The NIST-traceable fluorescein standard is supplied as a calibrated 50 μM solution of fluorescein in 100 mM sodium borate buffer, pH 9.5. Under these conditions, fluorescein is completely ionized and is therefore in its most fluorescent form. This standard meets the stringent criteria established by the National Institute of Standards and Technology (NIST) and is directly traceable to Standard Reference Material 1932 (SRM 1932). The NIST-traceable fluorescent standard can be used to assess day-to-day or experiment-to-experiment variation in fluorescence-based instrumentation as well as to determine the Molecules of Equivalent Soluble Fluorophore (MESF) value for an experimental solution.

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