Hand-powered ionization methods for the mass spectrometric detection of small molecules

Abstract

Miniaturization of ambient ionization source is of great importance to the popularization of mass spectrometry. However, current ambient ionization sources are typically connected to several accessory equipment such as high voltage power supply, gas cylinders, and injection pumps. We report hand-powered ionization methods for mass spectrometric detection of small molecules based on a piezoelectric element that transforms hand mechanical energy into electrical energy. The piezoelectric element only weighs 39 g and lengths 9 cm, and no extra accessory equipment is needed. Paper spray, nanoelectrospray, and pin-to-funnel discharge powered by the piezoelectric elements were achieved, and several small molecule standards, including drugs, herbicides, etc., were detected and confirmed using these devices with a benchtop mass spectrometer. In addition, terbuthylazine (a herbicide) on the surface of a tomato was detected using the hand-powered pin-to-funnel discharge coupled with a miniature mass spectrometer, which indicates a potentially broader application of these methods in the on-site detection field. The methods described here are low-cost, user-friendly, miniatured, and versatile. Although efforts are still needed for the improvement of the performance, the piezoelectric element shows the alternative pathway of the miniaturization of ambient ionization.