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The AccuTOF® Atmospheric Pressure Interface: an Ideal Configuration for DART® and Ambient Ionization


The DART ion source was developed on the JEOL AccuTOF time-of-flight mass spectrometer which allows the exit of the DART source to be positioned within millimeters of the sampling orifice (orifice 1) of the mass spectrometer atmospheric pressure interface (API). The AccuTOF vacuum system is robust, highly resistant to contamination, and capable of pumping helium DART gas without assistance.


Figure 1 shows a schematic diagram of the AccuTOF atmospheric pressure interface. The API consists of two offaxis skimmers (designated “orifice 1” and “orifice 2”) with an intermediate ring lens, followed by a bent RF ion guide. The off-axis skimmer design traps contamination -- ions are electrostatically guided upward toward orifice 2 whereas neutral molecules are pumped downward. Any contamination that enters the API is either pumped away into the rough pump (RP) or trapped on the lower part of orifice 2. The bent RF ion guide provides an additional level of protection. This makes the AccuTOF an ideal mass spectrometer for DART analysis of dirty “real-world” samples such as mud, biological fluids, melted chocolate, polymers, and even crude oil. In addition, orifice 1 is easily accessible and is operated at low voltage and current, making it a convenient platform for ambient ionization sources. 

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