The assay of insulin solutions by paper chromatography

Abstract

A method for the assay of insulin solutions by ascending paper chromatography is described. The solutions, after desalting and concentration, are applied to papers which are developed in the upper phase of butan-2-ol-l% acetic acid (11, v/v), then stained with bromocresol green. The dye is eluted and its concentration measured in a spectrophotometer with respect to standards run simultaneously. Treatment of the data as a four-point slope ratio assay gave results in good agreement with those obtained on the same solutions by the mouse convulsion method. Solutions of four-times-recrystallized insulin, stored in the frozen state for use as working standards, remained stable for periods up to 8 weeks at [long dash]30[degree], and could be refrozen and thawed up to 30 times in the presence of phenolic preservative without detectable loss of potency.