Sample Profiling of Pesticide Formulations Using UV and MS Detection for Component Identification

Significance of the Topic

A comprehensive profile of pesticide formulations is essential for ensuring consistent product quality, regulatory compliance, and environmental safety. Combining ultraviolet (UV) detection with mass spectrometric (MS) data increases sensitivity and selectivity, enabling the identification of active ingredients, isomeric forms, impurities, and formulation additives in a single analytical run.

Objectives and Study Overview

This study demonstrates the use of a dual-detection approach—photodiode array (PDA) at 220 nm alongside a compact mass detector (Waters ACQUITY QDa)—to characterize a commercial propiconazole fungicide formulation. Goals include resolving chiral diastereomers, detecting low-level components, and illustrating how MS enhances confidence in compound identification.

Methodology and Instrumentation

Sample Preparation:

• Weighed 1 g of formulation and diluted with 9 mL of 50:50 acetonitrile/water.
• Sonicated for 10 minutes and filtered through a 0.2 µm PVDF membrane.
• Prepared standard propiconazole in the same solvent mixture.

Chromatographic Conditions:

• System: ACQUITY UPLC H-Class with BEH C18 column (2.1 × 150 mm, 1.7 µm) at 50 °C.
• Mobile phases: 10 mM ammonium formate in water (A) and acetonitrile (B).
• Gradient: from 70:30 (A:B) to 10:90 over 11 min, then re-equilibration; flow rate 0.60 mL/min; injection volume 3 µL.

Detection Parameters:

• PDA: 210–400 nm, sampling rate 20 Hz, monitoring at 220 nm.
• MS: ACQUITY QDa, ESI+ mode, capillary voltage 0.8 kV, source 150 °C, desolvation 500 °C, scan 100–1000 m/z, 5 Hz.
• Data processed with Empower 3 CDS Software.

Main Results and Discussion

UV chromatograms revealed two major peaks at 7.45 min and 7.54 min corresponding to propiconazole diastereomers and two minor peaks at 6.23 min and 6.43 min (1.2% and 0.8% area). The total ion chromatogram (TIC) from the QDa improved signal intensity for all components and disclosed additional low-level peaks between 0.8 and 3.0 min, consistent with a polymeric surfactant series (mass increments of +44 amu). Extracted ion chromatograms (XIC) at m/z 342 enhanced detection limits and reinforced compound assignments. Spectral comparison showed that peaks 1 and 2 share UV maxima and an isotopic chlorine pattern identical to propiconazole, confirming them as related diastereomeric impurities. Empower’s mass analysis window facilitated simultaneous review of UV, TIC, XIC, and spectral data for robust identification.

Benefits and Practical Applications

• Improved sensitivity and selectivity over UV detection alone, enabling detection of trace formulation components.
• Enhanced confidence in peak identity through combined UV and mass spectra.
• Efficient single-run profiling supports quality control, product development, and registration workflows.
• Cost-effective integration of MS detection into routine UPLC methods.

Future Trends and Potential Applications

Advances may include integration of high-resolution MS for accurate mass determination, automated multivariate data analysis for complex mixtures, and extension of the dual-detection approach to broader classes of agrochemicals and environmental samples. Portable mass detectors and real-time monitoring systems could further streamline field testing and regulatory compliance.

Conclusion

The combined use of PDA and ACQUITY QDa detection in UPLC provides a robust, sensitive, and selective platform for pesticide formulation profiling. MS data enhances detection limits, reveals components invisible to UV alone, and increases confidence in identifying active ingredients and related impurities in a single analytical workflow.

References

1. Ulrich EM, Morrison CN, Goldsmith MR, Foreman WT. Chiral Pesticides: Identification, Description and Environmental Implications. Rev Environ Contam Toxicol. 2012;217:1–74.
2. Joint FAO/IAEA Division. Quality Control of Pesticide Products. IAEA TECDOC-1612; 2009.
3. Toribo L, del Noza MJ, Bernal JL, Jimenez JJ, Alonso C. Chiral separation of some triazole pesticides by supercritical fluid chromatography. J Chrom A. 2004;1046:249–253.