Associate Professor Michael Dawson

Webb, R.R., Doble, P.A. & Dawson, M. 2009, 'Optimisation of HPLC gradient separations using artificial neural networks (ANNs): Application to benzodiazepines in post-mortem samples', Journal Of Chromatography B-Analytical Technologi..., vol. 877, no. 7, pp. 615-620.
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Artificial neural networks (ANNs) were used in conjunction with an experimental design to optimise a gradient HPLC separation of nine benzodiazepines. Using the best performing ANN, the optimum conditions predicted were 25 mM formate buffer (pH 2.8), 10% MeOH, acetonitrile (ACN) gradient 0-15 min, 6.5-48.5%. The error associated with the prediction of retention times and peak widths under these conditions was less than 5% for six of the nine analytes. The optimised method, with limits of detection (LODs) in the range of 0.0057-0.023 mu g/mL and recoveries between 58% and 92%, was successfully applied to authentic post-mortem samples. This method represents a more flexible and convenient means for optimising gradient elution separations using ANNs than has been previously reported.

Beavis, A.D., Dawson, M., Doble, P.A., Scolyer, R.A., Bourne, R., Li, L., Murali, R., Stretch, J.R., Lean, C.L., Uren, R.F. & Thompson, J.F. 2008, 'Confirmation of sentinel lymph node identity by analysis of fine-needle biopsy samples using inductively coupled plasma-mass spectrometry', Annals Of Surgical Oncology, vol. 15, no. 3, pp. 934-940.
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Background: The sentinel lymph node (SLN) biopsy technique is a reliable means of determining the tumor-harboring status of regional lymph nodes in melanoma patients. When technetium 99 m-labeled antimony trisulfide colloid ((99) Tc-m-Sb2S3) particles ar

Cheluvappa, R., Shimmon, R.G., Dawson, M., Hilmer, S.N. & Le Couteur, D.G. 2008, 'Reactions of Pseudomonas aeruginosa pyocyanin with reduced glutathione', Acta Biochimica Polonica, vol. 55, no. 3, pp. 571-580.
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Pseudomonas aeruginosa is the most common cause of chronic and recurrent lung infections in patients with cystic fibrosis (CF) whose sputa contain copious quantities of P. aeruginosa toxin, pyocyanin. Pyocyanin triggers tissue damage mainly by its redox

huttunen, J., Doble, P.A., Dawson, M., Roux, C.P. & Robertson, J. 2008, 'Physical evidence in drug intelligence, Part 2: discrimination of packaging tapes by colour', Australian Journal of Forensic Sciences, vol. 40, no. 1, pp. 73-83.
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The authors have considered routine exploitation of physical evidence from seized shipments of illicit drugs for intelligence purposes. Part 1 of this series addressed the identification of polymer type within the adhesive pf packaging tapes and raised important issues with regard to how data should be collated in a databse as a basis for reliable drug intelligence. this article expands onthis topic by addressingt eh sue of colour for achieving the same aim. By using a relatively simple instrumental technique to analyse opaque 'brown' packaging tapes, it was found that colour was an effective way to discriminate between different adhesive tape samples. However, unitial results showed that the analysis of colour in packaging tapes was more complex than assigning seminsubjective names to particular hues (e.g. light brown, greenm brown etc). Instead, samples in the population often differed only slightly from one another and hence proved difficult to categorise. Thus, a database or analyst must avoid using such 'discrete' labels and instead make use of 'continuous' numerical data. Here, CIELab chromaticity coordinates were used to define representative colour spaces for each tape sample and these were then compared to determine whether two such volumes intersected. This process would decide whether or not the sampes could be discriminated. While several sets of data were compared, further work needs to be carried out into the consistency of colour within single rolls of tape or batches of tape.

Karim, R.Z., Scolyer, R.A., Li, W., McKinnon, J.G., Li, L., Uren, R.F., Lam, S., Beavis, A.D., Dawson, M., Doble, P.A., Hoon, D.S. & Thompson, J.F. 2008, 'False negative sentinel lymph node biopsies in melanoma may result from deficiencies in nuclear medicine, surgery, or pathology', Annals of Surgery, vol. 247, no. 6, pp. 1003-1010.
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OBJECTIVE: To investigate a cohort of melanoma patients with false negative (FN) sentinel node (SN) biopsies (SNBs) to identify the reasons for the FN result. SUMMARY OF BACKGROUND DATA: SNB is a highly efficient staging method in melanoma patients. However, with long-term follow-up FN SNB results of up to 25% have been reported. METHODS: Seventy-four SNs from 33 patients found to have had an FN SNB were analyzed by reviewing the lymphoscintigraphy, surgical data, and histopathology, and by assessing nodal tissue using multimarker real-time quantitative reverse transcription (qRT) polymerase chain reaction, and antimony concentration measurements (as a marker of "true" SN status) using inductively coupled plasma mass spectroscopy. RESULTS: Nine SNs (12%) from 9 patients (27%) had evidence of melanoma on histopathologic review. Twelve SNs (16%) from 10 patients (30%) were qRT(+). Four of these 12 SNs were positive on histopathology review and 8 were negative. Four patients (12%) were upstaged by qRT. Sixteen patients had their SNB histology, lymphoscintigraphy, and surgical data reviewed. Identifiable causes of the FN SNBs were not found after review of all modalities in 4 patients. SNs from all 4 patients had antimony levels indicative of an SN. Of the SNs evaluable by qRT, 1 was qRT(+) and 7 SNs from 2 patients were qRT(-). CONCLUSIONS: An FN SN can occur because of deficiencies in nuclear medicine, surgery, or pathology. qRT can detect "occult" metastatic melanoma in SNs that have been identified as negative by histopathology. A? 2008 Lippincott Williams & Wilkins, Inc.

huttunen, J., Austin, C.E., Dawson, M., Roux, C.P. & Robertson, J. 2007, 'Physical evidence in drug intelligence, Part 1: rationale based on hierarchic distribution of drugs using pyrolysis gas chromatography -mass spectrometry as an example', Australian Journal of Forensic Sciences, vol. 39, no. 2, pp. 93-106.
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A complementary intelligence-gathering tool is described for drug-crime investigation. Scientific analysis and interpretation of packaging materials from seized shipments of illicit drugs will assist law enforcement by creating a more holistic description of each seizure, thus allowing further inferences to be drawn and ultimately assisting in a more thorough understanding of the flow of drugs to or within a particular jurisdiction. The approach is intended as an extension to chemical and physical profiling methods already applied to the actual seized drugs by many law enforcement organisations around the world. Adhesives from 98 rolls of packaging tape were analysed by pyrolysis gas chromatography-mass spectrometry (PyGCMS) for the purposes of determining the types of polymers commonly found in such samples. Using these results as an example, models outlined within this document describe how drug and packaging analysis can complement each other, and how such data can be used in an intelligence capacity. Some limitations of the approach are also identified and discussed.

Kelly, T.L., Doble, P.A. & Dawson, M. 2007, 'A Fast CE Method For The Achiral Separation Of Methadone And Its Major Metabolites, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyr-rolidine And 2-ethyl-5-methyl-3,3-diphenyl-1-pyrroline', Electrophoresis, vol. 28, no. 19, pp. 3566-3569.
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The utilization of dynamic doubly coated capillaries for a fast separation of methadone and its two major metabolites, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and 2-ethyl-5-methyl-3,3-diphenyl-l-pyrroline (EMDP) was investigated. The coa

Webb, R.R., Doble, P.A. & Dawson, M. 2007, 'A Rapid Cze Method For The Analysis Of Benzodiazepines In Spiked Beverages', Electrophoresis, vol. 28, no. 19, pp. 3553-3565.
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A rapid CZE method was developed for the simultaneous determination of nine benzodiazepines in spiked beverages (nitrazepam oxazepam, alprazolam, flunitrazepam, temazepam, diazepam, 7-aminoflunitrazepam, 7-aminonitrazepam and 7-aminoclonazepam). The meth

Burger, F.J., Dawson, M., Roux, C.P., Maynard, P.J., Doble, P.A. & Kirkbride, P. 2005, 'Forensic analysis of condom and personal lubricants by capillary electrophoresis', Talanta, vol. 67, no. 2, pp. 368-376.
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Condoms may offer sexual assailants a simple and relatively effective means by which they may remove and dispose of the biological evidence of their contact with the victim. Without this valuable probative evidence, the investigator may need to turn to s

Esseiva, P., Anglada, F., Dujourdy, L., Taroni, F., Margot, P., Du Pasquier, E., Dawson, M., Roux, C.P. & Doble, P.A. 2005, 'Chemical profiling and classification of illicit heroin by principal component analysis, calculation of inter sample correlation and artificial neural networks', Talanta, vol. 67, no. 2, pp. 360-367.
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Artificial neural networks (ANNs) were utilised to validate illicit drug classification in the profiling method used at Institut de Police Scientifique of the University of Lausanne (IPS). This method established links between samples using a combination

Kelly, T.L., Doble, P.A. & Dawson, M. 2005, 'Chiral analysis of methadone and its major metabolites (EDDP and EMDP) by liquid chromatography-mass spectrometry', Journal Of Chromatography B-Analytical Technologies In The Biomedical And Life Sciences, vol. 814, no. 2, pp. 315-323.
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Racemic methadone (MET) is administered to heroin users undergoing methadone maintenance therapy (MMT) in Australia. The enantiomers of methadone possess different pharmacological effects, and the enantioselective metabolism of methadone to its two major

Paull, B., Roux, C.P., Dawson, M. & Doble, P.A. 2004, 'Rapid screening of selected organic explosives by high performance liquid chromatography using reversed-phase monolithic columns', Journal of Forensic Science, vol. 49, no. 6, pp. 1-6.

Scolyer, R.A., Thompson, J.F., Li, L., Beavis, A.D., Dawson, M., Doble, P.A., Soper, R., Uren, R.F., Stretch, J.R., Sharma, R. & McCarthy, S.W. 2004, 'Antimony concentrations in nodal tissue can confirm sentinel node identity', Modern Pathology, vol. 17, pp. 1191-1197.
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Scolyer, R.A., Thompson, J.F., Li, L., Beavis, A.D., Dawson, M., Doble, P.A., Ka, V.S., McKinnon, J.G., Soper, R., Uren, R.F., Shaw, H.M., Stretch, J.R. & McCarthy, S.W. 2004, 'Failure to remove true sentinel nodes can cause failure of the sentinel node biopsy technique: evidence from antimony concentrations in false-negative sentinel nodes from melanoma patients', Annals of Surgical Oncology, vol. 11, no. 3, pp. 174S-178S.

Casamento, S.G., Kwok, B.K., Roux, C.P., Dawson, M. & Doble, P.A. 2003, 'Optimization of the separation of organic explosives by capillary electrophoresis with artificial neural networks', Journal Of Forensic Sciences, vol. 48, no. 5, pp. 1075-1083.

Dawson, M., Doble, P.A., Beavis, A.D., Li, L., Soper, R., Scolyer, R.A., Uren, R.F. & Thompson, J.F. 2003, 'Antimony by ICP-MS as a marker for sentinel lymph nodes in melanoma patients', The Analyst, vol. 128, no. 3, pp. 1-6.
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A sensitive, accurate and specific method for the analysis of antimony by ICP-MS is presented as a marker of the sentinel lymph node in melanoma patients.

Doble, P.A., Sandercock, P.M., Du Pasquier, E., Petocz, P., Roux, C.P. & Dawson, M. 2003, 'Classification. of premium and regular gasoline by gas chromatography/mass spectrometry, principal component analysis and artificial neural networks', Forensic Science International, vol. 132, no. 1, pp. 26-39.
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Detection and correct classification of gasoline is important for both arson and fuel spill investigation. Principal component analysis (PCA) was used to classify premium and regular gasolines from gas chromatography?mass spectrometry (GC?MS) spectral data obtained from gasoline sold in Canada over one calendar year. Depending upon the dataset used for training and tests, around 80?93% of the samples were correctly classified as either premium or regular gasoline using the Mahalanobis distances calculated from the principal components scores. Only 48?62% of the samples were correctly classified when the premium and regular gasoline samples were divided further into their winter/summer sub-groups. Artificial neural networks (ANNs) were trained to recognise premium and regular gasolines from the same GC?MS data. The best-performing ANN correctly identified all samples as either a premium or regular grade. Approximately 97% of the premium and regular samples were correctly classified according to their winter or summer sub-group.

Kelly, T.L., Doble, P.A. & Dawson, M. 2003, 'Chiral separation of methadone, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrol (EDDP) and 2-ethyl-5-methyl-3,3-diphenyl-1-pyrroline (EMDP) by capillary electrophoresis using cyclodextrin derivatives', Electrophoresis, vol. 24, no. 12-13, pp. 2106-2110.
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A stereoselective method was developed for the simultaneous determination of methadone and its two major metabolites, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP) and 2-ethyl-5-methyl-3,3-diphenyl-1-pyrroline (EMDP) by capillary electrophoresis. Five -cyclodextrin (CD) background electrolyte (BGE) additives were evaluated for resolution efficiency. The conditions for baseline resolution of each of the three enantiomer pairs was determined to be 1 mM heptakis-(2,6-di-O-methyl)--cyclodextrin (DMCD) in 100 mM phosphate at pH 2.6. This method represents the first successful method for the resolution of the six enantiomers associated with the metabolism of methadone. The utilisation of doubly coated capillaries in conjunction with CD derivatives for a faster separation of the methadone-related enantiomers is also reported. The coated capillaries were prepared using a polycation of poly(diallyldimethylammonium chloride) (PDDAC) and a polyanion of dextran sulfate. Baseline resolution of the methadone enantiomers was achieved with a BGE of 8 mM (2-hydroxy)propyl--cyclodextrin (HPCD) in 100 mM phosphate at pH 2.6. The migration times for the stereoselective methadone separation were approximately 4 min, which represented a reduction by a factor of approximately three, compared to that attained using analogous conditions with the uncoated capillary.

Dawson, M., Fryirs, B., Kelly, T.L., Keegan, J.T. & Mather, L. 2002, 'A rapid and sensitive high-performace liquid chromatography-electrospray ionization-triple quadrupole mass spectometry method for the quantitation of oxycodone in human plasma', Journal of Chromatographic Science, vol. 40, no. 1, pp. 40-44.
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A sensitive method for the determination of oxycodone concentrations in plasma by high-performance liquid chromatography (HPLC)?electrospray ionization?triple quadrupole mass spectrometry is described. The method is rugged, reliable, selective, and rapid with a run time of 2 min. One milliliter of plasma is made basic and extracted with 2-mL duplicate portions of 2% isoamyl alcohol in n-butyl chloride. The combined extracts are then evaporated to dryness, reconstituted in 100 ?L of the mobile phase (15% methanol?85% water containing 0.1% acetic acid), and injected onto the HPLC. The limit of quantitation is 1 ng/mL, and the estimated limit of detection is 33 pg/mL (signal-to-noise = 3). Standard curves are linear over the range of 1 to 100 ng/mL with all correlation coefficient values greater than 0.9989. The method is used to determine the concentration of oxycodone in human plasma following the intravenous infusion of doses ranging from 5 to 15 mg in which the analysis of over 3000 plasma samples is required.

Lee, G.S., Brinch, K.M., Kannangara, G.K., Dawson, M. & Wilson, M.A. 2001, 'A Methodology Based on NMR Spectroscopy for the Forensic Analysis of Condoms', Journal of Forensic Sciences, vol. 46, no. 4, pp. 40-53.
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Both solution and solid state Nuclear Magnetic Resonance (NMR) spectroscopic techniques have been used to determine differences in commercially available condoms. Whilst solid state NMR is useful for determining the polymer backbone, it is not useful for forensic analysis due to the commonality of the latex condom. However solution NMR spectra obtained following a simple extraction procedure using hexane, provides a fingerprint of the additives in the lubricants. Following the development of a flow chart, basing decisions on the presence of particular peaks present in the solution spectra, 33 of 38 condoms could be individualized. Samples were also analyzed after having the lubricant manually removed and soaking the condom in water for 3 to 24 h. These experiments were performed to simulate a case of the sample having been used and disposed of by flushing down the toilet, as may be experienced in a case of a sexual assault. The results indicated that the only significant water soluble component was polyethylene glycol. The overall results suggest that the method developed may be a quick and useful technique in characterizing condoms. The information obtained can be used to provide associative evidence between suspect and crime, and so be useful in sexual assault cases.

Maynard, P.J., Allwell, K., Roux, C.P., Dawson, M. & Royds, D. 2001, 'A Protocol for the Forensic Analysis of Condom and Personal Lubricants Found in Sexual Assault Cases', Forensic Science International, vol. 124, pp. 140-156.
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Lee, G.S., Taylor, R., Dawson, M., Kannangara, G.K., Wilson, M. 2000, 'High Resolution Solid-State C Nuclear Magnetic Resonance Spectra or 3,4-Methylenedioxyphetamine Hydrochloride and Related Compounds and Their Mixtures with Lactose', Solid State Nuclear Magnetic Resonance, vol. 16, no. 0, pp. 225-237.