LGA technology



The LGA is built using the knowledge from our EC-MS analysis instrument, which is sold globally for R&D to renowned universities. We transformed this to the LGA, made for inline process monitoring. We made some design changes to ensure durability and robustness for harsh environments but kept the high precision and capabilities of the EC-MS technology.

The LGA is made with the production process in mind to offer production managers valuable insight and smart online data collection. An alarm system can be set up to avoid breakdowns of the production process and significantly reduce waste to offer both an economic gain and reduce a negative environmental impact.


Illustration of the working principle of the LGA system. (Bottom-left): Graph of a mass spectrum at a given time. (Bottom-right): A MS signal over time graph.

The LGA uses a coupled quadrupole mass spectrometer (QMS) to measure real-time concentrations of gasses and volatile species of fluids in, for instance, biogas fermentation or wastewater treatment tanks. The mass spectrometer works in a high vacuum to give precise measurements and therefore needs a membrane interface toward the liquid/gas environment. This is achieved in the LGA using our patented microchip design that controls the flow of molecules to the QMS. 

The mass spectrometer gives a signal value for each m/z ratio which, by knowing the flow of molecules, can be translated to a real-time concentration graph of, for instance, H2, CH4, NH3, N2, O2, H2S, N2O, NO2, EtOH, and light VFA’s (e.g., formic acid). Additionally, the mass spectrometer allows the user to add any additional compounds to be measured.


Picture of the LGA installed at a Biogas production facility in Southen Jutland, Denmark.

The LGA is designed with durability in mind to be employed in a harsh environment. The vulnerable parts, such as the mass spectrometer, are protected by an aluminium casing while keeping it relatively compact. This reduces the risk of damage from accidentally bumping into it. 

Furthermore, the detector itself is self-cleaning to avoid biofilm growth. This can be seen in action here. The wetted components are surface treated and made of chemically resistant materials such as stainless steel 316 and SiO2, meaning that they can withstand the harsh chemical environment of the fermentation liquid.

Interface Microchip

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.

Illustration of the membrane chip showing from the side.

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.