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Techniques & Tools Sample Preparation

Unlocking the Sample Prep Black Box

Academic researchers working on sample preparation are not communication champions, apparently. Research in the area has been outstandingly successful, but still fails to excite outsiders. Regarded more as if it has reached a plateau where there is a lack of fundamental challenges, many believe that the focus can only be on the novel application of what is already known. Clearly, the discipline has not been effective enough at projecting its advances and has acquired the image of a slow-paced discipline in a ‘big bang’ era of analytical instrumentation.

One of the underlying causes for this communication failure stems from presenting sample preparation advances in the context of “applications” and “simplicity” while overlooking the potentially complex science and engineering efforts behind them. As a result, sample preparation is seen as a sequence of activities: samples are exposed to (small) amounts of an extractant phase, and then something happens and the analytes are pre-concentrated in/on the extractant phase. In other words, sample prep is a ‘black box’ with inputs and outputs – and little knowledge of internal workings.

Our own eagerness to present ultimate black-box simplicity led to an associated misconception: “sample prep is simple and there is no theory to it”. Well, there must be some theory, and chemical equilibrium is not the only candidate.

A few years ago, Brian Arthur, a leading economist and complexity thinker, described technology as “exploiting a phenomenon for useful purposes”. Sample preparation techniques can be viewed as bodies of technology built around discoveries of phenomena like diffusion, sorption or evaporation, to name a few. If we want to fully exploit these phenomena, we first need to understand them, and this is not always an easy task.

To start with, analytes have to “cross” interface(s); the effect of different experimental parameters on this interphase analyte transfer can be complicated or nearly impossible to describe – especially given that several basic interfacial properties (like the intrinsic acidity of the water interface and its charge) are still under vigorous debate. Even the very simple step of sample agitation is a subject of intensive research in many engineering disciplines and, as surprising as it may sound, our ability to predict the performance of turbulent mixing in multiphase systems is severely limited.

I believe that the fundamental challenges underlying sample prep are too exciting to ignore. We work with microextraction, a sub-discipline of sample prep that has the unique feature of simulating processes found in natural and engineered systems on a small scale. Just like in any other discipline, we have to face a number of fundamental challenges (or ‘brain teasers’ as we enjoy calling them) every time we unlock the black box. Our studies on the effect of reduced pressure on headspace SPME is a prime example, proving that there are still fundamental challenges underlying even well established microextraction techniques. Solving this ‘brain teaser’ required us to work effectively across disciplinary boundaries. We had to import engineering models and approaches previously applied to natural bodies, which brought new insights on SPME and helped us better understand, control and eventually exploit headspace SPME.

Our own eagerness to present ultimate black-box simplicity led to an associated misconception.

Looking at the bigger picture, the small-scale simulation feature of microextraction could be considered a platform that can be used to tackle problems in other disciplines. For example, microextraction technologies played the leading role in previous bioavailability and photodegradation simulation studies. But to deploy such platforms, we must take the risk of asking unconventional questions and interacting with creative scientists from other disciplines. Thinking big can be a talent, but it can also be a skill that can be developed by exposing ourselves to other disciplines.

In short, sample preparation needs to get the attention it deserves in academia. One way of doing this is by communicating a systems-thinking approach, where analyte extraction is the emergent property of an interrelated whole. We have to continue developing knowledge of other fields and embrace fresh perspectives on the phenomena we are exploiting. Our commitment to unlocking the black box may only go a short way to addressing the under-recognition of sample prep – but it’s a good start.

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About the Author

Melanie Voigt, Anika Gold, Christina Blaesing, Timo Hoelscher and Martin Jaeger are researchers at Niederrhein University of Applied Sciences, Department of Chemistry, Instrumental Analytical Chemistry, Germany.

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