Enantioseparation and detection of triazole fungicides in wheat grain and wheat straw using Convergence Chromatography and mass spectrometry

The safe use of crop protection products is of paramount importance to the agricultural chemicals manufacturing industry. Extensive studies and trials are carried out in support of product registration. These studies ensure that any risks associated with using the product are characterized and properly understood so that it can be safely applied to the field.

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

Liquid chromatography (LC) on chiral stationary phases (CSPs), such as polysaccharide stationary phases including amylose and cellulose, has been the most commonly used chiral separation technique. More recently, there has been an increasing adoption of using supercritical fluid chromatography (SFC) on CSPs for chiral separation. The properties of a supercritical fluid, its high diffusivity and low viscosity in particular, enable high efficiency chiral separations with shorter run times. For example, triazole fungicides, such as tebuconazole are a commonly used group of pesticides due to their potent activity against a broad spectrum of crop diseases. Using HPLC, the analysis times for the enantiomeric resolution of tebuconazole range from 13 to 45 min. Similar resolutions have been achieved for tebuconazole using SFC, but the analysis times were reduced to 10 min.

UltraPerformance Convergence Chromatography (UPC²) applies the performance advantages of UPLC to SFC, combining the use of supercritical CO₂ with sub-2-μm particle columns. UPC² is an orthogonal analytical technique to reversed-phase LC and can be used to solve complex separations challenges. The detection sensitivity and specificity offered by tandem MS/MS is advantageous for determining trace levels of pesticides in complex matrices like field crops or soil.

In this study, ACQUITY UPC² and tandem quadrupole mass spectrometry were used for the enantioanalysis of five triazole fungicides in wheat grain and/or wheat straw. Benefits of this approach include:

• Enantiomeric detection and quantitation of triazole fungicides at parts-per-trillion levels (ppt).
• Improved enantiomeric resolution and shorter analysis times using SFC compared with normal-phase HPLC chiral separations resulting in higher sample throughput.
• Reliable and reproducible measurement of the enantiomer ratios for use in enantioselective degradation studies.

For more details, download the Application Note in its entirety.