Complete inhibition of hexavalent chromium formation from chrome-tanned leather with combined inhibitors / Koki Ogata in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 101, N° 1 (01-02/2017)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 101, N° 1 (01-02/2017) . - p. 27-32 Titre : Complete inhibition of hexavalent chromium formation from chrome-tanned leather with combined inhibitors Type de document : texte imprimé Auteurs : Koki Ogata, Auteur ; Yuki Kumazawa, Auteur ; Yoichi Koyama, Auteur ; Keiji Yoshimura, Auteur ; Koji Takahashi, Auteur Année de publication : 2017 Article en page(s) : p. 27-32 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Chrome hexavalent Cuir -- Teneur en chrome hexavalent Extraction (chimie) Inhibiteurs (chimie) Oxydoréduction Phosphate de potassium Le phosphate de potassium est le nom générique pour les sels formés des ions phosphate et potassium résultant de l'attaque de l'hydroxyde de potassium (KOH ou potasse, base) par l'acide phosphorique. Statistique Index. décimale : 675 Technologie du cuir et de la fourrure Résumé : Hexavalent chromium (Cr6+) is formed in chrome-tanned leather due to oxidation of trivalent chromium (Cr3+) under certain conditions and may induce dermatitis and cancer. Specifically, significant amounts of Cr6+ are generated during the heat-ageing process by pre-heating at 80°C for 24 hours in accordance with ISO rnethod17075, promoting the formation of Cr6+ from Cr3+ in chrome-tanned leather. Thus, inhibiting or minimizing the production of Cr6+ is needed badly. A previous report demonstrated that 0.1mol/L potassium phosphate buffer (P-buffer ; pH5.5) was highly efficient as an extractant for the measurement of Cr6+ from chrome-tanned leather as compared with P-buffer (pH8.0). The present report describes efforts to control the redox behaviour of Cr3+ with the goal of inhibiting the formation of Cr6+ in chrome-tanned leather using a low-molecular weight (At 9,400) collagen peptide (CP-9), 2, 6-di-t-butyl-4-methylphenol (BHT), 3(2)-t-butyl-4-hydroxyanisole (BHA), and ascorbic acid (AsA) as inhibitors, even with heat-aged leather. Chrome-tanned leather was treated with the inhibitors, and the resulting leather samples were extracted with P-buffer (pH5.5) to determine the amount of Cr6+ in the extracts. The results showed that CP-treatment significantly reduced the amount of Cr6+ formed, probably due to a combination of chelation of CP on the Cr3+ complex, quenching of reactive oxygen, and radical scavenging. The BHT, and BHA, and AsA treatments also reduced the amount of Cr6+ formed, probably due la scavenging radicals from the oxidative products of the fatliquoring agent and alterations in the reducing conditions. However, treatment with any of the inhibitors individually did not cause complete inhibition of Cr3+ oxidation. Therefore, the action of the combined inhibitors was investigated. The results demonstrated that treatment with BHA + CP and with BHA + AsA produced a synergistic reduction in Cr6+ production. Use of BHA + AsA + CP completely inhibited the formation of Cr6+ from heat-aged leather samples. Note de contenu : - Materials - Treatment of the leather sample with inhibitor - Extraction of Cr from the treated leather sample - Analytical methods - Statistical analysis En ligne : https://drive.google.com/file/d/1iYCWrvmmpRnUAnE4Xf8BR9QBsfNnBDPz/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=27986 [article]

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Measurement of hexavalent chromium in chrome-tanned leather : comparative study of acidic condition extraction with alkaline extraction / Koki Ogata in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 99, N° 6 (11-12/2015)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 99, N° 6 (11-12/2015) . - p. 293-296 Titre : Measurement of hexavalent chromium in chrome-tanned leather : comparative study of acidic condition extraction with alkaline extraction Type de document : texte imprimé Auteurs : Koki Ogata, Auteur ; Yuki Kumazawa, Auteur ; Yoichi Koyama, Auteur ; Keiji Yoshimura, Auteur ; Koji Takahashi, Auteur Année de publication : 2015 Article en page(s) : p. 293-296 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Analyse quantitative (chimie) Bases (chimie) Cuir -- Teneur en chrome hexavalent Extraction (chimie) Oxydoréduction pH -- Mesure Statistique Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Hexavalent chromium (Cr)E causes dermatitis and cancer, and is often quantified from chrome-tanned leather. Analysis for Cr6+ is generally carried out after extraction into 0.1 M potassium phosphate buffer (P-buffer pH8.0) according to the method of ISO 17075. However, since the pH value of chrome-tanned leather and sweat due to wear are on the acidic side, the abovea method for Cr6+ should be validated using acidic extracts. In the present study, acidic extracts from chrome-tanned leather were analyzed for Cr6+ comparing the results with those using alkaline extracts. A sample of commercial chrome-tanned leather was used to investigate the influence of pH an the extractability of Cr6+. Chromium was extracted from the leather with P-buffer (pH3.0-11.0), acidic artificiel perspiration (pH5.5) or 0.2% sodium sulfate (pH5.5). The contents of total chromium (Cr) and Cr6+ in each extract were respectively measured by inductive coupled plasma atomic emission spectroscopy and colorimetry with diphenylcarbazide. Less Cr was extracted in the range of pH5.5-8.0, whereas more Cr was extracted in the more acidic and alkaline regions. By contrast, the amount of Cr6+ extracted increased moderately with increasing pH. When the P-buffer extract (pH8.0) was adjusted to pH3.0-11.0, the amount of Cr6+ increased with increasing pH, suggesting occurrence of a reversible conversion between Cr6+ and Cr3+. The extraction with P-buffer (pH8.0) may thus pravide a falsely high value due to this conversion. P-buffer (pH5.5) showed a significantly higher extraction of than tests with artificiel perspiration (pH5.5) and 0.2% sodium sulfate (pH5.5). The residue remaining after each extraction was re-extracted with a fresh aliquot of the appropriate extractant. The amount of Cr6+ in the second extract with P-buffer (pH5.5) exhibited a Iow extractability (about 9% of the amount of the first), whereas artificiel perspiration (pH5.5), 0.2% sodium sulfate (pH5.5), and P-buffer (pH 8.0) showed a high extractability (about 41-67% of the amount of the first). lt is thus concluded that extracting with P-buffer (pH5.5) is most efficient of the tested extractants for analyzing Cr6+ from chrome-tanned leather. Note de contenu : - Materials - Extraction of chromium for the leather sample - Measurement of the redox potential of the extract - Analytical methods - Statistical analysis En ligne : https://drive.google.com/file/d/1dCAAo1C3S3vOZgMvheWua20AaoPSaNgW/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=25102 [article]

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Self-conversion of hexavalent chromium formed in chrome-tanned leather during longterm storage and perfect inhibition with an inhibitor combination / Koki Ogata in JOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC), Vol. 102, N° 2 (03-04/2018)  

[article]  inJOURNAL OF THE SOCIETY OF LEATHER TECHNOLOGISTS & CHEMISTS (JSLTC) > Vol. 102, N° 2 (03-04/2018) . - p. 53-58 Titre : Self-conversion of hexavalent chromium formed in chrome-tanned leather during longterm storage and perfect inhibition with an inhibitor combination Type de document : texte imprimé Auteurs : Koki Ogata, Auteur ; Yuki Kumazawa, Auteur ; Shunji Hattori, Auteur ; Keiji Yoshimura, Auteur ; Koji Takahashi, Auteur Année de publication : 2018 Article en page(s) : p. 53-58 Note générale : Bibliogr. Langues : Anglais (eng) Catégories : Chrome hexavalent Cuirs et peaux -- Analyse Cuirs et peaux -- Teneur en eau Echantillonnage Extraction (chimie) Inhibiteurs (chimie) Pyrolyse La pyrolyse est la décomposition ou thermolyse d'un composé organique par la chaleur pour obtenir d'autres produits (gaz et matière) qu'il ne contenait pas. L'opération est réalisée en l'absence d'oxygène ou en atmosphère pauvre en oxygène pour éviter l'oxydation et la combustion (L’opération ne produit donc pas de flamme). Il s'agit du premier stade de transformation thermique après la déshydratation. Elle permet généralement d'obtenir un solide carboné, une huile et un gaz. Elle débute à un niveau de température relativement bas (à partir de 200 °C) et se poursuit jusqu'à 1 000 °C environ. Selon la température, la proportion des trois composés résultants est différente. Réduction (chimie) Index. décimale : 675.2 Préparation du cuir naturel. Tannage Résumé : Complete inhibition of Cr6+ formation from chrome-tanned leather can be achieved by treatment with a three-component inhibitor containing 1.0mmol 3(2)-t-butyl-4-hydroxyanisole, 0.01mmol ascorbic acid, and 0.001mmol collagen peptide. In the present paper, chrome-tanned leather was heat-aged at 80°C for 24 hours and then stored at relative humidity of 33%, 65% or 97% for 12 months to investigate spontaneous conversion of Cr6+ to Cr3+ and to clarify availability of these inhibitors over long-term storage. The amount of Cr6+ decreased as the storage period increased, and was undetectable after 8 months. However, a second reheat-ageing resulted in reformation of Cr6+. This conversion to Cr3+ increased with the water content of the leather. Chrome-tanned leather treated with the three-component inhibitor maintained perfect inhibition of Cr6+ formation for 12 months, even if heat-aged again. Note de contenu : - Materials - Preparation of the leather samples with various water content - Storage of leather samples in RH33%, 65% and 97 % - Extraction of Cr from the treated leather samples - Treatment of the leather with three-component inhibitor - Analytical methods - Statistical analysis - Table 1 : Features of commercial chrome-anned leathers (1-5) - Table 2 : Contents of Cr6+ and total Cr (T-Cr) extracted from heat-aged leather samples with different water content En ligne : https://drive.google.com/file/d/1dluqXwRv-2CUaqX0xOiWs-QUWqYefCP_/view?usp=drive [...] Format de la ressource électronique : Pdf Permalink : https://e-campus.itech.fr/pmb/opac_css/index.php?lvl=notice_display&id=30556 [article]

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