Polarization of raw sugar without basic lead acetate: International collaborative test

With the determination of the 100 degree point and the rotatory dispersion of quartz at near infrared (NIR) wavelengths reported at ICUMSA’s 22nd Session at Berlin in 1998, it became possible to properly specify an alternative polarization method for raw sugar that uses NIR wavelengths and does not require the use of a basic lead acetate clarifying agent.

On instructions from ICUMSA’s Referee for Raw Sugar, Mr Ross Urquhart, Central Laboratory drafted an ICUMSA Method for polarization using as a basis the method already in use by the US sugar industry. This draft method was then subjected to a collaborative test conducted among ten participating laboratories drawn from seven countries according to internationally accepted IUPAC protocols. The r and R values of 0.16 ºZ and 0.27 ºZ compare reasonably with those for the “wet lead” method whose r and R values of 0.10 ºZ and 0.25 ºZ were established in a comparable test.