TOC Analyzer Analytical Method
For many TOC analyzers – that is, total organic carbon (TOC) analyzers, or meters – the detection and quantification of total organic carbons are the two most important steps in TOC analysis process. For the purpose of detection two methods are commonly used in modern TOC analyzers: 1) Conductivity Method. 2) Non-dispersive infrared (NDIR).
TOC Analyzer Use of the NDIR Technology
The use of the NDIR technology in a TOC analyzer has the distinction of being the only interference-free method of detection of CO2 in TOC analysis. The main advantage that you get by using the NDIR method instead of conductivity is that you will be able to directly and specifically measure the CO2 produced as a result of the oxidation of the organic carbon in the oxidation reactor; in conductivity you’ll be measuring the secondary effect. However, the PPM or PPB level of total organic carbon at which you seek to measure should also determine your choice of TOC analyzer.
In a conventional TOC analyzer ‘s NDIR detector, the flow of oxidation product into and out of the detector is continuous. Infrared absorption region (normally 4.26 µm) is measured. A reference measurement not CO2 specific is also taken. The immediate concentration of CO2 in the detector is calculated from the differential result. The measurements made over time create a peak. The TOC analyzer then makes integration and correlation of this peak to the total concentration of the gas in the sample aliquot.
TOC Analyzer Recent Technological Development in NDIR
TOC Analyzer’s recent developments in NDIR technology can be seen in the introduction of Static Pressurized Concentration (SPC). In comparison to the flow-through cell technology, in which the flow of the oxidation product is measured over time, SPC measures the total amount of the oxidation products present in the sample in one reading, thereby making the measurement process more sensitive and precise.
TOC Analyzer Analysis Method
The pressurization of the sample gas stream within the TOC analyzer is achieved by closing the exit valve of the NDIR. Time is given to the gases in the detector so that they reach the equilibrium state. Once this is achieved, the concentration of CO2 is analyzed. The output signal is proportional to the concentration of CO2 in the carrier gas; the gas is formed by the oxidation of the sample aliquot. A combination of UV/ Persulfate oxidation with NDIR detection results in a TOC analysis method that is relatively fast and has multiple applications, such as purified water (PW), drinking water and ultra-pure water analysis, that is used in many modern TOC analyzers.