Modern analytical instruments are increasingly capable of processing smaller sample volumes in shorter timeframes with high sensitivity and selectivity. Most analytical platforms, therefore, require minimal amounts of sample extract, such as a few microliters in the case of GC-MS or LC-MS.
Despite this, researchers are routinely tasked with preparing large volumes of samples and conducting numerous clean-up and enrichment steps to achieve the optimal concentration of analyte for quantification. Not only are these protocols time- and resource-intensive, but they are also prone to well-known risks of analyte loss, as well as the potential for contamination. In addition, many of these methods are still manual. It is therefore not surprising that analytical chemists spend up to two-thirds of the total analysis time on sample preparation.
As a solution to these challenges, there is a growing trend towards the development and use of rapid, accurate, and miniaturized sample preparation methods, known as micromethods. Using reduced sample volumes makes it possible to avoid dilution and evaporation, and even work completely solventless and online. In this resource, learn more about the utility and advantages of micromethods, explore compatible technologies, and discover turnkey solutions and protocols for research fields spanning food, environmental, pharma, life science analysis, and beyond.
Micromethods represent an important contribution to the improvement of sample preparation performance while supporting green analytical chemistry (GAC) principles through minimizing hazardous solvents, reducing the sample volume requirement, and limiting the use of consumables.
Commonly used microextraction techniques include solid-phase microextraction (SPME), stir bar sorptive extraction (SBSE), micro solid-phase extraction (µSPE), and dispersive liquid/liquid microextraction (DLLME). Comparable workflows also exist for volatiles analysis using the syringe headspace method or the in-tube extraction dynamic headspace solution (ITEX-DHS).
Solid-phase extraction (SPE) is a reference technique in modern laboratories for sample preparation and clean-up. The application of micro SPE (µSPE) employs miniaturized SPE cartridges. µSPE prevents the typical dilution by SPE elution and thus avoids an additional evaporation step and reduces solvent use. Unlike classical SPE using a vacuum manifold, the flow rates applied to the µSPE cartridge can be precisely controlled with a liquid syringe on a PAL RTC autosampler.
Download this brochure to explore how micro-SPE cartridges can be used to achieve a significantly better QuEChERS clean-up performance than traditional dispersive-SPE.
ITEX Dynamic Headspace
As an alternative to purge and trap (P&T) thermal desorption, in-tube extraction (ITEX) dynamic headspace offers excellent sensitivity for the analysis of volatiles and semi-volatile organics in solid, liquid and gas samples, without the cost and complexity of classical P&T systems.
ITEX dynamic headspace uses a gas-tight syringe to collect the headspace and a microtrap inside the syringe needle to efficiently extract and concentrate volatile and semi-volatile compounds. This is a syringe-only concept with no sample loops, transfer lines, or switching valves that could be contaminated. The five stages of the ITEX procedure are shown below.
SPME is a cornerstone microextraction technique whereby analytes are extracted from a gaseous or liquid sample by absorption in, or adsorption on, a thin polymer coating fixed to a solid surface of a fiber. SPME combines analyte sampling, isolation, and enrichment into one single step. After extraction, the fiber is removed and inserted directly into a chromatographic instrument, usually GC or HPLC, for desorption and analysis.
CTC Analytics provides a wide range of SPME fibers as well as the more rugged and more sensitive SPME Arrow device for routine high-throughput sample preparation.
SPME Arrow provides up to 10x more sensitivity compared to classical SPME, enabling reliable and robust immersion extraction.
How do different extraction techniques compare?
The diagram below outlines the working ranges of the different techniques for GC headspace or immersion extractions.
Micromethods call for automation
When dealing with miniaturized sample volumes, automated platforms can offer researchers significant time savings, improve reliability and reproducibility, and prevent sample handling errors. Automated workflows can also lead to improved traceability for Good Laboratory Practice (GLP) and compliance with EU/OECD standards.
Micro-volumes ideally fit the automated workflows of robotic sample preparation systems such as PAL Systems by CTC Analytics, which enable direct application to analytical instruments. The automated workflow is highly economical. While the sample sequence is running the PAL starts the preparation of the next sample in parallel to the chromatographic run.
“An all-in-one autosampler customized for your needs”
“The delivery system of this autosampler is unmatched in terms of cleanliness and robustness. The autosampler contains dynamic washing steps that sets it apart from other autosamplers, ensuring no carryover or cross contamination. Versatile to hold plates and vials, this thermostat autosampler enables the user to add on features, making it customizable to your lab's needs.”
Sam Sansil, H. Lee Moffitt Cancer Center
A key benefit of using PAL Systems is access to ready-to-go workflows that provide turnkey solutions for automated sample preparation, extraction, dilution, clean-up, and derivatization procedures.
Covering a variety of applications spanning food, pharma, forensic, environmental research and more, these preprogrammed workflows are designed to enable reliable, high-throughput analysis whilst minimizing labor, solvent volume, and instrument maintenance.
The clean-up of QuEChERS extracts for the analysis of pesticides and environmental contaminants is one example of how robotic instruments can alleviate the demands of sample processing faced by researchers. Watch the video below to explore how this can be achieved using automated, miniaturized SPE and learn how this approach can improve analyte recovery and sample throughout while delivering significant time and cost savings, in this application compendium.
Another common task in food analysis is the quantification of oils, fat and fat containing food via fatty acid methyl esters (FAME) using the AOAC method 996.06. When adhering to this method, samples are often processed manually, which is both labor intensive and exposes lab personnel to potentially hazardous chemicals. This protocol demonstrates how FAME preparation, including injection into the GC, can be fully automated using the PAL RTC workstation to improve process safety, throughput, and traceability.
PAL Systems and PAL micromethods for automated sample preparation work with all brands of liquid or gas chromatography, mass spectrometry, NMR, UV or any other kind of analysis instrument. Many workflows are already implemented in turnkey solution packages, for instance with SPME, µSPE, dilution or derivatization workflows.
The PAL Method Composer (PMC) is an easy-to-use graphical tool that allows users to prepare customized automated workflows. By simply dragging and dropping the individual prep steps users can build a method in minutes. The parameters of the steps are default values that were experimentally determined. However, each step can be adjusted for specific methods.
PAL Method Composer works with the following CDS:
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