In an era of increasing human health concerns, solid-phase extraction has risen to the top as a viable method to ensure safety in food processes and the environment.

Solid-phase extraction (SPE) is one of the most common chromatographic processes, and, in recent years, the growth of automated SPE has catapulted its use in laboratories. As a result, SPE systems are becoming more integrated—being made more compatible with liquid chromatography mass spectrometry (LCMS) systems, or combined with LCMS in one system.

More efficient and accurate results allow SPE to be used in an array of applications. Perhaps the most important application of current SPE systems, however, is in the area of human health and food safety. According to the Food Marketing Institute’s (FMI) “U.S. Grocery Shopper Trends 2012” report, customer confidence in food safety is higher than ever, and yet, respondents “readily agree that food safety is a joint effort involving every step of the food process from farm to plate.” In an era when humans are increasingly aware of and cautious about food, particularly how food affects their health and bodies, SPE systems are used to ensure accuracy in the scientific part of the food safety process. 

SPE and human health

PerkinElmer’s Supra-d QuEChERS dispersive SPE turns sample prep into an easy two-step process by using the QuEChERS method. This common method helps ensure the safety of fruits and vegetables from contaminants.

The FMI report also indicates that 54 percent of respondents believe food safety issues occur at food processing and manufacturing plants—a number that is up 24 percent in the past six years. According to Waters Corp., a typical SPE device has 50 times more separation power than a simple, single liquid-liquid extraction device. Therefore, the use of SPE as a process for determining contaminant levels in food products is increasingly appealing. Consumers’ awareness of food safety concerns is forecasted to continue growing, so the use of SPE systems and consumables in laboratories should reflect that growth. 

As a separation technique, SPE dissolves or suspends compounds in a liquid mixture to separate a specific sample from other compounds in the mixture. Separating various compounds in one sample allows laboratories to concentrate and purify samples for proper analysis. SPE has the same fundamental basis as HPLC (high-performance liquid chromatography), yet the best SPE results that pertain to human health—those used when testing environmental water and fruits and vegetables—are achieved through reversed-phase chromatography. Reversed-phase chromatography uses a gradient of strong to weak polar solvents with a non-polar packing material, whereas normal-phase chromatography uses a gradient of non-polar solvents with a polar packing material. Regardless of a laboratory’s choice of process, there are a variety of SPE systems and consumables that can accommodate the testing of food and water.

The automation-friendly advantage

Life science and environmental industries use SPE systems to run analyses on a variety of samples. Horizon Technologies offers the SmartPrep Extractor, which is designed for scalable cartridge-based SPE. Mark Hamel, Horizon’s director of marketing and international sales, describes the extractor as “a sort of culmination of a lot of different machines or systems that have been on the market for some time.” The SmartPrep Extractor combines scalability, automatic sample rinsing, software flexibility, a smart liquid sensor and a reagent manager to provide a product that, according to Hamel, truly meets the needs of both environmental labs and a variety of life science applications.

One of the key features of this system is its scalability—users can start with one and add up to eight modules, all controlled by a single PC. Other features help to automate the tedious steps of manually feeding cartridges and performing SPE. For example, the automatic rinsing allows the machine to run unattended.

In addition, the smart liquid sensor can monitor how much water is being pulled through the cartridge when the sample is being pumped, while the reagent assistant manager can calculate how much solvent will be used for an entire run and determine how much waste fluids will be expelled out the back of the instrument.

“You can go home and let the machine run overnight, come back in the morning and the samples are ready and waiting for you,” Hamel says, adding that “the data quality is much more consistent because you don’t have an operator doing things differently day-to-day or hour-to-hour.”

The SmartPrep Extractor uses SPE cartridges and is compatible with most 1, 3 or 6 mL cartridges. This means that the system can be adjusted for various types of experiments.

“Cartridges are good for small volumes of various types of liquids,” Hamel says. “The SmartPrep, although ideally suited for water, can also work equally as well with other types of sample matrixes like urines, bloods, plasmas, fruit juices, beverages and food stocks.”

Horizon Technology’s SmartPrep Extractor delivers versatility and intelligent sample preparation capabilities for cartridge-based automated SPE. It is designed specifically for scalable, cartridge-based SPE of a range of contaminants in clean aqueous matrices.A fully integrated approach 

Automation is key in modern SPE systems—it makes results that pertain to human health all the more effective and efficient. Waters’ MassTrak Online SPE Analyzer is a fully integrated system that automates every step of the SPE sample preparation process.

The system boosts lab productivity by connecting the prepared SPE sample directly to its ACQUITY UPLC or ACQUITY TQD-based LCMS system for analysis, without requiring an operator. It also improves LCMS assay sensitivity and provides better cleanup for LCMS analysis.

The MassTrak Online SPE Analyzer uses SPE cartridges, which are suitable for water and food analyses. The system operates on Waters’ Design of Experiments (DoE) methodology. With this, the system can identify, test and control multiple variables in the SPE process—such as breakthrough, recovery and absorption of analytes—simultaneously. Development based on DoE methods allows operators to quickly conceive and better execute extraction processes with less effort. 

Consumables uptake

While the actual SPE systems do the bulk of the experimental work, all systems need fully functioning consumables to produce accurate results. SPE consumables include tubes, columns, disks and cartridges. Although consumables are generally used once in the process and then discarded, they remain an integral part of the extraction process.

The growth of SPE systems has propelled a new development of consumables—especially cartridges. Many SPE systems, including those for testing food and water, use small cartridges to extract samples. The problem with food samples, however, is that preparing the process for analysis can be complicated by the presence of pigments, fats, waxes and colors. To perform successful SPE for food and pesticide testing, PerkinElmer has released the Supra-d QuEChERS-based dispersive SPE solution.

QuEChERS—an acronym for quick, easy, cheap, effective, rugged and safe—is a two-step SPE process. PerkinElmer, a company that is no stranger to the human and environmental health market, has released the Supra-d solution as a means of better executing the second step of QuEChERS to improve clean-up.

“When collecting and preparing the sample to bring to the lab, before it goes into that instrument, there is a lot that goes on and our customers are always challenged by how to make that easier—that’s sort of a bottleneck in the lab,” says Mike DiVito, director of consumables at PerkinElmer. “This is one way to try and help remove that bottleneck.”

DiVito, a former chemist, says the Supra-d is a complete solution that considers the entire workflow and sample chain of an experiment. 

The solution helps identify and isolate pesticides and contaminants on food products, which in turn ensures the overall health of humans. It is offered in pre-packaged, pre-measured chemical clean-up kits, with a special kit for AOAC method 2007.01 and another for pigmented fruit and vegetable clean-up. 

“Users take some of the liquid from phase one, shake it for a minute or so, centrifuge it and then it’s ready to go,” says DiVito. “All that’s needed is a laboratory centrifuge, a mixer and a little basic acetonitrile, the rest comes in our kit.”

This ease-of-use is not the only perk of using Supra-d. The solution also capitalizes on the “effective” part of the QuEChERS method. For example, in terms of recoveries, if a researcher has 100 percent of pesticides, it would be nice to get back 100 percent. However, that is not always the case with chemistry. But, with the QuEChERS, 85 percent is not unusual, says DiVito.

Overall, DiVito says the Supra-d solution—as well as other SPE consumables and systems—will continue to benefit future human and environmental health.

“The whole area of food safety is really what drove the development of this product,” DiVito says. “PerkinElmer’s viewpoint is that there is a whole stream of things that happen along the way between the apple on the tree to the LCMS data analysis system.”