Peter T. Palmer

Mass spectrometry in the U.S. space program: Past, present, and future

Recent years have witnessed significant progress on the miniaturization of mass spectrometers for a variety of field applications. This article describes the development and application of mass spectrometry (MS) instrumentation to support of goals of the U.S. space program. Its main focus is on the two most common space-related applications of MS: studying the composition of planetary atmospheres and monitoring air quality on manned space missions. Both sets of applications present special requirements in terms of analytical performance (sensitivity, selectivity, speed, etc.), logistical considerations (space, weight, and power requirements), and deployment in perhaps the harshest of all possible environments (space). The MS instruments deployed on the Pioneer Venus and Mars Viking Lander missions are reviewed for the purposes of illustrating the unique features of the sample introduction systems, mass analyzers, and vacuum systems, and for presenting their specifications which are impressive even by today’s standards. The various approaches for monitoring volatile organic compounds (VOCs) in cabin atmospheres are also reviewed. In the past, ground-based GC/MS instruments have been used to identify and quantify VOCs in archival samples collected during the Mercury, Apollo, Skylab, Space Shuttle, and Mir missions. Some of the data from the more recent missions are provided to illustrate the composition data obtained and to underscore the need for instrumentation to perform such monitoring in situ. Lastly, the development of two emerging technologies, Direct Sampling Ion Trap Mass Spectrometry (DSITMS) and GC/Ion Mobility Spectrometry (GC/IMS), will be discussed to illustrate their potential utility for future missions.

Evaluation of two different direct-sampling ion-trap mass-spectrometry methods for monitoring halocarbon compounds in air

Two different direct-sampling ion-trap mass spectrometry (DSITMS) methods are evaluated for monitoring trace levels of volatile organic compounds (VOCs) in air. The first is based on the use of a sample introduction system that mixes the air sample into a helium stream prior to introduction into the ion trap through an open-split interface. The second utilizes a valve and uses zero air to flush the contents of the sample loop into the ion trap. Unique features of this system are its use of air in place of helium as a buffer gas for the ion trap, and the optimization of experimental parameters to maintain sensitivity and unit mass resolution. Dichlorodifluoromethane (CFC12) and carbon tetrachloride (CCI 4 ) were employed as test compounds for this study. Figures of merit for both sample introduction methods were comparable. Detection limits were approximately 50 parts per billion by volume in MS, selected ion monitoring (SIM), and MS/MS modes. Analysis speeds were on the order of 20 s or less per sample. The sensitivity of the ion trap, inherent selectivity of MS/MS, and fast response times of these sample introduction systems make these DSITMS techniques suitable for many applications that require on-line, real-time monitoring of VOCs in air.

The examination and conservation of a Spanish colonial sculpture with a silver halo

Abstract This is an article on the examination and treatment of a Spanish colonial sculpture of the Christ Child reported to have originated in South America. Its condition will be described first and then the examination, testing and treatment. The term Christ Child refers to how the owners considered the object though it can be recognized that it bears considerable reference to the putti of classical art. The conservation informed the art historical research and vice versa. Analysis of the silver halo components, or rays, by X-ray fluorescence spectrometry (XRF) indicated the silver originated in certain mines of South America. However, the rays may have been added at a later date than the original production of the statue. This integrates art historical background, scientific analysis and conservation treatment to re-create the process of how information from different disciplines can provide a depth of understanding leading conservators to modify treatment modalities and interact with owners and/or curators to establish treatment outcomes best suiting the interpretation of objects.

An expert system/ion trap mass spectrometry approach for life support systems monitoring

Efforts to develop sensor and control system technology to monitor air quality for life support have resulted in the development and preliminary testing of a concept based on expert systems and ion trap mass spectrometry (ITMS). An ITMS instrument provides the capability to identify and quantitate a large number of suspected contaminants at trace levels through the use of a variety of multidimensional experiments. An expert system provides specialized knowledge for control, analysis, and decision making. The system is intended for real-time, on-line, autonomous monitoring of air quality. The key characteristics of the system, performance data and analytical capabilities of the ITMS instrument, the design and operation of the expert system, and results from preliminary testing of the system for trace contaminant monitoring are described.