Simple spectrophotometric method for the estimation of algal polysaccharide concentrations

A rapid and simple spectrophotometric method is described for the estimation of microgram quantities of algal polysaccharides following the formation of soluble complexes with methylene blue dye. The binding of the dye to algal polysaccharides causes the absorption maximum (664 nm) to decrease, which is almost linear over the range of 0-30 microg for the algal polysaccharides studied. The absorbance at 664 nm can be measured immediately after the mixing of algal polysaccharides and dye solution and is stable over a period of 2 h. No heating, centrifugation, lengthy equilibration, or sophisticated instrumentation, which hamper other methods, is required. The interference due to individual monosaccharides, neutral polysaccharides, bovine serum albumin, sodium dodecyl sulfate, and high concentrations of inorganic salts is discussed.