ANALYSIS OF OIL IN WATER USING THE AGILENT CARY 630 FTIR

Significance of the Topic

This method addresses environmental monitoring of oil contamination in water, a critical parameter for regulatory compliance, ecosystem protection and industrial wastewater control.

Objectives and Study Overview

The study aimed to develop and validate a fast, safe and cost-effective procedure for quantifying total hydrocarbons in water using the Agilent Cary 630 FTIR and DialPath accessory. Key objectives included:

• Adopt ASTM D7678-11 and ARPA–APPA 75/2011 guidelines.
• Replace hazardous solvents with cyclohexane.
• Implement liquid–liquid extraction and FTIR measurement with DialPath.

Methodology

Water samples (500 mL) were acidified and extracted in three 15 mL portions of cyclohexane. Extracts were combined, concentrated under nitrogen to 0.5 mL and brought to volume with cyclohexane. Calibration used 14 standards of hexadecane/isooctane mixtures, covering 0–165 ppb HC. FTIR spectra collected between 1350–1412 cm⁻¹ monitored the methyl CH bending at 1380 cm⁻¹ for quantitation.

Used Instrumentation

• FTIR spectrometer: Agilent Cary 630
• Sampling accessory: DialPath (1000 µm)
• Optical materials: ZnSe windows, ceramic source
• Detector: DTGS
• Measurement conditions: 128 scans, 4 cm⁻¹ resolution

Main Results and Discussion

The calibration curve exhibited high linearity for total hydrocarbons, with a correlation coefficient exceeding 0.99. Relative standard deviations were below 3 % at test levels. Elimination of chlorinated solvents simplified sample handling and improved safety. Direct extraction in sample flasks enhanced hydrocarbon recovery.

Benefits and Practical Applications

• Safer, non-chlorinated solvent use
• Reduced analysis time and solvent costs
• Minimal liquid volume and rapid throughput
• Potential for on-site, field-deployable analysis

Future Trends and Opportunities

Expanding the method to other organic pollutants, integrating portable FTIR systems for field monitoring, and developing automated, high-throughput workflows with greener extraction solvents are promising directions.

Conclusion

The cyclohexane-based ASTM D7678-11 method on the Cary 630 FTIR DialPath provides a robust, eco-friendly, and efficient approach for total hydrocarbon analysis in water, matching classic FTIR performance without hazardous solvents.

Reference

• ASTM D7678-11: Standard Test Method for Total Petroleum Hydrocarbons in Water
• ARPA–APPA Guideline 75/2011
• Scardina P. et al., Agilent Technologies, 2014