New Method for Determination of Total Organic Carbon with GC-TCD

New Method for Determination of Total Organic Carbon with GC-TCD

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:

  1. Thermal oxidation

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.

  1. 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.

A new derivatisation reaction <br> for perfluorcaboxylic acids prior to  GC/MS analysis.

A new derivatisation reaction
for perfluorcaboxylic acids prior to GC/MS analysis.

Monika Strozynska, Manfred Hagmann, Katrin Schuhen

Perfluorocarboxylic acids (PFCAs) are anthropogenic organic compounds with very wide commercial use. This super-surfactants contain carbon-fluorine bonds, which provide their extremely high stability [1]. They have also many disadvantages, like bioaccumulation in the environment [2]. Moreover, the negative effects of PFCAs on human health are widely described [3]. Therefore, their reliable detection in water is imperative.

There are many analytical methods described in the literature using liquid and gas chromatography coupled with mass spectrometry (LC/MS and GC/MS) [4]. All these methods have many advantages but also some drawbacks. It is important to constantly improve the analytical methods and search the new possibilities.

We developed a novel, simple derivatisation reaction for determination of PFCAs (C3-C10) in water by GC/MS. The reaction is based on an acidic catalysed esterification of perfluorinated carboxylic acids to form their silylated derivative. Additionally to the methodologically development in the lab, we analysed various PFCAs in effluents from water treatment plants and well water in Baden-Wuerttemberg (Germany) to confirm the laboratory evaluation. Moreover, the total organic fluorine (TOF) was also measured by GC/MS for those samples. Due to sample preparation simplicity, the presented method can be an alternative for more expensive LC/MS analysis.

[1] Bao J; Liu W; Liu L; Jin Y; Dai J; Ran X; Zhang Z; Tsuda S (2011) Environ. Sci. Technol. 45 (19): 8075–8080. [2] Armitage JM; MacLeod M; Cousins IT (2009) Environ. Sci. Technol 43(15):5830–5836. [3] Stahl T; Mattern D; Brunn H (2011) Env. Sci. Eur. 23(38):1-52. [4] Shafiquea U; Schulze S; Slawik C; Kunz S; Paschke A; Schüürmann G (2017) Anal. Chim. Acta 949:8-11.