Two new, simple, rapid, and accurate iodometric amplification methods are described for the micro and submicro determination of hydrazine. The first depends on oxidation with a chloroform solution of iodine and removal of its excess, oxidation of the resulting iodide with bromine, and iodometric titration of the liberated iodate. The second method is based on oxidation with periodate at pH 8, masking of the excess of periodate with molybdate at pH 3, and iodometric titration of the iodate. The order of amplification involved in the two methods is 6- and 3-fold, respectively. Micro amounts of hydrazine sulphate and dihydrochloride were determined satisfactorily by both methods, the average recoveries being 98.6 and 99.4%.     

Micro and submicro iodometric determination of arsenite and sulphite ions by amplification reactions

Two methods are described for the micro and submicro iodometric determination of arsenite and sulphite ions involving 3- and 6-fold amplification reactions, respectively. The arsenite method is based on oxidation with an excess of periodate, masking of the unreacted periodate with molybdate, and final iodometric titration of the iodate released. The sulphite method depends upon oxidation with iodine and removal of its excess by extraction with chloroform, and oxidation of the iodide formed to iodate, which is determined iodometrically as usual. The two methods are simple, rapid, and accurate. The average recoveries obtained are 99.9 and 99.3% for arsenite and sulphite, respectively.     

Application of sodium metaperiodate for the determination of ribavirin in pharmaceutical formulations

Three simple and sensitive visible spectrophotometric methods (A-C) have been described for the assay of ribavirin either in pure form or in pharmaceutical formulations. They are based on the oxidation of ribavirin with excess sodium metaperiodate and estimating either the products formed (dialdehyde with MBTH, method A; iodate with metol-sulphanilamide, in the presence of Mo(VI) and iodide, method B) or the amount of periodate consumed (celestine blue in the presence of telurium (IV), method C). All of the variables have been optimized and the reaction mechanisms presented. The concentration measurements are reproducible within a R.S.D. of 1.0%. Recoveries are 99.2-101.2%.     

Chemical amplification methods for the sequential determination of trace amounts of ruthenium by titrimetric and spectrophotometric procedures

Two simple, inexpensive and rapid iodometric and spectrophotometric procedures were developed for trace amount determination of ruthenium. The proposed methods were based on the oxidation of ruthenium(II or III) with sodium periodate at pH 2.4-3.6, masking the excess periodate with sodium molybdate. The released iodate was then allowed to react with KI at pH 3, with subsequent determination of the released iodine spectrophotometry as triiodide at 350 nm or iodometry with 0.005 M sodium thiosulphate. This procedure offers an 18- and 15-fold amplification per Ru(II) or Ru(III) ion, respectively. Alternatively, the produced iodine was extracted with CHCl(3), shaken with an aqueous solution of sodium sulphite and the produced iodide ion was then allowed to react with bromine (or sodium periodate). The released iodate was subsequently determined by iodometry or spectrophotometry after addition of KI. The bromine and sodium periodate oxidation procedures offered 90- and 360-fold amplification per ruthenium(III) ion, and 108- and 432-fold amplification per ruthenium(II) ion. Ruthenium(IV) content was determined by these procedures after prior reduction to Ru(III) with sulphurous acid. The binary mixtures Ru(II)-Ru(III); Ru(III)-Ru(IV) and Ru(II)-Ru(IV) in aqueous solution at concentration 0.05 mug ml(-1) were successfully analyzed by the developed procedures. The utility of the proposed methods for the analysis of ruthenium in its complexes was demonstrated. Natural seawater and seawater spiked with ruthenium were analyzed satisfactorily.     

Determination of thiourea and its methyl derivatives by hypoiodite oxidation, and iodine monochloride end point; iodine bromide end point in the titration of thiourea with iodate

Summary Procedures have been described for the quantitative determination of thiourea and its methyl derivatives, wherein iodate, permanganate, and ceric sulphate have been used as direct titration solution, either following preoxidation by alkali hypoiodite via (ICI + KOH) or in case of thiourea, by iodine bromide method. Apart from using standard oxidants the methods have an added advantage of a high conversion factor due to oxidation of sulphur to sulphate. Alternative physical methods of detecting the end point is an added feature of these procedures.The authors wish to express their grateful thanks to Dr. S. S. Joshi, D. Sc. (London), for his kind interest in the work.     

Volumetric studies in oxidation-reduction reactions: Reduction with ferrous ethylenediamine sulphate ceric sulphate method

Ferrous ethylenediamine sulphate has been used as a reducing agent in acid medium for the indirect volumetric estimations of potassium chlorate, potassium bromate, potassium metaperiodate, potassium dichromate, potassium ferricyanide, potassium permanganate, potassium persulphate, hydrogen peroxide and ceric sulphate. The excess of ferrous ethylenediamine sulphate added to each of the substances in acid medium was titrated with standard ceric sulphate solution using ferroin as an indicator.     

Selective role of oxidants in the presence of cation-exchange resins in Na(+)-form for the detection and differentiation of acidic, basic and neutral amino-acids

A test for detection and differentiation of acidic, basic and neutral amino-acids is based on use of a sulphonic acid cation-exchange resin in Na(+)-form, in the presence of various oxidants (permanganate, dichromate, chromate, iodate, peroxide) and final detection with Nessler's reagent.     

Potentiometric studies in oxidation-reduction reactions: Reduction with ferrous ethylenediamine sulphate ceric sulphate method

Ferrous ethylenediamine sulphate has been used as a reducing agent to determine indirectly potassium permanganate, ceric sulphate, potassium chlorate, hydrogen peroxide, potassium persulphate, potassium dichromate and potassium bromate by a potentiometric method. An excess of ferrous ethylenediamine sulphate added to each of the substances in acid medium was titrated with a standard solution of ceric sulphate, using platinum foil as an oxidation-reduction electrode coupled with a saturated calomel electrode through an agar-agar potassium chloride bridge.     

Iodometric submicro determination of alpha-amino-alcohols by an amplification reaction

New methods are described for the iodometric submicro determination of alpha-aminoalcohols possessing primary, secondary or tertiary amino-groups which involve 6-, 12-, and 18-fold amplification reactions, respectively. The methods are based on reaction of the alpha-amino-alcohols with an excess of potassium periodate in a slightly alkaline medium, masking of the unreacted periodate with molybdate at pH 3.2 and, after addition of iodide, iodometric determination of the equivalent amounts of iodate released. In addition to being simple and rapid, the methods are sufficiently selective and specific and also highly accurate, being particularly suitable for the analysis of submicro amounts (50-150 microg); the average recovery is 99.9%.     

Indirect spectrophotometric methods for the determination of antibiotics with iodine or periodate, and metol and sulphanilamide

Two spectrophotometric methods are described for the determination of antibiotics. In the first method, penicillins, cephalosporins, streptomycin and griseofulvin are estimated by oxidizing them under neutral or slightly acidic conditions, after alkaline hydrolysis, by means of a known and excessive quantity of iodine solution. The excess of iodine is determined at pH 3.0 with metol and sulphanilamide. In the second method, dihydrostreptomycin, framycetin and the acid hydrolysis product of chloramphenicol are determined by a method involving oxidation with sodium metaperiodate, masking the excess of periodate with sodium molybdate, and using metol and sulphanilamide at pH 3.0 to determine the iodate formed. In both methods the absorbance of the resulting p-N-methylbenzoquinonemonoimine sulphanilamide charge-transfer complex is measured at 520 nm.     

Potentiometric studies in oxidation-reduction reactions: Reduction with ferrous ethylenediamine sulphate indirect determinations

Ferrous ethylenediamine sulphate has been used as a reducing agent to determine indirectly potassium dichromate, hydrogen peroxide, potassium permanganate, potassium persulphate, potassium chlorate, potassium bromate, and ceric sulphate by a potentiometric method. An excess of ferrous ethylenediamine sulphate added to each of the substances in an acid medium is titrated with a standard solution of potassium permanganate, using platinum foil as an oxidation-reduction electrode coupled with a saturated calomel electrode through an agar-agar potassium chloride bridge.     

Determination of colloidal electrolytes: amperometric titration of dodecylquinolinium bromide with inorganic anions

The possibilities of the amperometric titration of aqueous solutions of dodecylquinolinium bromide in 0.1 mol dm^?3 potassium bromide as supporting electrolyte with potassium dichromate, potassium hexacyanoferrate(III) and ammonium molybdate were investigated. Titrations were carried out in which dichromate, hexacyanoferrate(III) and molybdate anions were determined by titration of colloidal electrolyte solutions.     

Sequential flow injection determination of iodate and periodate with spectrophotometric detection

A flow injection (FI) system is described for the sequential determination of periodate and iodate based on their reaction with iodide at pH 3.5. Two sample plugs were injected into the same carrier stream sequentially. One injection is for the iodate determination and the other for the sum of iodate and periodate determination. For iodate determination, molybdate solution buffered at pH of 3.5 was used for selective masking of periodate. The influences of reagent concentrations were studied by a univariable method and the influence of FI manifolds was studied using univariable and simplex method. Periodate and iodate can be determined in the range of 0.050-5.0 and 0.050-10 microg/ml, respectively. The 3 sigma limit of detection was 0.030 and 0.050 microg/ml for periodate and iodate, respectively. The proposed method has been applied for the sequential determinations of periodate and iodate in water samples.     

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⁺].     

Chemiluminescence (CL) emission generated during oxidation of pyrogallol and its application in analytical chemistry. I. Effect of oxidant compound

An investigation of chemiluminescence (CL)-emission generated by the oxidation of pyrogallol using various inorganic oxidant compounds is reported in this F.I.A.-merging zone application. The oxidant compounds that showed measurable CL-emission were permanganate, periodate, hypochlorite anions, cerium(IV) and hydrogen peroxide. The different oxidant compounds showed CL-emissions at different pH-ranges. The CL-emission was limited by the inner filter effect and this was more intense for oxidants of selective oxidation. Kinetic effects were also found in the case of oxidation by permanganate. Plots of CL-emission against pH give evidence of speciation and or deactivation mechanism effects. The analytical parameters for the determination of the oxidants are given. Sensitivities of 895 600, 19 500, 33 723, 10 680 and 56 703 mV M(-1) were found for the determination of permanganate, cerium(IV), periodate, hypochlorite and hydrogen peroxide, respectively. The calibration curves of the oxidant determination were generally S-shaped; the S-shaped calibration curve of periodate was closer to a straight line relationship while that of hypochlorite was almost a straight line; detection limits in the range of 10(-4) M oxidant concentration were found for nearly all oxidants. The analytical parameters for determination of pyrogallol by the CL-emission generated through oxidation by the different oxidants at optimum conditions were 1.16x10(6) mV M(-1) for permanganate; 0.086x10(6) mV M(-1) for cerium(IV); 0.91x10(6) mV M(-1) for periodate; 0.012x10(6) mV M(-1) for hypochlorite; and 0.25x10(6) mV M(-1) for hydrogen peroxide. The detection limit was 1.0x10(-4) M. The nearly straight-line relationship (initial part of the plot) for CL-emission with oxidant concentration gives an indication that the CL-reaction of pyrogallol oxidation by hypochlorite proceeds through a process that involves energy transfer while the pronounced S-shaped curve produced by permanganate gives the indication that the reaction proceeds through a process that does not involve energy transfer according to the mathematical model of CL-emission that controls the F.I.A.-merging zone technique of the flow apparatus used in this work. The sequence of completeness of the oxidation process by each oxidant was MnO(4)(-)>H(2)O(2)>IO(4)(-)>OCl(-); the stoichiometric quantity of the oxidant per pyrogallol molecule for the rapid part of the overall oxidation by each different oxidant was attempted; this is an index-value of the oxidation state of the fluorescent excited molecule. Finally, the impact of the above findings for further analytical applications is discussed.