Laser Ablation Goes Primetime

FREMONT, Calif., Dec. 9 -- "CSI: Crime Scene Investigation," the hit TV show (CBS) about a team of forensic investigators who use both cutting-edge scientific methods and old-fashioned police work to solve crimes, recently used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to crack a particularly tough case.

In the episode "What’s Eating Gil Grissom," investigators are stumped by a crime scene comprised only of human skeletal remains and a near-microscopic blue chip. The sample size is too small for conventional forensics techniques, so they use a laser-ablation microscope to identify the material: a shard of human fingernail smeared with blue paint and motor oil.

Eventually, the evidence is crucial to unlocking the case. The killer’s modus operandi is to apply blue paint to a staircase railing and use motor oil to retard the drying process. He waits for a female victim to touch the railing, and when she tries to wash the paint off her hand, he attacks.

The story is fictional, but the technology is real. With ICP-MS, a pulsed laser vaporizes a minute amount of a solid sample. A gas stream carries the sample vapor into a high-temperature plasma, where it is ionized then extracted into the mass spectrometer for analysis.

"ICP-MS reveals elemental signatures that traditional forensics techniques cannot," said John Roy, vice president at New Wave Research, a Fremont, Calif., manufacturer of laser-based systems and modules for microelectronics and analytical instrumentation applications. "It is an excellent tool for analyzing minute samples, or differentiating between samples with physical, chemical and visual similarities. In fact, ICP-MS can distinguish samples that are chemically inert, of the same brand or from different batches of the same manufacturing run."

IC-MS is also less destructive, he said. Standard forensics techniques typically involve extensive sample preparation and hazardous substances, which can introduce contamination and destroy large amounts of a sample.

The ICP-MS system featured on CSI: Crime Scene Investigation is installed in numerous crime labs and employs the New Wave Research UP-213, a high-performance Nd:YAG deep UV (213-nm) laser ablation system.

For more information, visit: www.new-wave.com