conductivity unit 160 a valve 126 for delivering fresh water from the fresh water reservoir 124 to the uw detection unit 140 and the conductivity unit 160 a valve 130 for delivering a cleaning fluid from the cleaning fluid reservoir 128 to the uv detection unit 140 and the conductivity unit 160 a pump 122 for delivering the liquid sample the fresh water or the cleaning fluid from the sample manager 120 to the uv detection unit 140 and the conductivity unit 160 and a pressure sensor 132 valves 121 126 130 and the pressure sensor 132 are in communication with a logic controller 180 the pressure sensor 132 provides feedback to the logic controller 180 for controlling a cleaning cycle the pump 122 delivers the liquid sample to the uv detection unit 140 in the uv detection unit 140 the liquid sample is passed through a flow through cell 142 this flow through cell 142 is irradiated with uv light provided by a uv light source 144 located on one side of the flow through cell 142 a light detector 146 located on another side of the flow through cell 142 measures the absorbance of uv light as it traverses the liquid sample the light detector 146 is connected to a wavelength selector 148 and the logic controller 180 the raw data of uv light absorbance by the liquid sample is passed from the light detector 146 to the logic controller 180 for further data processing in a preferred embodiment a variable wavelength uv visible spectrophotometer is used such.