Hand-Held Nanoelectrospray Ionization with Frequency and Amplitude Tunability for Metabolomics of Saline Biosamples

Pulsed nanoelectrospray ionization (nanoESI) mass spectrometry has been proven to have several merits compared to its direct current (DC) counterparts, such as high sensitivity, high matrix tolerance, and low electrochemical interference. However, the reliance on external devices like signal generators and power amplifiers limits the technology's suitability for on-site use. Here, we developed a frequency-amplitude tunable hand-held pulsed high-voltage supply specifically designed for nanoESI. This portable detection system eliminates reliance on bulky ancillary equipment of conventional approaches, with a total mass of 185 g and an ergonomic hand-held configuration. Through systematic modulation of frequency (10-50 kHz) and voltage (1.5-6 kV), the device achieves optimal detection performance across diverse analytical standards and complex matrixes, including serum and cellular samples. The pulse-induced self-cleaning effect prevented nozzle clogging while maintaining functionality under high-salt conditions (855 mM NaCl). To demonstrate clinical applicability, we analyzed 198 serum specimens (100 from atherosclerotic cardiovascular disease patients (ASCVD) and 98 age-matched controls), identifying statistically significant dysregulation of multiple metabolites in the ASCVD cohort and achieving a diagnostic accuracy of 85%. Field deployment trials using portable mass spectrometers further validated the system's potential for rapid on-site diagnostics, establishing a new paradigm for point-of-care analytical technology.