The sampler was adapted from that of Pate, et al. [9]. In experiments in which SO 2 was generated by
permeation tube and collected in impingers containing H 2O2, untreated 0.8-μm cellulose ester membrane
filters were shown to allow complete passage of SO 2 [10]. In subsequent sampling of an atmosphere
containing ca. 10 ppm SO 2 at 1 L/min for 30 min, two treated filters were placed in series following a
cellulose ester membrane filter. Recoveries were: 0.667 mg SO 2 from the first treated filter, 0.02 mg
SO2 from the second treated filter, and less than 0.003 mg SO 2 in the backup impinger containing 0.3 N
H2O2 [11]. Cellulose ester filters spiked with 0.2 mg H 2SO4 gave the following recoveries: 83.5% using
H2O extraction, 98.5% using hot H 2O extraction, and 82.5% using 0.01 M HCl for extraction.
A study on filter impregnating solutions compared NaHCO 3 and KOH. The chromatograms of samples
from the KOH-treated filters had noticeably flattened and broadened peak shapes as well as retention
times reduced by approximately 10% when compared to the chromatograms of H 2SO4 spiked on filters
impregnated with NaHCO 3[1].