Novel Ionisation Technique Enhances Sensitivity and Reduces Matrix Effects in the UPLC-MS/MS Analysis of Crop Protection Chemicals and Their Metabolites

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Dr Michael Jones; Dr Peter Hancock
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Regulatory Authorities expect manufacturers of crop protection products to present evidence demonstrating a clear understanding of any risks associated with the use of their products.  This includes how long those products remain active, and the potential of both the products and their chemical degradants or biological metabolites for exerting negative effects on human health and the environment.  Trace level analysis in complex matrices can generate the information required to support both pre- and post- production registration.

Among the challenges in trace detection is the very low concentrations at which the target compounds may be present in the samples.  Tandem Quadrupole mass spectrometry provides high sensitivity and specificity and is an effective technique for determining trace levels of pesticides in complex matrices such as field crops and foods.   Developers of Tandem Quadrupole Mass spectrometers are continually striving towards higher instrument sensitivities, however this can highlight or exacerbate other issues such as solvent quality, co-extractive interferences etc.

In this poster presentation we describe the analysis of a range of crop protection chemicals and their metabolites in complex matrices utilising a novel ionisation interface, Unispray.  Unispray ionisation converts the LC stream into a nebulised spray directed at a stainless steel target held high at voltage. Interaction with the target creates a fine spray of charged droplets directed into the mass spectrometer.  The Unispray source offers enhanced sensitivity compared to traditional electrospray ionisation.  Pesticides were subsequently detected at fg / µL levels in a range of field crops and food matrices following UPLC-MS/MS analysis.    We also demonstrate how modulation of ion transmission parameters can be used to enhance selectivity of the analyte of interest compared to matrix interferences, lowering matrix effects and increasing confidence in obtained results at trace levels.

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