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Jahresbericht 2014 - Annual Report 2014

58 ELECTROPLATED NANOPARTICLES AS EFFICIENT TARGETS FOR LDI-MASS SPECTROMETRY Unique surface effects of metal nanoparticles (NPs) mixed with glycerol have been successfully utilized to enhance laser desorption/ionization mass-spectrometry (LDI-MS) of analytes for over 20 years. The LDI ac- tivity of these materials is mainly determined by thermal conductivity, size-dimensional factors and optical penetration depth. However, such suspension-type method suffer from an inhomogeneous analyte dis- tribution, resulting in low reproducibility and problems with vertical mounting of the sample holders. In this regard, a simple approach for the synthesis of Pd and Ag nano- structures with readily adjustable morphologies was developed using electrochemical deposition for application to surface-assisted laser desorption/ionization (SALDI) of small biological molecules. Analyte cations were generated from the galvanic surfaces upon UV laser irradiation such as potassium for a film thickness < 100 nm and Pd and Ag cluster ions for films with thickness > 120 nm. A range of fatty acids, triglycerides, carbohydrates and antibiotics were investigated and their LDI behavior compared to conventional organic matrix-assisted laser desorption/ionization (MALDI) analyses. Importantly, the galvanic nanostructures did not exhibit detrimental matrix interferences in the low m/z range as usually seen for MALDI. The films exhibited self-organizing abilities and morphologies adjust- able by changing electrochemical parameters, e. g. electrolysis time or current (Fig. 1). Electroplated NP targets based on Ag and Pd did not require any stabi- lizing agents, were inexpensive and easy to produce. LDI analysis showed that the materials were stable under ambient conditions and analytical results with excellent reproducibility and detection sensitiv- ity similar to parallel MALDI experiments were obtained. HIGHLIGHTS Fig. 1: Adjustable morphology of Ag galvanic nanostructure. Y. E. SILINA, M. KOCH 20-40 nm 120-300 nm 1000 nm 5 µm SALDI-MS tel1 tel2 tel3 tel4 ANALYTICS

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