Photometry of inulin and polyfructosan by use of a cysteine/tryptophan reaction.
Described are a macromethod for measuring 2 to 30 mug of polyfructoside in sample volumes of 0.5 ml and a micromethod for measuring 40 to 400 ng in 10-mul samples. The absorptivity of the cysteine/tryptophan color product is 2.5-to 10-fold those found with use of five other colorimetric methods for inulin. The method is highly specific for alkali-stable polyfructoside. Color, measured at 515 nm, was maximal on development at 56 degrees C for 25 min in dilute (57-58% by vol) sulfuric acid, after the addition of the combined cysteine hydrochloride/tryptophan reagent. Analytical recoveries of inulin and polyfructosan from plasma and urine were complete. With initial alkaline heating, the endogenous blank inulinoid values averaged 0.6 +/- 0.47 (SD) mg/liter for plasma and 0.05 +1- 0.024 mg/min for urine. The coefficient of variation of the macromethod was less then 3%; that for the micromethod ranged from 1.3 to 6.3%. The micromethod appears adaptable to the determination of nanogram quantities of polyfructoside in nanoliter volumes of biological fluids.
D000328:Adult; D003545:Cysteine; D006801:Humans; D007444:Inulin / Q000032:analysis* / Q000097:blood / Q000652:urine; D008722:Methods; D008832:Microchemistry; D011134:Polysaccharides / Q000032:analysis* / Q000097:blood / Q000652:urine; D013053:Spectrophotometry; D013464:Sulfuric Acids; D013696:Temperature; D014364:Tryptophan
D011134:Polysaccharides; D013464:Sulfuric Acids; D014364:Tryptophan; D007444:Inulin; D003545:Cysteine