Measurement of Hexavalent Chromium in Chrome-Tanned Leather: Comparative Study of Acidic Condition Extraction with Alkaline Extraction

作者：Ogata Koki^*; Kumazawa Yuki; Koyama Yoichi; Yoshimura Keiji; Takahashi Koji

来源：Journal of the Society of Leather Technologists and Chemists, 2015, 99(6): 293-296.

Hexavalent chromium (Cr6+) 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 above 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 on the extractability of Cr6+. Chromium was extracted from the leather with P-buffer (pH3.0-11.0), acidic artificial 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 Cr. The extraction with P-buffer (pH8.0) may thus provide a falsely high value due to this conversion. P-buffer (pH5.5) showed a significantly higher extraction of Cr6+ than tests with artificial 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 low extractability (about 9% of the amount of the first), whereas artificial 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). It is thus concluded that extracting with P-buffer (pH5.5) is most efficient of the tested extractants for analyzing Cr6+ from chrome-tanned leather.

• 出版日期2015-12