( ochemical polymerization is ...)Acrylamide Polymerization A Practical Approach

ochemical polymerization is initiated by riboflavin (or riboflavin-5'-phosphate), or by a combination of riboflavin and ammonium persulfate. Initiation and polymerization are catalyzed by TEMED. Because polymerization is initiated by the generation of free radicals from persulfate or riboflavin, it is not surprising that these compounds are reactive, and prone to oxidation or decomposition. The contaminants of the initiators tend to be the products of their own breakdown as well as other contaminating compounds.

TEMED is subject to oxidation, which causes the gradual loss of catalytic activity. This process is greatly accelerated by contaminating oxidizing agents. TEMED that contains oxidation products is characterized by a yellow color. The practical consequences of the oxidative process are the requirement for greater amounts of TEMED to achieve adequate polymerization, and a gradual loss of TEMED reactivity with time. TEMED is also very hygroscopic and will gradually accumulate water, which will accelerate oxidative decomposition. TEMED with maximum activity and shelf life is obtained by redistillation immediately prior to bottling, resulting in a product that is clear, water free, and greater than 99% pure (14.4 M).

Ammonium persulfate is also very hygroscopic. This property is particularly important, since ammonium persulfate begins to break down almost immediately when dissolved in water. Therefore, the accumulation of water in ammonium persulfate results in a rapid loss of reactivity. This is why ammonium persulfate solutions should be prepared fresh daily. Persulfate is consumed in the polymerization reaction. Excess persulfate can cause oxidation of proteins and nucleic ac
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