How do you determine the final concentration of XGAL and IPTG added on an agar plate?

10 February 2018 1 7K Report

Given 80 ug/ml XGAL stock, to add 40 ul AND given 100 mM IPTG, to use 10 ul

Do you mean you're putting it on the surface with a spreader?

Otherwise if you're just adding it to the molten agar just use the standard (initial concentration)*(initial volume)=(final concentration)*(final volume) equation to calculate it.

If you're spreading it then you'd need to know how many mLs of agar/plate (I think the typical volume is around 15 mLs for most standard petri dishes) and know that it will only be a rough estimate because spreading never actually results in an even distribution through the agar.

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