Detection of Organic Trace Substances
Dissolved organic-chemical compounds are, as a rule, analyzed by means of gas and/or liquid chromatography coupled with mass spectrometry (GC-MS, LC-MS). Due to the frequently low concentrations in the water, it is necessary to conduct an adequate sample preparation prior to the analysis. Important sample preparation steps include, in addition to filtration and extraction, the enrichment of the sample. Thermally labile substances require a derivatization reaction before the GC analysis. This can also be conducted in order to increase the volatility of the analytes or to reduce the polarity.
Different methods for the analysis of wastewater samples are compared and the limiting factors presented. For this purpose, two solid phase extraction techniques (SPE and SPME) are compared to the classic liquid-liquid extraction (LLE). All samples can be analyzed by means of GC-MS with the same parameters (flow, split, temperature program). Additionally, a derivatization method is being developed and optimized for the solid phase microextraction. This takes place directly after the extraction on the SPME fiber (on-fiber derivatization) and allows the analysis of polar analytes with COOH groups. As a derivatization reagent, pentafluorobenzyl bromide with a catalyst (triethylamine) is used.
This method allows, for example, the cost-effective detection of diclofenac in the water with a detection limit of 1 µg/l for GC-MS (TIC mode). The investigations were developed in the project StressDetect and are currently being driven forward in collaboration with our analytic partners.