title: Statistical comparison of mass spectra for identification of amphetamine-type stimulants.
abstract: A method for the statistical comparison of mass spectral data is demonstrated for applications in controlled substance analysis. The method uses an unequal variance t-test at each mass-to-charge ratio in the scan range to determine if two spectra are statistically associated or discriminated. If the two spectra are associated, a random-match probability is calculated to estimate the likelihood that the mass spectral fragmentation pattern in question occurs by random chance alone. If the two spectra are discriminated, the fragment ions responsible for the discrimination are determined. In this work, mass spectral data from case samples containing amphetamine, methamphetamine, 3,4-methylenedioxyamphetamine (MDA), 3,4-methylenedioxymethamphetamine (MDMA), phentermine, and psilocin were investigated. All spectra were collected in an accredited forensic laboratory using routine methods for controlled substance analysis. Using the statistical method, spectra of case samples were statistically associated to the corresponding reference standard at the 99.9% confidence level. In these instances, random-match probabilities ranged from 10-39to 10-29, indicating the probability that the characteristic fragmentation pattern occurred by random chance is extremely small. Further, spectra of case samples were discriminated from other reference standards at the 99.9% or 99.0% confidence level, with 1-26 ions responsible for discrimination in each comparison.
authors.affiliation: Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States; Forensic Science Program, School of Criminal Justice, Michigan State University, East Lansing, MI 48824, United States.
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Bodnar Willard
authors.affiliation: Department of Chemistry, Michigan State University, East Lansing, MI 48824, United States. Electronic address: mcguffin@msu.edu.
authors.forename: Victoria L
authors.initials: VL
authors.lastname: McGuffin
authors.affiliation: Forensic Science Program, School of Criminal Justice, Michigan State University, East Lansing, MI 48824, United States. Electronic address: rwsmith@msu.edu.
authors.forename: Ruth Waddell
authors.initials: RW
authors.lastname: Smith
mesh_terms: D000662:Amphetamines / Q000737:chemistry*; D000697:Central Nervous System Stimulants / Q000737:chemistry*; D006801:Humans; D013058:Mass Spectrometry; D010645:Phentermine / Q000737:chemistry; D011562:Psilocybin / Q000031:analogs & derivatives / Q000737:chemistry; D013223:Statistics as Topic
chemical_list: D000662:Amphetamines; D000697:Central Nervous System Stimulants; D011562:Psilocybin; D010645:Phentermine; C009105:psilocin
keywords: Amphetamine-type stimulants; Controlled substance identification; Gas chromatography–mass spectrometry; Mass spectral comparison