Also, if I work this out for all compounds, then work out the confidence interval as a percentage of the mean of each (eg 0.00344308 / 2.647154 * 100 = 0.1300676%), can I then average these values to give a rough generalised confidence interval?

I can not see any basis for this.

That is supposed to be the coefficient of variation (cv). cv = 100*sigma/mean.

Why would it be such that the cv would be constant and the same for all substances? What is the bases for that? It would be nice to see some evidence for chemical data to evaluate if this a good rule of thum.

Second, if the cv is constant, why would the mean of different cv:s for different compounds, be a good estimator? In what way would that give a 95% confidence interval?

- - -

I know that chemist are fond of taking n=3, but why? Sometimes you need n = 10000 and sometimes n=1.

In an anova, based on the normal distribution, the standard deviation is supposed to be constant. It is the nuisanse parameter. But in the gamma distribution the cv is constant and the nuisanse parameter. These compounds can not be negative. The normal distribution can be negative. So in a way it does not fit. But the gamma distribution can not be negative. So why not use the gamma distribution?

I don't know if it is possible to extract a sort of cv:s from variance components, but it is worth testing.

I hypothesize that, it is possible to do a general liklihood test over all samples and all compounds to test constancy of the cv, and to do a maximum likelihood estimate of its value.