Many chemical species absorb light in either the visible or ultra violet region of the electromagnetic spectrum. This absorption is caused by the changing electron energy levels in the molecule and is therefore characteristic of the molecular structure. The technique is particularly useful for performing rapid quantitative concentration measurements of organic species in solution. UV-Vis Spectroscopy is used to determine analyte concentration either at one time or often over a desired time period. The technique measures the absorption of light across the ultraviolet and visible light wavelengths through a liquid sample. Samples are dispensed into cuvette and placed in the path between a UV-Vis light and a detector. According to Beer-Lambert’s law, with a constant light path length and known absorption coefficient (dependent upon wavelength), the concentration of a compound in question can be determined from the light absorbed by the sample at that wavelength. Ideal Uses include: Quantitation of analytes, Quality assurance and control, Maximum wavelength determination. Technical Specifications: Wavelength range 190-1100 nm Strengths of UV spectroscopy include: Fast sample analysis, Suitable for a wide variety of analytes Much simpler than chromatographic techniques, User-friendly interface, Little maintenance required Limitations of UV spectroscopy include: Subject to fluctuations from stray light and temperature changes, Relatively low sensitivity, Other sample components may cause interferences, Not as specific as chromatography, Requires a relatively large sample volume, > 0.2 mL. Applications of UV and Visible spectroscopy include: Spectrophotometry, Suitable for colorimetric measurements, Specular reflection measurements, Trace organics analysis / monitoring, An extensive library of colorimetric and organic analysis methods is available including a wide range of applications such as clinical analysis, colour analysis, trace pollutant analysis.