An error which arises when the
absorbance of some samples changes with time, e.g. as a result of
photochemical reaction, formation of aggregates or adsorption on the cell wall.
Source:
PAC, 1988, 60, 1449
(Nomenclature, symbols, units and their usage in spectrochemical analysis - VII. Molecular
absorption spectroscopy, ultraviolet and visible (UV/VIS) (Recommendations 1988))
on page 1457