Analysis of Explosives by UHPLC with Dual-Wavelength Detection

Significance of the Topic

The reliable identification and quantification of nitroaromatic and nitramine explosives are critical for environmental monitoring, forensic investigations, and homeland security. Sensitive UV detection methods facilitate trace‐level analysis of these compounds in soil, water, and other matrices, supporting regulatory compliance and public safety.

Objectives and Study Overview

This work compares two UV detection technologies for high‐performance liquid chromatography (HPLC) analysis of a 20‐component explosive standard: the Agilent 1290 Infinity II Diode Array Detector (DAD) and the Agilent 1290 Infinity II Variable Wavelength Detector (VWD) operating in dual‐wavelength mode (254 nm and 214 nm). Key performance metrics include resolution, sensitivity (limits of detection and quantification), and calibration linearity.

Methodology and Instrumentation

Chromatographic separation was achieved on an Agilent Poroshell 120 SB C18 column (3 × 150 mm, 2.7 µm) at 50 °C, with a water/methanol gradient at 0.5 mL/min. Dual‐wavelength detection enabled simultaneous monitoring at 254 nm for nitroaromatics and 214 nm for nitramines. Calibration used a standard mixture ranging from 0.625 to 10 ng/µL per analyte.

Used Instrumentation

• Agilent 1290 Infinity II High Speed Pump (G7120A)
• Agilent 1290 Infinity II Multisampler (G7167B)
• Agilent 1290 Infinity II Multicolumn Thermostat (G7116B)
• Agilent 1290 Infinity II Diode Array Detector (G7117B) with 10-mm Max-Light cell
• Agilent 1290 Infinity II Variable Wavelength Detector (G7114B) with 10-mm flow cell
• Agilent OpenLAB CDS ChemStation Edition for data analysis

Main Results and Discussion

Resolution and chromatographic profiles at 254 nm were essentially identical between DAD and VWD. Dual‐wavelength VWD allowed detection of nitropenta at 214 nm, which is invisible at 254 nm. The VWD achieved more than twice the sensitivity (lower LOD and LOQ) for most analytes except the first two peaks. Both detectors demonstrated excellent linearity across the calibration range, with correlation coefficients exceeding 0.9999 for the majority of compounds.

Benefits and Practical Applications

• Enhanced sensitivity enables trace‐level detection of explosives in environmental and forensic samples.
• Dual‐wavelength acquisition streamlines analysis of mixed nitroaromatic/nitramine standards without detector change‐over.
• High linearity supports robust quantification for regulatory and investigative purposes.
• Comparable resolution ensures reliable peak separation across 20 structurally diverse analytes.

Future Trends and Opportunities

Advances may include integration with tandem mass spectrometry for increased specificity, miniaturized detectors for field‐portable systems, faster gradients for high‐throughput screening, and enhanced software automation for method development and instrument‐to‐instrument transfer.

Conclusion

The Agilent 1290 Infinity II VWD in dual‐wavelength mode matches or surpasses the performance of the 1290 Infinity II DAD for nitroexplosive analysis, offering superior sensitivity and equivalent resolution and linearity. This approach delivers a versatile, robust solution for trace‐level explosive detection in environmental and forensic laboratories.

References

• US Environmental Protection Agency. Method 8330B, Nitroaromatics and Nitramines by HPLC. Revision 2, October 2006.
• Kinghorn R; Milner C; Zweigenbaum J. Analysis of Trace Residues of Explosive Materials by Time-of-Flight LC/MS. Agilent Technologies Application Note 5989-2449EN, 2005.
• Huesgen AG. Instrument-to-Instrument Method Transfer of the EPA Method 8330A/B for Nitroaromatics from an Agilent 1200 Series to 1290 Infinity. Agilent Technologies Application Note 5991-1194EN, 2012.
• Huesgen AG. Optimizing Separation of 20 Nitroaromatics Using a Phenyl-Hexyl Column with π-π Interaction and a C18 Column on the 1290 Infinity. Agilent Technologies Application Note 5991-3212EN, 2012.