Playtime in the lab: Toy building blocks used to develop TLC/MS interface

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thumbnail image: Playtime in the lab: Toy building blocks used to develop TLC/MS interface

Building a LEGO® interface

LEGO® building blocks and electronic components have been used for the rapid and cheap development of a continuous TLC interface for ambient mass spectrometry.

There’s LEGO® in the lab and it’s not even take your child to work day. And before you get the wrong idea, it’s not to keep the research group entertained during coffee breaks, although that does seem like a good idea. On this occasion, bringing toys into the lab has a serious side, leading directly to the development of a new piece of kit for mass spectrometry.

Jentaie Shiea and his collegues from the Department of Chemistry at the National Sun Yat-Sen University in Taiwan were looking to develop a novel interface for linking thin-layer chromatography to ambient mass spectrometry. Although there have been numerous reports of TLC-MS interfaces to date, the technique has not really taken off yet. One reason may be “the lack of an automatic delivery system to continuously deliver the TLC plates to the AMS source for high-throughput analysis,” says Shiea.

When thinking about a new interface, the conventional design route would involve the use of simulation software and the machining and assembly of components, which can be time consuming and labour intensive. The Taiwanese solution was to construct an interface using LEGO® bricks and components, which is not as odd as it might sound. The building sets contain bricks of many different shapes and sizes as well as electric components like motors, so the design can be modified quickly in a few seconds during development.

Once a working model has been assembled and tested, then the plastic LEGO® components can be replaced by more appropriate materials that are prepared to specific tolerances, to provide a more stable operation.

Brick by brick

So, the main aim of the new interface was to introduce a system for automatically dispensing TLC plates to the ionisation zone of the ambient mass spectrometer. To accomplish this, a plate-dealing device was constructed from 115 bricks and other LEGO® parts, including rollers and a motor.

Up to 50 TLC plates could be stored in a special brick box before being dealt one at a time onto a short conveyor belt consisting of six elastic bands which is controlled by a step motor. The gap in the box was adjusted to allow only one plate at a time to be despatched. A LEGO® control box was fitted to manipulate the speed of the conveyor belt.

As each plate approached the ionisation source, a light sensor was triggered and the step motor began delivery of the next plate for continuous operation. A collection box, also made from building bricks, was positioned beyond the source to collect the plates after analysis.

The analytes on the TLC plates were ionised by electrospray-assisted laser desorption/ionisation (ELDI) using a pulsed UV (266 nm) or IR (1064 nm) laser which was focused on the centre of the rubber band conveyor. An aqueous solution of methanol was used for the spray with an applied voltage of 5 kV. The desorbed ions were directed to the inlet of an ion trap or single quadrupole mass spectrometer for analysis.

A viable prototype interface

The performance of the interface was assessed using four TLC plates that had been used to separate the dyes rhodamine 6G, crystal violet and methylene blue. The plates were added to the storage box and dealt one by one to the ionisation source. The extracted ion chromatograms and mass spectra of the dyes were recorded with ease, although the repeatability relative standard deviation was a little high at 33.3%.

There were some other problems related directly to the construction. For instance, the conveyor belt swayed gently, affecting the stability of the mass spectrometric signals of the dyes. In addition, the whole system shook while it was switched on and the bricks tended to work themselves loose. The light sensor was relatively large and difficult to fit in position and the LEGO® motor was not suitable for long-term continuous operation.

Nevertheless, the system demonstrated the feasibility of the interface design, which was the main aim of using readily available building bricks. So, by replacing the bricks with components made from “normal” materials, introducing an optical fibre instead of a light sensor and a better motor, the system became more stable.

The updated interface was used to analyse extracts of three over-the-counter drugs with contained acetaminophen, chlorpheniramine and ethenzamide as active components. The repeatability r.s.d. of the chlorpheniramine signal was better at 12.8%.

The new system of interface design, using LEGO® bricks, allows for quick modifications to be introduced, using bricks of different shape and size. It bypasses the need for machining new components until a viable design has been constructed, saving time and materials.

At the set belt speed, analysis of one 4-cm-long TLC plate was completed within 2.5 minutes allowing for the daily analysis of several hundred plates, which is in line with the requirements for pharmaceutical analysis and combinatorial chemistry.

Related Links

Analytical Chemistry 2012 (Article in Press): "Building blocks for the development of an interface for high-throughput thin layer chromatography/ambient mass spectrometric analysis: A green methodology"

Article by Steve Down

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

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