Loughborough University
Leicestershire, UK
LE11 3TU
+44 (0)1509 222222
Loughborough University

Centre for Innovative and Collaborative Construction Engineering

2012

Dhinesh Asogan

Dr Dhinesh Asogan

Google Scholar

Thesis

A non-contact laser ablation cell for mass spectrometry

Project Title

A Non-Contact Laser Ablation Cell for Mass Spectrometry

Company

Electro Scientific Industries Inc., New Wave Research Division

Supervisors

Academic:
Professor Barry Sharp
Professor Roger Smith

Industrial:   
Dr Damon Green 
Dr Ciaran O’Connor

Director of Research:
Professor Dino Bouchlaghem

Research Period

2005 - 2012

New Tuneable Laser Interface for Mass Spectrometry

Context and Background

Mass Spectrometry (MS) is an established technique that can be used to identify elements and molecular fragments according to their relative molecular masses. To do this, the analyte must first be ionised to form an ionised, gaseous compound which is then sent through a mass analyser to separate the ions by mass-to-charge ratio (m/z), finally being detected by a detector.

There are a variety of ionisation methods available, ranging from simple electron impact ionisation, where the sample is bombarded by high energy electrons, to the powerful Inductively Coupled Plasma (ICP). The mass analyser can also range in complexity, from the simple Time of Flight (ToF), where the analytes are separated by time taken to drift down a tube, to the complex Quadrupole mass analyser, where the analytes are separated by electronic stability.

Recent developments in MS, in particular those employing the ICP ionisation source, have opened up new areas of research related to the (bio)medical sciences. The potential applications have been discussed and reviewed by Jakubowski et al. in 2004. Work on combining elemental and molecular MS to date has mainly focussed on development of tuneable ionisation sources that provide both elemental and molecular information, i.e. sources that can achieve hard- and soft-ionisation. More recently Hieftje has described the concept of using dual sources e.g. an electrospray and an ICP coupled to a single ToF-MS. The benefits of bringing about a convergence of the complementary techniques of elemental and molecular MS have been discussed by Wind and Lehmann.

Mass Spectrometry for genomics and proteomics is dominated by tandem MS techniques and soft-ionisation ToF-MS. The general aim of these techniques is to control the degree of sample fragmentation to preserve molecular information. Whilst the soft-ionisation ToF-MS technique has very low limits of detection and is capable of analysing a high mass range, the requirement of a vacuum environment make this a predominantly offline technique.

Contrasting this, electrospray and nanospray ionisation sources are well suited to on-line coupling of, e.g., High Performance Liquid Chromatography (HPLC) to MS; however, the ionisation efficiency of both spray techniques is significantly lower than that of the ICP (0.001% compared to 30-100%). Additionally, the spray techniques are intolerant to high salt matrices, requiring a purification step preceding ionisation, and produce multiply-charged molecular species, complicating the mass spectrum considerably.

Acquisition of elemental and molecular data from a single sample fraction has a number of advantages. Molecular MS provides identification and information on structure whilst elemental MS provides direct identification of the metallome, generic detection of bio-molecules using phosphorous and sulphur and excellent powers of detection and quantitation. Further elemental MS enables ready implementation of isotope dilution and isotope dilution and isotopic identification in the absence of expensive, high cost/performance MS techniques such as Ion Cyclotron Resonance.

Aims and Objectives

The aim of the project is the development of a single, flexible laser-based interface coupled to an ICP and a ToF-MS to achieve both hard-and soft-ionisation. Thus both molecular and elemental information will be obtained from a single sample fraction.

The specific objectives of the project include:

  • Carry out a literature review to investigate the processes involved in laser-based mass spectrometry. Additionally, the literature review will assess the current status of technology and interfaces currently available.
  • Building on this work, develop a laser probe that can be operated at a range of fluences and pressures for the acquisition of both molecular and elemental information. A fully engineered probe with a supersonic gas jet for ion transport and close coupling to the mass spectrometers will be developed.
  • To test and validate this laser system with a variety of sample types, ranging from certified reference materials to real, biological samples.

Method and Current Status

Design of novel interfaces etc. will be carried out on a suitable CAD package. Build will be outsourced to a suitable firm. Testing and validation will be performed on currently owned mass spectrometry equipment.

Benefits and Expected Outcomes

By the end of the research period, a commercial product capable of adapting mass spectrometry to obtain simultaneous elemental and molecular information will be available.

Dhinesh, A. … et al. (2011). Numerical simulations of gas flows through an open, non-contact cell for LA-ICP-MS, Journal of Analytical Atomic Spectrometry, 26 (3), pp. 631-634. DOI: 10.1039/C0JA00166J
http://pubs.rsc.org/en/Content/ArticleLanding/2011/JA/C0JA00166J

Dhinesh, A. … et al. (2009). An open, non-contact cell for laser ablation-inductively coupled plasma mass spectrometry, Journal of Analytical Atomic Spectrometry, Vol 24 (7), pp. 917 – 923. DOI: 10.1039/B904850B
http://pubs.rsc.org/en/content/articlelanding/ja/2009/b904850b

Dhinesh, A. … et al. (2009). Apparatus and Method for Laser Irradiation. US Patent No: US 2010/0207038 A1
http://www.google.com/patents/US20100207038

Dhinesh, A. … et al. (2009). Oral – “Novel laser ablation cell with decreased sample washout and increased sensitivity”, European Winter Conference on Plasma Spectrochemistry – Graz, Austria.
https://inis.iaea.org/search/search.aspx?orig_q=RN:41070714

Asogan, Dhinesh; Sharp, Barry (2007). Poster – “Aerodynamic Lens Systems for Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry”, European Winter Conference on Plasma Spectrochemistry – Taormina, Sicily TuPo33.

 

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