Tag Archives: sample prep

MediaBox Sterile Liquids, EZ-Flow Gravimetric Diluter Automate Sample Prep

MediaBox broths and buffers are sterile, easy-to-use and come in a convenient stackable storage box with a long shelf life. Significantly reduce staff workload by removing weighing, measuring, mixing, autoclaving and cleaning glassware. MediaBox is supplied ready-to-use and is far easier to use than dry bags, which are difficult to fill, often leak and are not consistent from one bag to the next.

MediaBox directly connects to the EZ-Flow gravimetric diluter creating an automated system for weighing and diluting your samples. EZ-Flow automatically weighs samples and provides diluent from MediaBox for the correct dilution factor. Your lab will love the convenience and increased efficiency. Microbiology International offers a wide range of dosing systems to pair with your MediaBox of choice.

All MediaBox products pass strict quality control protocols and include Certificate of Analysis documentation. MediaBox sterile liquids come in 5L, 10L and 20L boxes.

Available types include Buffered Peptone Water, Modified UVM, mTSB, Demi-Fraser Broth Base, Phosphate Buffer, Butterfields, Lactose Broth, Sterile Water, LB Broth, PBS, and more. Custom formulations are available.

Find the Weak Link in Pesticide Residue Analysis

By Food Safety Tech Staff
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Plagued by false or inaccurate results during pesticide analysis? To get to the bottom of the issue, it’s important to find any weaknesses in your pesticide residue workflow. In a recent blog on Analyte Guru, Richard Fussell of Thermo Scientific discusses areas in which pesticide testing labs can identify the weak links, including:

  • Solvent extraction. QuEChERs (Quick, Easy, Cheap, Effective, Rugged and Safe) acetonitrile extraction method
  • Sample processing
  • Extraction efficiency

Get the details about how to find the weakest link in Fussell’s blog here.

More on pesticide analysis:

Rapid and Robust Technologies Improve Sample Preparation for Analyzing Mycotoxins

By Olga I. Shimelis
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Mycotoxins are produced as secondary metabolites by various mold species during the growth and harvest of grains, fruits, nuts and condiments. Their production is directly related to the dry/wet weather conditions during the growing season. Mycotoxins are very stable compounds and are not easily removed during storage, processing and preparation of raw agricultural commodities.

Mycotoxins & Grains
Mycotoxins can be found in a variety of grains.

Different classes of mycotoxins are distinguished on the basis of the structural similarity and originating mold species. For example, more than a dozen different aflatoxin compounds exist but only five of them are routinely tested (aflatoxins B1, B2, G1, G2, and M1). Aflatoxin B1 is of particular interest because it is listed as a Group 1 Carcinogen by the International Agency for Research on Cancer (IARC). Aflatoxin M1 is a metabolic product that can be present in milk upon ingestion of aflatoxin B1 by an animal. Aflatoxins are ubiquitous in important agricultural commodities including maize and peanuts, and are among the most studied mycotoxins.

Deoxynivalenol (DON) is produced by a different fungi species. It is prevalent in cereal crops grown under wet conditions and temperatures above 15o C (60o F). Chronic exposure of livestock to DON may result in slowed growth, impaired immune function and reduced rates of reproduction, particularly in non-ruminants.

Mycotoxins were discovered as the cause of poisoning outbreaks in both humans and farm animals in the mid-20th century. Since then, multiple government regulations were established to control the presence of these toxic compounds in food and feeds. For example, harvested grains are checked for mycotoxin contamination using rapid field screening methods prior to grain deposition into silos. If contamination is found, the crops are sent to an analytical laboratory to perform the confirmation analysis. Liquid chromatographic methods were often used for such analysis with both fluorescence and UV detection. In recent years, mass spectrometry has been employed as a detection method.

Sample Preparation for Laboratory Mycotoxin Analysis

When performing analysis, it is important to choose the right sample preparation method to ensure accuracy, sensitivity of detection, repeatability and robustness, as well as fast sample preparation for high throughput. During laboratory analysis of mycotoxins, the sample preparation procedure typically includes extraction, purification and concentration steps.

Extraction of mycotoxins from samples is conducted by mixing the ground sample with the mixture of organic solvent and water, such as acetonitrile:water (80:20). Using methanol is not recommended, because it does not provide complete extraction. Prior to cleanup, the sample is filtered. Historically, mycotoxin analysis required extensive extract cleanup to minimize interference by matrix components. This holds true as new regulations continue to require lower detection limits.

Cleanup methodologies often include the use of phase extraction (SPE). Of the different types of SPE, one of the most common is the use of immunoaffinity sorbents that result in the selective retention and cleanup of mycotoxins. The drawback to using the immunoaffinity sorbents in the lab is that they are not compatible with the mycotoxin extraction solvent. In order to load the extract into the immunoaffinity SPE tube, the extract must be diluted with water, sometimes 20-fold, to prevent precipitation or folding of the protein-based antibodies by exposure to organic solvent. This presents an additional sample preparation challenge, as the grain extracts tend to form precipitates upon the addition of water and can clog the SPE columns. Thus, apart from the high cost of immunoaffinity SPE columns, the methods tend to be labor and timeintensive.

Super Tox SPE cartridges
Super Tox is a line of SPE cartridges for mycotoxin families that eliminates extra sample prep steps.

It would be beneficial to a laboratory to eliminate these extra sample preparation steps required by immunoaffinity SPE. Such cleanup SPE procedures are available and can be applied directly to the mycotoxin extracts without the need for further dilution, filtration and evaporation. A line of SPE cartridges for different mycotoxin families was recently introduced to the market. These SPE cartridges are compatible with the extracts generated during mycotoxin extractions and can be stored at room temperature. The tubes can also be used for cleanup of multiple classes of mycotoxins.

Analysis of Aflatoxins and Zearalenone

SPE cartridges are available for aflatoxins and zearalenone.
SPE cartridges are available for aflatoxins and zearalenone.

The following results employed SPE cartridges for mycotoxins that can be used for two aflatoxin classes, aflatoxins and zearalenone, and were applied to the cleanup of grain and peanut extracts. Results were compared to cleanup using immunoaffinity columns.

AflaZea SPE cartridges are based on the “interference removal” strategy that requires fewer processing steps compared to the “bind-and-elute” strategy of the other SPE. Peanut extracts contain not only co-extracted protein and complex carbohydrates but also fat. This extract was successfully cleaned using AflaZea SPE. When the SPE tube and a leading IAC column were applied to the peanut extract, both methods demonstrated good recoveries for spiked aflatoxins B1, B2, G1, G2 with AflaZea recovery values of 101–108% and immunoaffinity recovery values of 79–100%. However, the AflaZea provided better reproducibility for detection with a relative standard deviation (RSD) of 2–4% RSD versus 10–25% RSD with immunoaffinity SPE. This is likely because sample preparation using AflaZea is less tedious and takes one tenth of the time compared to immunoaffinity SPE.

Analysis of Deoxynivalenol

Wheat samples can be analyzed for deoxynivalenol using a new SPE cartridge.
Wheat samples can be analyzed for deoxynivalenol using a new SPE cartridge.

The following compares a new SPE cartridge for the analysis of DON, one of the Fusarium mycotoxins, with immunoaffinity SPE. Analysis of DON often is conducted using liquid chromatography (LC) with UV detection, so sample cleanliness is important to permit the separation of the DON peak from background interferences. The new SPE DON cartridge was compared to the immunoaffinity SPE for the cleanup and analysis of wheat samples. Clean chromatography and good recovery of spiked DON was obtained by both methods (86–97% RSD). However, clogging of the filters by the immunoaffinity SPE sample was observed during cleanup and complicated the sample preparation procedure. The SPE DON cartridge provided faster sample preparation.

Analysis of Patulin

Patulin is a mycotoxin commonly found in rotting apples.
Patulin is a mycotoxin commonly found in rotting apples.

Another SPE technology for mycotoxin analysis is based on molecularly imprinted polymers (MIPs), which are sometimes called “chemical antibodies” and mimic the performance of immunoaffinity sorbents. MIPs have binding sites that conform to the shape and functionality of specific compounds or compound classes. Strong binding of the analyte to the MIP makes it possible to perform intensive SPE washes that lead to very clean samples. Unlike immunoaffinity sorbents, MIPs are compatible with organic solvents and strong acids and bases.

Foods containing apples and similar fruits are required to be tested for patulin toxin, as they are the most common source for patulin exposure in humans. The MIP SPE procedure for patulin is faster than other SPE or liquid-liquid extraction methods and provides selective retention and superior cleanup. It is a robust method for analyzing apple juice and apple puree with HPLC-UV detection. After cleanup, patulin is quantified in apple puree at 10 ppb levels, which meet most regulatory requirements. The MIP SPE cleanup method eliminated 5-(hydroxymethyl)furfural (HMF) from the matrix, which sometimes appears as an interfering chromatographic peak when other sample prep methods are used. An SPE wash using sodium bicarbonate removed the interfering organic acids, while patulin was stabilized during elution at the end of the SPE procedure by using acidified solvent. Thus, most problems encountered during patulin analysis were resolved during this single SPE procedure.

Conclusion

As government regulations and consumer demand warrant cleaner, non-contaminated products, mycotoxin analysis will continue to be performed around the world. Careful selection of sample preparation methods is required for such analysis to achieve accurate testing results, best method performance and high laboratory throughput. Although many sample preparation methods exist, laboratories should choose the methods that not only provide adequately prepared samples, but also result in time and cost savings. The SPE technologies discussed in this article are sample preparation techniques that provide the required analytical sensitivity without capital expenditure into higher-end LC-MS equipment; the LC-UV and LC-FL methods can still be used. In addition, these SPE methods are simple, more robust, and less-time consuming compared to other SPE methods or liquid-liquid extraction.

All images courtesy of Sigma Aldrich

Aaron Kettle is the Product Manager, Thermo Fisher

Need a Faster Sample Prep Method for Pesticide Residue Analysis? Try Accelerated Solvent Extraction

By Aaron Kettle
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Aaron Kettle is the Product Manager, Thermo Fisher

In a Q&A with Food Safety Tech, Aaron Kettle, sample preparation product manager at Thermo Fisher Scientific discusses the advantages of using accelerated solvent extraction for pesticide residue analysis and its applications in the food industry.

Food Safety Tech: What are the benefits of using accelerated solvent extraction versus other more time-consuming sample prep methods?

Aaron Kettle: It can save a considerable amount of time over techniques such as Soxhlet and sonication that are used in this industry. In addition, the amount of solvent you’re using is cut down by at least five fold using this technique. The other advantage over some of the other techniques is that it allows walk-away capability, so your samples can be loaded and you can run your methods overnight. It’s pretty much just load the buttons and walk away, and by the time you come in the next day, everything is ready for analysis.

FST: Discuss this method in the context of today’s environment as it relates to importance of detecting the presence of pesticide residue and harmful pollutants.

Kettle:
It’s certainly beneficial. It doesn’t have matrix limitations so you can use it for a lot of different sample types: High-fat content samples, such as avocados, dry samples like bread and grain, and high-water content samples like tomatoes.

FST: Are there specific food applications that benefit from accelerated solvent extraction, including those in which the method is underutilized?

Kettle: I don’t think the technique has a lot of use right now for high-water content samples, such as pesticide residue extraction for tomatoes, berries, etc. That primarily has to do with the fact that historically it hasn’t worked well with these kinds of samples. However, we’ve recently released a moisture-absorbing polymer that acts to remove residual water without interfering with the extraction and recovery of the analytes. That has allowed the accelerated solvent extraction to work with these sample types. That’s an area where’s it’s being underutilized right now, primarily because it is a relatively new product release for us. It’s an area where we’d like to see adoption continue to increase.

FST: What is unique about the polymer being used in this detection method?

Kettle: It’s a proprietary mixture that will remove water content up to 85%. There are no major specifics; it will work with any kind of matrix that has water in it—fruits, berries, etc.

FST: What are the top advantages of the technology?

Kettle: The ability to remove residual water is important. It happens prior to the sample being loaded in the extraction cell. There is no limitation with high-water content samples. It mixes well with the dispersing agent, so not only can you add a dispersing agent to help solvent flow through the matrix better, you can also add the polymer to help it through water. It helps expand the capability of the accelerated solvent extraction in what it can do in the food market for pesticide extraction.

FST: What are your expections of this technology within this niche moving forward?

Kettle: We would like to see it expand and have greater awareness and acceptance for the accelerated solvent extraction in this particular area. Right now, folks are using a manual technique for these types of samples, so we’re hoping these customers will accept the walk-away automation and the flexibility that this technique will provide.