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Lim A.Y.,Nanyang Technological University | Ma Z.,Nanofrontier Pte Ltd | Ma J.,Nanyang Technological University | Rowell F.,Roar Particles Plc.
Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences | Year: 2011

Two types of amorphous, silica nanoparticles have been produced and used as surface assisting agents during laser desorption/ionisation time-of flight-mass spectrometry (SALDI-TOF-MS). The first is hydrophilic possessing surface aminopropyl groups and the second hydrophobic containing surface phenyl groups. Each particle type acts as a solid phase adsorbent, adsorbing analytes according to their charge and hydrophobicity. The adsorbed analytes can be directly analysed on the particles using SALDI-TOF-MS. Intrinsically magnetisable versions of the hydrophobic particles act as magnetic solid phase extraction (MSPE) materials which are used to selectively adsorb analytes within a mixture deposited onto a surface, transfer the adsorbed components using a magnetic wand and to deposit the particles at a site adjacent to that of the original mixture. Non-adsorbed components remain at the original site. The extracted and residual analytes are then directly analysed on the surface by SALDI-TOF-MS. Using fingerprints as an example of a complex biological matrix, this new approach has been used to separate polar (amino acids) and non-polar constituents (squalene and fatty acids) within latent fingerprints deposited on a surface and for their subsequent direct analysis on the surface by SALDI-TOF-MS. Alanine, ornithine, lysine and aspartic acid which were undetected or poorly detected prior to separation showed improved signal detection after separation. © 2011 Elsevier B.V.

Benton M.,Nanofrontier Pte Ltd | Rowell F.,ROAR Particles Ltd. | Rowell F.,Nanyang Technological University | Sundar L.,ANT Nano PLC | Jan M.,Nanyang Technological University
Surface and Interface Analysis | Year: 2010

Sub-micron sizedhydrophobicsilicaparticlesdopedwith carbonblackhavebeenemployedwith latentfingermarksonglassand metalsurfaces todevelopasimplemethodfor detectingnicotineandcotinine using surface assisted laserdesorption/ionisationtime of flight-mass spectrometry (SALDI-TOF-MS) in positive ion reflectron mode. Dusting of surfaces enables location ofmarks for conventional identification of details but the particles also act as a laser desorption/ionisation enhancing agent (LDI) equivalent to a standardmatrix enhancer 2,5-dihydroxybenzoic acid used in matrix assisted LDI-TOF-MS (MALDI-TOF-MS). The method has been applied in the analysis of smokers' latent fingermarks on metal and glass surfaces. The metal surfaces were analysed following direct MS analysis of the pre-dusted prints, while the glass surfaces were analysed following lifting using commercial tape, and thenMS analysis of these pre-dusted prints. In all cases of smokers, amajor peak atm/z 163 (nicotine+1) and a less intense peak at m/z 161 (possibly anatabine+1) were found in the prints and in some cases additional peaks at 177 (cotinine+1) and 199 (possibly cotinine+Na) were observed. The presence of nicotine and cotinine in smokers' marks was confirmed using SALDI-TOF-MS-MS following high energy collision-induced dissociation when characteristic fragmentation patterns were observed for each compound. Copyright © 2010 John Wiley & Sons, Ltd.

Benton M.,Nanofrontier Pte Ltd | Chua M.J.,Nanofrontier Pte Ltd | Gu F.,Nanofrontier Pte Ltd | Rowell F.,ROAR Particles | And 3 more authors.
Forensic Science International | Year: 2010

Hydrophobic silica nanopowder has been used as an effective latent fingermark development agent and subsequently as an enhancement agent in the surface-assisted laser desorption/ionisation-time of flight (SALDI-TOF) mass spectrometry for analysis of fingermark components. The technique has been used in the detection of nicotine and cotinine in the fingermarks of smokers. In order to have confidence in concluding that the nicotine in such samples is indicative of cigarette usage, it is necessary to establish that contamination by environmental contact or from hand to hand contact with smokers or from passive smoking does not lead to false identification of non-smokers as smokers. To investigate this possibility, the background level of nicotine in fingermark material from a number of commonly used places was determined. In addition, a series of experiments was carried out to assess the extent to which nicotine can be transferred through handshakes and finger transfer as well as touching of door handles. The rate of loss of nicotine from latent fingermarks was also assessed over a 24-h period under ambient laboratory conditions. Finally, a laboratory-based model system was evaluated to ascertain the possible transport of nicotine in cigarette smoke from a source to adjacent areas to simulate cross-contamination of a non-smoker by passive exposure. It was observed that person-to-person transfer from a smoker to a non-smoker can occur following handshakes but at low levels and that passive cross-contamination from contact with surfaces is possible under simulated conditions. However, levels of nicotine in the wider environment were found to be too low for detection using this technique which may reflect the half-life of nicotine in latent fingermarks which was about 11. h. Likewise, transfer via smoke is possible to objects within about 0.1. m of the cigarette but it is unlikely that significant secondary nicotine contamination will occur on the faces and hands of adjacent non-smokers. © 2010 Elsevier Ireland Ltd.

Lim A.Y.,Nanyang Technological University | Gu F.,Nanofrontier Pte Ltd | Ma Z.,Nanofrontier Pte Ltd | Ma J.,Nanyang Technological University | Rowell F.,Roar Particles Plc.
Analyst | Year: 2011

This article examines the use of doped amorphous silica nanoparticles for surface-assisted laser desorption/ionisation-time of flight-mass spectrometry (SALDI-TOF-MS) of hydrophilic and hydrophobic compounds. A range of particles with surface aliphatic carboxylic, aminophenyl, phenyl or aminopropyl groups have been produced and these have been doped with carbon black, polyaniline or graphite. The effects of surface groups and dopants on the laser desorption/ionisation process were studied. The key factor in effective LDI was the presence of carbon black dopant carrying carboxyphenyl or phenyl residues for positive and negative ion formation. The second key factor was the presence of hydrophilic surface functional groups for hydrophilic amino acid analytes for their detection in positive or negative mode as protonated or de-protonated species respectively whereas hydrophobic surfaces were need for ionisation via cationisation for the hydrophobic analyte squalene. The mechanism for LDI of these particles appears to involve initial adsorption of the analyte onto the surface of the particle, formation of primary ions via adsorption of laser UV irradiation by carboxyphenyl residues attached to the carbon black network which act in an equivalent way to the matrix in matrix-assisted LDI. This is followed by reaction of the primary ions with neighbouring adsorbed analyte molecules. The latter are then released possibly via thermal desorption following proton donation or acceptance from/to via surface residues such carboxylate groups associated with the carbon black within the dopant. Alternatively in the absence of such proton donor/acceptor residues as with hydrophobic particles, the primary ions are released from the particles during desorption and form cation adducts as sodiated and potassiated species in the gas phase above the surface. © 2011 The Royal Society of Chemistry.

Lim A.Y.,Nanyang Technological University | Lim A.Y.,Nanofrontier Pte Ltd | Rowell F.,Northumbria University | Rowell F.,University of Sunderland | And 3 more authors.
Analytical Methods | Year: 2013

The ability of two mass spectrometric methods, surface assisted laser desorption ionization mass spectrometry (SALDI-MS) and direct analysis in real time mass spectrometry (DART-MS), to detect the presence of 5 drugs in latent fingermarks has been examined. It was found that each drug could be detected with good sensitivity for marks resulting from direct finger contact with a glass probe by DART-MS or onto stainless steel target plates using SALDI-MS. In contrast, for latent marks lifted from 3 surfaces (ceramic tile, wood laminate and backing of adhesive tape), no drug could be detected in dusted marks on the surface of a commercial lifting tape by DART-MS due to high background interference from the tape material, whereas all the drugs could be detected by SALDI-MS on equivalent marks. Also, it was demonstrated that drug spiked latent fingermarks pre-dusted with regular fingerprint powder and lifted using conventional lifting tape could be redeveloped with carbon black doped silica particles to enable MS interrogation via SALDI-MS. This journal is © The Royal Society of Chemistry.

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