Analytical Instrument Documents

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.

Several chemical compounds that are widely distributed in the environment have been found to possess hormone-mimicking activities. These compounds have been found to interfere with hormonal activity through a variety of mechanisms, and they may have adverse effects on the health of animals and humans. Terms used to describe these compounds include endocrine disruptors, hormone disruptors, and estrogen mimickers. Classes of compounds believed to have hormone-disrupting effects include phthalates (plasticizers), alkyphenols (detergents), organochlorine pesticides, PCBs, dioxins, and food packaging chemicals such as bisphenol A (BPA) and butylated hydroxyanisole (BHA). Efforts are underway in several countries to develop analytical methods for assessing the distribution of these compounds in the environment. In the US, the Environmental Protection Agency has established the Endocrine Disruptor Screening and Testing Advisory Committee (EDSTAC), and in Japan, the Environment Agency has organized the Environmental Endocrine Disruptor Group. We report the analysis of ppb-level samples of standard samples, river water and water from sewage treatment plants by both low-and high-resolution selected ion moniroting (SIM) mass spectrometry with benchtop GC/MS systems. We evaluate high- and low-resolution SIM with LC/MS methods as an alternative analytical approach that does not require derivatization.

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    Corona - Glow Discharge (DART Ion Source)

    January 28, 2022
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