Interference in the Kinetic Determination of Ascorbic-Acid by Sulfide and Sulfite
| dc.contributor.author | Konidari, C. N. | en |
| dc.contributor.author | Karayannis, M. I. | en |
| dc.date.accessioned | 2015-11-24T16:40:22Z | |
| dc.date.available | 2015-11-24T16:40:22Z | |
| dc.identifier.issn | 0039-9140 | - |
| dc.identifier.uri | https://olympias.lib.uoi.gr/jspui/handle/123456789/8269 | |
| dc.rights | Default Licence | - |
| dc.subject | 2,6-dichlorophenolindophenol | en |
| dc.title | Interference in the Kinetic Determination of Ascorbic-Acid by Sulfide and Sulfite | en |
| heal.abstract | The reduction of 2,6-dichlorophenolindophenol (DCPI) by sulphides and sulphites has been studied kinetically by the stopped-flow technique. The reaction is first-order with respect to each of the reactants. From the distribution diagrams for the species DH2+, DH and D- for DCPI and H2Q, HQ- and Q2- for sulphides or sulphites, a mechanism is proposed which suggests partial reactions of all possible combinations of the reacting species at any pH. An equation for calculation of the second-order reaction rate constants k at any pH is derived, which gives k as a function of [H+], the partial reaction rate constants and the dissociation constants of DCPI and H2S or H2SO3. Values of the overall reaction rate constants over a wide pH-range have been determined, together with values of k for all possible partial reactions. For particular pH-values the second-order reaction rate constant was determined by four different methods. Mean values of k = 251 +/- 1 and 240 +/- 1 1.mole-1.sec-1 were obtained for pH 3.15 and 4.17, respectively, for the DCPI-Na2S reaction and k = 137 +/- 1, 127 +/- 1 and 136 +/- 1 l.mole-1.sec-1 for pH 2.02, 4.25 and 5.10, respectively, for the DCPI-Na2SO3 reaction. From the slopes of the linear Arrhenius plots activation energies of 6.6 +/- 0.2 and 4.0 +/- 0.1 kcal/mole for the DCPI-Na2S and DCPI-Na2SO3 reactions, respectively were calculated. The effect of ionic strength on the reactions supports the proposed mechanism. | en |
| heal.access | campus | - |
| heal.fullTextAvailability | TRUE | - |
| heal.identifier.secondary | <Go to ISI>://A1991GJ40900012 | - |
| heal.identifier.secondary | http://ac.els-cdn.com/003991409180319U/1-s2.0-003991409180319U-main.pdf?_tid=70b2933b40deebcd165ba123ac5f08af&acdnat=1333030799_aa0733fe0cb7b20adf05c5c5f92e54ef | - |
| heal.journalName | Talanta | en |
| heal.journalType | peer reviewed | - |
| heal.language | en | - |
| heal.publicationDate | 1991 | - |
| heal.publisher | Elsevier | en |
| heal.recordProvider | Πανεπιστήμιο Ιωαννίνων. Σχολή Θετικών Επιστημών. Τμήμα Χημείας | el |
| heal.type | journalArticle | - |
| heal.type.el | Άρθρο Περιοδικού | el |
| heal.type.en | Journal article | en |
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