Last updated on Jul 12, 2024

What are the main advantages of using SPE over liquid-liquid extraction (LLE)?

Liquid-liquid extraction (LLE) is a common method for isolating and concentrating analytes from complex matrices, such as biological fluids, environmental samples, or food products. However, LLE has some drawbacks, such as high solvent consumption, low recovery, and emulsion formation. Solid phase extraction (SPE) is an alternative technique that can overcome these limitations and offer several advantages over LLE. In this article, we will explore what SPE is, how it works, and why it is superior to LLE in terms of efficiency, selectivity, and environmental impact.

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1 What is SPE?

SPE is a sample preparation method that uses a solid material, called a sorbent, to selectively retain the analytes of interest from a liquid sample, called a mobile phase. The sorbent is usually packed in a cartridge, a disk, or a well plate, and the sample is passed through it under vacuum or pressure. The analytes are then eluted from the sorbent with a small volume of a suitable solvent, called an eluent. The eluent contains the concentrated and purified analytes, ready for further analysis.

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2 How does SPE work?

SPE works based on the interactions between the analytes, the sorbent, and the mobile phase. Depending on the nature of these interactions, different modes of SPE can be used, such as reversed-phase, normal-phase, ion-exchange, or affinity. The choice of the sorbent and the mobile phase depends on the polarity, charge, and affinity of the analytes. The goal is to achieve a high retention of the analytes on the sorbent, while minimizing the retention of the interfering compounds. The eluent should be able to disrupt the interactions between the analytes and the sorbent, and elute them with high recovery and low solvent consumption.

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3 Why is SPE more efficient than LLE?

SPE is more efficient than LLE because it requires less time, labor, and solvent. LLE involves multiple steps of shaking, separating, and transferring the organic and aqueous phases, which can be tedious and time-consuming. LLE also requires large volumes of organic solvents, which can be expensive and hazardous. SPE, on the other hand, simplifies the extraction process by using a single cartridge or disk, which can be automated and integrated with other analytical instruments. SPE also reduces the solvent volume and waste, as the eluent is usually a fraction of the sample volume.

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Neeba Wilson

Biotechnology professional, Scientific writer and Educator
The most advantageous thing about SPE methods is the less solvent consumption. Because of decreased evaporation, less solvent is used and it also allows better extraction. For my projects on secondary metabolite extraction from plant extracts, I have got excellent results with HPTLC (SPE) methods which would not have been possible with conventional methods.
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4 Why is SPE more selective than LLE?

SPE is more selective than LLE because it offers a wider range of sorbent materials and mechanisms to target specific analytes. LLE relies on the partition coefficient of the analytes between the organic and aqueous phases, which can be affected by factors such as pH, temperature, and salinity. LLE also suffers from co-extraction of unwanted compounds, such as lipids, proteins, or salts, which can interfere with the analysis or damage the analytical column. SPE, on the other hand, allows for the fine-tuning of the sorbent properties and the mobile phase composition to achieve optimal separation and enrichment of the analytes. SPE also enables the removal of interfering compounds by using wash steps or selective elution.

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5 Why is SPE more environmentally friendly than LLE?

SPE is more environmentally friendly than LLE because it reduces the generation and disposal of organic solvents. Organic solvents are harmful to human health and the environment, as they can cause respiratory problems, skin irritation, fire hazards, or pollution. LLE consumes large amounts of organic solvents, which need to be properly stored, handled, and disposed of. SPE, on the other hand, minimizes the solvent usage and waste, as the eluent is usually a small fraction of the sample volume. SPE also allows for the reuse or regeneration of the sorbent materials, which can extend their lifetime and lower their cost.

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Neeba Wilson

Biotechnology professional, Scientific writer and Educator
If I take the example of HPTLC, SPE offers the avoidance of any toxic reagents to be sprayed for analyte detection. In fact, it only needs to scraped out for further analysis. This certainly means a more feasible and environmentally efficient approach to avoid tedious steps and unnecessary waste.
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6 Here’s what else to consider

This is a space to share examples, stories, or insights that don’t fit into any of the previous sections. What else would you like to add?

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What are the main advantages of using SPE over liquid-liquid extraction (LLE)?

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1 What is SPE?

2 How does SPE work?

3 Why is SPE more efficient than LLE?

4 Why is SPE more selective than LLE?

5 Why is SPE more environmentally friendly than LLE?

6 Here’s what else to consider

Sample Preparation

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