I did a mini-study this morning to find out what the minimum volume needed is to get an accurate reading in the nanodrop. I have 2 different cuvettes (semi-micro and micro) and I wanted to impact the cultures the least so I would like to use the micro cuvettes.
I used 5 semi-micro cuvettes and 2 micro cuvettes. I put increments of 100ul starting at 100ul in each cuvette (100 -> 500ul in the semi-micro and 100 and 200ul in the micro cuvette). At and above 400ul the nanodrop was able to effectively and consistently read the absorbance of the semi-micro cuvette (verified because the readings for 400 and 500ul were identical). For the micro cuvette, I looked at the profile (image above) and saw by eye that the height of the meniscus of the liquid media was roughly equivalent to the height in the semi-micro cuvette with 500ul. So I put this in the nanodrop and got an equivalent absorbance reading.
So in summary:
- For semi-micro cuvettes (and the Thermo Nanodrop 2000c), volumes of at least 400ul or more are sufficient for consistent readings.
- For micro cuvettes, volumes of 200ul are sufficient for consistent readings.