Ultraspurenbestimmung von Aminopolycarbonsäure Verbindungen mittels inverser IC-ICP-MS nach Komplexbildung mit Pd(II)

This work presents a sophisticated method based on the inverse on-line coupling of IC with ICP-MS. The method is used to determine aminopolycarboxylic acid based chelating agents (APCAs). The on-line coupling of ion chromatography (IC) and inductively coupled plasma mass spectrometry (ICP-MS) allows the usage of the molecular information provided by the IC and of the elemental information of the ICP-MS, with high sensitivity in a single chromatographic run. The main field of application of the IC-ICP-MS coupling is the analysis of elemental species. However, in this work the focus is different. An ultratrace analysis of aminopolycarboxylic acids and their palladium complexes is performed. The metal and therefore the complexes can be detected very sensitively via ICP-MS. The formation of anionic complexes is a requirement for the separation via IC. In a previus work the chelating agents were transformed into iron and indium complexes using an excess of Fe(III) or In(III). However with APCAs containing only three corboxylic groups no anionic complex is forming, and therefore those APCAs were not determinable. In this work Pd(II) is used as metal component of the complex. The palladium complexes of APCAs with three carboxylic groups are negatively charged. The investigated APCAs are NTA, β-ADA, MGDA, HEDTA, DTPA, EDTA, 1,2-PDTA and 1,3-PDTA. The first four of those chelating agents contain only three carboxylic groups. Due to the use of Pd instead of Fe or In, the sample preparation procedure has to be extended and optimised. Special attention has to be paid to the pH in the complexation step. This parameter is crucial for complex formation with APCAs. The separation of eight APCAs in one chromatographic run is carried out. The limits of detection are in the ng/L range. To verify the accuracy of the method, the results are compared to results of an external laboratory, which uses standard analytical methods for those analytes.