Patent ID: 8603830

Claim:
A method for the determination of polysorbate in a protein-containing sample, comprising the steps: (a) subjecting the sample to alkaline hydrolysis; (b) neutralizing the sample after alkaline hydrolysis; (c) optionally removing denatured protein precipitate from the neutralized sample by filtration or centrifation to form a filtered sample; (d) adding an aqueous mixture of a thiocyanatometal complex to the optionally filtered sample to form a sorbitan polyoxyethylenethiocyanatometal complex; (e) extracting said sorbitan polyoxyethylenethiocyanatometal complex formed in step (d) into a non-water miscible organic solvent; (f) measuring the absorbance of the extract obtained in step (e) to quantify the amount of said sorbitan polyoxyethylenethiocyanatometal complex formed in stop (d); and (g) calculating the amount of the polysorbate contained in the sample from the amount of said sorbitan polyoxyethylenethiocyanatometal complex determined in step (f).