A reliable analysis doesn't begin in the HPLC, UHPLC, GC, or LC-MS system. The decisive step often happens before that: in proper sample preparation. This is exactly where solid phase extraction, or SPE, comes in.

With SPE products from MACHEREY-NAGEL, samples can be purified, concentrated, and freed from interfering matrix components in a targeted way. The goal: cleaner extracts, reproducible results, and greater reliability in the subsequent analysis.

What is solid phase extraction (SPE)?

Solid phase extraction is a sample preparation technique in which analytes are retained from a liquid sample on a solid sorbent, cleaned up, and then eluted again. Depending on the application, interfering co-substances can be removed, target substances concentrated, or complex sample matrices prepared for instrumental analysis.

Typical application areas include:

• Environmental analysis
• Food analysis
• Pharmaceutical analysis
• Chemical quality control
• Forensics and toxicology
• Water analysis
• Sample preparation for HPLC, UHPLC, GC, and LC-MS

Especially with complex samples, clean SPE can make the difference between a stable method and results that are difficult to evaluate.

SPE from MACHEREY-NAGEL: CHROMABOND for different applications

With CHROMABOND, MACHEREY-NAGEL offers a broad SPE portfolio for many analytical questions. This includes classic SPE columns and cartridges, polymer phases, specialty phases, 96-well solutions for higher sample throughput, and accessories for manual or automated sample preparation.

Depending on the sample and target substance, different SPE mechanisms can be used, for example:

• Reversed phase for nonpolar to moderately polar compounds
• Ion exchange for acidic or basic analytes
• Mixed-mode phases for particularly selective cleanup
• Polymer-based phases for robust methods and broad pH ranges
• Specialty phases for demanding matrices and residue analysis

Selecting the right SPE phase is critical. Not every cartridge suits every sample. Parameters such as polarity, pH, matrix, solvent, sample volume, and desired recovery all need to fit together.

Why is SPE so important in analytics?

In many labs, a lot of attention is paid to the analytical instrument. But even the best HPLC or LC-MS system can only perform as well as the sample that goes into it.

Good SPE-based sample preparation can help reduce matrix effects, remove interferents, concentrate target substances, protect the lifespan of columns and instruments, and achieve reproducible results.

This is especially important when low concentrations need to be determined, or when samples come from difficult matrices — for example, food, wastewater, soil extracts, biological samples, or pharmaceutical formulations.

The typical SPE workflow

An SPE method usually consists of several steps:

1. Conditioning The SPE phase is activated with a suitable solvent. This prepares the sorbent and makes it wettable.

2. Equilibration The cartridge is adjusted to match the sample conditions, for example with water, buffer, or a suitable solvent mixture.

3. Sample loading The sample is passed through the sorbent in a controlled manner. The target substances are retained, or interfering components pass through the phase.

4. Washing Matrix components and unwanted impurities are removed without losing the target substances.

5. Elution The target substances are released from the phase again using a suitable elution solvent and collected for further analysis.

Common errors in solid phase extraction

SPE is a very powerful technique. At the same time, small errors can have a major impact on the result. The most common problems don't arise from the product itself, but from incorrect method selection or imprecise execution.

Error 1: Wrong SPE phase selected Choosing the sorbent is one of the most important points. If an unsuitable phase is used, target substances may not be sufficiently bound, or interferents may remain in the extract.

Example: A pure reversed-phase cartridge is not always ideal when ionic or highly polar substances are being examined. In such cases, ion exchange or mixed-mode phases can be more suitable.

Error 2: Conditioning forgotten or done incorrectly If the SPE cartridge is not conditioned properly, the sorbent is not optimally prepared. This can lead to poor recovery, inconsistent results, or uneven flow.

Important: Conditioning should match the method, and the cartridge should not be allowed to dry out unintentionally afterward, unless the method specifically calls for it.

Error 3: Sample pH not adjusted pH determines whether a compound is present in ionized or neutral form. This directly affects binding to the SPE phase. If pH is not accounted for, analytes can break through or be lost during washing.

pH adjustment is a key method parameter, especially for acidic or basic substances.

Error 4: Flow rate too high If the sample flows through the cartridge too quickly, there may not be enough contact time between the analyte and the sorbent. The result can be poorer recovery and incomplete binding.

A controlled, steady flow rate improves reproducibility.

Error 5: Cartridge overloaded Every SPE phase has a limited capacity. If the sample volume is too large or the matrix load too heavy, the sorbent can become overloaded. Target substances are then no longer fully retained, or interferents end up in the extract.

An appropriately sized cartridge, suitable sample pretreatment, or dilution can help here.

Error 6: Wash step too strong A common mistake is an overly aggressive wash step. If too strong a solvent is used, it can remove not only impurities but also the desired analytes.

The wash step needs to be chosen so that matrix components are removed while the target substances remain on the phase.

Error 7: Elution solvent doesn't match the application If the elution solvent is too weak, the analytes are not fully released from the phase. If it's unsuitable for the subsequent analysis, it can cause problems with HPLC, UHPLC, or LC-MS.

The eluate should therefore be compatible with both the SPE method and the downstream analysis.

Error 8: No control of blanks and recovery Without blank samples, control samples, and recovery experiments, it remains unclear whether the method actually works reliably. Controls are especially important in trace analysis, LC-MS applications, or regulated lab processes.

An SPE method shouldn't just "work" — it should be reproducible and verifiable.

Error 9: Poor documentation SPE methods are sensitive to small changes. Solvents, volumes, pH values, flow rates, drying steps, and elution conditions should be documented cleanly. This is the only way to compare results and trace errors later.

Advantages of a well-optimized SPE method

A properly built SPE method offers many advantages:

• Better reproducibility
• Reduced matrix effects
• Cleaner chromatograms
• Fewer disruptions in HPLC, UHPLC, GC, and LC-MS
• Higher sensitivity through enrichment
• Protection of instruments and separation columns
• Greater reliability in routine analyses

Especially with demanding samples, it pays off to carefully select and optimize the SPE method.

Conclusion: SPE is more than just a preparation step

Solid phase extraction is a key building block of modern analytics. It helps determine whether results are clean, reproducible, and robust. With SPE solutions from MACHEREY-NAGEL, labs have access to a broad portfolio for different samples, methods, and requirements.

Whether for routine analysis, research, quality control, or trace analysis: the right SPE method improves sample quality and lays the foundation for reliable analytical results.

Avoiding errors in phase selection, pH, conditioning, wash step, or elution gets significantly more out of SPE — and ensures clear results even before the actual measurement takes place.