The history of the cooperation of scientists at Duke University {USA}, at the Institute of Chemistry, Estonian Academy of Science {Estonia} and the Polymer Chemistry Laboratory of the University of Helsinki {Finland} began with the visit of two scientists from Estonia to Duke in the mid-1980's. From that visit, sponsored by the US-NAS - administered USA-USSR Scientific exchange, grew a lively development program combining chemometrics and novel measurement methods for the study of complex chemical substances. These substances include polymer, rubbers, geo-polymers like shale and other materials. The cooperation of scientists at the University of Helsinki became part of the program within 3 years of the start and has continued from that time. The decade + history of this cooperation has seen joint publications, additional visits of all three partners and events such as the re-establishment of the independence of the Estonian Republic. This page contains a sampling of the historical and recent work of the three partners. You can reach the authors via e-mail by clicking on their names in the papers in this section.
Recent Publications, Presentations and Communications &Notices
Estonian Chemical Society Medal
Professor Lochmüller was the 12th recipient in its' history of the Societal Medal of the
Estonian Chemical Society { Eesti Kemmia Selts}
May 7,
1997.
At the end of the Plenary session where Professor Lochmüller spoke on Chemistry: The Central Discipline and topics related to public science policy history in the USA, The Society President, Professor Juri Kann announced the decision of the EKS Board. This is the 12th such medal awarded. The EKS was founded in 1919 after Estonia became a free republic. The citation makes note of Lochmüller's life career in Chemistry and especially his long history of cooperation in research with Estonian scientists and support for Estonian Chemistry before and after liberation from the USSR..
NATO Grant Awarded:
The North Atlantic Treaty Organization Collaborative Research Program has awarded Professor Lochmüller and Dr. Mihkel Koel a grant under the Priority Area on Environmental Security Programme. The goal is to exploit their work of the last decade in Thermochromatography and Chemometrics . The Project title is: " Oil Shale Characterization: Thermochromatography, Supercritical Fluid Extraction, Chemometric Analysis". The initial award amount is 220 000 BF and is for travel of both partners to each other's labs for planning and experiments.Review Paper Published:
Dr. Mihkel Koel and Professor Mihkel Kaljurand have published a review of their work in the area of measurements on time-varying sample streams in Critical Reviews in Analytical Chemistry which can be downloaded and read also using the link: CRAC Paper and the Adobe Acrobat Reader.APPLICATION OF EVOLVING FACTOR ANALYSIS IN THERMOCHROMATOGRAPHY
[Chemometrics and Intellig. Lab. Systems, 30, 129-132 (1995)], Matti Elomaa * Laboratory of Polymer Chemistry, P.O.Box 55, FIN-00014 University of Helsinki, FINLAND, , C. H. Lochmuller Department of Chemistry, Duke University, Durham, NC USA 27708, and , Mihkel Kaljurand and Mihkel Koel Dept. of Analytical Chemistry, Institute of Chemistry, Estonian Academy of Sciences, Akadeemia tee 15, EE0026 Tallinn-26, Estonian RepublicABSTRACT
Thermochromatography (ThGC) is a temperature-resolved, multiple-injection, gas chromatography technique useful in the study of pyrolysis[1]. Consecutive chromatograms are collected during pyrolysis each at known temperatures and representing the headspace gas component distribution above the pyrolyzing material. Previous work with the ThGC has been limited entirely to the production of response surfaces of retention /temperature / FID response. Reported here are experiments where Evolving Factor Analysis (EFA) is applied to ThGC data structures. The EFA is used resolve overlapping, entire chromatograms based on their different origin in pyrolysis temperature. Simply, EFA deconvoluted the components of the pyrolysis process as differing thermal reactions leading to different product profiles. As a result, one gets sets of different chromatograms and their corresponding temperature profiles in the evolving headspace gases. A specific example of analysis of the pyrolysis of an ethylene-propylene-diene rubber (EPDM) is given.
THERMOCHROMATOGRAPHY - HYPHENATED EVOLVED GAS ANALYSIS TECHNIQUE
Mihkel Koel , and Mihkel Kaljurand Institute of Chemistry, Academy of Sciences of the Estonian Republic, Akadeemia tee 15, Tallinn, Estonia,EE0026 [4th InternationalSymposium on Hyphenated Techniques in Chromatography and Hyphenated Chromatographic Analyzers (Bruges,Belgium;February 7-9,1996)]
Thermochromatography (ThGC) is a temperature-resolved, multiple-injection, gas chromatography technique useful in the study of pyrolysis[]. In thermochromatography a pyrolysis reactor is coupled with gas chromatograph (GC) and a series of chromatograms of the headspace vapor of a sample are recorded during temperature programmed heating of the sample. Output data are presented in the form of 2D response surface in ordinates of temperature and chromatographic run time. The potential of this hyphenated analysis system to the produce response surface pictures as characteristic "fingerprint" plots has been demonstrated in polymer studies [] and in oil shale studies[]. The mass-loss curve related to detectable volatile products evolution can easily be constructed from the output of ThGC. Importantly, ThGC could provide information simultaeneously about the number of stages of degradation and the related headspace-gas composition as chromatograms,. Deconvolution by chemometric means of the contribution of each process to the observed response surface would be required.
Since a computer is necessary part of thermochromatographic equipment, it is relatively easy to include chemometric methods into the data processing software package of ThGC: (a) to improve signal to noise ratio by multiplex technique and (b) to decompose the thermochromatogram and provide kinetic information about the underlying reaction mechanisms.
In ThGC (after improvement with correlation chromatography when necessary) the chromatograms are recorded in a fixed sequence of progressing elution. That makes factor analytical methods like evolving factor analysis (EFA) useful for resolution of thermochromatographic profiles to uncover different thermal reactions in sample. EFA makes no a priori assumptions about the chromatograms/thermal peaks and helps the analyst recognize the thermal stages and to estimate the number of distinct stages. From this one can find out which evolving compounds dominate at given temperatures and are related to those stages. Analysis on polymeric and inorganic samples have demonstrated the techniques capability.
i
. Kaljurand, M., Küllik, E., COMPUTERIZED MULTIPLE INPUT CHROMATOGRAPHY. Ellis Horwood Limited, Chichester 1989, p. 139.i
i Sarvaranta,L., Elomaa,M., Järvelä,E., A Study of Spalling Behaviour of PAN Fibre-reinforced Concrete by Thermal Analysis, Fire and Mat., 17(1993)225-230.The high-resolution separation of polymer oligomers, their breakdown products and isomers is a significant challenge to modern separation science. The historically most successful methods are based on size- exclusion strategies and not mobile phase/ stationary phase partition in the conventional sense. In the last decade significant progress has been made in understanding the requirements for achieving elution chromatography of high {> 5kD} molecular weight organic polymers ranging from quite hydrophobic to quantitatively water soluble in character. This paper discusses retention mechanisms, the dynamics of the partition chromatographic process, evidence for significant delays in polymer equilibration to mobile phase conditions and the effect of the temperature dependence of polymer solubility. Conventional chromatographic behavior is shown to obtain for the separation of polystyrenes, polymethylmethacrylates, polyethylene oxides and polypeptides if proper steps are taken to carry out the experiment. The use of thermal gradients in spatial terms is shown to have significant value for achieving enhanced separations.
Evolved Gas Analysis of Inorganic Materials Using Thermochromatography:
Model Inorganic Salts and Palagonite
Martian Soil Simulants.
Mihkel Koel,*
vmihkel@argus.chemnet.ee Mihkel Kaljurand, and C. H. Lochmüller Anal. Chem., 69 (22), 4586 -4591, 1997Institute of Chemistry, Akadeemia tee 15, Tallinn, EE0026, Estonia, Institute of Chemistry, Tallinn Technical University, Ehitajate tee 5, Tallinn, EE0026, Estonia, and Paul M. Gross Chemical Laboratory, Duke University, Durham, North Carolina 27708
Evolved gas analyses are presented of several model inorganic salts and Mars's soil simulating palagonite minerals. The measurements are performed with a low-volume, thermal furnace, interfaced to a capillary gas chromatograph (GC) via a computer-controlled, pneumatic sample inlet device using pseudorandom injection and correlation analysis. The system, a thermochromatograph (ThGC), permits temperature-resolved, high-speed GC analysis of the evolving components in the pyrolyzing sample's headspace. The "information content" performance of this inherently simpler system is comparable to that of TG/GC/MS and TG/GC/IR systems when similar materials are analyzed.