Technology Forum: Sample Prep

Sample preparation is the basis for all separations-related research, with critical results (and large amounts of revenue) often hinging on how well a sample is prepared. With the spate of new and innovative sample prep techniques and products being introduced every year, it is hoped that many of the errors and problems encountered in this stage of research are now becoming things of the past.

This month, Chromatography Online's Technology Forum looks at the topic of sample preparation and the trends and issues surrounding it. Joining us for this discussion are Tom Hall of Fluid Management Systems; Luke Roenneburg of Gilson, Inc.; and Ron Majors of Agilent Technologies.

What new developments in sample preparation have you most intrigued?

Hall: Food safety, clinical, and homeland security applied markets will continue to grow at a rapid rate. Laboratories want to minimize human interaction through automating the whole sample prep process, not just parts of the process. They want it to be faster, cheaper, better, and greener than current techniques. The drivers behind sample prep techniques today are based on understanding the need to balance the cost of implementation, achieving consistent, repeatable results that deliver the lowest possible failure rate, and accomplishing the fastest throughput.

Roenneburg:Fraction Trapping.

Majors: I am impressed with the myriad of solvent-less (or at least greatly reduced solvent consumption) sample preparation techniques that emerged in the past few years. Starting with solid-phase micro-extraction that is now nearly 20 years old, researchers have come up with techniques like single-drop microextraction, liquid-phase microextraction, immobilized liquid extraction, stir-bar sorbent extraction, and dispersive liquid-liquid microextraction, all of which are effective ways of performing extractions on a miniaturized basis but use only a fraction of the solvent consumed by older techniques.

Do you expect any major developments/news about sample preparation to be presented at Pittcon 2009?

Hall: Sample prep systems will be introduced that provide a total solution for automating the whole sample prep process in key applied market segments such as food safety. Validated, guaranteed results consumables from the vendors of automated sample prep systems, to help prevent sample throughput issues due to inferior consumables.

Majors:It seems that more selective phases are being introduced. One recent example is solid extraction phases based on affinity technology, not only for large molecules, where it has been historically used, but also for small molecules like mycotoxins and other food- and environmental-pollutants. Affinity phases require the development of antibodies which is expensive and takes time so molecularly-imprinted polymers are affinity-like phases that are easier and cheaper to prepare yet offer some of the selectivity advantages. I would expect to see other selective phases show up at Pittcon 2009. In addition, polymeric SPE sorbents have gained widespread interest. Compared to silica-based sorbents, they are more rugged, can dry out without affecting recovery and reproducibility, and are starting to appear with new selectivities also.

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

Hall: Applications in food safety, drinking water, and homeland security.

Roenneburg:Solid phase extraction. More and more people are looking for automation of this process.

Majors:With the growing interest in food safety with all the recent problems of milk and pet food contamination and the widespread (sometimes rampant) use of pesticides on food that is imported from third world countries, the application of analyzing foodstuffs will be a driving force for reliable sample prep techniques in the next few years. QuEChERS (an acronym for Quick, Easy, Cheap, Effective, Rugged and Safe, pronounced “catchers”) is a technique that is simple and effective for the extraction and analysis of pesticides from fruit and vegetables. It uses small amounts of solvent which places it in the category of a “green” sample prep technique and has been used for the sample prep of over 500 pesticides in a variety of crops. Recently, it has also expanded its application to meat products. So I see this technique “catching on” in the future.

What obstacles stand in the way of sample preparation development?

Hall: Market resistance toward new sample prep technology and techniques. The lack of properly trained technicians performing sample prep.

Roenneburg:Software interfaces and ease of use. In order for more people to adopt automation in sample prep the software needs to continue to become easier and easier to use and understand. The biggest challenge is that most users still don’t want to sacrifice features. The more features and functions you have in a software package then the more complex it tends to become. So, the biggest challenge is to find the right balance of capabilities vs. complexity.

Majors:The biggest obstacle to the development of sample preparation is the attitude of laboratory chemists. Sample preparation has always been viewed by workers as labor-intensive, time consuming and boring and is frequently relegated to the most junior of chemists on the staff. Most analytical chemists would rather work on sophisticated analytical instruments than to spend their time improving or actually performing the sample prep tasks. Except for a few dedicated research groups, sample prep receives very little attention in the academic community, so advances are slow to come. Many of the major instrument companies do not develop or manufacture automated sample preparation instruments, so automation is often left to smaller more niche companies. If one only has a few samples per day, automation is hard to justify. Many of the popular sample preparation techniques have been around for decades and work quite well (even though they are slow and labor-intensive). So, there are existing methods that can do the job without a lot of investment other than labor.

What is the future of sample preparation?

Hall: Integrated sample prep systems that automate the whole sample process, not parts of it, will become more available. It is what the market is telling us they want. The sample prep systems in the laboratories of the future will be required to make the process faster, better, cheaper, and greener.

Roenneburg:The future of sample prep is just further automation and more sophisticated and simpler software to control it all. If the software can become so easy to use that anyone could walk up and run it, then it will only further the growth in the market place.

Majors:There are areas where sample preparation is absolutely necessary since the samples are too complex, analyte concentrations too low and even sophisticated analytical methodologies such as LC-MS/MS cannot provide adequate sensitivity and/or selectivity. The above cited food safety analysis is a prime example. Some food toxins are often present at very low concentrations and the matrices encountered can be challenging. Background interferences, such as ion suppression in mass spectrometry, necessitate the cleanup of samples. The same can be said for some environmental samples. Biological samples, particularly in the area of proteomics, can be very difficult where biomarkers can be a million-fold or more lower in concentration than “house-keeping” proteins. Somehow these trace proteins must be isolated and concentrated so further work can take place in identifying them. The analysis of drugs of abuse and forensics testing require some form of sample cleanup so that a precise analytical measurement can take place since and so that evidence can hold up in a court of law. So, there are many areas where better and faster sample preparation techniques are needed.