Abstract

Principles and Applications of Direct Analysis in Real Time - Mass Spectrometry

Juergen Gross, Head Mass Spectrometry Lab, Heidelberg University

Direct analysis in real time-mass spectrometry (DART-MS) is one of the most influential methods within the field of ambient MS [1-3]. To analyze a sample, it is simply exposed to the heated stream of ionizing gas in front of the atmospheric pressure ionization (API) interface of a mass analyzer. The ionization process in DART is initialized by metastable helium atoms, i.e., by electronically excited species carrying as much as 19.8 eV. Reagent ions are generated via a reaction cascade that basically results in a variant of atmospheric pressure chemical ionization (APCI). DART is capable of analyzing single chemicals as well as entire objects. DART effects desorption and ion generation from whatever surface that is being placed in the reaction zone between ionization source and API interface. This contribution briefly discusses the various ionization processes, describes the flexible setup of DART sources, and gives some representative examples of DART-MS. As applications of DART-MS, the aspect of mass calibration in positive-ion and negative-ion modes [4-6] and the use for the analysis of silicone rubbers [7] are dealt with. In particular, the use of DART-MS is demonstrated as a rapid screening technique for articles of daily use to assess their tendency to release silicones. The substantial release of silicones at elevated temperatures within seconds indicates a potential health hazard from daily use of such silicone items. Thus, a substantial dose of silicones may be taken up by humans, in particular during elongated exposure under extracting conditions as in case of pacifiers or teething rings or when used at elevated temperature as is the case with baking molds. Experiments were performed using a Apex-Qe FT-ICR instrument (Bruker Daltonik). A DART-SVP ionization source (IonSense) was mounted in front of the ceramics tube of the Vapur Interface [4-7].