Automated Solid Phase Extraction Instrument

This week, let’s talk about one of my best friends at INERIS: “Automated Solid Phase Extraction Instrument”. Before explaining his role to my daily life at INERIS, I would like to recap my personal information: “I am Pham Quynh Khoa, being one of the early stage researchers (ESR09) of the InnovEOX project funded by the European Union. My own project is to develop a sample preparation method for the monitoring of eAOP degradation products.”

These days, chromatography plays a central role in the modern analytical chemistry. It can simplify the analysis of complex samples by separating compounds present in those samples from each other and determining those compounds at low concentration levels with a very small amount of samples. Those are some of the advantages of the chromatography. However, the accuracy of the outcome data of a chromatographic analysis is strongly influenced by a sample preparation method because the sample preparation method is fundamental to cover complete information and downstream works only reflect compounds previously extracted. Hence, the development of a proper sample preparation method has a unique meaning and a vital role to chromatographers in particular and analytical chemists in general.

In environmental analysis, solid phase extraction (SPE) emerges to be a dominant method compared to liquid-liquid extraction and direct injection in terms of clean-up, coverage, concentration and simplicity. A whole process of an SPE method often includes 4 steps: condition, equilibration, loading and elution. The principle of the method is similar to that of the chromatography, namely that compounds present in a certain liquid sample will be absorbed on a solid sorbent when the sample passes through the sorbent under a positive or negative pressure and then, those compounds will be eluted from the sorbent with an elution solvent.

Figure 1. Manual Solid Phase Extraction Manifold under Vacuum

Of the techniques in solid phase extraction, a manual SPE-based method using an SPE manifold under vacuum is commonly used in laboratories today because of its low cost and convenience. The operational mechanism of this manifold is relatively simple. SPE tubes containing one or more specific sorbents are placed on the top of the airtight manifold connected with an external pump, solvents or samples are manually loaded onto these tubes and pass through the sorbents under the vacuum pressure adjusted by the pump that must be regularly checked with your eyes to ensure that the flow rate is constant during the process. Then, the elution solutions collected will be manually evaporated and reconstituted with a suitable solvent for the chromatographic analysis if necessary. The main disadvantage of the instrument is that it is not easy to keep the SPE parameters such as flow rate constant during the process or among samples, causing the error of the outcome data. Other ones are time-consuming and laborious, leading to the low throughput.

 

Figure 2. Automated Solid Phase Extraction Instrument
A: SPE tube compartment; B: liquid handling syringes; C: sample lines

I wondered myself if the limitations of the instrument could be overcome. “YES”, nothing is impossible. The solution to the problems of the manual instrument is “Automated Solid Phase Extraction Instrument”. At INERIS, our laboratory is equipped with two different versions of the automated SPE instrument and one of them is my best friend displayed in Figure 2. Basically, an automated solid phase extraction instrument has 3 main parts: liquid handling syringes whose function is to precisely deliver solvents used for the condition, equilibration, and elution from the solvent reservoirs to the SPE cartridges can automatically control the volume and flow rate of the solvents; sample lines where real samples are automatically loaded onto the SPE cartridges through the pump system; finally, SPE tube compartment known as the heart of the automated SPE instrument where SPE cartridges are installed and the SPE process (condition, equilibration, loading, and elution) occurs. The automated SPE instrument is completely automatically operated under a positive pressure, ensuring that all SPE parameters are controlled precisely and reproducibly from sample to sample and from batch to batch. What you need to do is simply to set up the SPE program on the computer and … “ENTER”. As a result of these advantages, the automated SPE instrument can simplify your SPE experiment and provide you with an efficient and reliable solution, leading to the robustness and high throughput.

Now, I hope that you may understand the important role of my best friend to my daily life at INERIS and to the scientific community.

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