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Sum parameter – Total Organic Carbon


                                          Determination of particulate organic


                                          carbon after filtration
                    SCA-130-107           (glass fiber suspension)


            A limnological research laboratory tackled the      ■ The field test
            problem of determining the particulate TOC          A TOC analyzer with autosampler was used
            content of the sample independently of DOC          for the field test. After calibration of the TOC
            (Dissolved Organic Carbon) content. The             system, the test  solution was measured 10
            water sample was filtered through  filters of       times. The test solution consisted of a glass
            varying pore sizes. Particles of varying sizes      fiber suspension in hydrochloric  acid (five
            remain on the filter. The question arose, how       glass  fiber  filters  dispersed  in  500  mL)  that
            particulate TOC can be best measured.               was      continuously      stirred     during
                                                                measurement. To test the catalyst, a
                                                                standard solution with a TOC of 50 mg/L was
                                                                                       th
                                                                injected  after  each  10   measurement.  After
                                                                100 injections and visual inspection of the
                                                                catalyst and the catalyst tube, the measuring
                                                                cycle was somewhat increased. Function of
                                                                the  catalyst  was  now  checked  using  the
                                                                standard  test  solution  only  after  every  20
                                                                injections of the glass fiber suspension.





                         Fig. Used glass fiber filter

            A possibility would be to shred the filter and
            disperse it in water, and to measure the
            obtained suspension directly using  the TOC
            system. This requires use of TOC-free glass
            fiber filters. This uncommon question requires
            a  field test.  Based  on  the  melting  range  of
            glass fiber (about 550 °C) it was necessary to
            ensure that the glass fiber content would not
            clog or deactivate the catalyst (680 °C) and to     After a  total of 450 injections,  no visible
            establish   where    the   oxidizing   power        change of the catalyst could be detected. Nor
            diminishes.                                         did the oxidative properties  change or
                                                                deteriorate in any way. Reproducibility of the
                                                                results also did not reveal any change.
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