Custom Premix Selecting "Custom Premix" option means that all of the beads you have chosen will be premixed in manufacturing before the kit is sent to you.
In UV-Vis spectrophotometry, water is used to prepare samples and standards, as a blank, and to rinse the cuvettes.
Water Quality Parameters
Some ions, like nitrites and nitrates, absorb in the UV-Vis region, and should therefore be removed. Also, transition metals could absorb in the visible range, therefore the concentration of those metals should be reduced as much as possible in the water selected. Highly conjugated organic molecules should also be removed because they absorb in the UV-Vis region. The water should be free of particulates because these can affect UV-Vis absorbance by scattering incoming radiation. Bacteria as well should be avoided, as they behave as particles and can release ions and organics.
Overall, water quality should be as follows:
High resistivity, ensuring the absence of ions
Low TOC, ensuring low concentration of organics
Particulate and bacteria-free
Pure or ultrapure water delivered with a 0.2 µm screen filter as final filter is recommended.