TOC

The Total Organic Carbon analyzer present at the GI facility is a TOC-L CPH/CPN analyzer (Shimadzu). More (pdf, 14 MB) information on the applications that can be carried out with this specific device. It is utilized to determine the Carbon-Nitrogen content in fluids and sludge.

Carbon measurement

TOC refers to a Total Organic Carbon analyzer, which utilizes a catalytic oxidation combustion technique at high temperature (the temperature raises up to 720 ºC), to convert organic carbon into CO₂. The CO₂ generated by oxidation is measured with a Non-dispersive Infra-Red (NDIR) sensor. By using special kits and (dilution) methods the device can be applied to determine the carbon concentration over an extremely broad range (theoretically from 4μg/L to 30 000mg/L), from pure drinking water to sea water with sludge. In addition, it is possible to indirectly determine the fraction of IC (= "inorganic carbon") arising from dissolved CO₂ and acid salts containing carbon.

Nitrogen measurement

By means of a chemi-luminescence reaction also the nitrogen content can be determined in above mentioned samples. Shimadzu's TNM-1, the Total Nitrogen Module, can accurately measure nitrogen over a broad range: Total Nitrogen (TN) from 100ppb to 4000ppm. A nitrogen-containing sample is combusted to NO and NO₂. The reaction products react with ozone to an excited state of NO₂. When falling back to the ground level, energy is emitted as light. The nitrogen is measured with a chemi-luminescence detector.

General preparation/submission of samples

• The sample flow line diameter is 0.5 mm. Therefore, , in order to prevent clogging, any particle larger than this size should be eliminated from the sample, for example by means of sedimentation.

• Check well whether filtered (0.45µm) or unfiltered samples are required

• Suspension should be first be treated with a ultra turrax to obtain as fine particles as possible. Discuss the procedure with Paul van der Ven.

Types of C or N analyses and corresponding sample submission

• TC = Total Carbon: all the carbon in the sample, consisting of both inorganic and organic carbon
  TC samples: Unfiltered homogeneous (well mixed) samples
• TIC= Total Inorganic Carbon (often referred to as inorganic carbon IC): carbonate, bicarbonate, and dissolvedcarbon  dioxide (CO₂).
  TIC samples: Unfiltered homogeneous (well mixed) samples
• TOC = Total Organic Carbon = TC - TIC: material derived from decaying vegetation, bacterial growth, and metabolic activities of living organisms or chemicals.)
  TOC samples: Unfiltered homogeneous (well mixed) samples. Before the actual measurement, samples are acidified and purged to get rid of the TIC.
• NPOC = Non-Purgeable Organic Carbon (commonly referred to as TOC; organic carbon remaining in an acidified sample after purging the sample with gas. See here above)
• DOC = Dissolved Organic Carbon: TOC in a filtered sample.
  DOC samples: samples filtered through 0.45 μm pores
• POC = Particulate Organic Carbon = SOC = Suspended Organic Carbon: Carbon present in particles larger than 0.5 mm (on our device)
  No POC samples in our current setup
• TN = Total Nitrogen : all nitrogen present in the samples
  TN samples: Unfiltered homogeneous (well mixed) samples
• TON = Total Organic Nitrogen: total nitrogen minus the NO₃, NO₂ and NH₄ fraction (to determine on the auto-analyzers).
  TON samples: Unfiltered homogeneous (well mixed) samples
• DON = Dissolved Organic Nitrogen: total nitrogen in a filtered sample minus the NO₃, NO₂ and NH₄ fraction (to determine on the auto-analyzers).
  DON samples: homogeneous (well mixed) samples filtered through 0.45µm pores.