Analysis of semi-volatile residues using diffuse reflectance infrared Fourier transform spectroscopy

Abstract

Semi-volatile residues on aerospace hardware can be analyzed using Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). This method can be correlated with quantitative Mil-STD 1246 NVR measurements while simultaneously providing qualitative identification of a large variety of compounds. Its high sensitivity supports the direct sampling of small areas of critical surfaces. This method involves transferring the contaminant film to a small solvent-saturated wipe, followed by extraction of the wipe, then concentration of the solvent extract and subsequent spectroscopic analysis using an FT-IR with a diffuse reflectance accessory. A library of standard curves for different classes of typical aerospace contaminants has been established. Quantitative analysis has been proven successful over orders of magnitude and detection limits exceeding 0.1 ug/cm 2 are routinely achieved. Several practical applications have been performed using this analytical method and detailed discussion of analysis techniques is presented. The discussion will include: instrumentation setup, selection and preparation of sample collection materials, sample extract preparation, preparation of standard calibration curves and spectral interpretation.

Contamination control of the SABER cryogenic infrared telescope

“…Solvent wipe samples were also collected and quantitatively analyzed by the ultra-sensitive diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) technique. 15 Results ranged from < 0.01 to 2.1 µg/cm 2 (Level A/100 to Level B). The highest NVR detected appeared to be residual perfluorinated polyether (Braycote or Krytox) that was probably transferred to the spacecraft frame from contaminated gloves and is difficult to remove using 2-propanol.…”

Mass Spectrometry of Spacecraft Contamination Using Direct Analysis in Real-Time Ion Source

“…As demonstrated previously, the solvent swab methods developed for sampling hardware for molecular contamination are readily used for DART MS [7,12]. The sensitively of the DART-MS method is very useful for monitoring biomarker compounds.…”

“…Spacecraft surfaces from the Mars Science Laboratory were monitored for molecular (oily) surface contamination. Metallic surfaces were sampled directly from the hardware using solvent swabs, and the dissolved residue was then measured gravimetrically or by using infrared spectroscopy [11,12]. The DART MS, using the same sampling method, provided additional component identification for complex mixtures.…”

Planning Considerations Related to the Organic Contamination of Martian Samples and Implications for the Mars 2020 Rover

“…Initial cleaning. MSL sample acquisition, processing, and handling (SA/SPAH) hardware surfaces were cleaned to an initial level of approximately £ 25 ng/ cm 2 (average) as determined by FTIR analysis (Herrick et al, 2002) of dichloromethane solvent rinses of witness coupons that accompanied individual pieceparts through the cleaning process. Surface residue was not quantified below 20 ng/cm 2 because the requirement was 100 ng/cm 2 .…”