Research interests

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CE - what's that? Information for non-chemists

A) Capillary electrophoresis with fluorescence detection in oligosaccharide analysis:

The determination of oligosaccharides is still a great challenge in anlytical chemistry. Though sugars and their derivatives are some of the most important chemical compounds both in nature and technique, there are several analytical problems to overcome. Their separation is complicated by the vast number of substructures and their manifold stereochemistry as well as by the poor detectability due to the lack of chromophores. Ion exchange or size exclusion chromatography  (IEC, SEC) are state of the art today, but both techniques lack of resolution and sensitive detection. Hence CE is a highly recommendable alternative due to high separation efficiency, peak capacity and good selectivity. Detectability is strongly enhanced by using fluorescence detection. The afforded fluorescent tags are simpliest introduced by reductive amination at the open-chained carbonyl function. Several fluorescent tags have been described in literature, but a classification has not been done yet.

In this work, three blocks have been investigated:
  • In the first part, a collection of seven mostly literature-known fluorescent tags suitable for reductive amination (Fig.1) was examinated and classified with respect to fluorescence yield (related to an internal standard) and optimal reaction time with the model compound maltose (determined by kinetic studies). So, ANDS (7-aminonaphthalene-1,3-disulfonic acid) and 1-AP (1-aminopyrene, introduced by our working group) turned out to be the most sensitive labels.
  • In the second part, a novel fluorescence detector was validated. The Argos 250 B (FLUX Instruments, CH) shows a unique design featuring spatial separation of fluorescence excitation and emission and fibre optics and it has been designed to provide limits of detection in the order of magnitude of a commercial LIF detector (Laser-Induced Fluorescence) at the price of a UV detector. The determination of the signal linearity, the limits of detection and the signal-to-noise ratio for the seven fluorescent tags were in the focus of this part. With the most sensitive tags, a limit of detection of about 3 ppb (!) maltose could have been reached. A direct comparison of a label suitable for both laser and UV excitation on a commercial LIF detector system pointed out that the Argos 250 B UV-based detector reaches a LoD differing from that of the LIF system only by a factor of 3.4.
  • In the last part, the results from the first two parts were reviewed with respect to the behaviour of the derivatisation with ANDS in multi-component mixtures. Kinetic studies with Dextrin 20 mixtures and investigations of the linearity of the derivatisation reaction confirmed that the transfer from the model compound to the real sample mixture is possible. Finally, the suitability of the developed method for the analysis of oligosaccharides in real samples was demonstrated with 10 different beer samples (a.o. Fig. 2).
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Fig. 1 Fig.2

(click to enlarge)

A summary of these results was presented on the HPCE 2001 (Boston, MA) and is ready for download on the homepage of our group (.pdf-file).

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B) Sieving matrices in the CE analysis of polyelectrolytes:
In this project supported by the Deutsche Forschungsgemeinschaft (German Research Association, DFG), I am investigating the range of characterisation of polymers and polyelectrolytes by CE by using sieving matrices. As I am still at the beginning of this work, I would like to recommend you the excellent homepage of my colleague Mr. Oliver Grosche if you have any further questions to that topic.

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C) Cooperation projects:

Agilent Technologies: AgilentLogo.gif (502 bytes)
For Agilent Technologies, one of the world-leading manufacturer of analytical equipment (former Hewlett-Packard), I am currently working on two different projects dealing with EOF modifications and method development for CE.
Bayer AG:  BayerLogo.gif (1659 bytes)
Project with the Bayer AG, Leverkusen, for CE method development in pharmaceutical analysis
Selected links about chemistry:
homepage of our institute

common info about CE and CEC
Sigma-Aldrich Homepage
- highly recommendable for chemical informations and MSDS-sheets
Agilent Technologies
- free NMR processing software
detailed page about analytics
ChemWeb - Lots of Info and quite powerful literature search engine
Association of German Chemists
Meet the young analytical chemists association!
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The last update is from 03.05.02 by Markus Martin.