US firm Electro-Chemical Devices (ECD) is offering a series of analysers that can monitor any two selected parameters in separate measurement ranges for ammonia, nitrate or chemical oxygen demand (COD 254 nm).
ECD’s CA-6 UV analyser family is said to provide a highly accurate, reliable and economical on-line sampling system that’s designed with UV absorption sensor technology to monitor harmful pollutant parameter levels. The CA-6 analyser’s sensors are available in multiple parameter measurement ranges: Ammonia from 0-10 mg/L or 0 to 1000 mg/L; nitrate from 0-30 mg/L, 0-100 mg/L, or 0-250 mg/L and COD 254 nm from 0-200 mg/L or 0-20,000 mg/L.
Each model comes with either a single parameter or dual parameters in the factory pre-calibrated measurement ranges. Everything needed comes in one box ready to install and start-up. A single technician can complete the installation process in 15 minutes by connecting the sample, waste and cleaning solution (reagent) lines and powering up the analyser. Accessing the chosen factory pre-calibrated parameter data or customising an analysis routine is easily done with user-friendly intuitive menus and a touch screen display.
Each parameter is analysed based on the measurement of UV absorption in the sample. The absorbance of the solution or gas is measured through a quartz flow cell at a specific wavelength using a long-life Xenon lamp and photo detectors. The absorbance level is directly related to the sample concentration.
To measure ammonia, a reagent is added to the liquid sample and converts the ammonia to gas for measurement by the CA-6’s UV sensor with a fast Fourier transform algorithm that provides a measurement equivalent to the level of Ammonia. A water temperature probe performs automatic temperature compensation for high accuracy.
In measuring the nitrate found in turbid, organic rich waste water, the CA-6 UV’s advanced self-cleaning design relies on the strong absorption of UV light by the chromophore N-O, which again is according to Beer-Lambert’s Law. Automatic internal linearization compensates for high concentrations of nitrate.  A second wavelength and detector compensates for dirty matter in the flow cell to ensure high accuracy and reliability.
For the measurement of COD 254 nm, the CA-6’s sensor detects UV light absorption by unsaturated organic molecules at the 254 nm wavelength. COD 254 nm levels in river water and municipal wastewater are closely correlated to the permanganate and dichromate water standard methods. Measurement is extremely responsive, in less than 10 seconds.
