Featured Article
The right upstream separation helps MS detection find almost anything related to a crime
The job keeps getting more complicated for forensic scientists. “Over the past 15 years,” says Thomas J. Gluodenis, forensic and forensic toxicology marketing manager at Agilent Technologies (Santa Clara, Calif.), “there’s been remarkable growth in caseloads around the world for the forensic industry, which demands more productivity.” He adds, “There’s been a fundamental shift in the toxicology world from traditional street drugs to designer drugs and prescription-pharmaceutical abuse.” Researchers1 used mass spectrometry (MS) to develop metabolic profiles for new synthetic cannabinoids that are about to be listed as illegal drugs in several countries. Changes like these drive the need for technologies that can identify a greater number of compounds more quickly, and in ways that create legally admissible evidence.
Forensic science consists of a vast array of disciplines, and MS is most prevalent in toxicology and criminalistics investigations. Forensic toxicology includes tests like blood and urine analysis, which are used to determine cause of death, for example, or whether or not someone was driving while intoxicated. Urine sampling can also be used for drug testing of athletes or workers. In criminalistics, forensic scientists can use MS to investigate suspected cases of arson and to analyze samples of hair, fibers or explosives. “Any type of forensic analysis includes a screening step,” Gluodenis explains.
“This includes a presumptive positive identification of a causal agent followed by a confirmation step.” MS is often used in the confirmation step, “because it provides an unambiguous fingerprint for a sample,” Gluodenis says. A lab runs the sample and then compares it to a published database of compound fingerprints.
Getting the best and fastest results depends on the type of MS used, as well as the separation used upstream.
Conclusive combinations
Many forensic studies separate samples with gas chromatography (GC) and then analyze the sample with MS. “For many years, GC/MS has been the gold standard, because many materials tested by forensic scientists go into the gas phase and fragment so that you get a very nice fingerprint,” Gluodenis explains. To get even better resolution, forensic scientists can add a second round of MS, making it GC/MS/MS.
To advance the resolution, forensic scientists often use time-of-flight (TOF) or quadrupole-TOF (Q-TOF) MS. “Rather than separate the sample by mass-to-charge ratios,” says Gluodenis, “Q-TOF separates fragments based on the time it takes them to traverse a defined distance in a vacuum.” He adds, “You get much better resolution in these time-of-flight instruments.” Traditional quadrupole-MS provides unit-mass resolution, like 325, but Q-TOF measures out to four decimal places, like 324.7843. As Gluodenis says, “Q-TOF gives very high specificity.”
After using robots or agents in padded suits to collect bomb fragments, FBI agents can study them with mass spectrometry. (Image courtesy of the FBI.)As the number of compounds in the spectra database grows, such as through the addition of “designer” drugs, forensic scientists need more comprehensive tools, and Q-TOF provides these. “Sometimes, you’re dealing with new, never-seen-before drugs and their metabolites,” Gluodenis explains. “So you must screen for knowns and unknowns.”
The database must include the growing collection of potential compounds, plus anything the body might produce from them. That makes a nontargeted tool, like Q-TOF, almost indispensable for certain forensic work.
This mass spectrum of wastewater taken from a river in Queens, New York, at the intake for a wastewater treatment plant reveals several opiates. Repeating this type of analysis over time can track the severity of a region’s drug problem. (Chromatogram courtesy of Marta Concheiro-Guisan, John Jay College of Criminal Justice, New York, N.Y.)Gluodenis describes a common situation at a crime scene: It is clear that the victim took something, but when the body goes to the coroner and samples are sent to a forensic lab the typical screens find nothing. The report goes back to the medical examiner, who tells the lab to look again, because some sort of poisoning clearly caused the death. “If the lab used TOF or Q-TOF,” Gluodenis says, “the forensic scientists could go back and retrospectively look for anomalies in the data, and identify the formula of the potentially causal agent based on the accurate mass without having to reanalyze samples.”
Other kinds of MS can also be used in some forensic applications, as shown in work by Varga et al.2 They used inductively coupled plasma/MS (ICP/ MS) to determine when plutonium was produced, which can be used in nuclear forensics or to safeguard weapons. They found that, “Age dating results of two plutonium certified reference materials … are in good agreement with the archive purification dates.”
Leaning on liquid
Some compounds, like prescription pharmaceuticals, don’t go into a gas very well, and that makes liquid chromatography (LC) a good option. “One of the major uses of LC/MS in forensics is for toxicology,” says Bob Classon, LC/MS business development manager at Shimadzu Scientific Instruments (Columbia, Md.). “LC/MS can be used in both presumptive drug screening and for drug confirmation tests.” He adds, “Screening methods have been developed using this technique that allow detection of hundreds of drugs in just minutes.” An emerging area for LC/MS is the analysis of dried blood spots. This approach has been employed for opioids3 and it can be used to identify amphetamines, cathinones and most other drugs-of-abuse as well as their metabolites.
Some medical examiners’ offices use ultrafast triple-quadrupole-LC/MS, which provides quantitative analysis of known compounds while simultaneously screening for unknown compounds present in a sample by conducting data-dependent analysis (DDA), which is a standard mode of MS. Designer amphetamines and novel synthetic cannabinoids are constantly modified to foil normal analysis, but DDA can be used to detect these drugs. Many of these modified drugs have been discovered using ultrafast LC/MS/MS detection in complex matrices.
Other crime scenes, such as those in which weapons and residues from explosives are found, also benefit from LC/MS analysis. “LC/MS can identify the type of explosive to help determine how it was manufactured,” Classon says. “For example, the Semtex explosive used in the Pan Am Flight 103 that was brought down over Lockerbie, Scotland was analyzed and confirmed using LC/MS techniques.”
Samples can be analyzed with LC/MS following exposure to extreme conditions, such as being buried underground or submerged in water. “Some pieces of pottery were discovered in Maya ruins in Belize that date from over 2000 years ago,” Classon says. “Even after being buried for thousands of years, it was still possible to reconstruct what food was present in the pottery millennia ago.”
LC/MS/MS was used for “comprehensive and reliable confirmation of drugs and pharmaceutical compounds in samples analyzed.”4 Using a Q-TOF instrument, “51 compounds representing important illegal drugs, members of various pharmaceutical compound classes and metabolites thereof” were identified.
The Agilent 6500 Series of Accurate-Mass Quadrupole Time-of-Flight LC/ MS provides the sensitivity for a variety of forensic applications. (Image courtesy of Agilent Technologies.)Even more disparate forensic applications exist. “LC/MS is also not limited to simple drug analysis,” Classon notes. “It can be used to determine various food toxins, protein-based poisons such as those found in venoms, and to evaluate where something actually originated.” He adds, “Another area where LC/MS has been used is in the analysis of inks to determine document authenticity.” The difference in the inks of the original and the forgery can be analyzed. “LC/MS can determine the type of the ink based on the ingredients and the age of the ink based on how the oils oxidize over time,” Classon explains.
Quadrupole analyzers, generally the most sensitive types of mass spectrometers, are very robust and provide data that is easy to interpret. These include the Shimadzu LCMS-8050 and 8060 triple-quad platforms, and Agilent 6500 Series Accurate-Mass Quadrupole Time-of-Flight (Q-TOF) LC/MS.
With the growing applications of forensic MS and increasing number of potential compounds, scientists and labs will continue to look for ways to identify smaller amounts of sample more quickly.
References
- Andersson, M.; Diao, X. et al. Metabolic profiling of new synthetic cannabinoids AMB and 5F-AMB by human hepatocyte and liver microsome incubations and high-resolution mass spectrometry. Rapid Commun. Mass Spectrom. 2016, 30, 1067–78.
- Varga, Z.; Nicholl, A. et al. Plutonium age dating (production date measurement) by inductively coupled plasma mass spectrometry. J. Radioanal. and Nuclear Chem. 2016, 307, 1919–26.
- Verplaetse, R. and Henion, J. Quantitative determination of opioids in whole blood using fully automated dried blood spot desorption coupled to on-line SPE-LC-MS/MS. Drug Testing and Anal. 2016, 8, 30–8.
- Steger, J.; Arnhard, K. et al. Successful adaption of a forensic toxicological screening workflow employing non-targeted liquid chromatography-tandem mass spectrometry to water analysis. Electrophoresis 2016, doi: 10.1002/elps.201500511.
Mike May is a freelance writer and editor living in Ohio. He can be reached at [email protected].