A.
General
The Shimadzu TOC-5000A with autosampler is capable of
four different measurements on filtered samples in solution: Total Carbon (TC),
Inorganic Carbon (IC), Total Organic Carbon (TOC) and Non-Purgeable Organic
Carbon (NPOC). The instrument is PC controlled by
a Micron computer.
B. Theory of Operation: TC, IC,
TOC and NPOC
Measurement of TC: Sample is combusted or
decomposed to CO2 in a column filled with oxidation catalyst that resides
within a furnace heated to
680C. The carrier gas containing the combustion product flows through
the IC reaction vessel and is cooled and dried by a dehumidifier. It
is then sent into a sample cell set in a non-dispersive infrared gas
analyzer.
Measurement of IC: Sample is introduced into the IC
reactor vessel which contains an acidified solution and carrier gas flowing
in the form of tiny bubbles. Only the IC
component of the sample is decomposed to CO2. IC concentration is then
determined using the same procedure as TC concentration described above.
Measurement of TOC: TOC concentration is determined by
subtracting the IC concentration from the TC concentration.
Measurement of NPOC: Sample is acidified prior to
being set in the equipment. The sample is sparged with high purity air,
eliminating the IC component. Sample is then injected onto the column and
combusted to CO2.
The CO2 is detected by a non-dispersive infared gas
analyzer which outputs a detection signal (analog) which generates a peak.
The area of the peak is proportional to the carbon component of the sample
and concentration can be calculated by comparing to standard solution.
