Mass spectrometry allows to monitor in real time the gas composition of the atmosphere in contact with a biological sample: living cells (microalgae, bacteria, single cells ...) or purified enzymes. This technique is used to characterize the photosynthetic exchange of oxygen or carbon dioxide or hydrogen photo-production in microalgae or cyanobacteria. It allows monitoring the gases dissolved in a liquid suspension. Added stable isotopes of oxygen can be used to determine the unidirectional flow and discriminate between oxygen formed by photosynthesis from oxygen uptaken in the light.
Mass spectrometer Prima ∂B. Credit: E. Billon/CEA
Measurement of gas exchange by MIMS (Membrane Inlet Mass Spectrometry)
The gas dissolved in the liquid sample the measurement chamber (typical volume of about 2 mL) diffuse through a Teflon membrane, and then pass through a vacuum line to the ion source of the mass spectrometer . This technique allows to analyze in real time gas exchange on different types of biological material (microalgae, bacteria, enzymes, ...). The suspension can be illuminated in white light via an optical fiber, or a green light provided by 3 LEDs for homogenous illumination.
Plan of a MIMS spectrometric cell.
Mass spectrometers
The platform consists of a quadrupole analyzer Prismaplus (Pfeiffer Vacuum) and an analyzer Prima dB magnetic sector (Thermo Scientific).