5. AOACSPDSMethods-2018AwardsV3

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( b ) Hydrochloric acid (0.1 M) - Dilute 2.5 mL of 4 M hydrochloric acid to 100 mLwith deionized water.

( c ) Sodium hydroxide (3.5 M) – Dissolve 14.0 g of sodium hydroxide in 100 mLdeionized water.

( d ) Sodium acetate (0.001 M) – Dissolve 136 mg of sodium acetate in 1000 mL ofdeionized water.

( e ) Ferric chloride acidified (0.37 M) – Dissolve 10.0 g of ferric chloride in 100 mL of 0.1 M hydrochloric acid. ( f ) Hydroxylamine hydrochloride (2 M) – Dissolve 13.9 g in 100 mL of deionizedwater. This solution must be prepared for use on the day of analysis. ( g ) Alkaline hydroxylamine hydrochloride – Mix equal volumes of hydroxylamine hydrochloride and sodium hydroxide solution. This reagent must be prepared for use on the day of analysis.

E. Optimization of pH ( a ) The optimum pH for color development needs to be in the range of 1.0 –1.4.

( b ) Mix 1.0 mL of deionized water, 2.0. mL of alkaline hydroxylamine hydrochloride, 0.7 mL of 4 M hydrochloric acid and 1.0 mL of ferric chloride.

( c ) The pH should be in the range of 1.0 – 1.4. If not, modify the amount ofhydrochloric acid used.

( d ) If the pH is not acidic enough a brown precipitate will form, if too acidic the color response is diminished. F. Preparation of Test Solutions (a) Preparation of calibration standard solutions.–Accurately weigh 50 ± 5 mg of acetylcholine chloride into a 50 mL volumetric flask. Record the weight to thenearest 0.01 mg, dissolve and dilute to volume with sodium acetate solution. Label as “Stock Standard Solution”. This standard must be prepared for use on the day of analysis. Prepare calibration standard solutions in separate centrifuge tubes as shown in the table below. Standard solutions 1–5 should be prepared in duplicate (Table 2018.14A ). (b) Preparation of liquid sample test solutions.–Accurately weigh (to the nearest 0.1 mg) the amount listed in the table below into a 10 mL volumetric flask. Dilute to volume with water and pass through a 0.45 µm filter if the solution is not clear. Transfer 1.0 mL of this solution into separate centrifuge tubes. The samples should be prepared in duplicate and assayed on the day of preparation ( Table 2018.14B ). (c) Preparation of powdered sample test solutions.–Accurately weigh (to the nearest0.1 mg) the amount listed in the table below into a 50 mL volumetric flask. Add approximately 35 mL of water and place in an ultrasonic bath for 30 minutes. Cool to room temperature, dilute to volume with water and pass through a 0.45 µm filter. Transfer 1.0 mL of this solution into separate centrifuge tubes. The samples should be prepared in duplicate and assayed on the day of preparation. (d) For aloe vera samples of high polysaccharide (>20%) and high fiber content.–Shake the solutions at 200 rpm on an orbital shaker overnight in at least 35 mLof water, transfer to a 50 mL volumetric flask, dilute to volume with water and pass through a 0.45 µm filter. Transfer 1.0 mL of this solution into