as the labeled concentration and C2 = 90% of this, then -G/k, is the shelf-life at temperature T, (assuming no overage in the product).
An advantage o( this method is that the activation energy and shelf-life can be estimated without assuming a particular reaction order. An average value for E can be estimated by appropriately grouping data into sets with each set having a different a value, then solving them simultaneously by weighted nonlinear regression to estimate an average E across sets and a -Glka for each set.
An analogous technique has been used in thermogravimetric analysis ( 4 4 , in which a number of nonisothermal experiments were performed at different linear heating rates. The logarithm of the reaction rate at a selected percentage decomposition versus 1/T was plotted using this technique. The reaction rate at a specific fraction of decomposition was estimated by linear interpolation. In the method suggested previously, t , can be estimated similarly by linear interpolation, by alternative methods (e.g., cubic splines, polynomial regression), or by assuming knowledge of the functional relationship v( C)] as was done previoulsy ( 1 ) .