ASTM E573 Standard Practices for Internal Reflection Spectroscopy

Get Certified ASTM E573 for Uncompromising Quality and Project Success

Laboratories use ASTM E573 to ensure no change or variation in internal reflection spectra across different instruments and operators. Accurate material identification and confident comparison of various samples and testing facilities are made possible by the reliable data that can be acquired from the spectrum. Matestlab assists labs that use calibrated FTIR-ATR equipment and trained analysts who practice this to ensure reliable spectral results.

The scope of ASTM E573 includes:

• Material type: Solid, liquid, or semi-solid samples placed in contact with an internal reflection element for infrared analysis.
• Purpose: General guidance for obtaining and interpreting internal reflection infrared spectra.
• Properties evaluated: Molecular structure and chemical composition revealed through infrared absorption at the sample-crystal interface.
• Testing Method: Analysts direct infrared light into a high-refractive-index crystal in contact with the sample and record the resulting spectrum with an infrared spectrometer.
• Result: An infrared spectrum that identifies chemical composition and molecular structure at or near the sample surface.
• Test Limitations: This practice recommends a procedure rather than material requirements, and spectral quality depends heavily on crystal contact and sample geometry.
• Use conditions: Analysts control the angle of incidence and select a crystal with a refractive index higher than the sample for effective internal reflection.
• Applications: Supports polymer characterization, chemical composition verification, and comparison of spectral data across laboratories and instruments.

What are the Uses of ASTM E573 Testing?

The use of ASTM E573 spans consistent spectral collection, material identification, and cross-laboratory comparison in infrared analysis. Laboratory scientists rely on the recommended technique to reduce variability caused by poor crystal contact or inconsistent geometry. Quality assurance teams apply the same guidelines to compare spectral data across instruments and facilities. This standard-

• Standardizes the procedure for obtaining internal reflection infrared spectra.
• Reduces spectral distortion caused by poor crystal contact or inconsistent sampling geometry.
• Supports polymer and composite characterization across research and quality control programs.
• Enables comparison of spectral data across different laboratories and instruments.
• Strengthens confidence in infrared data used for material identification and process monitoring.

Which Materials Can Be Tested Under ASTM E1388?

ASTM E1388 applies to fire debris samples submitted in sealed cans, jars, or bags carrying potential ignitable liquid residues. Light to medium range ignitable liquids, such as light oxygenates and lacquer thinners, respond best to this technique, while heavy range compounds recover poorly. Analysts also transfer liquid evidence into a suitable container before sampling when the original packaging does not suit direct heating. A sample that arrives already opened or compromised risks contamination that affects the screening result.

Why is ASTM E1388 Important?

The importance of ASTM E1388 lies in the direct link between sampling technique and reliable screening results. Inconsistent heating, syringe handling, or container contamination produces a false negative or misleading screening result in a fire debris investigation. Consistent application of this practice lets forensic laboratories generate defensible findings that support arson investigations and insurance evaluations.

ASTM E573 Testing Process and Data Collection 

ASTM E573 testing begins with sample selection and crystal choice suited to the sample’s refractive index. Technicians press the sample against the crystal face and confirm uniform contact across the active area. The spectrometer directs infrared light through the crystal and records the resulting spectrum. Analysts then interpret the recorded spectrum and compile the findings into the sample’s infrared analysis report.

Common Challenges and Troubleshooting in ASTM E573

Common problems and troubleshooting include poor sample-crystal contact in internal reflection spectroscopy: absorption bands are weak because of air gaps between the sample and the crystal, which can also cause distortion in the spectrum. Contamination from crystals and the angle of incidence also degrade spectral quality. To solve these problems, technicians remove the crystal between samples, press it against the sample with even pressure, and check that the angle of incidence is correct.

• Analysts evaluate spectra at the selected angle of incidence, with 45° commonly used as a reference condition for comparing internal reflection spectra.
• For multiple-reflection measurements, many single-pass internal reflection elements use approximately 25 reflections, increasing spectral absorption and measurement sensitivity.
• With f/4.5 optics, the incident beam can have an angular spread of approximately ±5°, which analysts consider when evaluating variations in effective path length and penetration depth.
• For micro internal-reflection measurements, sampling areas can range from approximately 0.5 to 2 mm in diameter, allowing localized regions of a specimen to be examined.
• Analysts compare the positions, shapes, and relative intensities of the recorded absorption bands with reference spectra while considering the refractive index, crystal material, angle of incidence, and number of reflections.
• Laboratories document quantitative test conditions, including the angle of incidence (θ), number of reflections (N), wavelength range, IRE material, and relevant instrument settings alongside the interpreted spectrum.

Link to ASTM E573