TLC begins office romance

Skip to Navigation


  • Published: Mar 8, 2010
  • Channels: Ion Chromatography
thumbnail image: TLC begins office romance

For most analytical scientists, the office and the laboratory are separate and distinct places. But now a team of German and Canadian scientists has brought the office into the laboratory by conducting thin-layer chromatography (TLC) with an inkjet printer and scanner.

Like paper chromatography (see Follow the paper trail), TLC, in which samples migrate over a flat surface such as a silica gel-covered glass plate, is a bit of a poor relation to liquid and gas chromatography. But it is still widely used as a quick and cheap form of chromatography, especially for analysing pharmaceuticals.

Nevertheless, it's not as cheap as it could be due to the need for specialised instruments that can deposit precise amounts of a sample onto TLC plates and some kind of image capture system to detect the separated analytes. Furthermore, the instruments and systems that are currently available don't work too well with the latest form of TLC, known as ultrathin TLC (UTLC), which utilises small plates covered with a layer of silica gel less than 10µm thick.

Current sample application instruments, such as piezoelectric ejectors and aerosol applicators, are designed for larger plates with thicker separation layers and so are unable to apply small enough sample droplets. The small samples also make it difficult to produce high resolution images of the separated analytes, especially as UTLC plates, unlike conventional TLC plates, are partly transparent.

What is needed is a cheap and simple system for precisely applying small droplets on UTLC plates and producing high resolution images of the separated analytes. Such a system should also be as automated as possible. Could the answer be found in something as simple as an office inkjet printer and scanner, wondered Gertrud Morlock from the University of Hohenheim in Germany?

Inkjet printers utilise print cartridges that hold ink in numerous small chambers. Applying a pulse of electrical current to these chambers forces a droplet of ink onto the paper, either by vaporising the ink via a burst of heat or by causing some electrically-responsive material in the chamber to change size or shape. Perhaps the same mechanism could be used to deposit sample droplets onto UTLC plates.

Together with colleagues form the University of Alberta and the NRC National Institute for Nanotechnology, both in Canada, Morlock tested this idea with a Canon Bubble Jet printer that could print onto CDs. They chose this type of printer because it allowed them to insert the UTLC plate into the special draw meant for CDs.

Morlock and her team poured a mixture of food dyes into an empty printer cartridge and then used drawing software to get the printer to deposit the food dye mixture onto the UTLC plate as bands or spots of defined size. They then removed the plate from the printer and conducted a normal TLC separation, after which they placed the plate face-down on a scanner. To deal with the partial transparency of the UTLC plate, they simply placed a white sheet of paper on top of it.

The inkjet printer and scanner performed just as well, and in some respects much better, than conventional piezoelectric ejectors, aerosol applicators and image capture systems. The inkjet printer was able to apply smaller spots and bands than the ejector and applicator, while the scanner was able to produce higher resolution images than two conventional image capture systems.

But this is only the first step, because Morlock's ultimate aim is to produce an automated system based on a combined printer and scanner that can perform all aspects of a TLC analysis. To this end, she has already shown that an inkjet printer can be used to apply the mobile phase to a TLC plate.

'We discovered that printing the mobile phase was also possible and even the generation of a minor forced flow,' she told separationsNOW. 'Thus, the potential for a fully online, automated routine system was discovered to be highly realisable and of immense potential for speeding up routine analysis.' She is already speaking with a number of instrument producers about developing a commercial version of this all-in-one TLC system.

The views represented in this article are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd.



Social Links

Share This Links

Bookmark and Share


Suppliers Selection
Societies Selection

Banner Ad

Click here to see
all job opportunities

Most Viewed

Copyright Information

Interested in spectroscopy? Visit our sister site

Copyright © 2018 John Wiley & Sons, Inc. All Rights Reserved