Ten NIOSH (National Institute for Occupational Safety and Health) Analytical Methods - Phosphorus Pentachloride

摘要

The NIOSH validated method for the determination of phosphorus-pentachloride (10026138) is described. Forty eight liters of air (flow rate at 0.2 liters per minute) is drawn through a polyvinyl-chloride filter followed by a midget bubbler containing 15 milliliters (ml) distilled water. The contents of the bubbler are transferred to a 50ml volumetric flask. Five ml of a solution of 25.0 grams (g) sodium-molybdate per liter of 10 normal sulfuric-acid, and 2ml of 1.5g hydrazine-sulfate per liter distilled water are added to the flask. The flask is diluted to the mark with distilled water and immersed in a boiling water bath for 10 minutes. After cooling, the absorbance of the solution is measured at a wavelength of 830 nanometers. The concentration as phosphoric-acid is determined by comparison with a calibration curve obtained by analyzing aliquots of 0.1389g per liter potassium-dihydrogen-phosphate solution. The equivalent amount of phosphorus-pentachloride is calculated. The method can determine phosphorus-pentachloride in concentrations of 0.55 to 2.00 milligrams per cubic meter (mg/cu m) with a standard deviation of 0.05mg/cu m. Sensitivity is 0.42mg/cu m. Airborne water soluble compounds containing phosphorus in the plus 5 oxidation state can interfere with determination.