For the best measurement results, wells should be at least half full depending on the application. If your sample volume is not enough to fill even half of your well, try a “low volume” or “half area version” of a 96 or 384 well plate. Most plate manufacturers have an alternative to standard 96 and 384 well plates with lower working volumes. This will fill up more of your well, raise the sample closer to the optic for measurement and help eliminate meniscus effects.
BMG LABTECH also offers a special low-volume microplate, the LVis plate. This accessory for the SPECTROstar Nano and spectrometer based microplate readers of the Omega series, offers 16 micro-drop wells for low volume aborbance measurements. For more information see: http://www.bmglabtech.com/products/microplate-reader/lvis-plate.cfm