Evaluation of 1percent Neutral Buffered Potassium Iodide Procedure for Calibration of Ozone Monitors.

摘要

The 1percent neutral buffered potassium iodide procedure,as specified for calibration of ozone monitors in the Environmental Protection Agency (EPA) reference method for measurement of photochemical oxidants,was evaluated. The procedure was found to be vulnerable to error in three major areas: (1) the time allowed for measurement of iodine absorbance, (2) purity of potassium iodide reagent,and (3) type of impinger used. Variations in results produced by minor changes within the specifications of the procedure suggest that the method is difficult to control. Improved specifications and procedures were documented to minimize the effect of these parameters on results and to aid the user in proper use of the procedure. The improved procedure shows a positive bias of 7.5 +or - 3.4percent. The Environmental Monitoring and Support Laboratory (EMSL),EPA,has decided that further work to improve the procedure is not warranted and has initiated work on a program to evaluate candidate procedures to replace the neutral buffered potassium iodide procedure.