Page:NIOSH Manual of Analytical Methods - 5035.pdf/3

 SUPER ABSORBENT POLYMERS: METHOD 5035, Issue 1, dated 15 August 1994 - Page 3 of 6

6. 7. 8.

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11. 12. 13.

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within about 4 h before use). Add 14 mL of deionized water. Cap the vial. Place the vial into an ultrasonic bath for 15 min. Collect the copper-polymer precipitate on a 25-mm cellulose ester filter (0.45-µm pore size) by vacuum filtration. NOTE: The copper-polymer precipitate should be collected within about 4 h after the addition of copper acetate solution to samples and blanks. Particles containing copper may appear in copper acetate solution if the solution stands for a few days. These particles would cause a positive interference. Rinse the vial with two 12-mL portions of deionized water, and add the rinses to the filtration apparatus. If blue particles of copper-polymer precipitate are observed in the vial after the two rinses, rinse the vial with additional water until blue particles are not observed in the vial. Add the additional rinses to the filtration apparatus. Recover super absorbent polymer from the interior surface of the front piece of the cassette filter holder. a. Seal inlet of front piece of the cassette filter holder with a plug. b. Add 5 mL of 0.07 M copper acetate to this cassette piece. c. Place this cassette piece into a clean ultrasonic bath for about 30 sec. NOTE: If a visible coating of copper-polymer precipitate does not become dislodged during ultrasonic treatment, the coating may be dislodged with a glass stirring rod. d. Pour solution from cassette piece to the vacuum filtration apparatus. e. Rinse cassette piece with 5 mL of deionized water. Transfer the 25-mm cellulose ester filter with collected precipitate to a 125-mL Phillips beaker. Cover with a watch glass. Rinse the bottom part of the top piece of the filtration apparatus with deionized water in a 50-mL beaker. Assemble the vacuum filtration apparatus with a clean 25-mm cellulose ester filter. Add the rinse from the 50-mL beaker to the filtration apparatus. Transfer the 25-mm filter to the same Phillips beaker (step 10). NOTE: Steps 12 and 13 are applicable if the vacuum filtration apparatus is the type that sandwiches the filter between the top piece (vertical column) and the bottom piece. When the vertical column is separated from the filter, water with copper-polymer precipitate may travel by capillary action to the underside of the vertical column. Also, precipitate may cling to the inside wall of the vertical column. Add 10 mL of 70% nitric acid and 1 mL of 70% perchloric acid to filters in the Phillips beaker. NOTE: Use of perchloric acid is optional. a. Cover the beaker with the watch glass. b. Place the beaker onto a hot plate at 150 °C, and reflux overnight. c. Remove the watch glass, and heat the mixture just to dryness at 150 °C. d. Remove the beaker from the hot plate. Add 0.5 mL of 4:1 70% nitric acid:70% perchloric acid (v/v) or 0.5 mL of 70% nitric acid (choice depends on whether the standard solutions contain perchloric acid). e. Dilute the mixture to 10 mL with deionized water.

CALIBRATION AND QUALITY CONTROL: 15.

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Determine the amount of water present in a bulk sample of the super absorbent polymer. Place an accurately weighed 20-g sample of the super absorbent polymer into an oven at 130 °C for about 16 hours. Determine the weight loss, and calculate the amount of water in the original sample (percent by weight). Calibrate with at least six working standards. a. Prepare a series of working standards of super absorbent polymer in sucrose by dilution of portions of the calibration stock mixture with sucrose. Calculate the quantities of calibration stock mixture which will be diluted with about 8 g of sucrose in order that 50 to 300 mg of each working standard contains a desirable quantity of anhydrous super absorbent polymer NIOSH Manual of Analytical Methods (NMAM), Fourth Edition, 8/15/94