Analysis of Pharmaceuticals in Water Using Automated On-line SPE-LC-MS/MS

Significance of the Topic

Pharmaceutical residues in environmental waters represent an emerging concern due to their low concentration levels and potential ecological impacts. Sensitive and reliable analytical methodologies are essential for monitoring trace levels of these contaminants to ensure water quality and protect public health.

Objectives and Study Overview

This study demonstrates an automated on-line solid-phase extraction coupled with liquid chromatography–tandem mass spectrometry (on-line SPE-LC-MS/MS) method for simultaneous extraction and quantification of 13 widely used pharmaceuticals in water matrices. The approach utilizes EVOLUTE EXPRESS ABN cartridges to achieve high throughput, minimal sample handling, and reduced solvent consumption.

• Atenolol
• Ranitidine
• Ciprofloxacin
• Tolytriazole
• Azithromycin
• Erythromycin
• Prednisolone
• Carbamazepine
• Clarithromycin
• Fluoxetine
• Sertraline
• Atorvastatin
• Diclofenac

Methodology

The method involved injection of 1 mL spiked hard water samples onto a 30 mm × 2.1 mm on-line SPE cartridge under 2% aqueous acetonitrile for 4 minutes. Analytes were backflushed onto an ARC18 analytical column using a gradient of formic acid–water and acetonitrile at 0.4 mL/min. Total cycle time per run was 20 minutes. Quantification was performed using multiple reaction monitoring (MRM) transitions and external matrix-matched calibration curves over 0–150 ng/L. Limits of detection were estimated as four times the standard deviation of blank replicates (n=4).

Used Instrumentation

• CTC PAL RTC autosampler with 10-port loading and 6-port selection valves
• Shimadzu LC-20AD pumps for loading and elution
• Waters EVOLUTE EXPRESS ABN on-line SPE cartridges (30 × 2.1 mm)
• Thames RESTEK Raptor ARC18 column (100 × 2.1 mm, 2.7 µm)
• Waters Ultima Pt QQQ mass spectrometer
• MassLynx 4.0 software for data acquisition and processing

Main Results and Discussion

The method achieved recoveries between 75% and 108% for all analytes with repeatabilities (RSD, n=4) below 10% at 75 ng/L. Calibration curves demonstrated excellent linearity (r² > 0.99). Limits of detection ranged from <0.2 ng/L to 4.7 ng/L, enabling reliable trace-level quantification. Representative chromatograms confirmed clear separation and sensitive detection of target compounds.

Benefits and Practical Applications

This fully automated on-line SPE-LC-MS/MS workflow reduces manual sample preparation, solvent usage, and analysis time while maintaining high precision and sensitivity. It is well suited for routine monitoring of pharmaceuticals in environmental and drinking water laboratories, quality assurance, and regulatory compliance testing.

Future Trends and Opportunities

Emerging directions include expansion to broader contaminant panels, integration with high-resolution mass spectrometry for non-target screening, and development of miniaturized or field-deployable platforms for in situ water quality assessment. Advances in automation and data analytics will further enhance throughput and analytical robustness.

Conclusion

The presented on-line SPE-LC-MS/MS method offers a rapid, sensitive, and reproducible approach for trace analysis of pharmaceuticals in water. Its automated design, low solvent consumption, and reliable performance make it a valuable tool for environmental monitoring and laboratory workflows.