HELP! Problem with Pharmacia's Genequant Spec

[Julie McGrew]

Hello,

We are having problems with getting consistent readings using 
Pharmacia's Genequant spectrophotometer.  The technique we are using 
in the lab requires a very accurate reproducible reading for DNA 
concentration, absorption, and DNA/RNA ratio.  

For the first year and a half the machine gave consistent results 
(while it was still under warranty), but since this time we have been 
unable to accomplish this.  We have tried different cuvettes and have 
cleaned the cuvettes before, after, and between samples with a dilute 
alkali and dilute acid wash followed by distilled water.  We have 
also shipped the Genequant to Amrad Pharmacia Biotech for them to 
have a look at it.  The response that we got from them was that the 
wavelength accuracy was O.K.  We have also discussed this with other 
labs who have the same piece of equipment, and wonder if this is a 
common problem.

Do you or someone you know have a Genequant spectrophotometer from 
Pharmacia? Do you have any suggestions that would help resolve this 
problem?  Your advice would be greatly appreciated.

Many thanks,

Julie McGrew 
mcgrew at zool.canterbury.ac.nz