Electrochemical Modulation of the Sample Stream in Mass Spectrometry

• Published in: Analytical chemistry (Washington) 1996-01, Vol.68 (2), p.243-249
• Main Authors: Ren, Hong, Szpylka, John, Anderson, Larry B
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Carbon dioxide; Chemical reactions; Chemistry; Electrochemistry; Electrolysis; Exact sciences and technology; Mass spectrometry; Sampling methods; Scientific imaging; Spectrometric and optical methods
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac951005v

Sampling methods are described, suitable for mass spectrometric identification of volatile species in aqueous solutions. Submillimolar concentrations of oxygen and carbon dioxide were sampled during electrolysis and identified within a second of the time they were electrolyzed. The electrolysis process modulates solution concentrations near a 100 μm thick silicone rubber membrane sampling device, which transmits the information to the mass spectral source as a periodic variation in the partial pressure of the analyte. Consequently, ion currents vary at the same modulation frequency. Correlation analysis quantitates a phase shift between the mass spectral response and the electrochemical excitation as a function of modulation frequency. The time required for various molecules to diffuse through the membrane is derived from these correlation spectra. The silicone membrane thus becomes an ultrashort chromatographic column, interfacing a condensed phase sample stream with a sensitive and discriminating mass spectrometric detector.