National Institute for Occupational Safety and Health

“ For samples containing > 4 mg acetic anhydride, dilute an aliquot of the bubbler solution to 50 mL at this step. Apply the appropriate dilution factor in calculations. 9. Pipet 5 mL ferric chloride solution into the flask. 10. In an ice bath, mix equal volumes of sodium hydroxide solution, hydroxylamine hydrochloride solution and ferric chloride solution. Add this solution to bring the solution in the 50-mL volumetric flask to the mark. The purple complex is formed rapidly. ”

“ The average of concentrations obtained at 20 mg/m 3 for the overall sampling and measurement technique was 2.5% higher than the true concentrations representing a non-significant bias for a limited number of experiments [1] . ”

“ Wash the stem with 1 to 2 mL absorbing solution and add the wash to the bubbler. 6. Seal the bubbler tightly with a hard, non-reactive stopper and transport the samples by hand. Alternatively, transfer contents of each bubbler to a glass vial, rinsing bubbler with 1 to 2 mL absorbing solution. Cap the vial securely for shipment.
NIOSH Manual of Analytical Methods (NMAM) , Fourth Edition, 8/15/94 ACETIC ANHYDRIDE: METHOD 3506, Issue 2, dated 15 August 1994 - Page 3 of 4 SAMPLE PREPARATION: 7. Transfer sample solution to a 50-mL volumetric flask. 8. ”