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Dr Patrick Sears

Senior Lecturer
+44 (0)1483 689580
04 AZ 02

My publications


Costa Catia, van Es Elsje M., Sears Patrick, Bunch Josephine, Palitsin Vladimir, Mosegaard Kirst, Bailey Melanie (2019) Exploring Rapid, Sensitive and Reliable Detection of Trace Explosives Using Paper Spray Mass Spectrometry (PS?MS), Propellants, Explosives, Pyrotechnics 44 (8) pp. 1021-1027 Wiley-VCH Verlag GmbH & Co
In this publication we work towards providing fast, sensitive and selective analysis of explosive compounds collected on swabs using paper spray mass spectrometry. We have (a) increased the size of the paper spray substrate to 1.6×2.1 cm for compatibility with current practise
in swabbing for explosive material; (b) developed a method for determining a successful extraction of analyte from the substrate to reduce false negative events; and (c) expanded the range of analytes that can be detected using paper spray to include the peroxide explosive HMTD, as well as nitroglycerine (NG), picric acid (PA) and tetryl. We report the development of a 30 s method for the simultaneous
detection of 7 different explosive materials using PSMS with detection limits below 25 pg, as well as detection of HMTD at 2500 pg, showing an improvement on previously published work.
Costa Catia, Frampas Cecile, Longman Katherine A., Palitsin Vladimir, Ismail Mahado, Sears Patrick, Nilforooshan Ramin, Bailey Melanie J. (2019) Paper spray screening and LC-MS confirmation for medication adherence testing: a two-step process, Rapid Communications in Mass Spectrometry Wiley

RATIONALE: Paper spray offers a rapid screening test without the need for sample preparation. The incomplete extraction of paper spray allows for further testing using more robust, selective and sensitive techniques such as liquid chromatography mass spectrometry (LC-MS). Here we develop a two-step process of paper spray followed by LC-MS to (1) rapidly screen a large number of samples and (2) confirm any disputed results. This demonstrates the applicability for testing medication adherence from a fingerprint.

METHODS: Following paper spray analysis, drugs of abuse samples were analysed using LC-MS. All analyses were completed using a Q Exactive" Plus Orbitrap" mass spectrometer. This two-step procedure was applied to fingerprints collected from patients on a maintained dose of the antipsychotic drug quetiapine.

RESULTS: The extraction efficiency of paper spray for two drugs of abuse and metabolites was found to be between 15-35% (analyte dependent). For short acquisition times, the extraction efficiency was found to vary between replicates by less than 30%, enabling subsequent analysis by LC-MS. This two-step process was then applied to fingerprints collected from two patients taking the antipsychotic drug quetiapine, which demonstrates how a negative screening result from paper spray can be resolved using LC-MS.

CONCLUSIONS: We have shown for the first time the sequential analysis of the same sample using paper spray and LC-MS, as well as the detection of an antipsychotic drug from a fingerprint. We propose that this workflow may also be applied to any type of sample compatible with paper spray, and will be especially convenient where only one sample is available for analysis.