Chip-based nanoelectrospray ionization with Fourier transform mass spectrometric detection to screen for local anesthetics intended to mask limb sore in walking horses.

We report a high-throughput chip-based nanoelectrospray ionization method coupled with Fourier transform mass spectrometry to screen for local anesthetics in samples collected by swabbing. These drugs have been used to mask pain on the limbs of walking horses after forbidden practices of soring or physical abuse. Optimized for lidocaine, the method afforded sub-ppm mass accuracy for nine local anesthetics included in the study. From doped cotton swabs, two third and all of the analytes were detected after adding 10 ng and 100 ng of each drug, respectively. Benzocaine and/or lidocaine were found on positive swab samples collected during walking horse competitions.