Solid phase extraction (SPE) is a cornerstone of sample preparation in analytical laboratories, widely used for both sample clean-up and concentration. Its popularity stems from its ability to selectively capture, clean, and concentrate analytes while efficiently removing interfering compounds. As a result, SPE has become the gold standard for preparing samples ahead of chromatographic analysis. However, despite its widespread use, traditional SPE designs often introduce variability that can compromise data quality.
Challenges with Traditional SPE Formats
Conventional SPE plates and cartridges typically use a loosely packed bed of resin or silica held between two frits. While effective in principle, this configuration presents several limitations. Variations in packing density can lead to voids, channelling, and inconsistent bed weights. These factors influence flow rates, analyte–sorbent interactions, and ultimately recovery and reproducibility. The result is often increased data variability reflected in high relative standard deviations (RSDs), reducing analytical confidence.
Figure 1: Illustration of the drawbacks of traditional silica-based media.
The Microlute® Approach
To address the limitations of traditional loose-packed SPE formats, Porvair Sciences developed Microlute® SPE – a technology that replaces the loose-packed sorbent bed with a rigid, porous composite structure. In this design, active chromatographic media is combined with inert polyethylene to form a single, sintered composite. The interconnected pores provide uniform pathways for controlled flow of liquids and gases, while the embedded active resins maximise analyte–sorbent interactions, ensuring efficient and reliable extraction.
Figure 2: Schematic illustration of Microlute® composite technology.
Uniform Flow for Enhanced Reproducibility and Data Reliability
One of the key advantages of the Microlute® composite SPE design is its ability to deliver consistent, uninterrupted sample flow. As illustrated in Figure 3, comparative studies showed that samples passed evenly through every well of the Microlute® composite SPE plate, while traditional loose-packed formats displayed highly variable flow rates between wells. This uniform flow enhances analyte recovery, shortens processing times, and, most importantly, results in exceptionally low RSDs.
Figure 3: Flow comparison between a loose-packed plate and a Microlute® composite plate.
The Microlute® is manufactured under strict quality controls to ensure precise and uniform bed weights, minimising variability in performance across all wells. Within the composite, the active resins are immobilised and evenly distributed throughout the porous matrix, eliminating common issues associated with loose-packed formats such as channelling and void formation. This robust, stable structure promotes uniform flow and consistent analyte recovery, delivering reliable and reproducible results.
In a comparative study between loose-packed and composite SPE products (Figure 4), both prepared using the same bed weight and resin batch, the composite plate demonstrated markedly improved reproducibility with no reduction in recovery.
Figure 4: Improved reproducibility using Microlute® composite SPE compared to loose-packed.
Product Range and Application Flexibility
To support a wide range of analytical applications, Microlute® SPE is available in both polymeric and silica-based composite formats, enabling laboratories to adopt the composite technology without losing compatibility with existing methods.
- Microlute® CP – Composite Polymeric SPE
Offers stability across a broad pH range, high loading capacity, and consistent performance even after drying. Available in HLB, SAX, and SCX chemistries, with 2 mg or 10 mg bed weights in a 96-well format. - Microlute® CSi – Silica-Based SPE
Combines the familiar selectivity of silica with the enhanced structural and performance benefits of the composite design. Available in C18, SAX, and SCX chemistries, with 2 mg or 10 mg bed weights, allowing straightforward method transfer from traditional silica-based SPE products.
Conclusion: Setting a New Standard for Reproducible Sample Preparation
Microlute® SPE technology from Porvair Sciences represents a significant advancement in solid phase extraction, moving beyond the limitations of traditional loose-packed formats. Its rigid, porous composite structure ensures uniform resin distribution, controlled flow dynamics, and consistent analyte–sorbent interaction across every well. This innovative approach eliminates common issues such as channelling and void formation, resulting in superior reproducibility, improved data quality, and greater analytical confidence.
At the same time, the inherent consistency of the Microlute® design reduces the need for repeat extractions, lowering solvent consumption and supporting more sustainable laboratory practices. With straightforward method transferability and broad application versatility, Microlute® SPE sets a new standard for reliable sample preparation – enabling laboratories to achieve faster and more reproducible analytical results.
If you are new to SPE or looking to improve your method, Element Lab Solutions is here to support you. Please contact our technical support team at [email protected].
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