Development of the analytical method for chromium in air adapted to the revision of substances requiring priority action

Abstract

An improved analytical method for the determination of total and hexavalent chromium in air has been developed to meet the requirement of revision of substances requiring priority action in Japan. Total Cr was measured using energy dispersive X-ray fluorescence spectrometry, and hexavalent chromium was measured by alkali digestion followed by ion chromatography coupled with postcolumn diphenylcarbazide absorption spectrophotometry. A trace amount of hexavalent chromium was always found in the extraction solution, and sodium hydroxide was a possible contamination source. The recovery of hexavalent chromium through the analytical procedure developed in this study was almost 100%. Changes in the chemical form of chromium, Cr^VI to Cr^III or vice versa, were not observed during 1 week of air sampling. The concentrations of total Cr were 6.5±4.9 ng/m³, those of Cr^VI were 1.0±1.0 ng-Cr^VI/m³, and the ratios of Cr^VI to total Cr were 17.4±15.1%, in PM_2.5 collected in Yokohama, Japan, from January, 2012 to July, 2013 (n=14).