UV-Vis Spectroscopy for White Mineral Oil Analysis per ASTM D2269-10

Significance of the Topic

The purity of white mineral oils is critical in pharmaceutical manufacturing to ensure patient safety and product efficacy. Regulatory standards such as ASTM D2269-10 and pharmacopoeial monographs (USP-NF, EP) mandate rigorous testing for impurities like naphthalene, a polycyclic aromatic hydrocarbon. Reliable, high-throughput analytical techniques are essential for quality control laboratories to meet these requirements.

Objectives and Study Overview

This study evaluates the performance of an Agilent Cary 3500 Multicell UV-Vis spectrophotometer coupled with Agilent Cary UV Workstation software for ASTM D2269-10 testing of white mineral oils. Three commercial mineral oil samples were analyzed to determine their naphthalene content against the USP-NF acceptance limit.

Methodology

A standard naphthalene solution (7.0 mg/L in isooctane) was prepared and used to define an impurity absorbance threshold at 275 nm. Mineral oil samples were extracted with hexane and dimethyl sulfoxide (DMSO) and measured in triplicate. Data collection parameters included a wavelength range of 260–350 nm, 2 nm spectral bandwidth, 0.1 s signal averaging, and 1 nm data interval. The Cary UV Workstation end-of-sequence analysis feature calculated the acceptance threshold (Abs ≤ 0.0997) automatically.

Instrumentation

• Agilent Cary 3500 Multicell UV-Vis spectrophotometer
• Agilent Cary UV Workstation software (version 1.6)
• 3.5 mL, 10 mm pathlength quartz cuvettes
• Spectroscopic grade isooctane, naphthalene standard, hexane, DMSO

Results and Discussion

Two of the three mineral oil samples exhibited absorbance values below the calculated threshold, passing the ASTM D2269-10 purity criteria. Sample 3 exceeded the limit, indicating elevated naphthalene levels. Precision assessments demonstrated excellent repeatability (maximum variation ±1.28×10⁻³ Abs) and reproducibility across operators (maximum ΔSD ±1.16×10⁻³ Abs), both within ASTM-specified limits.

Benefits and Practical Applications

• Simultaneous measurement of up to seven samples improves laboratory throughput.
• Automated threshold calculation and audit trail features enhance data integrity and compliance.
• Streamlined report generation in PDF format accelerates quality control workflows.

Future Trends and Applications

Integration of UV-Vis data with laboratory information management systems (LIMS) and advanced chemometric tools will further improve impurity profiling. Miniaturized multicell spectrophotometers and real-time monitoring capabilities are emerging directions for in-line quality assurance of excipients and raw materials.

Conclusion

The Agilent Cary 3500 Multicell UV-Vis system, in combination with Cary UV Workstation software, provides a robust, precise, and efficient solution for ASTM D2269-10 purity testing of pharmaceutical-grade white mineral oils. Its high throughput and automated data processing support regulatory compliance and operational productivity.

References

1. Pirow R. et al. Critical Reviews in Toxicology, 2019, 49(9).
2. Weber S. et al. Analytical Chemistry Insights, 2018, 13.
3. USP-NF Mineral Oil Monograph, 2024.
4. ASTM D2269-10, ASTM International, 2020.