Extraction of Oil & Grease from Water Samples Using ISOLUTE® O&G Solid Phase Extraction Columns

Significance of the Topic

Oil and grease determination per EPA Method 1664 is crucial for monitoring water quality and ensuring compliance with environmental regulations. Solid phase extraction of hexane extractable material provides an efficient approach to assess contamination by petroleum derived compounds.

Objectives and Study Overview

This note details a solid phase extraction protocol using ISOLUTE O&G columns to isolate total oil and grease from water, with optional fractionation into non-polar TPH and polar components, enabling gravimetric quantification after solvent evaporation.

Methodology

• Sample Acidification and Solvation: Adjust sample pH to 1.9–2.1 with 6 M HCl to neutralize fatty acids, add methanol, and cool to 4 °C for samples rich in fatty acids.
• Column Conditioning: Rinse columns with methanol and acidified water to prepare the sorbent bed.
• Sample Loading: Process 1 L water samples at up to 10 mL/min, with potential to increase flow rate after validation.
• Interference Elution: Rinse sample containers with acidified water and acetone to transfer residuals onto the column.
• Column Drying: Dry columns under vacuum manifold or nitrogen/carbon dioxide gas flow (~4 L/min) until no cool sensation remains.
• Analyte Elution: Elute non-polar fraction with hexane and polar fraction with hexane/THF (1:1, v/v), incorporating 2-minute soak steps for each volume.
• Concentration and Gravimetric Analysis: Evaporate eluents under nitrogen at ≤35 °C and weigh residues when mass change is below 1 mg.

Used Instrumentation

• ISOLUTE O&G SPE columns (1 g/6 mL and 3 g/70 mL formats) with integral depth filters
• Vacuum manifold or nitrogen/carbon dioxide gas supply for controlled drying
• Analytical balance for precise gravimetric measurements

Key Results and Discussion

The SPE procedure achieved high recovery of total oil and grease alongside effective removal of interferences. Dual elution allowed selective analysis of non-polar hydrocarbons and polar constituents. Integrated depth filters prevented clogging by particulate matter, and optimized flow rates supported high throughput without compromising performance.

Benefits and Practical Applications

• Reliable quantification of oil and grease across diverse water matrices
• Flexible analysis for total HEM or fractionated TPH and polar components
• No prefiltration required for particulate-laden samples due to depth filter design
• Seamless integration into environmental monitoring and QA/QC workflows

Future Trends and Applications

Automation of SPE steps, on-line coupling with GC-FID or GC-MS detectors, and development of advanced sorbents with enhanced selectivity for emerging contaminants will further extend application of the method.

Conclusion

The ISOLUTE O&G SPE method presents a robust and efficient workflow for determination of oil and grease in water, meeting EPA Method 1664 requirements and supporting regulatory and industrial quality assurance objectives.

References

• Biotage Application Note IST1005A.V.1, 2020