Automated Solid Phase Extraction of 14 Explosives in Tap Water Based on U.S. EPA Method 8330 Using Hydrophilic Reversed-Phase Cartridge Followed by HPLC with UV Detection

Importance of the Topic

The release of nitroaromatic and nitramine explosives into soil and water from military activities poses significant environmental and health hazards due to their toxicity, mutagenicity, and persistence.

Study Objectives and Overview

This work presents an automated solid-phase extraction (SPE) method combined with HPLC-UV detection to quantify fourteen explosive compounds in tap water according to U.S. EPA Method 8330. The goal was to streamline sample preparation, achieve trace-level sensitivity, and assess method performance.

Methodology and Instrumentation

The sample preparation and analysis workflow consisted of automated off‐line SPE followed by reversed‐phase HPLC:

• SPE Sorbent: SolEx SPE HRPHS polymeric cartridge (6 mL, 500 mg)
• Conditioning: 5 mL methanol, then 10 mL water; dry under nitrogen for 5 min
• Loading: 100 mL fortified tap water at 10 mL/min
• Washing: 5 mL water to remove hydrophilic interferences
• Elution: 5 mL acetonitrile

HPLC separation was performed on an Acclaim Explosives E2 column (3 µm, 3.0 × 250 mm) using 48/52 v/v methanol/water at 0.3 mL/min, 25 °C, with 5 µL injection and UV detection at 254 nm.

Instrumentation Used

• Dionex AutoTrace 280 automated large-volume SPE system
• Thermo Scientific Dionex UltiMate 3000 HPLC system with DGP 3600M pump, SRD 3600 degasser, TCC-3000 column compartment, WPS-3000 autosampler, and DAD-3000 detector
• Thermo Scientific Acclaim Explosives E2 analytical column

Main Results and Discussion

Chromatographic separation of all fourteen explosives—including HMX, RDX, TNT, Tetryl, nitrotoluenes, and dinitrotoluenes—was achieved within a 50-minute run. Coelution issues occurred only between RDX and 1,3,5-trinitrobenzene, and between TNT and Tetryl. Recoveries for spiked tap water samples ranged from 95 % (RDX) to 120 % (2-nitrotoluene) with relative standard deviations below 6 %, confirming method robustness and minimal matrix interference.

Benefits and Practical Applications

• Automated SPE streamlines sample handling and reduces manual labor.
• High recoveries and precision at low-ppb levels support regulatory compliance.
• The workflow is suitable for environmental monitoring of explosive residues in water matrices.

Future Trends and Opportunities

Integration of online SPE with tandem mass spectrometry could enhance sensitivity and specificity. Miniaturized and field-deployable systems may enable on-site screening. Expansion of sorbent chemistries could broaden analyte scope to include related emerging contaminants.

Conclusion

The automated SPE-HPLC-UV method based on EPA Method 8330 delivers reliable, high-throughput quantification of fourteen explosive compounds in tap water with excellent recoveries and reproducibility, simplifying environmental analysis workflows.