The use of impregnated filters to collect traces of gases in the atmosphere

Abstract HA and AA Millipore filters impregnated with 5% potassium bicarbonate and dried were found to be suitable for sampling concentrations of sulfur dioxide in air. The impregnation technique and filter loadings are described; flow rates are relatively unaffected by impregnation. The apparatus and procedures used for preparation and sampling known concentrations of sulfur dioxide in air are described. Comparisons of actual and theoretical concentrations in the 0.1 to 10 p.p.m. range showed that the concentrations prepared must be assayed. The collection efficiency of impregnated filters was evaluated for sodium tetrachloromercurate-(II) (less than 10% which is in contrast with the 100% efficiency found with TCM as a scrubbing solution) and potassium bicarbonate (greater than 95%). The capacity of the filters was such that sampling a 10 p.p.m. sample for at least 1 h is possible.