Technology Forum: Sample Preparation

With the continual quest for ‘faster’, ‘cheaper’, ‘greener’ and ‘better’, the pressure to improve sample preparation methods has never been higher.

Janet Kelsey, Electronic Editor, LCGC Europe put five questions to our panel of experts and asked them for their opinions. Joining us for this discussion are Gary Dowthwaite from Biotage; Vivek Joshi and Estelle Riche from Millipore and Paul Wynne from SGE.

What, if any, new developments in sample preparation have interested you most over the course of 2009?

Dowthwaite: The growth of techniques such as dispersive SPE within the pesticide residues arena.

Joshi and Riche: The use of solid-phase separation for sample preparation has improved recovery and reproducibility, and presents a great opportunity for further improvements in this technology. The most recent advances in this area include paramagnetization of the solid phase, enabling efficient isolation from the liquid phase, and affinity purification using solid phases that selectively retain analytes of interest.

The past year has shown a dramatic trend toward using smaller pore sizes in membrane microfiltration of samples used for extremely sensitive downstream analysis. Specifically, the increased popularity of ultra-high pressure liquid chromatography (UHPLC) demands that samples be free of even the smallest particulates, and leads users to prepare samples by filtration through membranes with 0.2 micron pores.

Wynne: SGE has an interest, by way of the MEPS product line, in the extraction of small volume liquid samples and so I will comment mainly on that area.

At a fundamental level, the chromatographic basis for solid-phase extraction is being rediscovered and consequently we are finding ways of harnessing these sorbents in ways that are very effective. For example, at SGE we are using low void devices and controlling flow-rate to improve extraction reproducibility for very small volumes.

The introduction of MEPS on the eVol electronic syringe drive has enabled a hand-held precision in microextraction that was simply not available before. It is a product that bridges the development gap between design and implementation of a new method or that can support routine operations in its own right.

At a more advanced level, the growing number of high quality affinity sorbents is very encouraging and reflects the interest in pushing SPE beyond a simple matrix exchange or desalting technique.

Do you expect any new advancements to be revealed at Pittcon 2010?

Dowthwaite:This is a key meeting for instrument vendors and I would expect there to be the usual activity of product launches and advancements in technology.

Joshi and Riche:We expect advances in nanoscale sample preparation, as well as new separation technologies optimized for ultra-sensitive analytical methods. It is likely that the current emphasis on automation and high throughput will continue.

At Pittcon 2010, one of the products featured on Millipore’s booth will be the Q-POD Element system, which provides ultrapure water for trace elemental analysis, where it is used in sample dissolution and dilution processes, as well as for cleaning sample containers, washing plastics and preparing blanks and standard solutions.

Wynne: At PittCon SGE will showcase the Xchange system on the eVol drive. When fitted with MEPS, the eVol system offers the flexibility and speed of hand-held microextraction with precise volume and flow-rate control.

We will also introduce Syngles, which are single use microlitre volume syringes. Syngles are designed for use with autosampler platforms such as the CTC-PAL but for those working in sample preparation, the real attraction will be MEPS-Syngles – a single use MEPS device. The product will have strong appeal to those analysts that are working with very complex samples or those that are seriously investigating real-time high throughput analysis.

What is the sample preparation area that you see growing the fastest?

Dowthwaite:Food safety has certainly had a consistently high profile throughout the year. With increasing focus on national health, food contaminants such as melamine and nutrients such as Vitamin D, developing robust methods for their analysis is becoming more important than ever.

Joshi and Riche:As mass spectrometry (MS) becomes more and more routine, moving out of core facilities into individual laboratories, there is an increasing demand for sample preparation technologies that are geared for MS analysis. Because MS is incredibly sensitive, signals are easily confounded by the presence of contaminating molecules; therefore, samples must be extremely pure. One way to help ensure optimum sample purity is to use freshly-drawn ultrapure water during sample prep and LC–MS analysis.The need for dedicated, MS-specific sample preparation tools that are compatible with a broad range of sample compositions is driving rapid growth in this area of sample preparation.

Wynne: Sample preparation is still overcoming the paralysis it experienced during the growth of benchtop LCMSⁿ and to a large extent, that period has shaped how many people still perceive sample preparation. Effective sample speciation prior to analysis is certainly an area to watch.

The biggest area of growth will be in small scale extractions as laboratories endeavour to reduce sample and solvent consumption. The impact of sample size has ramifications for the whole sample chain from collection and transport right through to waste disposal.

Many users will also realize that as they reduce scale, they also reduce the time taken for extraction. Microextraction is inherently fast and reduced extraction time opens up the possibility of increased throughput. For me, the exciting part of that is the realization that analysis using fractions from several fast and specific extractions can be more effective and richer in information content than one less specific extraction using current approaches.

Are there any improvements that you would like to see in the samplepreparation industry over the next few years?

Dowthwaite:The reality is that there has been a trend to minimize the need for sample preparation as much as possible, but with issues such as analytical column lifetime and MS instrument downtime becoming an issue, customers will begin to realize the benefits of good sample preparation. In some application areas, this does seem to be going full circle, even with the advancement of analytical systems.

Joshi and Riche:The industry should be aiming towards the automated, seamless integration of sample preparation with its corresponding downstream analytical application, built into a single, dedicated instrument. Achieving this goal will require close collaboration between analytical equipment and sample preparation technology developers.

Wynne: There is a synergy that exists between instrument platforms and enabling consumables so I think we will see new techniques such as MEPS and Syngles act as the catalyst for change in autosampler design and in microfluidic systems.

The products themselves will grow in terms of available packing materials and with iterative developments that will see them adapted into new platforms or applications. As sample preparation is incorporated into the flowpath, I think we will see sample preparation redefined as a digital LC, if not in name then at least in concept. From that position, sample preparation is likely to become an integral part of hybrid analytical techniques.

The other area where some effort is needed is in education. If we are to push sample preparation into areas where mechanical and chemical gating work in concert then effective teaching tools are a necessary part of that process.

What is the future of sample preparation?

Dowthwaite:In general, there will always be a need for some form of sample preparation, particularly for the more complex matrices. With increasingly sophisticated analytical techniques and changing throughput and cost-saving needs, the requirements and formats of sample preparation will continue to evolve.

Joshi and Riche:The future promises continuation of current trends towards higher throughput and automation compatibility. More efficient preparation of small volume samples or complex samples (such as biological solutions or complicated food matrices) containing multiple analytes will be required. Technologies that will improve the signal-to-noise ratios in analysis of complex mixtures will include advancements in enriching specific analytes of interest, either by affinity purification or by depletion of molecules other than the desired analyte. As these new technologies are developed, high purity water will undoubtedly continue to play an important role in reducing potential contamination of samples and instruments.

Wynne: I suspect that the future will be one with more selective approaches to sample preparation than are considered now. We are likely to see a tailored whole of platform approach to individual applications rather than a continuation of the one size fits all paradigm. To achieve this sort of flexibility, sample preparation must go on-line rather than stand apart from the rest of the sample analysis as it does now.

The form of that change is, I think, likely to encompass innovation in extractant selectivity coupled with micro-fluidic systems as a development of instrument injectors or as a front end for other analytical techniques.

If you are interested in participating in any upcoming Technology Forums please contact Janet Kelsey for more information.