Cocaine profiling method retrospectively developed with nontargeted discovery of markers using liquid chromatography with time‐of‐flight mass spectrometry data

Abstract

Illicit drug profiling performed by forensic laboratories assists law enforcement agencies through providing information about chemical and/or physical characteristics of seized specimens. In this article, a model was developed for the comparison of seized cocaine based on retrospective analysis of data generated from ultrahigh performance liquid chromatography with time-of-flight mass spectrometry (UHPLC-TOF-MS) comprehensive drug screening. A nontargeted approach to discover target compounds was employed, which generated 53 potential markers using data from cocaine positive samples. Twelve marker compounds were selected for the development of the final profiling model. The selection included a mixture of commonly used cocaine profiling targets and other cocaine-related compounds. Combinations of pretreatments and comparison metrics were assessed using receiver operating characteristic curves to determine the combination with the best discrimination between linked and unlinked populations. Using data from 382 linked and 34,519 unlinked distances, a classification model was developed using a combination of the standardization and normalization transformations with Canberra distance, resulting in a linked cut-off with a 0.5% false positive rate. The present study demonstrates the applicability of retrospectively developing a cocaine profiling model using data generated from UHPLC-TOF-MS nontargeted drug screening without pre-existing information about cocaine impurities. The developed workflow was not specific to cocaine and thus could potentially be applied to any seized drug in which there are both sufficient data and impurities present.

Cannabis profiling of seized samples: An intra‐location variability study using gas chromatography–mass spectrometry profiles and multivariate data analysis

“…IS normalization (N), which was considered as the reference method, was carried out on the raw data to reduce the instrumental variation. Subsequently, additional preprocessing was performed by the following combinations, often applied in illicit drug profiling 7,12,13,40 : N + square/fourth root, N + log transformation, N + row scaling to constant total, N + standardization (S), N + S + square/fourth root, N + min/max transformation. Furthermore, PCCs were then calculated and thresholds, which decide whether two samples are considered as linked or not, were calculated for the 95% and 99% CLs.…”

“…Because of the large number of seizures, law enforcement is particularly interested in illicit drug profiling in the context of a criminal case. For this purpose, the police collaborate with forensic institutes in trying to find links between seizures by analyzing the physical and chemical properties of the samples 7 . Depending on the drugs, specific information can be gathered about a synthesis pathway, a clandestine laboratory, a production batch or a geographical origin that could indicate a possible connection between seized specimens (dealer/user networks) 8 .…”

“…For this purpose, the police collaborate with forensic institutes in trying to find links between seizures by analyzing the physical and chemical properties of the samples. 7 Depending on the drugs, specific information can be gathered about a synthesis pathway, a clandestine laboratory, a production batch or a geographical origin that could indicate a possible connection between seized specimens (dealer/user networks). 8 This knowledge can then be used as additional evidence in court.…”

Addressing the challenges in forensic drug chemistry II

“…This retrospective approach-when treated with chemometric tools-aided in the development of a comparative profiling model without prior knowledge of links between samples or prior knowledge of the target markers. 11 One of the questions associated with clandestine drug production in houses relates to their fate and/or their degradation following their deposition on surfaces inside dwellings. Mayer et al presented a proof-of-concept study that investigated the interaction of methamphetamine with the common gaseous indoor oxidant nitrous acid and found that the detection of the suspected carcinogenic and mutagenic N-nitrosomethamphetamine could potentially present a risk to public health in properties contaminated with methamphetamine.…”

“…The authors selected 12 marker compounds and employed combinations of pretreatment and distance measures. This retrospective approach—when treated with chemometric tools—aided in the development of a comparative profiling model without prior knowledge of links between samples or prior knowledge of the target markers 11 …”