Why do different batch of reagents produce different results

[raychaw]

Using different batch of reagents, the results obtain from the 2 experiments differ. Why so?

[biohazard]

The guys making your reagents haven't quite got their methods standradized properly?

Well, along that, for e.g. human/calf/etc serum preparations or other biological reagents you never really know what all the serum etc. actually contains, since every individual is different. So they make one batch where they mix sera of different individuals and all units of that batch are similar. But then they make a new batch and they've obtained it from different individuals or same ones in different condition, so there is bound to be differences -> the batch is not the same and your experimental conditions vary because of that.

Chemical reactions are usually much easier to standardize, but even these can give a bit different outocomes if you add a couple of milligrams more of Reagent X to the batch 2 than you did with the batch 1.

The more variables the preparation of some reagent has, or the source of the reagent has, the more difficult it is to get exactly similar product each time. The unitis wihtin a batch are usually pretty much identical, because they have been manufactured the same time from same reagents in same conditions and just divided to smaller units. But then you do the whole process again and something may change.

[raychaw]

The methods are already standardize. However, it seems that every time we carry out an experiment, the fluorescence readings that we obtain seems to deviate around a few hundreds to a thousand. Although this difference is unanimous throughout all that particular experiment, it really makes us wonder why would there be such variation

[mith]

Noise probably? Are the results statistically significant? What's the supposed accuracy of the method?

[raychaw]

Fluorescence? Noise? Link? Anyways it is statistically significant for some cases. The deviation is rather great