Sampling:

Because most of the measurements within phosphorescence are carried out in rigid media at cryogenic temperatures of liquid nitrogen we required to use solvents which have certain special features. It is the most significant requirement besides good solubility of the analyte. A solvent must form a clear rigid glass at 77 K i.e., the temperature of measurement. Further, it should be highly pure so in which there is practically nil background phosphorescence.  Not several solvents qualify to be used for the phosphorescence measurement.  Ethanol is an excellent solvent for polar molecules though it might needs addition of small quantities of acid or base to generate a clear solid. Instead a mixture of diethyl ether, isopentane and ethanol within the ratio of 5: 5: 2 correspondingly, generally called EPA is an excellent choice for non-polar compounds.

In a classic phosphorescence measurement, a sample is placed within a narrow quartz tube of an internal diameter of 1 to 3 mm.