Bradford assay help

[Joe98]

So I was doing a Bradford assay using spectronic 200 . The standard BSA absorbance I got for 1.00 mg/mL and 1.4 mg/mL was 1.2 and 1.4 which is out of the spectrometer LoL. My lab technician told me that it’s normal.  Does anyone know why it’s assumed that we have a linear relationship above an absorbance of 1.00??

[BabcockHall]

My own experience is that the shape of the standard curve depends upon the identity of the protein.  However I generally put little trust in absorbance values of greater than 1.0 in the Bradford assay, even using a research-grade instrument, let alone one that is not.  The problem is that there is not as much excess Bradford reagent as one moves higher in protein concentration.  A standard curve should be made, preferably with the same protein that is being assayed.