Negative reading on Shimadzu - (Oct/28/2008 )

Hey guys,

My friend is measuring the purity and conc. of DNA of a Shimadvcu uV spectrophometer. after performing the blank , we keep getting negative absorbance . THe DNA source is from purified PCR result. The DNA was analyzed on gel before and it showed bright band ie adequate amount of DNA . so the negative reading is quite fishy.

As i am a user of nanodrop i am not really sure how to explain this situation .

Could anyone tell us what's the underlying problem for this?

thanks

Be sure the cuvettes are clean.
Check that the reading of the cuvettes filled with the solvent are the same.
Check with a spectrum that your not measuring at a slope.
For dummy's, I've seen the problem, be sure that you that blank and sample are in the correct cuvettes