UV254 / Sac
The UV 254 parameter is measured in units of absorbance (abs) or UV transmittance (%) . UVA is a how much UV light is absorbed by a sample and UVT is how much UV light at the 254 nm is transmits through a water sample. .
The two terms are related and are different ways of expressing the same thing (details are in the support section). UV254 compares the sample to a reference sample. This reference sample is ideally deionised (DI) or distilled water. The difference between the two samples will be the impurities.
The UV254 will respond to Aromatic bonds, such as those found in TOC, COD and BOD. The UV254 absorption will grow linearly with concentration.