AOAC 2018 Methods

AOAC Official Method 2018.14 Quantitation of Aloe Vera Polysaccharides O-Acetyl and UV-VIS Spectrophotometry First Action 2018 Caution: This method uses common reagents. Refer to the appropriate safety data sheets to ensure that the safety guidelines are applied before using chemicals. Hydrochloric acid and sodium hydroxide .–Causes burns and eye damage. Wear protective gloves, clothing and eye protection. Use only in an effective fume removal device to remove vapors generated. A. Principle The acetyl groups from the 1,4-acetylated polymannose are reacted with hydroxylamine to form acetohydroxamic acid. This resulting compound is then reacted with ferric chloride to form a reddish ferric-acetohydroxamic complex. The amount of aloe vera polysaccharide is determined by measuring the absorbance of the complex at 540 nm and comparing to a calibration curve using acetylcholine as a reference standard. This method is able to quantify aloe vera polysaccharide content from 0.03–100%. Since this method is non-specific and has not been validated for formulated finished products, its use is limited to the analysis of processed raw materials only. B. Apparatus ( a ) UV-VIS spectrophotometer set to 540 nm. ( b ) Cuvettes - 1 cm quartz or optical glass. ( c ) Analytical balance – accurate to ± 0.01 mg. ( d ) pH meter. ( e ) Ultrasonic bath. ( f ) Vortex. ( g ) Orbital shaker ( h ) Adjustable pipettors – 10–200 µL, 100-1000 µL, and 0.5–5mL. ( i ) Centrifuge tubes –15 mL disposable ( j ) Reagent bottles – 100 mL. ( k ) Volumetric flasks – 10, 50, and 1000 mL. ( l ) 0.45 µm syringe filters. ( m ) Graduated cylinder – 250 mL C. Reagents ( a ) Water , HPLC grade ( b ) Gum acacia , Cat. No. 511985 (Sigma-Aldrich, St. Louis, MO, USA; www.sial.com) ( c ) Hydroxylamine hydrochloride , reagent grade ( d ) Acetylcholine chloride , Cat. No. A6625 (Sigma-Aldrich, St. Louis, MO, USA; www.sial.com) ( g ) Sodium hydroxide , reagent grade ( h ) Sodium acetate , reagent grade D. Solutions ( a ) Hydrochloric acid (4M) - Dilute 67 mL of 12 M hydrochloric acid to 200 mL withdeionized water. ( e ) Ferric chloride hexahydrate , reagent grade ( f ) Hydrochloric acid (12M) , reagent grade