O48 Application News No.
LAAN-A-TC-E025
Application
News
O48
Total Organic Carbon Analysis
Measurement of TOC in High-Salt Sample with
High-Salt Sample Combustion Tube Kit
No.
The quantity of organic matter in seawater is important
in the research and monitoring of marine pollution as
an indicator of organic pollution. The salt content in sea
water is typically about 3.5 %, but using the Shimadzu
total organic carbon analyzer, it is possible to measure
the TOC directly without dilution or other pretreatment
procedures. Further, it is possible to reduce running
costs by using the high-salt sample combustion tube
kit, which can prolong the life of the catalyst and
combustion tube, as well as reduce the frequency of
maintenance.
Here, we introduce an example of measurement of
organic carbon in aqueous solutions of sodium chloride
using the TOC-LCSH total organic carbon analyzer with
the high-salt sample combustion tube kit installed.
n High-Salt Sample Combustion Tube Kit
Fig. 1 shows a high-salt sample combustion tube.
Compared to the standard combustion tube, it has a
larger diameter, and also, because a portion of the
catalyst used consists of particles of greater diameter, it
serves to alleviate the clogging of salts. Also, sulfuric
acid is used for acidification when conducting NPOC
measurement, so sulfate salt is accumulated in the
combustion tube, which reduces the frequency of
combustion tube replacement. Thus, in the case of
seawater samples, up to 2500 measurements can be
conducted without the need for maintenance (using
40 µL injection volume).
Fig. 1 High-Salt Sample Combustion Tube
n Measurement of TOC in High-Salt Sample
We installed the high-salt sample combustion tube kit in
the TOC analyzer, and then conducted measurement of
sodium chloride aqueous solutions. The salt solution was
prepared by dissolving sodium chloride reagent in pure
water to obtain a solution concentration of 3.5 %. This
solution was then spiked with potassium hydrogen
phthalate solution as an organic substance to obtain
sample solutions spiked with TOC concentrations of 2.0 –
0.2 mgC/L, and we then conducted TOC measurements.
The results are shown in Fig. 3 and Table 1.
The instrument was calibrated using potassium hydrogen
phthalate solutions at 0 and 3 mgC/L (mg/L carbon
concentration), and a calibration curve was generated
(Fig. 2). To eliminate the effect of the carbon portion
associated with the pure water used for preparation of
the standard solutions, a correction was applied to the
calibration curve using the shift-to-origin feature.
Since the TOC concentration of the sodium chloride
solution is approximately 0.08 mgC/L, the TOC
concentration of each of the solutions became about
0.1 mgC/L higher than the spiked concentration. The
measured TOC concentration of the salt solution spiked
with 0.2 mgC/L was about 0.3 mgC/L, indicating that
accurate quantitation was achieved.
<Measurement Conditions>
Analyzer:Shimadzu TOC-LCSH Total Organic Carbon Analyzer + high-salt
sample combustion tube kit + B type halogen scrubber
Catalyst
:High-salt sample catalyst
Injection volume :150 µL
Measurement item :TOC (=NPOC: TOC by acidification and sparging)
Calibration curve:2-point calibration curve using potassium
hydrogen phthalate solutions at 0 – 3.0 mgC/L
Reagent
:Sodium chloride (potassium hydrogen phthalate for
water quality testing, Wako Pure Chemical Industries)
TOC Spike substance :Potassium hydrogen phthalate (potassium hydrogen
phthalate, high grade, Wako Pure Chemical Industries)
Fig. 2 Calibration Curve
Application No. O48
News
Table 1 TOC Measurement Data of Sodium Chloride Solution
Sample Name
TOC Concentration (mgC/L)
3.5 % sodium chloride solution
0.083
3.5 % sodium chloride solution + TOC 0.2 mgC/L
0.289
3.5 % sodium chloride solution + TOC 0.5 mgC/L
0.590
3.5 % sodium chloride solution + TOC 1.0 mgC/L
1.083
3.5 % sodium chloride solution + TOC 2.0 mgC/L
2.087
3.5 % sodium chloride solution
3.5 % sodium chloride solution +
TOC 0.2 mgC/L
3.5 % sodium chloride solution +
TOC 1.0 mgC/L
3.5 % sodium chloride solution +
TOC 0.5 mgC/L
3.5 % sodium chloride solution +
TOC 2.0 mgC/L
Fig. 3 TOC Measurement Data Using Sodium Chloride Solutions
First Edition: Feb. 2014
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© Shimadzu Corporation, 2014
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