Measurement of Impurities in Ethanol Using UV-Vis Spectrophotometer

Importance of the Topic

Ethanol has become a critical disinfectant amid growing public health challenges. Ensuring its quality and purity according to international pharmacopoeial standards is essential to safeguard efficacy and patient safety. Ultraviolet-visible spectrophotometry offers a rapid, non-destructive approach to detect trace impurities in ethanol by monitoring characteristic absorbance in the UV range.

Objectives and Study Overview

This application note demonstrates the use of a UV-Vis spectrophotometer to measure "Other impurities (absorbance)" in anhydrous ethanol as defined by the Japanese, European and United States Pharmacopeias. The study aims to automate the pass/fail assessment of pharmacopoeial absorbance limits using dedicated software, thereby streamlining quality control workflows.

Methodology and Instrumentation

The absorption spectrum of ethanol samples was acquired over 235–340 nm using a 5 cm path-length cell and ultrapure water as blank. Acceptance criteria are:

• Absorbance ≤ 0.40 at 240 nm
• Absorbance ≤ 0.30 between 250 and 260 nm
• Absorbance ≤ 0.10 between 270 and 340 nm

The Shimadzu UV-1900i UV-Vis spectrophotometer recorded spectra under medium scan speed, 0.5 nm sampling pitch and 1 nm slit width. Automated evaluation employed LabSolutions UV-Vis software with point-pick and maximum-value algorithms to read single-point and range-maximum absorbance values.

Key Results and Discussion

Spectrum analysis of anhydrous ethanol showed smooth, descending absorbance curves without notable peaks or shoulders. All measured values fell within pharmacopoeial limits. Simulated failing samples clearly displayed red-highlighted exceedances in the evaluation table, confirming the software’s ability to flag non-compliance instantly.

Benefits and Practical Applications

The integration of spectral evaluation functions significantly reduces manual data review time and minimizes human error. Laboratories can perform rapid, reproducible pass/fail judgments for ethanol purity, enhancing throughput in pharmaceutical QC, disinfection product manufacturing and regulatory compliance testing.

Future Trends and Opportunities

Prospective developments include online real-time monitoring systems, integration with laboratory information management systems (LIMS), and incorporation of advanced chemometric or machine-learning tools for multifaceted spectral interpretation. These innovations could further advance impurity profiling and bring predictive analytics into routine QC.

Conclusion

This study confirms that UV-Vis spectrophotometry coupled with automated evaluation software provides an efficient, reliable method to assess ethanol impurity levels according to major pharmacopeial standards. The approach delivers rapid results, reduces workload and supports consistent quality assurance.