Field Method for the Determination of Insoluble or Total Hexavalent Chromium in Workplace Air

Abstract

National Institute for Occupational Safety and Health method 7703 is a portable field procedure for the analysis of workplace air filter samples for hexavalent chromium (Cr^VI) content immediately after the samples are collected. The field method prescribes Cr^VI extraction from air filter samples with an ammonium sulfate/ammonium hydroxide extraction buffer using ultrasonic extraction (UE). Strong anion-exchange solid-phase extraction (SAE-SPE) is then used to separate Cr^VI from trivalent chromium and other interferences. Portable spectrophotometric measurement of Cr^VI is then conducted using the 1,5-diphenylcarbazide (DPC) method. However, it has been found that the ammonium extraction buffer does not adequately bring insoluble Cr^VI compounds into solution during the UE process. Thus, it was deemed necessary to modify the field method so that it would provide acceptable recoveries for insoluble Cr^VI compounds. To this end, a more alkaline extraction solution—sodium carbonate/sodium bicarbonate buffer—was investigated. The modified procedure using the highly alkaline extraction solution was demonstrated to be compatible with SAE-SPE cartridges when determining insoluble Cr^VI in air filter samples. It was found that the carbonate/bicarbonate buffer was equally effective for complete dissolution of both insoluble and soluble forms of Cr^VI. Furthermore, the modified procedure met desired performance criteria established for air sampling and analytical methods.

Keywords:

• field method
• hexavalent chromium
• insoluble chromates
• on-site analysis
• sample preparation
• workplace air

ACKNOWLEDGMENTS

The authors thank Paul Pierce for generating welding samples, and Mandi Hopkins for conducting interference check experiments; both are with the CDC/NIOSH Spokane Research Laboratory. This research was conducted under the auspices of a CDC/NIOSH project on field measurement of metals in workplace air.

Mention of company names or products does not constitute endorsement by the Centers for Disease Control and Prevention.

Notes

^A Standard deviation.

^B Relative standard deviation.

^A Polyvinylchloride.

^B Mixed cellulose ester.

^A Standard deviation.

^B Polyvinylchloride.

^C Mixed cellulose ester.

^D Relative standard deviation.

^A Standard deviation.

^A Polyvinylchloride.

^B Mixed cellulose ester.

^C Standard deviation.

^A Polyvinylchloride.

^B Mixed cellulose ester.

^C None detected.

^D Standard deviation.

^A Polyvinylchloride.

^B Mixed cellulose ester.

^C None detected.

^D Standard deviation.