Page 40 - Application Handbook - TOC
P. 40

Sum parameter – Total Organic Carbon




                                          TOC – Determination in ammonia or
                                          ammonium salt solutions
                   SCA-130-307


            Basic chemicals may contain organic                 ■ Sample preparation
            contaminants polluting  end products. This is       The ammonium nitrate solution was diluted
            why quality control of the reactants is a must.     with ultrapure water to a ratio of 1:10. Dilution
                                                                was carried out manually in a 50 mL
            In the TOC determination of ammonia water           volumetric flask under addition of several
            or concentrated ammonium salt  solutions,           drops of concentrated sulfuric acid (25%).
            various issues must be considered. Ammonia
            and some ammonium salts are alkaline. The            Compound
            catalyst and combustion tube are sensitive to         (Concen-          Dilution         Conc.
            alkaline media and are subjected to                    tration)
            increased wear.                                                       1 : 10 diluted
                                                                  Ammonium        (5 ml / 50 ml)
                                                                    nitrate       add. 1-2 drops    Approx.
                                                                   solution      Sulfuric acid until   4%
                                                                    (40%)         pH<7  (Note:
                                                                                generation of heat)


                                                                Calibration of the TOC-L system was
                                                                executed using the automatic dilution function
                                                                in the range of 0.5 mg/L to 10 mg/L.




            The solutions should, therefore, be acidified
            and possibly be diluted.


            The decomposition during oxidation of the
            ammonium      or   ammonia     proceeds    to
            completion without the formation of residues
            on the catalyst. Therefore, it is not necessary
            to use a high-salt kit.
                                                                            Fig. Multi-point calibration
            In the case described below, the NPOC                            with dilution function
            content of a 40% ammonium nitrate solution
            was determined. The required detection limit
            was < 10 mg/L.
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