Publications

Research Thesis: The Ultra-Trace Level Analysis of Xanthates by High Performance Liquid Chromatography

M.J.E. Trudgett, M.Sc.(Hons) Thesis, University of Western Sydney, 2005

Abstract:

An ion-interaction, reversed-phase high performance liquid chromatographic method was developed for the simultaneous analysis of seven xanthates of simple alcohols. The effects on chromatographic behaviour of mobile phase composition changes (level of organic modifier, buffer type and pH) and different ion-pairing (IP) reagents as well as IP concentrations were examined. An assessment was also made of detection limits and the accuracy and precision of quantitation by peak area and peak height – at the two strongest xanthate (UV) absorbance wavelengths of 227 nm and 300 nm. Linearity of response for all xanthates was confirmed within the concentration range encompassing three orders of magnitude: 10 μg L-1 to 50 mg L-1. The most efficient separations were achieved when using tetrabutylammonium bromide as the ion-pairing reagent. Near-baseline separation of the seven xanthates was achieved with isocratic elution and a run time of less than nine minutes. Absolute limits of detection were between 0.08 ng and 0.42 ng.

The high degree of accuracy and precision of this method has been demonstrated in field trials involving the analysis of tailings samples and wastewater from several mines in north-western New South Wales, Australia. This method has proven to be a simple, rapid and inexpensive means of determining trace xanthate levels for the purposes of environmental assessments and process monitoring.

Original Research Article: Theoretical description of a new analytical technique - Comprehensive online multidimensional fast Fourier transform separations

M.J.E. Trudgett, G. Guiochon, R.A. Shalliker, J. Chromatogr. A 1218 (2011) 3545.
ERA Journal Ranking: A*

Abstract:

Comprehensive multidimensional separations are today dominated by systems that are fundamentally limited to highly asymmetrical online separations sacrificing separation space, or to lengthy, time consuming offline separations. With the exception of pulse-modulated methods, separations have thus been limited to two dimensions. It is proposed that some of the limitations and shortcomings of these methods may be ameliorated or overcome by employing multi-dimensional detection whereby each analyte is effectively labelled in the frequency domain by a series of pulsed-injections, and a symmetrical, comprehensive online analysis performed with the resulting signal processed by sequential Fourier analysis. A semi-empirical computer model of this system was developed and its feasibility positively demonstrated in simulations of high-efficiency separations in two dimensions. Separations of higher dimensionality were shown to be possible but involved signal-processing challenges beyond the present work. By eliminating wrap-around effects and enabling the separation of physically unseparated peaks, the technique facilitates significant improvements in peak capacity per unit of analysis time as well as greatly improved signal to noise ratios. Because these comprehensive online multidimensional Fourier transform separations depend heavily upon the practical lifetime of imposed injection pulses, it is envisaged that this method will leverage emerging high-efficiency micro- and nanoscale separations technologies.

Patent (pending): Method for analysing a sample comprising a plurality of analytes

M.J.E. Trudgett, R.A. Shalliker, PCT/AU2012/000142

Abstract:

Disclosed herein is a method and system for analysing a sample comprising a plurality of analytes. The method comprises the steps of passing the sample through a first separating zone and a second separating zone, whereby each of the plurality of analytes have a first speed in the first separating zone and a second speed in the second separating zone; generating temporal information by sensing the plurality of analytes at a plurality of spaced apart positions at the second separating zone; and generating time dependent spectral information from the temporal information.

International Conference, Poster Presentation: Towards Accelerated Peak Production Rates via Comprehensive Online Multidimensional Frequency Transform Separations

40th International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC 2013), Hobart, Australia.

M.J.E. Trudgett,  and R.A. Shalliker

Abstract:

Comprehensive Online Multidimensional Frequency Transform Separations (COMForTS) is a new analytical method that accelerates peak production by the correlation of analyte retention time with velocity where these data are derived from time-dependant frequency transformation of pulsed analyte signals.

Utilising a makeshift COMForTS instrument consisting of a two-dimensional capillary liquid chromatography system with arrayed on-column CCD-based ultra-violet absorbance detection, multiple injections of a multi-component solution were made such that the separations achieved from one injection severely overlapped those of adjacent injections (Figure 1a). Aggregation of multiple detector signals provided virtual analyte pulses and conventional time-time chromatograms were obtained by translation of the (Fourier-related) Radon transform of the resulting signals. In all cases, all analytes were resolved regardless of extensive wrap-around (Figure 1b). Previously reported interferences were either eliminated or greatly reduced.

The nature of COMForTS dictates that virtual peak production is always some higher multiple of physical peak production. This early work has demonstrated that COMForTS increases peak production by at least an order of magnitude and is equally applicable to separations in three or more dimensions where effective peak production increases exponentially with dimensionality.

We also discuss physical and computational requirements of COMForTS, potential applications and further improvement through evolved sophistication in signals processing methods.

International Conference, Oral Presentation: Theory and modelling of a new analytical technique: Comprehensive Online Multidimensional Fast Fourier Transform Separations

36th International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC 2011), Budapest, Hungary.

M.J.E. Trudgett,  G. Guiochon and R.A. Shalliker

Abstract:

Practical comprehensive multidimensional chromatography is today dominated by systems that are fundamentally limited to highly asymmetrical online separations sacrificing separation space, or to lengthy, time consuming offline separations. With few exceptions, separations have thus been essentially limited to two dimensions. It is proposed that these limitations may be overcome by employing multi-dimensional detection whereby each separation dimension is effectively encoded in the frequency domain by inter-dimensional pulse-modulated flow, and a symmetrical analysis performed online and re-constructed by sequential Fourier analyses, across the time domain, thus affording detection in both the time and frequency domains.

The pulse frequency regime employed depends upon the physical relationship of the detector to the separation phases. In the case of separations where detection is made after elution from the stationary phase, the frequency of the pulsed injections must be altered over time such that different retention-time related frequencies are presented to the detector. By contrast, detectors that measure analyte responses during a separation are presented with analyte signals of differing linear velocities. In this case a constant frequency pulse-injection produces analyte pulses of the same physical dimensions that appear to the detector to have differing frequencies proportional to their relative velocity. The technique may be used for high speed comprehensive analyses in multiple dimensions with negligible increases in the total analysis time. Whilst band-broadening will eventually result in the complete dissipation of measureable pulses, the technique is unique in its capacity to numerically resolve physically unresolved peaks and has been shown, in theory, to be applicable to short, high-efficiency separations, producing extraordinarily high peak capacities per unit of analysis time. A semi-empirical computer model of this system was developed and the validity of the theory and the feasibility of practical implementation positively established.

It is envisaged that these comprehensive online multidimensional Fourier transform separations will leverage emerging high-efficiency micro- and nano-scale separations technologies.

Research Thesis: Towards Comprehensive Online Multidimensional Frequency Transform Separations

M.J.E. Trudgett, Ph.D. Thesis, University of Western Sydney, 2014
(Approved)

Summary:

This thesis represents the foundation research for a powerful new method in analytical chemistry: Comprehensive Online Multidimensional Frequency Transform Separations (COMForTS). The method was invented in response to the growing need to separate large numbers of chemicals from complex mixtures in order to better our understanding of biological processes.

Existing state-of-the-art separations were nearing their physical performance limits and required costly compromises between analytical power and analysis time. Computational modelling and laboratory experiments showed that by mathematically extracting fundamental separation information that had hitherto been lost, COMForTS can overcome these compromises, dramatically increasing the effective resolving power of multidimensional separations.