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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