It is always good to run Blank controls that was run along with the experiment containing everything else except the protein. Get absorbance readings for these controls done at exactly the same concentration and dilution as the samples. Youshould be able to largely eliminate any intereference from buffer components. Remember even if a 2 % SDS concentration at a 20 times dilution is still 0.1 %. Diluting it to 1 ml for Bradford assay from a 100 Ál sample is still 0.01 % SDS which can still cause significant interference.
best of luck