October 2017 Abstracts

Ion Chromatography with Post Column Derivatization for the Determination of Hexavalent Chromium in Dyed Leather. Influence of the Preparation Method and of the Sampling Location

by Mathilde Fontaine, Nicolas Blanc, Jean-Claude Cannot and Claire Demesmay

Since 2015, a European restriction limits the hexavalent chromium content to not more than 3 mg/kg in leather products (UE-301-2014, 25 March 2014, §47, annex XVII of REACh). Owing to spectrophotometric interferences encountered with the established European standard EN ISO 17075:2007 when colored leathers have to be analyzed, this article proposes the analysis of hexavalent chromium using ion chromatography with post-column derivatization and spectrophotometric detection. In order to avoid any pre-treatment of the crude extract an on-line solid phase extraction step is introduced by inserting a high capacity reversed phase guard column. The efficiency of the on-line purification is demonstrated (quantitative removal of the dye present in the extract) and allows the direct analysis of crude extracts in less than 6 minutes. The overall chromatographic method is validated following procedures described by the French standard NF T90-210. The measurement error (bias) was determined at 7.2% at the presupposed limit of quantification 5 µg/L (corresponding to a hexavalent chromium content of 0.25 mg/kg in leather) and at the medium concentration level and at 4.0% for the high-level concentration, with relative standard deviations of 5.1%, 2.9% and 2.4% respectively. The recovery yields measured with spiked leathers range from 92 to 96% depending on the hexavalent content. The reliability of the method is also demonstrated through two inter-laboratories test involving several European laboratories. The crucial influence of the sample preparation is also assessed in this work. It is demonstrated that the hexavalent chromium content of leathers is systematically underestimated when the extraction is applied to leathers cut in small pieces and not ground. In parallel, additional tests on leather sampling location show that the shoulder zone is not representative of the rest of the skin in terms of hexavalent chromium content since it has a higher hexavalent chromium content than all other sampling zones.

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Antioxidant Effects of Keratin Hydrolysates

by Ján Matyašovský, Ján Sedliacik, Katarína Valachová, Igor Novák, Peter Jurkovic, Peter Duchovic, Matej Micušík, Angela Kleinová and Ladislav Šoltés

The antioxidant and antimicrobial properties of keratin hydrolysates from acid and from oxidative hydrolyses were studied. For in vitro studies of antioxidant properties of the keratin hydrolysates, high-molar-mass hyaluronic acid (HA) that is especially sensitive to the effect of oxidants was used as a substrate. Cu(II) ions and ascorbate-mediated degradation of hyaluronan in the absence and presence of keratin hydrolysate as antioxidant were examined using the method of rotational viscometry. Results indicate that keratin effectively inhibited HA degradation and thereby the formation of hydroxyl-, alkoxy- and peroxy-type radicals. Results of the ABTS assay show that keratin hydrolysate efficiently reduced ABTS•+ cation radical. The keratin hydrolysates also had antimicrobial effects on selected bacterial strains and caused decreases in formaldehyde emission from urea-formaldehyde bonded materials.

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Non-polar Medium Enables Efficient Chrome Tanning

by Palanisamy Thanikaivelan, Selvaraj Silambarasan, Rathinam Aravindhan And Jonnalagadda Raghava Rao

Converting raw hides and skins into leather through chrome tanning in water medium creates huge environmental burden by contaminating the precious water resource on the one hand and discharging more chromium on the other. Here, a non-polar green solvent, heptane, alternate to water has been evaluated for chrome tanning employing both pickle-based and pickle-less method. The preceding (pre-tanning) and succeeding (post-tanning) processes were water mediated for comparison. The results show that the color and other organoleptic properties of both wet blue and crust leathers are comparable to conventional leathers. The strength and structural properties of experimental crust leathers are comparable to that of control leathers. The main benefits in switching over to heptane medium are improved exhaustion of chromium during both pickle-based and pickle-less chrome tanning, better chromium distribution and recycling ability. The process also helps in reducing the chemical oxygen demand, biological oxygen demand and total solids levels in the composite liquor significantly.

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Effect of Fatliquoring on Leather Comfort. Part III: Moisture Absorption-Desorption of Leather

by A.M. Manich, J. Barenys, L. Martínez, J. Lloria, J. Carilla and A. Marsal

The comfort of tanned hide/skin is an added value, which is decisive for the choice of leather in articles for footwear or clothing, compared to other alternatives whose design excludes this component. This comfort is related to the capacity of absorption and desorption of moisture and with the physical, mechanical and organoleptic characteristics of the leather. After tanning, fatliquoring and retanning are the operations that more intensively modify the characteristics of leather articles.

This work is a continuation of two previous ones that have studied the influence of fatliquoring on softness and compressibility of leather and on grain and corium quality of leather assessed by ball bursting and tearing tests. In this case, the effect of fatliquoring on moisture absorption-desorption characteristics of leather is studied. The experimental work has been carried out in the pilot plant of Trumpler Española S. A. and the moisture absorption-desorption tests in the Laboratory of Thermal Analysis and Calorimetry of the IQAC. The behavior of non-fatliquored leather and that of leather fatliquored with a combination of sulphited triglycerides of colza oil and fatty polymer (TCSi/PGR) or fatliquored separately with their components TCSi and PGR, or with phosphoric ester ESF or sulphited fish oil Psi has been determined.

The determination of the size of the moisture absorbing monolayer (Xm), the binding energy constants of the monolayer C and the multilayer K, the maximum absorption capacity at saturation X1 and the hysteresis (Hyst.) between absorption and desorption, enabled us to classify the different fatliquoring agents according to stage (crust-blue, finished-red) by applying factorial analysis (see following graph). Finishing is the factor that best explains this behavior. Finishing decreases the size of the monolayer and increases the binding energy constants. Fatliquoring decreases the maximum absorption capacity and hysteresis, partially affecting the reduction of the monolayer size.

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