Application of robotic sheath-flow probe electrospray ionization (sfPESI) to wet and dry agricultural products and insecticides.

Rapid analysis of food and agricultural products is important for evaluating quality and detecting contaminants, but the chemical complexity and physical heterogeneity of these matrices can make traditional workflows challenging and time-consuming. In our previous work, a touch sensor for sheath-flow probe electrospray ionization (sfPESI) was developed to enable automated analysis of liquid samples by detecting displacement currents upon surface contact. By coupling the sfPESI probe with a table-top 3-axis robot, consecutive point analyses of various complex samples were performed. However, its applicability was limited to liquid and wet solid matrices. In this work, a touch sensor equipped with a lock-in amplifier was developed to enable the automated analysis of both wet and dry samples. The system was demonstrated across a range of matrices, including vegetables, meats, insecticides, and insect repellents, substantially expanding the applicability of automated sfPESI for rapid, surface-resolved chemical analysis of complex food and agricultural products.