G.Gelen, M. Strozynska and M. Hagmann SAS Hagmann GmbH, Weberstraße 3, D-72160 Horb a. N., Germany
The TOC, the total organic carbon, is an important sum parameter and specifies the organic carbon compounds contained in a water sample. A number of recognized methods are available to determine the total organic carbon using various oxidation techniques. No oxidation technique is specified in the European Pharmacopoeia 2.2.44. Two important examples of oxidation technique are:
Thermal oxidation converts the carbon compounds in CO2 at high temperature with the use of catalyst. The CO2 is then detected with a NDIR detector.
Wet Chemical oxidation
Wet chemical oxidation is the combination of UV radiation and persulfate for oxidation.
This work describes the optimization of a new method for TOC determination. This method uses the oxidation of organic compounds by the combination of sulphuric acid and potassium permanganate. The generated carbon dioxide is captured by means of a gas chromatograph with a thermal conductivity detector.The suitability of a new method must be demonstrated in a system suitability test according to Pharmacopoeia. For the test, a calibration is made from 1,4benzoquinone and fructose with the same standard concentrations.
The response efficiency for the System Suitability Solution is calculated by the formula:
(r ss (1.4-Benzoquinone)-r w (TOC-water))/(r s (fructose)-r w (TOC-water)) × 100
The system is suitable if the response efficiency is not less than 85% and not more than 115% of the theoretical response. Here is the response 110% and is therefore suitable.
The advantage of this method is that every laboratory equipped with GC-TCD can apply this method without having to buy a TOC analyzer.