Introduction
The following sections describe the instrumental analysis resources within the Preservation Research and Testing Division (PRTD) at the Library of Congress.
Subsections include specialty instruments in microscopy and imaging, general spectroscopy, elemental spectroscopy, mass spectrometry, chromatography, other analytical chemical techniques, physical measurements, and audio signal processing analysis, as well as other general equipment.
The general services and analysis types are covered in the Services of the Preservation Research and Testing Division web page.
Themes
Non-invasive analysis, minimal sample preparation, and small spot size testing — Many instruments require no sample preparation at all, and allow PRTD staff to analyze inks, pigments, and other material in situ. PRTD scientists are dedicated to the development of non-invasive analytical techniques. This means that whenever possible, analyses are done without taking a sample. Non-invasive techniques include hyperspectral and microscopic imaging; portable X-ray fluorescence (XRF), FTIR, and sometimes, environmental scanning electron microscopy (ESEM). However, if a sample is deemed necessary, the PRTD makes every effort to reduce the spot size to where it is as small as possible (i.e., well below what people can see with the naked eye).
Volatiles analysis — This work involves sampling the environmental space around a sample in non-destructive ways, or generating volatiles from small sample sizes (e.g., for study using the DART MS or head-space analysis GC-MS).
Accelerated aging to predict stability and lifetime — All materials, both natural and synthetic, change over time. Because our mandate is to preserve the collections of the Library of Congress, we use temperature- and humidity-controlled chambers to simulate aging on a manageable timescale, then analyze the visual and chemical responses of the material to aging.
Digital Microscopy and Imaging
Qualitative and quantitative study of materials — The color, morphology, and other optical properties of collection materials (and of the media contained on them) provide information about their identity, the impact of environmental factors on their longevity, and the effects of conservation treatments on their integrity. Digital documentation of the images is essential for the evaluation of materials over generations of preservation activities.
- Environmental Scanning Electron Microscopy
- Hyperspectral Imaging
- Compound Digital Microscopy
- Stereo Digital Microscopy and Image Analysis
- Image Analysis Workstation
Elemental Spectroscopy
Spectroscopic determination of inorganic elements in a variety of collection and housing materials — The elements studied include most of the periodic table; metals and nonmetals that are important both from a fundamental formulation perspective, as well as for their catalytic (and sometimes buffering) role in degradation.
- Energy-Dispersive X-Ray Spectroscopy
- Inductively Coupled Plasma — Optical Emission Spectrometry with Laser Ablation
- Portable X-Ray Fluorescence Spectrometry
Organic Mass Spectrometry
Determination of the identity of organic and inorganic species — Mass spectrometry is used to identify and structurally characterize organic species present in collection and housing materials, in collection environments, and in materials that have been artificially aged. A large variety of compounds can be determined using different ionization methods (e.g. electron impact, positive and negative ion chemical ionization, electrospray, fast atom bombardment, DART ionization), and different inlets (e.g. direct insertion probe, liquid chromatograph, gas chromatograph, pyrolysis, headspace).
- Direct Analysis in Real Time Mass Spectrometry
- High Resolution Mass Spectrometry
- Head-Space Analysis and Pyrolysis Quadrupole Gas Chromatography Mass Spectrometry
General Spectroscopy
Spectroscopic determination of both organic and inorganic species in a variety of collection and housing materials — These methods are largely dedicated to the identification and characterization of organic materials. Activities include evaluating aging characteristics such as photodegradation, oxidation, and decomposition products; verifying the identity of collection materials; and developing materials specifications, especially for binding and storage.
- FTIR and FT-Raman Spectroscopy
- UV-VIS-IR Fluorescence Spectroscopy
- Micro-Scale Spectroscopy
- Colorimetry/Spectroscopy
- Brightimetry/Spectroscopy
Chromatography
Separation and analysis of complex mixtures — Collection items and housing materials are composed of complex mixtures of organic and inorganic species, some of which are best determined using chromatographic separation techniques and specialized detectors. These materials include high-molecular weight polymers contained in magnetic media (polyurethanes) and paper (cellulose), and trace-levels of inorganic and organic ions, all of which can be characterized using special chromatographic techniques.
- Size Exclusion Chromatography
- Ion Chromatography
- High-Performance Liquid Chromatography
- Gas Chromatography with Flame Ionization Detection
Other Analytical Techniques
Thermal analysis; pH and alkaline reserve determination — These other analytical methods relate to examining the step-wise effects of increasing temperature on materials; and determining the pH and alkaline reserve of paper.
Digital Audio Signal Processing Analyzer
Digital audio/data analysis Digital recordable media store music, writing, and other data. But like analog recording material, these materials (e.g. optical discs made of polymers, organic dyes, and metals) degrade. PRTD staff must determine the long-term stability of digital CD and DVD recordings, which requires the use of analyzers that can measure parameters that reflect optical disc degradation.
Physical Measurements
TAPPI and other physical testing — A large number of TAPPI (Technical Association of the Pulp and Paper Industry) and other physical testing instruments are used in a TAPPI environmental room. Instruments include:
- Tensile strength tester
- Tear tester
- Bending resistance tester
- Rub tester
- Digital abraser
- Fold endurance testers
Other General Equipment
General laboratory equipment — Other laboratory equipment are used in research and testing endeavors. These include:
- Weatherometer
- Temperature and humidity-controlled aging ovens
- Microwave extractor
- Top-loading balances
- Analytical balances
- Microbalance
- Vacuum ovens
- General purpose ovens
- Muffle furnaces
- Explosion-proof freezers and refrigerators
- Walk-in freeze-drying chamber
- Reverse-osmosis water purification system
- Gas standard generator
- Rapid-vacuum evaporative system
- Mini-reaction heater
- Centrifuges
- Water baths
- Digital cameras for photodocumentation of work
