Inexpensive Ultrasonic Nebulization Coupled with Direct Current Corona Discharge Ionization Mass Spectrometry for Liquid Samples and Its Fundamental Investigations

Abstract

The concept of direct mass-spectrometric analysis, especially exploited by ambient desorption/ionization (ADI) methods provides numerous means to convenient sample analysis. While many simple and versatile ionization sources were devel-oped, a critical challenge lies in efficient sample introduction.To provide improved desorption performance for a most well-undrstood ionization source, APCI, a surface acoustic wave nebulization (SAWN) device was coupled as an efficient ioniza-tion process applied to both polar and nonpolar analytes. We have previously demonstrated surface acoustic wave nebuli-zation (SAWN) with APCI as a novel direct mass-spectrometric method. The SAWN-APCI significantly improved ion signals by up-to four-orders of magnitude obviating the need for modifications of mass spectrometers. This approach generated comparable ion signal to conventional ESI. Meanwhile, multiply charged ions of macro-molecules also enabled direct de-terminations of bio-analytes. Unfortunately, the high-cost SAWN devices limited the accessibility. Herein, we report on an analogous implementation of APCI with an ultrasonic nebulizer based on a commercial room humidifier which appears to demonstrate equivalent performance. We apply the method for direct screening of milk for antibiotic drugs and further in-vestigate the overall softness of the methods.