Monitoring Systems for Evaluation of Terrestrial Contamination in a Lunar Sample Transfer Facility
Authors: Wszolek PC , Holland PT , McFadden WH , Burlingame AL , Wilder JT , Simoneit BR 
Published: March 2009

A lunar sample transfer facility has been assembled in our laboratory to maintain a high level of lunar sample integrity and purity with respect to terrestrial water, terrestrial organic and bio-organic compounds, and other terrestrial contaminants. The facility consists of two tandem glove boxes and an entrance vacuum antechamber all of which are located in a certified class 100 clean room (100 particles/ft3)

Nitrogen gas from liquid nitrogen is circulated through the glove boxes at a rate of about 0.5 ft3 /min. It is purified by passing it through a bed of finely divided copper and then molecular sieves. A stainless steel tubing analysis line connects the boxes with three monitoring systems. A continuous flow of nitrogen gas is maintained in the analysis line by a small diaphragm pump situated at the exit of the line. A valving arrangement allows the sampling of either the inlet or outlet nitrogen stream, to or from the glove boxes. The level of contaminants in the glove box atmosphere is assessed by three monitoring systems: (1) Water content is determined using an electrolytic cell water analyzer (duPont-CEC Instruments, Model 26-303) which can detect 0.1 ppm of water in the nitrogen stream. (2) Permanent gases (oxygen, carbon dioxide, carbon monoxide, menthane, etc.) are analyzed by a Varian-Aerograph trace gas analyzer (Model 1732-20) fitted with dual ultrasensitive helium ionization detectors which are sensitive to all atoms and molecules except neon. For most gases detection limits are in the 10 ppb range. A 20 ft by 1/8-in. stainless steel column packed with 5 A molecular sieve is used to determine argon, oxygen, methane, and carbon monoxide. The other column is 10 ft by 1/8-in. stainless steel packed with Poropak Q and is used to determine CO2 and C2 and C3 hydrocarbons. (3) Low volatility organic matter is monitored primarily by bubbling the glove box exhaust gas through dichloromethane in a gas washing bottle cooled to −30 to −60° C. Auxiliary monitoring consists of exposing sintered aluminum plaques in the glove box atmosphere and subsequently extracting them with dichloromethane to release absorbed contaminants. During the simulated distribution of lunar material, still another monitor was available, that is, the Ottawa sand which was manipulated and transferred in lieu of the lunar material and which was subsequently extracted with dichloromethane.2 Extracts from each of these monitors were concentrated at 0°C to retain as much of the volatile components as possible. Analysis of the extracts is achieved by capillary gas liquid chromatography, (GLQ using a hydrogen flame detector whose minimum detectable level per component is 0.5 ng. The C1 0 to C3 0 hydrocarbon range is covered by the GLC conditions used. High resolution mass spectrometry for total extract analysis and gas chromatography/mass spectrometry (GC/MS) for individual component identification are also available when needed. Efficiencies of various steps in the analytical scheme were determined by control experiments. Monitoring results will be presented for several periods including simulated distributions of lunar material, distribution of Apollo 14 and 15 special environment sample container (SESQ and distribution of Apollo 14 rocks 14047 and 14049. The level of individual permanent gases was usually a few parts per million (ppm) or lower. Low volatility organic contamination was at the parts per billion (ppb) level or lower.