11/29/2012
Fast and Reliable TOC/TNb Determination in Saline Water Using the multi N/C® Series
Bernd Bletzinger , Analytik Jena GmbH+Co. KG
In many areas of application - extending far beyond drinking and waste water analysis - a fast and reliable TOC/TNb determination is required. The catalytic high temperature combustion with subsequent selective and sensitive detection of the combustion products CO2 and NO is an established determination method.
This measuring technique is used, for example, in the agricultural pedological area when determining the microbial biomass carbon or nitrogen in soil, using the fumigation extraction method. Soil samples are purged by chloroform to kill microorganisms as well as to destroy the cells and, subsequently, extracted with a 0.5 molar potassium sulfate solution. This highly saline solution is then directly analyzed with a NPOC/TN method at the analyzer.
Another application area is the process monitoring of chlorine alkali electrolysis in chemical industry. The used brines have a NaCl content of 26-28 percent by weight (saturation of 100°C), whereas the TOC content is process-crucial and must be monitored with measurement technology. This also applies to brines used in medical areas. The concentrated acids and bases produced in chemical industry and used to various processes are analyzed for contamination just as thoroughly, whereas the TOC parameter often must be monitored in the range of 1-10 ppm. Also for surface finishing industry, the TOC sum parameter is a guiding parameter for the quality of a galvanic bath. Due to the high metal salt concentrations, this matrix also implies a challenge for TOC analyzers. In the area of global ecosystem monitoring, the DOC and TDN content (Total Dissolved Nitrogen), amongst others, are of peculiar interest in different seawater levels and streams. Especially deep-sea samples from several hundred meters are taken which usually have DOC or TDN contents lower than 0.7 ppm and, thus, exclude the sample dilution to reduce the matrix load.