Illustration of the membrane chip showing from the side.

The membrane chip creates a direct coupling between the fermentation liquid and the high vacuum of a mass spectrometer (MS) without differential pumping.

The membrane chip creates a well-defined liquid-gas-vacuum interface and controls the transfer of volatile molecules from the fermentation liquid to the mass spectrometer. Inside the chip, a buried sampling volume equilibrates to the outer environment without letting liquid in. The pressure in the sampling volume is precisely controlled by our embedded gas handling system. Any makeup gas can be used to pressurize the sampling volume. Owing to the small size of the sampling volume and of the electrolyte layer, equilibration between the gas and the liquid is nearly instantaneous. During equilibration, all volatile species in the liquid fill the sampling volume based on Henry’s law. The sampling volume is connected to the MS by a capillary designed to limit the flow of molecules to exactly 1015 molecules/sec. No differential pumping stage is thus necessary. Because the flow is known and all the molecules are collected by the MS, direct conversion of mass spectrometry signal to mol/sec is possible. This makes the Spectro Inlets the only existing truly quantitative Liquid-gas-analysing system.