• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.41 no.4
• /
• pp.33-42
• /
• 2009

This study was performed to evaluate the hexavalent chromium content in flexography inks and organic pigments used as colorants for the ink. The digestion of sample was carried out under alkaline condition, and the content of soluble hexavalent chromium extracted from samples was determined by UV-visible colorimetric analysis method after alkaline digestion. Duplicate sampling system to obtain two digested samples, was applied in this study. To determine the hexavalent chromium content in the flexography ink and organic pigment colorimeteric analysis was employed. Because the organic pigment is the main ingredient of flexography ink it is important to remove the errors associated with the colorant of the ink in colorimetric determination. The duplicate sampling system allowed us to correct the errors associated with the colorimeteric measurement. The additional filtration was found an essential step to exclude colorimeteric error derived from the various precipitates. The soluble hexavalent chromium content in flexography inks was generally less than 5 ppm. Yellow, violet and some magenta colors showed higher soluble hexavalent chromium contents. The content of hexavalent chromium in organic pigments was greater than flexography inks, and yellow, violet and some magenta pigments contained greater amount of hexavalent chromium, which indicated that the hexavalent chromium in inks derives from the colorants. The soluble hexavalent chromium content in linerboards were below 1 ppm, and no hexavalent chromium was detected in UKP. Results suggested that flexography ink is the main factor to cause hexavalent chromium in linerboard and organic pigments.