Liquid Chromatography Detectors - The UV Detectors > The UV Absorption Detectors > Page 39

To restrict peak dispersion, the radius of the cell must also be reduced as (l) is increased. Thus, less light will fall on the photo–cell, the signal–to–noise ratio will be reduced and thus the detector sensitivity or minimum detectable concentration denigrated. Thus, increasing the detector sensitivity by increasing the path length has limitations and a well–designed cell involves a careful compromise between cell radius and length to provide the maximum sensitivity. Most modern UV detector sensors have path lengths that range between 1 and 10 mm and internal radii that range from about 0.5 to 2 mm

                   Now,          

                           where (A) is termed the absorbence

Now (DA) is sometimes employed to define the detector sensitivity where the value of (DA) is the change in absorbence that provides a signal-to-noise ratio of two.

               Thus                 

where (Dc) is the detector concentration sensitivity or minimum detectable concentration.