What is the protocol for puricifcation of polymerase chain reaction
(PCR) product using ethanol precipitation in order to obtain a PCR
product free from enzymatic contaimants?

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Clean PCR reaction by ethanol precipitation. Make a mix containing
(per sample): 50 ?l 95% Ethanol, 2 ?l 3M NaOAc pH 4.6
Add 52 ?l of the mixture to each well, cover the plate with sealing
mat, and invert 10 times to mix.
Incubate for 15 min at room temperature.
Centrifuge for 30 min at 2000g, remove seal, invert plate onto a stack
of paper towels to drain ethanol.
Add 150 ?l 70% Ethanol.
Centrifuge for 10 min at 2000g. Invert onto paper towels.
Centrifuge inverted plate at 50 g for 1 min.
Let dry plate air dry for 5 min.

If the question is for more than just your own edification, you may
want to look into kits that are specifically designed to clean up PCR
rxns. Both Qiagen and Eppendorf make spin kits. They're generally very
easy and much faster than EtoH purifications. Also in my hands, the
resulting product is much clener and there's less loss.