Uncovering Dimensional Variability in Standard Microtiter Plate Types


First created in the 1950’s, microplates have become so common place that in 2004, the Society for Biomolecular Screening (SBS) established standards defining multiple dimensions within a plate.  These dimensional standards have since been published through the American National Standards Institute (ANSI), and cover dimensions such as well-to-well spacing, plate height, plate footprint, etc for 96-, 384- and 1536-well plates. The accepted standards are: i) ANSI/SBS 1-2004 “Footprint Dimensions”, ii) ANSI/SBS 2-2004 “Height Dimensions”, iii) ANSI/SBS 3-2004 “Flange Dimensions”, and iv) ANSI/SBS 4-2004 “Well Positions”.

While these published specifications and tolerances have helped establish the so-called “SBS standard plate”, they do not cover all dimensions within the plate. For example, the ANSI specifications are largely silent on well geometry, and differences in uniformity therein (other than center-to-center spacing). Thus, in spite of the ANSI standard dimensions, natural variation in well-by-well dimension does exist. For some assays, this well dimensional variation may not matter.  However for other types of testing, which are dependent upon uniform well volume, such variation may have a direct, and possibly silent, impact.

One example of testing where deviations in well geometry can have a direct impact is the use of microtiter plates for measuring liquid volumes. To determine an unknown volume dispensed into a plate well, accurate well dimension needs to be known for each well used. Any dimensional deviation from one well to its neighbor will only add to the deviation between measurements. Thus, determining well dimensional variations found to exist within a 384-well plate type can aide in optimizing this, and other types of testing. Such differences can only be found through exacting analytical procedures.

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