Journal article
False-positive result when a diphenylcarbazide spot test is used on trivalent chromium-passivated zinc surfaces
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.
Language: | English |
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Publisher: | Blackwell Publishing Ltd |
Year: | 2018 |
Pages: | 315-320 |
ISSN: | 16000536 , 01051873 and 13966669 |
Types: | Journal article |
DOI: | 10.1111/cod.12955 |
ORCIDs: | 0000-0001-5855-440X , Lampert, Felix and Din, Rameez Ud |
Contact allergy DPC spot test EU regulation False-positive result Hexavalent chromium Trivalent chromium passivation of zinc
Chromium Chromium Compounds Colorimetry Diphenylcarbazide False Positive Reactions Materials Testing Oxidation-Reduction Photoelectron Spectroscopy Zinc chromium hexavalent ion contact allergy false-positive result false‐positive result hexavalent chromium trivalent chromium passivation of zinc