Analysis of DNPH-derivatized Aldehydes and Ketones using Agilent iQ Single Quadrupole LCMS

Importance of the Topic

Aldehydes and ketones serve as key indicators in environmental and industrial monitoring due to their toxicity and prevalence.
Derivatization with DNPH enhances chromophore formation but traditional UV detection can miss low-concentration or non-UV active compounds.
Implementing LC-MS provides deeper insight and increased sensitivity for trace analysis.

Study Objectives and Overview

This work aims to assess a single quadrupole LC-MS system for quantifying DNPH-derivatized carbonyls.
Key goals include lowering detection limits, identifying interferences, and enabling simultaneous identification and quantitation in air samples.

Methodology and Instrumentation

A standard mixture of DNPH-derivatized aldehydes and ketones was analyzed in triplicate across concentrations from 1 to 1000 ppb.
An extracted air filter sample was prepared with acetonitrile and injected on a C18 column under a quaternary gradient of water, acetonitrile, methanol, and 0.1% formic acid over 40 minutes.
Detection combined a diode array detector at 360 nm and electrospray LC-MS in negative mode, using both full scan and single ion monitoring to build an interference library.

Used Instrumentation

• Agilent iQ Single Quadrupole LC-MS with electrospray ionization
• Agilent Poroshell EC C18 column (3.0 × 150 mm, 1.9 μm)
• Diode Array Detector operated at 360 nm
• Quaternary pump delivering a 0.50 mL/min gradient

Main Results and Discussion

LC-MS achieved limits of detection down to 0.75 ppb and quantitation limits as low as 1.5 ppb, representing an order of magnitude improvement over UV (45–90 ppb).
Calibration curves showed excellent linearity (r2 = 0.999) across most analytes from 0.105 to 1500 ppb.
Spike recoveries ranged from 100.5% to 103.5%, confirming method accuracy.
Real sample analysis revealed compounds detectable only by LC-MS, underscoring enhanced selectivity and sensitivity.

Benefits and Practical Applications

• Significantly lower detection and quantitation limits facilitate trace-level monitoring.
• Combined library searching and quantitation accelerates identification of unknown interferences.
• Optional exclusion of DAD data reduces run times and improves throughput.

Future Trends and Potential Applications

Wider adoption of single quadrupole LC-MS in industrial hygiene and environmental laboratories can support portable screening tools.
Integration with high-resolution MS and automated sample preparation will expand multi-analyte profiling capabilities.
Method adaptation for field-deployable devices and real-time monitoring offers promising avenues for on-site air quality assessment.

Conclusion

The Agilent single quadrupole LC-MS method for DNPH-derivatized carbonyls delivers superior sensitivity and selectivity compared to conventional UV detection.
This approach enables reliable quantitation of trace aldehydes and ketones in complex air matrices, streamlining environmental and industrial monitoring workflows.

References

• Fu R, Cao M, Wang Y. Carbonyl-DNPH derivatives in indoor and in-car air by UHPLC and triple quadrupole LC/MS. Agilent Technologies (Shanghai) Co. Ltd; Agilent PN 5991-2125EN; 2023.
• US EPA. Determination of carbonyl compounds by high performance liquid chromatography (HPLC); Method 8315a. Environmental Protection Agency; Washington, DC; 1996.
• Schneider S. Analysis of DNPH-derivatized aldehydes and ketones using the Agilent 1220 Infinity LC system with diode array detector. Agilent Technologies Inc.; Agilent PN 5991-1545EN; 2023.