FLUORIMETER (FLUOROMETER)

Typical Number in Hospital: 3

Cost Bands: 5

References: 5,9

The fluorimeter or fluorometer is an instrument used in the clinical chemistry laboratory to determine the concentration of particular substances in samples of body fluids. The instrument is based on the property of some molecules to emit light in a characteristic spectrum when illuminated by light of another (usually shorter) wavelength. The fluorescent materials may be in the samples to be analysed or they may be produced by combination with reagents.

The normal layout for the instrument is a slit-lamp light source (often ultraviolet), a filter to make sure that the expected fluorescent spectrum is not present in the illuminating light, and a cuvette containing the sample. Very dilute samples are used since this avoids re-absorption of the light produced and is also economical in the required quantity of the sample. The light emitted is normally detected at right angles from the incident light through a secondary filter to the photometer.

Not many materials exhibit fluorescence, but those that do can be determined by fluorometry, with much greater sensitivity than by using a spectrophotometer. The principal disadvantage of fluorometry is the sensitivity of its determinations to temperature and pH of the sample.