Dear Members

We are using a in-house fabricated flow through dissolution cell for release studies of some compound. The cell is open type in which we collect samples for 15 minutes for 10 hours with flow rate maintained at 1ml/minutes. All samples are subsequently analyzed by HPLC and all the studies are in triplicates.

To chart the cumulative amount released vs. time, we sum up the average (of replicates at given time point) amount released in previous intervals.

We want to plot the standard deviation error bars for the cumulative amount. So how we should determine the standard deviation for cumulative amount.

I was of opinion that we can determine the standard deviation from this relation:

Variance of cumulative amount at nth point=variance of first interval+variance of second interval +.................+ variance of nth point + 2X covariance of (1,2,3....n time point).

Standard deviation of cumulative amount is square root of variance by above formula.


Would it be correct procedure to find standard deviation for cumulative amount?