ANALYSIS OF OIL IN WATER USING THE AGILENT CARY 630 FTIR

Significance of the Topic

Detecting oil in water is critical for environmental monitoring and regulatory compliance. The ability to rapidly quantify total hydrocarbons supports water quality assessment and pollution control in industries and natural resources management.

Objectives and Study Overview

The study aimed to develop and validate a method for total oil analysis in water based on ASTM D7678-11 and Italian guideline ARPA APPA 75 2011 using the Agilent Cary 630 FTIR. Key goals included replacing hazardous solvents with cyclohexane and integrating the DialPath liquid sampling system to improve safety speed and cost efficiency.

Methodology and Instrumentation

• Sample extraction involved three sequential liquid liquid extractions of acidified 500 mL water with 15 mL cyclohexane per step.
• Extracts were combined reduced under nitrogen to 0.5 mL and adjusted by weight if required.
• Analysis was performed on Agilent Cary 630 FTIR equipped with 1000 µm DialPath accessory ZnSe optics ceramic source and DTGS detector.
• Spectra were acquired over 128 scans at 4 cm-1 resolution with cyclohexane background.
• Calibration used 14 standards of hexadecane and isooctane covering 0 to 165 ppb hydrocarbon equivalents.

Main Results and Discussion

The methyl bending peak at 1380 cm-1 provided a direct correlation to hydrocarbon concentration. Calibration showed linear response across the tested range with relative standard deviations below 3 percent. Real sample analyses yielded total hydrocarbon values read from the calibration curve. A secondary measurement after purification on a Fluorisil column enabled differentiation of oil and grease components.

Benefits and Practical Applications

• Elimination of chlorinated and fluorinated solvents reduces health environmental and disposal concerns.
• The DialPath accessory minimizes sample volume and cleaning time while improving throughput.
• The method delivers sensitivity comparable to traditional FTIR procedures at lower cost.
• Direct extraction in the sampling flask enhances hydrocarbon recovery and simplifies workflow.

Future Trends and Potential Applications

Advancements may include integration with automated sampling systems expanded spectral libraries for compound specificity coupling with chemometric tools for multicomponent analysis and application to other matrices including soils and wastewaters.

Conclusion

The method described provides a fast safe and cost effective approach for total hydrocarbon determination in water using cyclohexane extraction and Agilent Cary 630 FTIR with DialPath. It meets regulatory requirements offers robust performance and reduces hazardous solvent use.