An error which arises if the two beams in a double-beam @S05837@ are not fully equivalent in transmitted @P04792@ nor are corrected to be so (e.g. due to unmatched cells).
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 1456 [Terms] [Paper]