Methods for extraction of sulfate from glass-fiber hi-vol and Teflon lo-vol samples were evaluated. Efficiencies were found to vary with sampling location up to 20%. Mechanical shaking in water at room temperature was significantly more efficient than ultrasonic or reflux techniques with hi-vol samples. While Teflon filters are not wet by water, pre-wetting of filters with methanol did not significantly enhance sulfate extraction. A turbidimetric sulfate method using SulfaVer IV was evaluated for ruggedness, precision and intermethod agreement. Its precision was at least equal to that of a conventional turbidimetric method, but its accuracy was somewhat less, especially at lower sulfate levels. The Dionex Model 10 ion chromatograph was evaluated for low level sulfate analysis using both a sample preconcentrator and large (0.5 ml) sample loop. The latter was the preferred technique for samples = or < 20 microgram/ml. Accuracy was within 15% in the range 2 to 20 microgram/ml with a median C.V. of 6.5% for 24 atmospheric samples collected with dichotomous samplers. Use of a sample pre-concentrator permitted analysis of samples containing < 1 microgram/ml sulfate.

"Project Officer John C. Puzak, Quality Assurance Division"--T.p. "Air and Industrial Hygiene Laboratory Section, California Department of Health Services, EPA Grant No. 805-447-1"--T.p. "April 1980"--Cover.