A gas-to-liquid membrane interface for analysis of volatile organics in the gas phase by electrospray ionization mass spectrometry

摘要

The new probe produced the best response with acetonitrile + acetic acid (0.1percent v/v) as its carrier solvent system for the test compound aniline. Signal response increased 10-fold as a result of decreasing liquid flow rate from 5uL/min to 2uL/min. Below 2uL/min electrospray stability became a major issue, though this could be addressed by replacing the standard ESI source needle with a smaller-diameter custom needle. Heating the probe from room temperature to just below the solvent's boiling point resulted in a 5-fold signal increase with respect to room temperature. Exceeding the boiling point resulted in signal loss. Signal response increased by only 20percent with gas (sampling) flow rates from 240mL/min to 950 mL/min. Several unidentified ions were detected by directly sampling wine headspace from the bottle, demonstrating that the new probe can be used to quickly and easily obtain information about components in a complex gas mixture. Aniline was detected at 1ppb, but optimization of operating parameters based on more recent results should be able to improve this limit.