A Study on the Filter Collection of Hydrogen Cyanide in Air for Trace Analysis

A new method for the collection of trace concentration of hydrogen cyanide in air was studied for the purpose of economizing the sampling time, Hydrogen cyanide was captured reacting with the reagent coated on a filter. Alkali and nickel salts were examined as the coating reagent. The most suitable filter for collection is prepared as follows. The filter ordinarily used for aerosol collection was dipped in an aqueous solution of ammoniacal nickel chloride (or nitrate). Then it was air-dried and stored in a desiccator which had been saturated with ammonia gas just before its use. The collection efficiency depended on the volume of sample air and was more than 95% when the air containing 5～200ppb hydrogen cyanide was led at avelocity of 5 meters per minute. It was hardly affected by variations of temperature and humidity and by the presence of sulfur dioxide or nitrogen dioxide in the concentration of the order of urban atmosphere. The recovery of hydrogen cyanide of ppb order ranged from 90 to 100%, when the sample air was led to the filter at flow rate of 200 liters per minute for 20minutes using high volume air sampler with sampling area of 400 c㎡