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. 2014 Feb 10;58(4):413–423. doi: 10.1093/annhyg/met078

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© The Author 2014. Published by Oxford University Press on behalf of the British Occupational Hygiene Society.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.

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Typical response curves obtained for the measurement of acid-extractable (a) iron, (b) nickel, (c) chromium, and (d) copper. The linear response generated for each metal was 1.1–10 µg Fe, 1–10 µg Ni, 0.15–6 µg Cr, and 1.5–8 µg Cu. µPAD error bars are based on measurements between samples (N ≥ 4). Colorimetric intensity was determined using a desktop scanner. Raw samples images for each metal are included to the right of each calibration graph.