Crystal growth of cephalothin sodium in frozen solution. I. Determination of crystallinity in frozen solution

Abstract

Investigation has been made to obtain the crystallinity of cephalothin sodium in seeded and frozen aqueous solution from electrical conductivity (conductivity), with a result that crystallinity (α(t)) can be given by the equation of α(t)=λ(T)-λ(t)λ(T), where λ(T) is the initial conductivity and λ(t) stands for the conductivity obtained after t hours. Observed values of crystallinity by the conductivity method are in good agreement with crystallinity data by infrared method and X-ray diffraction method of the freeze-dried material. Further investigation has been made to find out whether it is possible to apply the no-seeding conductivity method for the cystallinity of dicethiamin hydrochloride in solution capable of spontaneous nucleation and transformation to its crystalline state. The result has consequently demonstrated that, in some cases of no-seeding, the phase transition is not uniform, or otherwise, the conductivity change provides an incomplete indication of nucleation and growth of perfect crystals. From the above, it may as well be said to be safe to set a limit to a seeded system, when the authors' conductivity method is applied for obtaining the crystallinity of a drug in frozen solution.