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False‐positive result when a diphenylcarbazide spot test is used on trivalent chromium‐passivated zinc surfaces
Author(s) -
Reveko Valeriia,
Lampert Felix,
Din Rameez U.,
Thyssen Jacob P.,
Møller Per
Publication year - 2018
Publication title -
contact dermatitis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.524
H-Index - 96
eISSN - 1600-0536
pISSN - 0105-1873
DOI - 10.1111/cod.12955
Subject(s) - zinc , chromium , patch test , test (biology) , chemistry , nuclear chemistry , metallurgy , inorganic chemistry , medicine , materials science , allergy , immunology , biology , paleontology
Summary Background A colorimetric 1,5‐diphenylcarbazide (DPC)‐based spot test can be used to identify hexavalent chromium on various metallic and leather surfaces. DPC testing on trivalent chromium‐passivated zinc surfaces has unexpectedly given positive results in some cases, apparently indicating the presence of hexavalent chromium; however, the presence of hexavalent chromium has never been confirmed with more sensitive and accurate test methods. Objectives To examine the presence of hexavalent chromium on trivalent chromium‐passivated zinc surfaces with a DPC‐based spot test. Methods A colorimetric DPC spot test was used for the initial detection of hexavalent chromium on new and 1‐year‐aged trivalent chromium‐passivated zinc surfaces. Then, X‐ray photoelectron spectroscopy (XPS) was performed for all samples. Results The DPC spot test indicated the presence of hexavalent chromium in aged, but not new, trivalent chromium passivation on zinc; however, subsequent analysis by XPS could not confirm the presence of chromium in a hexavalent state. Conclusions Unintended oxidation of DPC induced by atmospheric corrosion is suggested as a possible reason for the false‐positive reaction of the DPC test on a trivalent chromium‐passivated zinc surface. Further validation of the use of the DPC test for chromium‐containing metallic surfaces is required.