Analytical Instrument Documents

JEOL introduced the AccuTOF-DART in 2005 as the first commercially available ambient ionization mass spectrometer system. The atmospheric pressure ionization interface (API) for the AccuTOF system, originally designed as a simple, rugged and reliable LC/MS interface, became the ideal platform for developing the Direct Analysis in Real Time (DART) ion source. Because the DART ion source can be positioned directly in front of the AccuTOF sampling orifice without additional interface hardware, a variety of ambient ionization techniques are available to the AccuTOF-DART operator without removing the DART ion source. The third-generation AccuTOF-DART 4G system is an “ambient ionization toolbox” that allows the analyst to choose ionization methods that are best matched to the samples to be analyzed.

Smokeless powders (Figure 1) are often used in improvised explosive devices. The formulations for smokeless powders vary between manufacturers and between brands from a given manufacturer; ingredients include energetics, stabilizers, plasticizers and deterrents. Chemical analysis of smokeless powders can provide valuable forensic evidence. Here we show that the AccuTOF-DART mass spectrometer can rapidly identify the organic components in smokeless powders and provide a chemical fingerprint that can be used to identify individual powder particles.

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.