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| Based on ultrasound-assisted on-line hydrolysis, a rapid and simple flow injection method is developed for the spectrophotrometric determination of polysaccharides with 3,5-dinitrosalicylic acid color reaction. In hydrolysis coil, placed in an ultrasonic and heating water bath, polysaccharides in dilute HCl solution were on-line hydrolyzed into reducing sugars. When the concentration of HCl solution was 2.5 mol L-1, the polysaccharide (glucan) of molecular weight 500,000 could be quickly and quantitatively hydrolyzed. Then the reducing sugars reacted with alkaline 3, 5-dinitrosalicylic acid solutions to form a red compound and the absorbance at 540 nm were measured. Expressed in glucose, the detection limits and linear ranges were 10 µg mL-1 and 20 -- 150 µg mL-1, respectively. The sampling rate was 45 h-1 and the average recoveries of known amount of the polysaccharide ranged between 96.0-102 %. |
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| Keywords:Polysaccharides; FIA; Ultrasound-assisted on-line hydrolysis; Spectrophotometry |
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