How Solid Phase Extraction (SPE) Disks Differ for Hexane Extractable Material

Significance of the Topic

Monitoring hexane-extractable materials (HEM), often termed oil and grease, is critical for environmental compliance and water quality assessment. Accurate quantitation of low-volatility lipophilic substances ensures regulatory limits are met and supports risk management in industrial and municipal wastewater treatment.

Study Objectives and Overview

This study compared the performance of Biotage Pacific® Premium and Pacific® SPE disks against seven competing brands under identical conditions. Key metrics included blank background levels, recovery of spiked standards, and flow rates during extraction of HEM from 1 L purified water samples.

Methodology and Instrumentation

Samples were acidified to pH ~2 and passed through either 90 mm or 47 mm SPE disks under –20 inHg vacuum. After rinsing, hexane elution was performed and extracts were evaporated at 40 °C. Performance evaluations comprised:

• Blank background determination (12 replicates)
• Recovery of a 40 mg standard spike (n-hexadecane and stearic acid, 12 replicates)
• Processing time for spiked and blank samples

Instrumentation

• SPE-DEX® 3000XL Oil & Grease Automation System (Horizon/now Biotage)
• Mettler AE 200 analytical balance
• Speed-Vap evaporator

Key Results and Discussion

Blank background levels varied significantly across brands. Pacific® Premium and Pacific® disks exhibited the lowest backgrounds (1.11 ± 0.49 mg/L and 0.03 ± 0.17 mg/L respectively), well below the ISO 11349 blank limit of 3 mg/L. Recovery data for a 40 mg spike showed:

• Pacific® Premium: 97.7% ± 1.2%
• Pacific®: 90.5% ± 2.0%
• Competitors: ranged 88.7–94.2% with higher variability

Flow-rate measurements indicated that Pacific® disks processed 1 L in approximately 1.3–1.9 min, outperforming many alternatives (up to 12.4 min). High retention capacity, prefilters, and glass wool support rapid throughput even with particulate loads.

Benefits and Practical Applications

Use of Pacific® Premium and Pacific® SPE disks delivers:

• Consistently low background for gravimetric analysis
• High and reproducible recoveries at low concentration levels
• Reduced extraction times and solvent consumption
• Compatibility with automated workflows for high throughput

Future Trends and Potential Applications

Advances may include integration of online SPE-GC-MS systems for speciation of oil fractions, miniaturized disk formats for micro-volume sampling, and adaptation to emerging contaminants such as microplastics and polar lipid species. Enhanced disk chemistries could further improve selectivity and robustness across diverse water matrices.

Conclusion

Biotage Pacific® Premium and Pacific® SPE disks demonstrated superior performance in blank background, recovery accuracy, and processing speed compared to leading competitors. Their adoption supports reliable, efficient monitoring of hexane-extractable materials in environmental and industrial water analysis.

References

1. US EPA Method 1664B: n-Hexane Extractable Material (HEM)—Oil and Grease and Silica Gel Treated n-Hexane Extractable Material (SGT-HEM) by Extraction and Gravimetry, 2010.
2. ISO 11349: Water Quality—Determination of Low-Volatility Lipophilic Substances—Gravimetric Method, 2010.