The Interdepartmental Equipment Facility
TOC - Total Organic Carbon Analyzer
Total Organic Carbon (TOC) measurement is the standard method for the evaluation of organic matter content in domestic and industrial wastes, as well as in surface and ground waters. It is also used routinely for testing purified water needed for semiconductor, pharmaceutical and power-generation industries. The amount of organic matter present in water is an important criterion for its quality.
The Shimadzu TOC-VCPH Carbon Analyzer is used for determination of organic and inorganic carbon in liquid samples. Nitrogen concentration can also be monitored in parallel, by using the nitrogen detection accessory. Another accessory facilitates the analysis of solid samples for both organic and inorganic carbon.
For Total Carbon (TC) Analysis, a liquid sample is combusted at 680oC in the combustion tube, where it is converted to CO2 and H2O. The CO2 is swept by the carrier gas through a dehumidifier, to be measured by the Infrared Detector. A wide range of carbon concentrations, between 0.004 and 25,000 mg/l, can be measured directly in this manner. Measurements are calibrated using external standards.
For Inorganic Carbon (IC) Analysis, the sample is acidified in the "sample pre-treatment injection system". The acidified sample is sparged with the carrier gas (purified air) to convert only the IC in the sample to carbon dioxide; this carbon dioxide is next measured by the IR detector. IC measurements are calibrated with sodium bicarbonate as standard.
The Total Organic Carbon (TOC) content of the sample can be calculated from the difference between the Total and Inorganic Carbon: TOC = TC - IC. Alternatively, the TOC is measured directly by acidifying the sample and sparging the vial in the autosampler with the sparging gas, thus releasing the IC into the atmosphere. Under these conditions TOC = TC.
The ASI-V autosampler can hold 93 vials of 24 mL each, or 68 vials of 40 mL each. Samples can be sparged with gas coming from the TOC before they are measured. Magnetic stirrers are installed for the samples at the measurement position and previous position to provide agitation prior to measurement.
The solid sample combustion unit - SSM-5000A permits analysis of 1g of solid sample with up to 30 mg of carbon. There are two separate channels, for organic and inorganic carbon respectively. Sample introduction and analysis is carried out manually. Materials tested include soils, sludges and sediments. Aqueous samples containing large amounts of suspended matter can also be analyzed by the SSM-5000A.
The Nitrogen content in samples can be measured simultaneously with TOC analysis, as the two processes share the same combustion tube as well as most other steps in the process. Nitrogen compounds are oxidized in the combustion tube to NO, which flows with the carrier gas through the IR detector into the TNM-1 nitrogen detector. The NO gas (Nitrogen Monoxide) is measured by chemiluminescence. Measurements can be carried out over a wide range, up to 4000 mg/L.