Frozen solutions, stability

Goff, H.D. and Sahagian, M.E. 1996. Glass transitions in aqueous carbohydrate solutions and their relevance to frozen food stability. Thermochim. Acta 280, 449 164. 

Stock Solution Stability. The stability of stock solutions of drug and the internal standard should be evaluated at room temperature for at least 6 h. If the stock solutions are refrigerated or frozen for the relevant period, the stability should be documented. After completion of the desired storage time, the stability should be tested by comparing the instrument response with that of freshly prepared solutions. 

Twenty-two derivatives of spiro[(27/-l-benzopyran)-2,2 -benzo-l, 3 -dithiole] (117) were prepared (35-80% yield) and studied. Most existed in solution only in the spiro form, and were fast faders so that photochromism was observable only in frozen solutions at 77 K. The colored forms (Amax usually in the 550-600-nm region) were stabilized by 7-diethylamino and 7,8-benzo groups. The benzodithiolane and benzoxathiolane spiropyrans exhibit positive solvatochromism, rather than the... 

Exhaustive electrolysis of the zinc(II) catenate at the first reduction wave plateau (-1.1 V) leads to the formation of a pink-red solution (2 iax = 530 mn, e 1000 cm ) of the corresponding monovalent complex. EPR measurements performed on a frozen solution of the electrochemically generated monovalent zinc catenate show the presence of a paramagnetic radical species (g = 2.00246, A/7 = 11.46 G). The reduced states Zn.S and Zn.5", containing formally monovalent and zerovalent zinc, respectively, are better described as zinc(II(-stabilized anion radicals. 

Solutions of crude preparations of hyaluronidase can be stored frozen for several months without losing important amounts of activity [26,50,73]. Purified hyaluronidase rapidly loses all activity when stored frozen unless stabilizing agents like detergents or high concentrations of salts are added [63]. At neutral pH, solutions of hyaluronidase can be stored at room temperature for several days [50], The temperature profile of activity of the enzyme shows a sharp decline at a temperature of about 50°C. Hyaluronidase is rapidly inactivated when stored at 55-60°C [14,50,52], but it can be kept at 40°C for at least one hour without losing activity [30,50]. 

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