These materials may be used on a routine basis to calibrate and monitor the performance of Fluorescence Spectrophotometers. They are very stable and convenient to use and with
reasonable treatment, will remain usable for many years. Normally the reference materials are used in a comparative mode; the instrument is adjusted to give a useful reading for a standard of known concentration, this may be directly in concentration or an arbitrary figure, eg. one corresponding to a test limit. A suitable standard is then measured under identical conditions and the intensity noted. For future assays, it is no longer necessary to prepare a standard each time the test is performed, as the reference material may simply be inserted, using the original
instrument settings. Any deviation from the original reading is removed by adjusting the gain, making the instruments’ read out identical to when it was calibrated.

The reference material should be selected so that there is reasonable overlap between the excitation and emission bands with that of the sample, as this will provide the best match between the readings, so that only small adjustments to the instrument gain will be needed in order to obtain suitable readings and reproducibility will be maximized.

The reference materials may also be used to monitor instrument performance and for
standardization. If readings for the reference material are recorded on a regular basis, using the original instrument settings, ie. before adjusting the gain to standardize the
instrument, they may be used to construct a Quality Control (QC) chart. Such a chart may be used to detect variations in instrument

performance, such as long term drift due to deterioration of the source or optical surfaces, also to eliminate errors that arise from any
incorrect setting up or an instrument
malfunction. The materials are solid, so they do not contribute any noise to the
measurements caused by convection currents or striations. Multiple readings may therefore be taken and used to provide an accurate
estimate of instrument precision, an important requirement for many QC situations.

The fluorescent materials are dissolved in methylmethacrylate and the solution is then polymerized to produce a polymethyl
methacrylate (PMMA) matrix which provides a stable environment for the fluorescent
compounds. Being solids, there can be no
evaporation of solvents or any significant photo-decomposition of the material, thus
producing long term stability. This high
stability ensures that any observed variation in readings is due to instrumental variation, rather than chemical or physical effects which may affect liquid fluorescence standards.

Some advantages of solid reference materials
• No significant photo chemical degradation
• Easy to store
• No chemicals to mix and dilute
• No evaporation problems
• Long term stability
• Low overall costs