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Dr Patrick Sears


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

Biography

Affiliations and memberships

Royal Society of Chemistry
Fellow of the RSC (FRSC)
British Mass Spectrometry Society
Member of BMSS and committee member for the ambient ionisation special interest group

Research

Research interests

My teaching

My publications

Publications

Lewis Holly-May, Webb Roger, Verbeck Guido F, Bunch Josephine, De Jesus Janella, Costa Catia, Palitsin Vladimir, Swales John G., Goodwin Richard J. A., Sears Patrick, Bailey Melanie Jane Nanoextraction coupled to liquid chromatography mass spectrometry delivers improved spatially resolved analysis, In: Analytical Chemistry91(24)pp. 15411-15417 American Chemical Society
Direct analyte probed nanoextraction (DAPNe) is a technique that allows extraction of drug and endogenous compounds from a discrete location on a tissue sample using a nano capillary filled with solvent. Samples can be extracted from a spot diameters as low as 6 µm. Studies previously undertaken by our group have shown that the technique can provide good precision (5%) for analysing drug molecules in 150 µm diameter areas of homogenised tissue, provided an internal standard is sprayed on to the tissue prior to analysis. However, without an isotopically labelled standard, the repeatability is poor, even after normalisation to and the spot area or matrix compounds. By application to tissue homogenates spiked with drug compounds, we can demonstrate that it is possible to significantly improve the repeatability of the technique by incorporating a liquid chromatography separation step. Liquid chromatography is a technique for separating compounds prior to mass spectrometry (LC-MS) which enables separation of isomeric compounds that cannot be discriminated using mass spectrometry alone, as well as reducing matrix interferences. Conventionally, LC-MS is carried out on bulk or homogenised samples, which means analysis is essentially an average of the sample and does not take into account discrete areas. This work opens a new opportunity for spatially resolved liquid chromatography mass spectrometry with precision better than 20%.
Jang Min (2020)On the relevance of detecting drugs in a fingerprint University of Surrey
This thesis explores the feasibility of testing for drugs from a fingerprint. Previous publications have reported drug detection in fingerprints from either drug users or after contact with a substance. There are possibilities to exploit these findings either for forensics (where a finger-mark is deposited at a crime scene to give intelligence about a donor) or for drug testing (where fingerprints are deposited under controlled conditions). In forensic science, it may be sufficient to know that a drug has been either handled or ingested within a specific time frame. In contrast, for drug testing, it may be necessary to exclude handling of drugs as a possible source. In either case, it is necessary to understand the significance of detecting a drug or its metabolite in a fingerprint. This thesis explored the significance of detecting a selection of illicit drugs in fingerprints. In Chapter 4 and Chapter 5, a rapid analysis method based on paper spray high resolution mass spectrometry is developed and validated for cocaine and its metabolite, benzoylecgonine (BZE), and the method is applied to the fingerprints of non-drug users and drug users respectively. As a result, cocaine and BZE were found in samples from both non-drug users (set as environmental cut-off) and drug users. The detection rate from drug users was above 90 % and there were no false positive using this method. Moreover, handwashing involvement became indicative of either ingestion of cocaine OR recent contact with cocaine. In Chapter 6 and 7, imaging mass spectrometry techniques were employed to determine whether contact and ingestion scenarios can be distinguished via spatial distribution of analytes. Those results supported the hypothesis that hot spots would be formed in fingerprints after contact whereas analytes would be evenly distributed in fingerprints after ingestion. The presence of BZE was also used to in distinguishing fingerprint samples from the two scenarios. In Chapter 8 and 9, the paper spray mass spectrometry methodology was expanded to a selection of novel psychoactive substances (NPS) relevant to a prison environment using fingerprints for the first time. The method was applied to the fingerprints of prisoners before and after participants washed their hands. As a result, NPS substances were not detected from any participants, in agreement with their urine testing. Finally, in Chapter 10, the data collected in Chapter 4 and 5 was analysed retrospectively for detection of heroin and 6-AM in fingerprints to explore the possibility of carrying out an untargeted analysis. The sensitivity of the method was not as good as for cocaine and benzoylecgonine (BZE), which led to the lower detection rate of heroin and 6-AM than that of cocaine and BZE. However, this study proved that the paper spray method could still provide qualitative and quantitative results of heroin detection in fingerprints. This study demonstrates that in the future with a suitable, deployable high resolution mass spectrometer, paper spray mass spectrometry could be used to detect cocaine, its metabolites and NPS for evidential purposes within the confines of a police station.
Costa Catia, van Es E.M., Sears P., Bunch J., Palitsin Vladimir, Cooper H., Bailey M.J. (2019)Exploring a route to a selective and sensitive portable system for explosive detection– swab spray ionisation coupled to of high-field assisted waveform ion mobility spectrometry (FAIMS), In: Forensic Science International: Synergy1pp. 214-220 Elsevier
Paper spray mass spectrometry is a rapid and sensitive tool for explosives detection but has so far only been demonstrated using high resolution mass spectrometry, which bears too high a cost for many practical applications. Here we explore the potential for paper spray to be implemented in field applications with portable mass spectrometry. This involved (a) replacing the paper substrate with a swabbing material (which we call “swab spray”) for compatibility with standard collection materials; (b) collection of explosives from surfaces; (c) an exploration of interferences within a ± 0.5 m/z window; and (d) demonstration of the use of high-field assisted waveform ion mobility spectrometer (FAIMS) for enhanced selectivity. We show that paper and Nomex® are viable collection materials, with Nomex providing cleaner spectra and therefore greater potential for integration with portable mass spectrometers. We show that sensitive detection using swab spray will require a mass spectrometer with a mass resolving power of 4000 or more. We show that by coupling the swab spray ionisation source with FAIMS, it is possible to reduce background interferences, thereby facilitating the use of a low resolving power (e.g. quadrupole) mass spectrometer.
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, In: 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.

Costa Catia, van Es Elsje M., Sears Patrick, Bunch Josephine, Palitsin Vladimir, Mosegaard Kirst, Bailey Melanie Exploring Rapid, Sensitive and Reliable Detection of Trace Explosives Using Paper Spray Mass Spectrometry (PS‐MS), In: Propellants, Explosives, Pyrotechnics44(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.

Additional publications