TOC Analysis: Common Terminology
These are some common terms used in describing a TOC analysis process:
Total Carbon (TC) refers to all carbon (i.e. all organic and inorganic carbon) within the sample.
Total Organic Carbon (TOC) refers to carbon derived from living sources. Example of organic carbon includes bacteria, vegetation, materials derived from the metabolic activities of living organisms, materials derived from the decay of living organisms, etc. Non-Purgeable Organic Carbon (NPOC), which consists of the remaining organic carbon in an acidified sample after purging it with gas, is also commonly referred to as TOC.
Purgeable Organic Carbon (POC), also known as Volatile Organic Carbon (VOC), refers to the organic carbon that has been removed from a neutral or acidified sample by purging with an inert gas. Also known as, Volatile Organic Compounds (VOC), these compounds are usually determined by Purge and Trap Gas Chromatography.
Dissolved Organic Carbon (DOC) refers to organic carbon remaining in a sample after filtering (typically 0.45 micrometer) the sample.
Suspended Organic Carbon (no common acronym), also known as Particulate Organic Carbon (PtOC), refers to particulate form carbon that is too large to pass through a filter (typically 0.45 micrometer).
Total Inorganic Carbon (TIC), also known as Inorganic Carbon (IC) consists of carbon derived from non-living sources. Examples of inorganic carbon include dissolved carbon dioxide, carbonate, bicarbonate, etc.
Adv: Click here for information on Coolpix S60.
Total Carbon Breakdown - Inorganic Carbon and Organic Carbon
TOC Analyzer: How Do They Measure Total Organic Carbon? Part 1/2
TOC analyzers usually works by measuring the carbon dioxide (CO2) released during the oxidization of organic carbon and/or acidifying of inorganic carbon. The TOC analyzer then draws the relationship between the amounts of CO2 to the amount of organic/in-organic carbon to decide the total organic carbon level.
However, it is rare (or impossible?) for TOC analyzers to measure organic carbon directly due to technical constraints.
One method of measuring total organic carbon in the water sample is by either measuring the total carbon left over after purging all inorganic carbon. Another method, which is quite the opposite, measures the difference between the background (initial) carbon level and the carbon level after oxidizing the organic carbon in the sample water.
The difference in measurement method varies from analyzer to analyzer and the suitability of the instrument depends on the application.
Common organic carbon oxidation methods employed by TOC analyzers include:
- Pt-catalyzed Combustion
- Heated Persulfate
- UV/Persulfate
Common CO2 detection method employed by TOC analyzers include:
- Non-Dispersive Infrared (NDIR)
- Direct Conductivity
- Membrane Conductivity
TOC analyzers are usually segmented into their measurement range (e.g. ppm, ppb and ppt), and/or their applications (i.e. online or offline). Online TOC analyzers are installed within the production line and usually provide “live” readings while offline TOC analyzers are usually used in lab environments.