• Application Note

Improving the Analysis of Triazole Fungicides in Wheat Straw Samples using UniSpray Ionization with ACQUITY UPC2

Improving the Analysis of Triazole Fungicides in Wheat Straw Samples using UniSpray Ionization with ACQUITY UPC2

  • Jane Cooper
  • Marian Twohig
  • Waters Corporation

This is an Application Brief and does not contain a detailed Experimental section.

Abstract

When a crop protection active ingredient contains one or more stereogenic centers the enantioselective behavior must be studied as it is known that enantiomers can exhibit different bioactivities. Analytical methods that are, used to evaluate the influence of stereochemistry on degradation dynamics, environmental fate, and final residue levels, help to establish a more accurate risk assessment of crop protection products.

This technology brief, evaluates the potential of Waters UniSpray source coupled with the ACQUITY UPC2 System and Xevo TQ-XS Mass Spectrometer, versus ESI to improve peak response, repeatability and signal-to-noise (S/N), considering the analysis of triazole fungicides as a model.

Benefits

  • Improved response achieved using the UniSpray ionization source for the analysis of triazole fungicides.
  • Novel ionization source enables an increased range of ionization modes for atmospheric ionization MS techniques.

Introduction

When a crop protection active ingredient contains one or more stereogenic centers the enantioselective behavior must be studied as it is known that enantiomers can exhibit different bioactivities. Analytical methods that are, used to evaluate the influence of stereochemistry on degradation dynamics, environmental fate, and final residue levels, help to establish a more accurate risk assessment of crop protection products.

UniSpray is a novel ionization source with a simplified probe design that can be used for broader compound coverage. It offers greater ionization efficiency, comparable robustness and linearity to ESI, and spectra comparable with current ionization modes.

Having the ability to screen for a broader range of compounds, with increased ionization efficiency offers increased scope during method development. 

Figure 1. Xevo TQ-XS Mass Spectrometer with the UniSpray ionization source.

Results and Discussion

UniSpray has a grounded probe, and a stainless steel pin which is held at high voltage. The liquid stream is converted into a nebulized spray and directed at the stainless steel target (Figure 1), which creates a fine spray of charged droplets that is directed at the ion inlet orifice of the mass spectrometer. The resulting ions are sampled by the first vacuum stage of the mass spectrometer. Increased ionization efficiency, is achieved due to the enhanced desolvation and droplet evaporation.

The Xevo TQ-XS, is a high performance tandem quadrupole instrument, which offers the ultimate in reliability, reproducibility, specificity, and sensitivity, making it ideal for the determination of trace compounds in complex matrices such as field crops or soil.

UltraPerformance Convergence Chromatography (UPC2) is a separation technique that uses carbon dioxide as the primary mobile phase, with a co-solvent such as acetonitrile or methanol to give similar selectivity as normal phase LC. MRM transitions, and MS parameters were optimized for the compounds considered. ACQUITY UPC2 Separation parameters, using the Trefoil AMY1, 2.5 µm Column, were optimized in order to resolve the chiral triazole fungicides with a run time of 7 minutes (Figure 2). After a QuEChERS extraction, followed by a solid phase cleanup using Oasis MCX, sample extracts and standards were analyzed using the established MS and UPC2 conditions, using either UniSpray or ESI modes.

When using UniSpray coupled with ACQUITY UPC2 and Xevo TQ-XS for the analysis of triazole fungicides solvent standards, a 4.4-fold increase in peak area, 1.4-fold increase in S/N, and a 1.8-fold improvement in reproducibility were observed when compared against ESI results.

Figure 2. ACQUITY UPC2 MRM chromatograms showing the enantioseparation for triazole fungicides in a 10 ng/mL wheat straw matrix matched mixed standard, using a.) UniSpray, or b.) ESI.

As illustrated in Figure 2, for the analysis of a 10 ng/mL wheat straw matrix matched triazole fungicide mixed standard, the UniSpray source produced higher signal intensities (typically 2- to 5-fold) compared to ESI under exactly the same conditions.

Conclusion

Unispray, the novel ionization source, offers:

  • Increased range of ionization modes for atmospheric ionization MS techniques.
  • Increased ionization efficiency. 
  • Improved scope for method development. 
  • Improved response, repeatability and S/N using UniSpray versus ESI ionization sources for the analysis of traizole fungicides.

720005759, September 2016

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