Why is there a difference in terms of absorbance ratio A260/A230 between two sets of DNA extracted from a same sample?

I extract DNA from liquid manure (Powersoil DNA Isolation Kit from MOBIO) but I constated that if I treat my sample by centrifugation twice as long at 14000 rpm I have a better yield (three time...

16 June 2014 3,274 6 View