Anyone experiencing bacterial OD600 samples run on Cary 3500 and only getting half expected result compared to other Agilent UV-Vis models?

Bacterial OD600 measurement is a measurement of scatter - as the amount of bacteria in the sample increases, so does the degree of scatter and so less of the transmitted light reaches the detector (resulting in an apparent increase in absorbance).  This type of measurement is also influenced by how close the detector is to sample - the closer it is the more scattered light is captured and vice-versa.  The detector on the Cary 3500 is very close to the cuvette so this is why the scatter values are lower compared to other Agilent UV-Vis models.

Hi Rob,

We are pre-designing a comparability study with our fermentation process, but my engineer will need some help on this for the OD600 on Cary 3500.  If its OK with you, can I provide your contact information?  Short story is we looked at turbidity standards and performed some measurements that don't correlate to one another right now.  We expect all of our turbidity measurement to be consistent between Cary 3500 and model 8453, but even these values do not correlate quite right.  We can share the information with you once Joel my engineer contacts you.

Thanks,

Robert Catolos