Determination of aminopolycarboxylic acids at ultra-trace levels by means of online coupling ion exchange chromatography and inductively coupled plasma-mass spectrometry with indirect detection via their Pd2+-complexes

• 8 important APCA’s analyzed in one run instead of 3 in the previous method.
• Pd2+ extents the methods applicability to 3 and more dentate amino carboxylic acids.
• Separation system optimized for the isocratic determination of important APCA’s.
• Thermodynamic stability of APCA–Pd2+ complexes is higher than for Fe3+ and In3+.
• Pd2+ is kinetically much slower than Fe3+ and In3+ and makes the method more rugged.

A new indirect IC-ICP-MS method for the determination of aminopolycarboxylic acids in water samples is described. It is based on the addition of an excess of Pd(II) to water samples. The analytes are forced into very strong and negatively charged palladium complexes, separated by ion exchange chromatography and detected by their palladium content, utilizing an on-line coupled ICP-MS. This method is suitable to determine the concentration of 8 aminopolycarboxylic acids (nitrilotriacetic acid (NTA), (2-carboxyethyl) iminodiacetic acid (β-ADA), methylglycinediacetic acid (MGDA), 2-hydroxyethyl) ethylenediamine triacetic acid (HEDTA), diethylene triamine pentaacetic acid (DTPA), ethylendiamine tetraacetic acid (EDTA), 1,3-diaminopropane tetraacetic acid (1,3-PDTA) and 1,2-diaminopropane tetraacetic acid (1,2-PDTA) at the ng kg−1 level. The method is faster and easier than the established gas chromatography (GC)-method ISO 16588:2002 [1] and up to two orders of magnitude more sensitive than the ion pair chromatography based method of DIN 38413-8. Analytic performance is superior to ISO 16588:2002 and the comparability is good.

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