Analytical Instrument Documents

In MS Tips No. D031 we introduced the example of high polar compound analysis with DART. This application note introduces the example of the analysis of low polar compounds.

Ionic liquids have drawn much attention from various engineering fields, such as tribology, because of their unique properties of electrical conductivity, extremely low vapor pressure, low viscosity, low combustibility, etc. The sample was analyzed by dipping a glass rod to the sample and presented it directly to the DART™ ion source.

The identification of pressure-sensitive tapes such as duct tape and electrical tape is an important forensic application. Here we show the application of thermal desorption and pyrolysis combined with Direct Analysis in Real Time (DART) mass spectrometry to distinguish between manufacturers and brands of duct tapes. X-ray fluorescence (XRF) provides complementary information about the atomic composition of the different tapes.

The AccuTOF-LC time-of-flight mass spectrometer equipped with a DART ion source and AutoDart HTC PAL autosampler, was used for examination of beer in this study. Donprep® immunoaffinity columns (R-Biopharm) was employed for selective isolation of target analyte from the sample. Briefly, 10 mL of beer with added internal standard (¹³C₁₅-deoxynivalenol, 500 ng/ml) were passed through the cartridge, which was then washed with 5 mL of water. Deoxynivalenol was subsequently eluted with 4.5 mL of methanol. Calibration standards containing deoxynivalenol in the range from 100 to 1500 ng/mL and fixed amount of internal standard (500 ng/mL) were prepared for quantification.

The AccuTOF-DART can detect a variety of substances in biological fluids such as urine, blood, and saliva with little or no sample preparation. These substances include drugs, amino acids, lipids, and metabolites.

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.

A new high-current trochoidal electron monochromator1 has been designed and interfaced to a JEOL AX505 magnetic-sector mass spectrometer. The electron monochromator provides a means for controlling the ionizing electron energy over the 0 eV to 30 eV range with an electron energy resolution of +/- 0.3 eV and output currents in excess of 200 μA. This permits the direct formation of negative ions without using an energy-moderating buffer gas, and it provides a means for measuring electron capture resonances and forming ions in specific energy states. The electron monochromator has demonstrated a detection limit of 10 fg of hexachlorobenzene (splitless injection) with a signal-to-noise ration of 31:1. A linear response has been measured for octafluoronapthalene with concentrations ranging over seven orders of magnitude. Linked-scan MS/MS and selected reaction monitoring have been used to examine energy-dependent fragmentation.

In this work, we report the identification of impurities and degradation products of Ziracin, a member of the Everninomicin class of antibiotics. Everninomicins belong to an important group of oligosaccharides, isolated from the fermentation broth, Micromonospora Carbonaceae, and are found to be highly active against Gram-positive bacteria including Methicillin resistant Staphylococci and Vancomycin resistant Enterococci. With the emergence of drug resistant strains of bacteria, a major effort is being directed towards the reevaluation of the efficacy of existing oligosaccarides and identification of new potential oligosaccaride antibiotics. Currently, the Everninomicin antibiotic Ziracin (SCH27889, Schering-Plough Corporation) is undergoing extensive trials to determine its clinical efficacy. Preliminary results suggest that Ziracin is safe and effective and if it proves successful in the large scale clinical trials, it could become a very important drug for treatment of human infections.