Academic journal article Forensic Science Communications

Elemental Analysis of Glass: Scientific Working Group for Materials Analysis (SWGMAT)

Academic journal article Forensic Science Communications

Elemental Analysis of Glass: Scientific Working Group for Materials Analysis (SWGMAT)

Article excerpt

July 2004

1. Scope

1.1. This guideline describes methods for determining the concentrations of major, minor, and trace elements in glass fragments. The methods described may be used to measure either absolute or relative element concentrations in glass fragments ranging in mass from gram(s) to less than one microgram.

1.2. The analytical considerations for the use of scanning electron microscopy-energy dispersive X-ray spectrometry (SEM-EDS), X-ray fluorescence spectrometry (XRF), inductively coupled plasma-optical emission spectrophotometry (ICP-OES), and inductively coupled plasma-mass spectrometry (ICP-MS) are described. Other analytical techniques, such as atomic absorption spectrophotometry may also be used but are not specifically included in this guideline because they are not as widely used as those listed.

1.3. Several of the analytical methods described are destructive. Therefore, all nondestructive examinations must be completed and legal considerations concerning the destruction of evidence must be satisfied prior to conducting these measurements.

1.4. This guideline does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this guideline to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use.

1.5. This guideline provides general considerations, rather than detailed instrumental operating instructions. Measurement of element concentrations in glass fragments can be reliably obtained using any of many makes and models of instruments, each with its own specific instructions. The examiner should use this guideline in conjunction with instructions provided by the manufacturer of the particular instrument being used and with validated internal laboratory procedures for the characterization of glass evidence.

2. Reference Documents

2.1. Scientific Working Group for Materials Analysis Documents

Trace evidence recovery guidelines

Quality assurance guidelines

2.2. American Society for Testing and Materials Standards

D1193 Specifications for Deionized Water

E50 Reagent Purity

E135 Standard Terminology Relating to Emission Spectroscopy

2.3. Environmental Protection Agency Test Method

Method 200.7 Inductively Coupled Plasma-Atomic Emission Spectrometric Method for Trace Element Analysis of Water and Wastes

3. Terminology

Analytical blank is a solution containing all reagents in the proportions used to prepare glass samples, processed in the same manner as a glass sample without the presence of the glass.

Analytical curve is the functional relationship between instrument response and analyte concentration.

Analytical sample is that portion of a specimen analyzed.

Calibration standards are a series of known standards used for calibration of the instrument (i.e., preparation of the analytical curve). A calibration standard containing zero added concentrations of analytes is referred to as a calibration blank.

Calibration verification standard is a single-element or multielement standard of known concentrations, obtained from a different source than those used for the calibration, used to monitor and verify instrument performance on a daily or case-by-case basis.

Classification is the placement of a specimen into a particular product-use or manufacturer source category based upon the comparison of measured attributes with a database of known attributes for each category. Examples of classes include sheets, containers, light bulbs, tableware; or Libby-Owens-Ford, Pilkington, Corning; or float line A, float line B from a given manufacturing plant.

Dead time in X-ray spectrometry is the amount of time that a detector is receiving a signal that is not being counted. …

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