Sample Preparation Technology Forum

Sample preparation is the basis for all separations-related research. In this forum, we asked three industry experts to provide their views on the technique and to explain how they saw its future. Joining us for this discussion are Michael Rummel, Sample Preparation Product Manager, Phenomenex; Bruce E. Richter, Sample Preparation Product Line Manager, Thermo Fisher Scientific and Kaj Petersen, Marketing Manager, Gerstel.

What developments in sample preparation have been most significant over the course of 2011?

Rummel: Products manufactured with higher specification and intent toward specific analyses have been a growing trend. Polymeric based solid-phase extraction (SPE) products intended for use with drugs of abuse analysis that do not require conditioning steps have been introduced, saving significant time and money for the analyst. Additionally these specifically designed products raise the bar in value as they are quality control checked with the exact analytes that are being tested for in the industry. In another sector, the food safety industry, QuECHeRS for clean-up of pesticide residues is seeing an exponential adoption rate due to its ability to target a broad range of pesticides. There may also be some applicability of this technique for other non pesticide-related compounds specifically advancing the breadth of tests for food safety testing.

Richter: First described in 1996, the use of various sorbent materials along with the samples in the extraction cells to change the selectivity during the process of accelerated solvent extraction (ASE) is not a new idea. However, during 2011, we saw more widespread use and acceptance of this technology. This is a very powerful concept for sample preparation, especially for complex samples. With the proper choice of solvent, temperature and sorbent, sample extracts can be obtained that are essentially free from interferences. After such an extraction, all that is required is to take the sample to the appropriate volume and load the sample into the autosampler vial for analysis. No further sample clean-up is necessary. The use of this technology greatly simplifies sample preparation and improves productivity because several preparation steps (extraction, filtration and clean-up) are combined into a single process.

Petersen: Miniaturization is gaining pace. Analysis methods can be performed based on ever smaller samples because mass spectrometers are becoming more sensitive and selective. This means that sample preparation is increasingly automated using µL-scale volumes. The main benefits are productivity gains, significant savings on expensive solvents and standards, and a better laboratory work environment due to reduced usage of toxic solvent.

Do you expect to see any major breakthroughs in sample preparation at shows such as Pittcon in 2012?

Rummel: Addressing sources of matrix interference effects has been a long time concern in LC–MS analysis. In response to this concern, sample preparation products that address phospholipid-based suppression will continue to evolve in 2012. A relatively new technology, these type of products still have a few shortcomings to improve upon. Newer generation phospholipid removal products that provide a more comprehensive phospholipid removal solution, reduce non-specific analyte binding, and have improved flow properties will likely be the progression in 2012.

Richter: A revolutionary breakthrough in solid phase extraction (SPE) will be showcased at Pittcon 2012. Sample preparation is an important part of the overall analytical process which is continually changing and improving. The showcase at Pittcon 2012 will provide next-generation SPE, redefine levels of reproducibility and offer enhanced performance in elution volumes and extract cleanliness which will be of significant benefit to the analyst.

Petersen Major breakthroughs, even when they occur, take a while to be widely accepted, let alone implemented. I expect to see useful improvements in 2012, but no imminent paradigm shift. Today’s highly productive laboratories are always looking to improve their operation in terms of analytical performance, cost per analysis, productivity and utilization (i.e., return on investment for lab instruments). Constant efficiency gains in automated sample preparation are what I expect to see.

In which area is sample preparation growing the fastest?

Rummel: The evolution of increasingly powerful LC–MS technology is allowing for measurement of lower level analyte concentrations than ever before. Analysts are truly looking for a needle in a haystack. To fully realize the capability of these instruments, removal of matrix interferences and reduction of background noise is extremely important to obtain the desired results at low concentrations. Implementing SPE, one of the most selective sample preparation techniques, prior to LC–MS analysis gives the analyst the necessary tool to find the needle.

Richter: Based on our experience, we believe that food safety is one of the fastest growing areas for sample preparation in general. There are many countries that want to export more food. More regulations are being put in place because of recent issues with food safety and health concerns. Food samples can also represent very complex matrices that can be difficult to extract. We all want our food supply to be safe. All of these and other factors combine to put pressure on laboratories that prepare and analyze food samples, so they are constantly looking for better and faster ways to get the job done. However, bioanalysis and clinical workflows continue to be a major user of SPE, and will continue to be so for the foreseeable future. These high throughput environments will continue to come under pressure from FDA guidelines which will concentrate on reproducibility of their assays. As a result new levels of reproducibility will be demanded from their SPE protocols, and this is where new SPE technological breakthroughs will play a fundamental role.

Petersen: Automated liquid handling. This includes adding internal standards to samples; generating dilution series and calibration standards; adding derivatization agents, performing SPE and introducing the prepared sample to the analysis system. On the GC side, solvent-free techniques are very much on the rise.

How difficult is it to find sample prep technology that is safe, fast, environmentally friendly and cost efficient?

Rummel: It is a matter of progressing from older techniques to newer, greener technologies that exist. Traditional liquid/liquid extraction in separation funnels requires the use of large volumes of harmful organic solvents such as dichloromethane, hexane etc. The disposal of these solvents is costly and it is generally a goal to minimize analyst exposure to these type solvents due to health and safety concerns. Although you can not completely avoid these solvents, there has been at least some movement away from them or minaturazation of the volumes required. The QuEChERS technique implements the use of acetonitrile as the extraction solvent that is a much safer solvent as compared to dichloromethane or hexane. SPE allows the analyst to use much smaller solvent volumes to extract analytes, 100 mL, which is required in sep funnel liquid/liquid procedures. Additionally SPE can be automated, which drastically reduces human exposure to harsh organic solvents.

Richter: The answer to this can be dependent on the application area being considered. If one is considering environmental or food samples it is relatively easy to find safe, fast, environmentally friendly and cost efficient technology for sample preparation. The use of Dionex ASE instruments from Thermo Fisher Scientific satisfies these requirements for many sample types including environmental, food, chemical, consumer products and other application areas. However, there are other application areas or sample matrices for which sample preparation technology that satisfies these criteria might not be readily available.

Petersen It’s actually quite easy -- just take solvent usage as an example: On the GC-side, several extraction and analyte concentration techniques require little or no solvent. Examples are Headspace, SPME, Thermal Desorption and Stir Bar Sorptive Extraction (SBSE/Twister). For both LC and GC sample prep, even if you can’t eliminate solvents completely, you can often reduce usage significantly through miniaturization on a dedicated autosampler. This translates directly to improved safety and lower cost: Many solvents are toxic and the ultra-clean solvents required for today’s sensitive instruments are also ultra-expensive. Automation and miniaturization also improve productivity and make laboratories a lot safer to work in since there is less around. It is fair to say that miniaturization offers a breath of fresh air.

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