Fast and sensitive method for detecting volatile species in liquids.

Area of Science:

• Electrochemistry
• Analytical Chemistry
• Materials Science

Background:

• Traditional methods for analyzing volatile species in liquids often face limitations in time-response or sensitivity.
• Existing techniques like differential electrochemical mass spectrometry (DEMS) offer fast kinetics, while membrane inlet mass spectrometry (MIMS) provides high sensitivity.
• There is a need for analytical tools that combine the advantages of both DEMS and MIMS for comprehensive in situ studies.

Purpose of the Study:

• To introduce and characterize a novel "sniffer-chip" apparatus for the direct extraction and analysis of volatile species from liquid samples.
• To demonstrate the capability of the sniffer-chip to perform quantitative in situ measurements of electrochemical reactions with high sensitivity and fast time-response.
• To benchmark the performance of the sniffer-chip by quantifying hydrogen and oxygen evolution and CO stripping on platinum electrodes.

Main Methods:

• Development of a "sniffer-chip" device featuring a perforated, hydrophobic membrane for ultrafast transfer of volatile species into a carrier gas stream.
• Direct transport of volatile species to a mass spectrometer via a narrow capillary, eliminating the need for differential pumping.
• In situ electrochemical experiments on polycrystalline platinum thin films, including hydrogen/oxygen evolution and CO stripping, coupled with mass spectrometry detection.

Main Results:

• The sniffer-chip system successfully quantified hydrogen and oxygen evolution on platinum electrodes at absolute faradaic currents as low as approximately 30 nA.
• A CO-stripping experiment demonstrated the system's ability to quantitatively measure less than 1% of a monolayer of surface-adsorbed CO.
• The measurements were performed in situ at a potential scan rate of 50 mV/s, showcasing the method's rapid response.

Conclusions:

• The sniffer-chip represents a significant advancement, merging the fast time-response of DEMS with the high sensitivity of MIMS.
• This novel apparatus enables precise, quantitative in situ analysis of electrochemical processes involving volatile species at very low current densities.
• The sniffer-chip technology holds great promise for advancing in situ electrochemical studies and reaction mechanism investigations.