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.     

Titrimetric microdetermination of isoniazid by amplification reactions

An amplification method for the determination of (0.01–2.0 mg) isoniazid is described. It depends on oxidation of the isoniazid sample solution with a chloroform solution of iodine and removed of its excess, oxidation of the resulting iodide with bromine, and iodometric titration of the liberated iodate after 6-fold amplification. Alternatively, the liberated iodine is reduced to iodide, and again oxidized to yield 36 iodide ions for every iodide ion originally present. The coefficient of variation does not usually exceed 1.5% for above 0.5 mg of isoniazid but increases to 3.6% at the 0.01-mg level.     

Titrimetric microdetermination of uric acid and thioglycollic acid by amplification reactions

A simple amplification method for determination of 0.05-2 mg of uric acid or thioglycollic acid has been worked out. It depends on iodine oxidation of the uric acid or thioglycollic acid solutions, removal of the excess of iodine, oxidation of the resulting iodide with bromine, and iodometric titration of the resulting iodate. The coefficient of variation ranges from 0.7 to 2.4% for uric acid and from 0.5 to 1.9% for thioglycollic acid, depending on the amount of the acid.     

Application of the Iodide Ion-Selective Electrode in the Potentiometric Determination of Chloral Hydrate

Abstract

A simple and sensitive micro method for chloral hydrate determination based on oxidation with iodine in chloroform solution is described. The produced iodide ion in the extract is determined using the iodide ion-selective electrode by either a direct measurement, standard addition technique or potentiometric titration with standard silver nitrate solution. Samples containing 0.1 - 4.0 mg chloral hydrate are analyzed with an average recovery of 99-9% and standard deviation of 0.1%.     

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.     

Titrimetric microdetermination of salicylic, acetylsalicylic, and p-hydroxybenzoic acids by amplification reactions

A novel titrimetric method with amplification has been developed for the determination of 0.05–2.0 mg of salicylic, acetylsalicylic, or p-hydroxybenzoic acid. It depends on bromination of these compounds by bromine to tribromophenylhypobromite, which liberates iodine when treated with iodide. The liberated iodine is extracted with chloroform, reduced to iodide, oxidation of the resulting iodide with bromine, and iodometric titration of the iodate produced gives the sixfold amplification method. The coefficient of variation does not exceed 1% for above 0.5 mg of the studied compounds, but increases to 2.8% at the 0.05-mg level.     

Iodometric microgram determination of Mn(II) in aqueous media by an indirect chemical amplification reaction

A rapid, simple and highly sensitive iodometric amplification method is described for the determination of microgram amounts of Mn(II). The method is based on oxidation of Mn(II) with an excess of periodate in acetate buffer (pH 2.8-3.0), masking of the unreacted periodate with molybdate, and after addition of iodide, titration of the liberated iodine is with thiosulphate. The proposed method offers 20-fold amplification for Mn(II) and was found suitable for the determination of Mn(II) in the presence of permanganate ions. Mn(II) in tap water and an industrial waste water has been successfully determined by the proposed method.     

Iodimetric determination of organolead compounds

A sensitive, rapid and accurate titrimetric method has been developed for the determination of 50-5000 mug of ethyl-lead or phenyl-lead compounds, based on their oxidation with a chloroform solution of iodine, removal of the excess of iodine, oxidation of the resulting iodide with bromine, and iodometric titration of the iodate formed. The coefficient of variation does not exceed 1.2% for amounts > 1000 mug of the organolead compound, but increases to 2.8% for the 50-mug level. The ethyl- and phenyl-lead compounds can be determined independently in mixtures.     

Microdetermination of arsenale and arsenite ions by using an amplification reaction with iodate resp. Iodine

Summary Simple and accurate methods are described for the microdetermination of arsenate and arsenite ions using 12- and 14-fold amplification reactions. The arsenate method is based upon reaction with calcium iodate and iodometric titration of the liberated iodate, whereas the arsenite method depends upon reaction with iodine and oxidation of the resulting iodide with bromine. This is followed by iodometric titration of the iodate in addition to the arsenate present in solution. The overall recovery amounts to 99.51 and 99.63% for arsenate and arsenite respectively.

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Mikrobestimmung von Arsenat- und Arsenitionen mit Hilfe einer Vervielfachungsreaktion mit Jodat bzw. Jod

Zusammenfassung Ein einfaches und genaues Verfahren mit 12- bzw. 14facher Vervielfachung wird beschrieben. Die Arsenatbestimmung beruht auf der Reaktion mit Calciumjodat und jodometrischer Titration des freigesetzten Jodats, die Arsenitbestimmung auf der Reaktion mit Jod, Oxydation des erhaltenen Jodids mit Brom und jodometrischer Titration des gebildeten Jodats zusammen mit dem aus dem Arsenit entstandenen Arsenat. 99,51 bzw. 99,63% von eingesetztem Arsenat bzw. Arsenit konnten wiedergefunden werden.

     

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%.     

Iodometric microdetermination of carboxyl function by indirect and direct procedures

Two iodometric procedures have been described for the microdetermination of certain organic acids which can be adopted for evaluating 0.03–0.1 meq of these acids. These methods consist of treating the acid sample with an excess of neutral potassium iodide and iodate. In the indirect method the iodate used up is measured whereas the direct procedure is based on the titration of the liberated iodine. The latter procedure has been applied to determine acids in a water-alcohol medium also. The effect of various factors influencing the stoichiometry of the reactions involved has also been studied.     

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

New methods are described for the iodometric submicro determination of α-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 α-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 μg); the average recovery is 99·9%.     

Iodometric microdetermination of arsenic and antimony in organic compounds by use of amplification reactions

Summary A six-fold iodometric amplification method is described for the determination of arsenic and antimony in organic compounds. It is based on the oxidation of arsenite (antimonite) with periodate and subsequent reaction of arsenate (antimonate) and iodate with iodide. Average recoveries were 99.8 and 99.5%, average standard deviations 0.22 and 0.34% for As and Sb, respectively.     

Titrimetric microdetermination of inorganic or organic mercury by amplification reactions

A simple titrimetric method for estimation of 0.05-7 mg of Hg(II) is presented. The acidic sample solution is treated with a measured and excessive amount of iodide, then mercuric iodide is extracted at ph 2-3.5, and the unreacted iodide is determined iodometrically after 6- or 36-fold amplification by use of bromine water for oxidation of iodide to iodate. Periodate oxidation of excess of iodide gives 24-fold amplification. The coefficient of variation does not usually exceed 1% for above 1 mg of mercury but increases to 4% at the 0.05-mg level. The 6-fold amplification method is used for microdetermination of organically bound mercury following oxygen-flask combustion. The average absolute error for 10 determinations (3 compounds) amounted to +/-0.6%; one determination takes less than one hour.     

Application of the two stage ascorbic acid-iodate titration to the determination of iodine and iodide

Summary An extension of the two stage titration of ascorbic acid against iodate to the determination of iodine and iodide in a solution is described. A known excess of ascorbic acid, standardized against iodate, is added to a mixed iodine and iodide solution and the excess ascorbic acid together with the total iodide is titrated against the same iodate to the two end points under controlled conditions of acidity. The differential method of calculation gives the amount of iodine and iodide with a blank and a direct titration. The accuracy of the results provides a useful evidence for the mechanism suggested for the two stage titration of ascorbic acid against iodate.Our sincere thanks are due to Professor S. S. Joshi for kind interest in the work.     

Determination of hypophosphite and phosphite by their reduction of iodine,iodate, or periodate and mercury(I) titration of iodide

A new potentiometric method is adopted for the accurate determination of hypophosphite and phosphite alone or in their mixtures using alcoholic iodine, iodate, and periodate. Hg(I) was used as titrant for the produced iodide in case of using alcoholic iodine as oxidant or for the excess added iodide in case of iodate and periodate as oxidants using silver amalgam as the indicatior electrode. The potential breaks which average 300 mV per 0.1 ml of titrant were sharp enough for precise determination of endpoints, and hence the high accuracy of the present method.     

Indirect amplification method for determining mercury by direct-current polarography. Application to organomercury compounds

An amplification method for the determination of 0.5–70 ppm (2.5 × 10⁻⁶ to 3.5 × 10⁻⁴ M) of Hg(II) is described. Hg(II) is reacted with a slight excess of KI, and the excess iodide is oxidized by bromine water and measured polarographically as iodate with sixfold amplification. Alternatively, the iodate formed is reacted to liberate iodine which is then reduced to iodide, and again oxidized to yield six iodate ions for every iodide ion originally present;

2. Microdetermination of Mercury in Organomercurial Compounds

polarographic reduction requires 36 electrons. Oxidation of the excess iodide with periodate yields four iodate ions for every iodide ion and therefore allows 24-fold amplification.Microdetermination of mercury in organomercurials is achieved using the sixfold method following closed flask combustion: the average percentage error for 10 determinations is ±0.40 and the time required for one sample run is 45 min.     

The use of iodate and periodate with iodide in the potentiometric titration of arsenite,sulfide, and sulfite with mercury (II)

A new potentiometric method is adopted for the accurate microdetermination of arsenite, sulfide and sulfite. The reductant is added to a known excess of standard iodate or periodate properly acidified with sulfuric acid. To the brown solution containing iodine equivalent to the reductant, an excess of standard iodide solution is added followed by titrating unreacted iodide with mercury (II) potentiometrically using the silver amalgam as indicator electrode. The potential breaks which averaged 350 mV per 0.1 ml of 0.05 M titrant were sharp enough for the precise determination of end points, and hence the high accuracy of the present method. In addition, besides simplicity and rapidity the stoichiometry of the reaction between iodate or periodate with the above reductants is still maintained even with the very low concentration.     

Study of acid and reductant functions of hydrazine sulphate by iodate-iodide mixture

Summary Hydrazine sulphate was found to liberate two atoms of iodine per molecule, when treated with an excess of iodate and iodide, and this was determined by thiosulphate or arsenious oxide in borax-boric acid buffer. The study of the action of iodate-iodide mixture on hydrazine sulphate at different stages of neutralisation and decomposition was carried out and iodometric relationships were verified. An interesting titration involving hydrazine sulphate both as a titrant and the titrating solution following its different reactions towards iodate-iodide mixture and iodine, is described. Hydrazine sulphate is found to be a satisfactory standard for the titration of iodine in presence of an alkaline buffer.Sincere thanks of the authors are due to Dr. S. S. Joshi, D. Sc. (London), for kind interest in the work.