Nerve agent markers screening after accumulation in garden cress (Lepidium sativum) used as a model plant object

In this research an accumulation of nerve agent markers in garden cress (Lepidium sativum) as a model plant object was studied using LC-QTOF hybrid system. For the determination of methylphosphonic acid and alkyl methylphosphonates, which are specific markers of sarin, soman, VR and VX, simple and sensitive approach was developed. Direct analysis of aqueous extracts on the reversed phase column with polar endcapping allowed to achieve satisfactory retention factor for methylphosphonic acid, which has high polarity and is usually very weakly retained on the ordinary reversed phase columns. Application of the QTOF mass spectrometer with high mass resolution led to the increase in the accuracy of the conducted measurements. The HPLC-HRMS technique developed exclusively for this study has been validated for linearity, limit of detection, limit of quantification, precision, accuracy and matrix effect prior to the analysis of plant extract samples. Hydroponic growth model was employed to examine accumulation of nerve agent markers in garden cress. It was found that after elimination of nerve agent markers from the plant growth medium, garden cress was able to store these substances for at least 5 weeks providing high retrospectivity of the analysis. Moreover, during the cress growth, no metabolization of alkyl methylphosphonates was observed. This allows not only to reveal the fact of nerve agents release into environment, but also to define its type after a long period of time.