Laser Ablation-inductively Coupled Plasma Mass Spectrometry
Laser Ablation-inductively Coupled Plasma Mass Spectrometry
Laser ablation-inductively coupled plasma mass spectrometry (abbreviated LA-ICPMS) is a high technology device that analyzes trace matter samples within forensic science and other areas of science. In LA-ICPMS, a pulsed laser focuses on and vaporizes a very small amount of a solid sample (the LA within the acronym LA-ICPMS). A gas stream transports the resultant vapor into high temperature plasma (the ICP) where the vapor sample is ionized before being extracted into a mass spectrometer for analysis (the MS). Because of its advanced mechanisms, LA-ICPMS provides very reliable analysis of forensic evidence alongside strong improvements in sample size, sensitivity, and speed, when compared with traditional methods. For example, LA-ICPMS can detect microscopic samples such as clothing fibers and glass fragments at a level of parts per billion (ppb), providing forensic experts the ability to determine a material's origin often as precisely as to a particular manufacturer or brand. This expensive technology is an important part in countering domestic and international crimes that increasingly requires more innovative and systematic use of forensic science.
Before the availability of LA-ICPMS as a method for analyzing forensic samples and characterizing physical evidence , forensic scientists used such traditional techniques as Fourier transform infrared (FTIR ) analysis, microscopy, refractive index, and X-ray fluorescence (XRF). However, these older techniques were not always able to analyze small samples or discriminate between chemically, physically, and visually similar materials. Some older techniques also required lengthy preparation times for the samples and used hazardous substances within the analysis, which both increased the potential for sample contamination and destroyed large amounts of samples.
On the other hand, LA-ICPMS is a valuable tool for analyzing elemental and isotopic characteristics of samples and accurately comparing samples with chemical, physical, and visual similarities. The ability to analyze microscopic samples can help investigators with the job of connecting a criminal suspect to a crime scene, where earlier technology was unable to do so. For instance, a sample that is very small in size is more likely and easily moved undetected by a criminal from a crime scene. Shattered glass, for example, produces small splinters, which can become attached to clothing, shoes, and other materials that can uniquely identify a criminal. Unlike traditional forensics techniques, such distinctive signatures can only be analyzed with LA-ICPMS.
LA-ICPMS is also far less destructive than traditional forensic techniques. LA-ICPMS requires only a minute sliver of a sample, often less than one microgram, which preserves the original sample and enables further measurements if authentication is needed. For this reason, LA-ICPMS is often described as an almost non-damaging technique with respect to the forensic sample.
see also Chemical and biological detection technologies; Infrared detection devices; Isotopic analysis; Laser; Scanning electron microscopy; Scanning technologies; Spectroscopy.