Analysis of Bisphenol A and Nonylphenol using LC-MS

Importance of the Topic

Endocrine disrupting chemicals such as Bisphenol A (BPA) and Nonylphenol (NP) are widespread environmental contaminants originating from plastics and industrial processes. Even at trace concentrations, these phenolic compounds can interfere with hormone function in humans and wildlife. Sensitive analytical strategies are essential for monitoring their occurrence, assessing exposure risks, and guiding remediation efforts.

Study Objectives and Overview

This application data sheet presents a direct liquid chromatography–mass spectrometry (LC-MS) method for quantifying BPA and NP without chemical derivatization. The aim is to demonstrate the method’s performance in terms of sensitivity, linearity, and reproducibility over environmentally relevant concentration ranges.

Methodology and Experimental Approach

Analysis was performed in both scan and selected ion monitoring (SIM) modes. Scan chromatography provided qualitative confirmation of target analytes via mass spectra. SIM mode enabled enhanced sensitivity and quantitation. Calibration standards ranged from 0.1 to 50 ppb, and five replicate injections were used to evaluate precision. Key performance metrics included linear correlation coefficients and coefficient of variation (CV) values for area counts.

Instrumentation Used

• LC Column: Shimadzu VP-ODS (2.0 mm I.D. × 150 mm)
• Mobile Phases: A = water, B = methanol; gradient 20 % B to 90 % B over 5–22 min
• Flow Rate: 0.2 mL/min; Injection Volume: 500 µL; Column Temperature: 40 °C
• Ionization: APCI in negative mode; probe voltage –3.0 kV; probe temp 400 °C; CDL temp 200 °C; block heater 200 °C; nebulizing gas 2.5 L/min
• Mass Analysis: m/z 50–500 scan (1 sec/scan); SIM at m/z 227.00 (BPA) and 219.00 (NP); Q-array voltages per vendor settings

Main Results and Discussion

Mass chromatograms in scan mode confirmed retention of BPA (~15 min) and NP (~19 min). High-resolution mass spectra showed characteristic ions at m/z 227.05 and 219.05, consistent with deprotonated molecular species. SIM chromatograms at trace levels (0.1 ppb BPA, 1 ppb NP) yielded sharp, well-resolved peaks.

Calibration curves were linear across tested ranges:

• BPA: 0.1–5 ppb, r² = 0.99983
• NP: 1–40 ppb, r² = 0.99903

Precision over five replicates exhibited CVs between 2 % and 7 % for standards spanning low to high concentrations. An antioxidant impurity (BHT) was observed near 20 min in the NP chromatogram but did not interfere with quantitation.

Benefits and Practical Applications

This direct LC-MS approach eliminates time-consuming derivatization prior to analysis, simplifying workflow and reducing potential artifacts. The method achieves sub-ppb detection limits with excellent reproducibility, making it well suited for environmental monitoring, water quality testing, food safety analysis, and regulatory compliance.

Future Trends and Opportunities

Advances in high-resolution mass spectrometry and ultrahigh-performance liquid chromatography (UHPLC) will further enhance sensitivity and throughput. Integration with automated sampling, online solid-phase extraction, and miniaturized systems could enable real-time field monitoring of endocrine disruptors. Coupling this method with non-targeted screening will expand capabilities for comprehensive contaminant profiling.

Conclusion

The described LC-MS method provides a robust, efficient, and sensitive protocol for quantifying BPA and NP at trace levels without derivatization. Its high linearity and precision support reliable environmental and food safety assessments, offering a valuable tool for analytical chemists and quality control laboratories.