QUANTIFICATION OF COMPLEX POLYCYCLIC AROMATIC HYDROCARBONS OR PETROLEUM OILS IN WATER WITH CARY ECLIPSE FLUORESCENCE SPECTROPHOTOMETER ACCORDING TO ASTM D 5412-93 (2000)

Significance of the Topic

Quantifying polycyclic aromatic hydrocarbons (PAHs) and petroleum-derived compounds in water is critical for environmental protection, public health assessment, and regulatory compliance. Carcinogenic PAHs such as benzo[a]pyrene demand sensitive and reliable analytical methods to detect trace concentrations in complex matrices.

Study Objectives and Overview

This study implemented ASTM D5412-93 (Reapproved 2000) using an Agilent Cary Eclipse fluorescence spectrophotometer to determine PAH levels in water. The focus was on evaluating method performance for naphthalene, benzo[a]pyrene, and anthracene, assessing calibration linearity, detection limits, and recoveries according to the standard’s protocols.

Methodology and Instrumentation

The procedure followed Section 10 and 11 of ASTM D5412-93 with key elements:

• Fluorescence Spectrometer: Agilent Cary Eclipse with quartz cells (1 cm path, 5 cm height).
• Standards: Naphthalene and anthracene (instrumental references) and benzo[a]pyrene (target analyte) in cyclohexane.
• Sample Preparation: Solutions prepared in amber glass vials, employing plastic Eppendorf pipette tips to minimize cross-contamination.
• Measurement Conditions:
  
  • Naphthalene: Ex 250 nm, Em 324 nm (slits 10 nm/5 nm); alternative Ex 268 nm for compatibility with benzo[a]pyrene.
  • Benzo[a]pyrene: Ex 268 nm, Em 405 nm (slits varied from 5 nm/2.5 nm to 10 nm/5 nm for sensitivity assessments).
• Quality Control: Solvent and water blanks, triplicate measurements, compliance with ISO/IEC 17025 precision and bias requirements; LOD/LOQ calculated by 3s and 10s criteria.

Main Results and Discussion

Short-term precision (RSD) remained below 0.1 for low and 0.02–0.05 for medium concentrations. Long-term repeatability and day-to-day variance met ASTM criteria. Calibration curves showed excellent linearity (r > 0.99) for both PAHs:

• Naphthalene LOD/LOQ: 0.13 µg/mL and 0.5 µg/mL under optimal slits; switching to Ex/Em 268/324 nm provided LOD 0.5 µg/mL.
• Benzo[a]pyrene LOD/LOQ: down to 0.005 µg/mL with wider slits, demonstrating sub-µg/mL capability.

Recovery experiments for neat solutions and mixtures yielded biases within ±15%, complying with Sections 12–13 of the standard. Artificial mixtures of three PAHs returned recoveries within specification over 0.03–0.5 µg/mL total PAH.

Benefits and Practical Applications

This fluorescence-based approach offers:

• High sensitivity for trace PAH detection, including sub-µg/mL levels of benzo[a]pyrene.
• Rapid analysis with straightforward sample preparation and minimal solvent usage.
• Full compliance with ASTM D5412-93 and ISO/IEC 17025 quality requirements.

It is well suited for environmental monitoring, wastewater testing, and quality control in industrial laboratories.

Future Trends and Potential Applications

Emerging directions include automating sample handling, integrating chemometric deconvolution for complex mixtures, and extending fluorescence methods to wider contaminant classes. Miniaturized or field-deployable fluorescence sensors may enable in situ PAH screening.

Conclusion

The Agilent Cary Eclipse fluorescence spectrophotometer, following ASTM D5412-93, delivers reliable quantification of PAHs in water with excellent precision, sensitivity, and linearity. The method is operationally simple, meets regulatory standards, and supports environmental and industrial analytical needs.

References

• ASTM D5412-93 (Reapproved 2000) Standard Test Method for Quantification of Complex Polycyclic Aromatic Hydrocarbon Mixtures or Petroleum Oils in Water.
• ISO/IEC 17025:2005 General Requirements for the Competence of Testing and Calibration Laboratories.
• IUPAC 1998 Recommendations for Limits of Detection and Quantification in Chemical Analysis.
• Doerffel K. Statistik in der Analytischen Chemie, Deutscher Verlag, Leipzig, 1994.
• Bayrakceken F. Spectrochim. Acta A, 2005, 61(6), 1069–1074.
• Donaldson DJ et al. Faraday Discuss., 2005, 130, 227–239.