Spectrophotometry is a method used to determine the concentration of a chemical substance in solution by measuring the absorption of light as it passes through the sample. The basic principle is that each compound absorbs or transmits light over a specific range of wavelengths. Spectrophotometry is a widely used method for quantitative analysis in various fields such as chemistry, physics, biochemistry, material and chemical engineering as well as clinical applications. Hach offers a wide range of spectrophotometers and colorimeters that suit the needs of many laboratories. Hach specthrophotometers and colorimeters are best suited for water samples providing more than 250 pre-programmed methodes for a wide range of parameters from Ammonia to Zinc. With Hach spechtrophotometers, it is possible to create a user method suitable for any need.