EVALUATION OF AN ACCURATE-MASS QUADRUPOLE TIME-OF-FLIGHT (Q-TOF) LC/MS SYSTEM FOR THE DETERMINATION OF TRACE-LEVEL NONYLPHENOL POLYETHOXYLATES IN EFFLUENTS FROM NONACTIVATED SLUDGE BIOFILM REACTORS

Importance of the Topic

Nonylphenol polyethoxylates (NPEOs) are non-ionic surfactants widely used in industrial processes. Their breakdown products can mimic hormones, posing risks to aquatic life. Accurate detection of trace NPEOs in wastewater is critical for environmental protection and regulatory compliance.

Objectives and Study Overview

This study evaluated an Agilent 6550 iFunnel Q-TOF LC/MS system coupled with a 1290 Infinity UHPLC for quantifying and confirming NPEOs at sub-µg/L levels in complex biofilm reactor effluents. The approach follows EU Commission Decision 2002/657/EC on identification points (IPs) for organic contaminants.

Methodology and Instrumentation

• Sample sources: Effluents from non-activated sludge biofilm reactors sampled in 2012 and 2013.
• Chemicals: NP10EO standard, LC-MS grade solvents, ammonium acetate additive.
• Sample preparation: Pressurized fluid extraction (PFE) with acetonitrile, cleanup by strong cation exchange (SCX), evaporation and dilution in acetonitrile.
• UHPLC conditions: Agilent 1290 Infinity binary system, ACE Excel 2 Phenyl column (150×2.1 mm, 2 µm), gradient elution from 40% to 97% acetonitrile, flow rate 0.44 mL/min.
• MS conditions: Agilent 6550 Q-TOF in positive ESI mode, m/z 100–1700, narrow quadrupole isolation (~1.3 m/z), lock masses at m/z 121 and 922.

Main Results and Discussion

• Ionization and adduct formation: Positive mode efficiently detected NP2EO–NP20EO; sodium adducts dominated low EO species, ammonium adducts prevailed from NP6EO upwards.
• Precision and sensitivity: Sub-µg/L quantitation with <5% RSD for individual ethoxymers, linearity excellent below 0.05 mg/L, minor saturation above.
• Mass accuracy and identification: Mass errors within 0.1–2.4 ppm; MS/MS fragmentation yielded characteristic ions, supporting IP requirements.
• Ion suppression: Complex matrix caused significant suppression; 5× and 10× dilutions increased signal by factors of 3.4 and 5.9, respectively, highlighting need for calibration strategies.

Benefits and Practical Applications of the Method

The high-resolution Q-TOF LC/MS approach offers reliable sub-µg/L detection of NPEO oligomers in challenging matrices, fulfilling regulatory identification criteria. Enhanced peak capacity from UHPLC and accurate mass measurements facilitate both quantitative monitoring and confirmatory analysis in environmental laboratories.

Future Trends and Potential Applications

Ongoing advancements may include optimized sample cleanup to reduce matrix effects, adoption of isotopically labeled internal standards, further miniaturization of UHPLC columns for high throughput, and application of HRMS for broader screening of environmental pollutants.

Conclusion

The Agilent 6550 Q-TOF LC/MS system with UHPLC demonstrated robust performance for trace-level NPEO analysis in wastewater. Its precision, sensitivity, mass accuracy, and confirmatory capabilities align with EU guidelines. Addressing matrix suppression through dilution or tailored calibration will enhance method reliability.

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