Semiconductor chip technology is enhancing our lives in many ways. Emerged from semiconductor technology, MEMS chip technology is also present in devices around you in the form of sensors. Think of your smartphone that captures your voice and senses the smartphone position, orientation and movement by means of Micro Electro Mechanical Systems (MEMS). Adding those features is barely impacting the physical dimensions of a smartphone: it still fits in your hand and pocket.
This blog is about instrument miniaturization by MEMS chip technology and the benefits of miniaturized gas flow instruments for application in the field of gas chromatography. As a MEMS Product Manager at Bronkhorst High-Tech, I can see the benefits of miniaturization by MEMS technology in such applications.
IQ+ FLOW solution based on MEMS modules
Miniaturization by MEMS chip technology
Further miniaturization is achieved by combining MEMS modules in customer specific flow solutions.
In a laboratory environment, it is advantageous to work with desktop-sized equipment. Advantages of increasing functionalities in table top equipment are: reduced space requirements, enhanced ease of operation and often reduced cost of ownership.
Gas chromatography equipment is a good example of a concentration of functionalities on a small footprint. Many types of gas composition and vapour composition can be analysed with high accuracy and for very low concentration levels. Additionally, there is a certain degree of automation involved. This is all within arm’s reach of a laboratory analyst.
The goal of gas chromatography analysis is to identify and measure the concentration of gas components in an analytical gas sample. Within the gas chromatograph (see picture 3), there is often a need for gas flow or pressure control. The picture shows a gas flow controller for the carrier gas stream (red) and a pressure controller for the split flow stream (yellow).
The principle of gas chromatography involves a controlled carrier gas stream that passes an injector, column and detector. A sample gas is injected for a short period of time, creating a gas sample plug. The gas sample plug is separated into gas components across the column, which become visible as peaks during detection.
Picture 4 shows an example of a gas chromatography output.
Let’s zoom in on dynamic headspace sampling that is used in combination with gas chromatographys. Headspace sampling refers to the gas space in a chromatography vial containing a liquid sample. The liquid sample is a solvent, containing material to be analysed. E.g. volatile organic compounds in environmental samples, alcohols in blood, residual solvents in pharmaceutical products, plastics, flavor compounds in beverages and food, coffee, fragrances in perfumes and cosmetics.
This is explained in picture 5. Dynamic headspace sampling is performed by purging the gas space and the adsorbent. The adsorbent collects the sample gas. After transport, the adsorbent is purged again to release the sample gas into a gas chromatograph.
Where a gas flow controller comes into play is at purging the headspace with a constant Helium or Nitrogen flow for a pre-determined period of time at a specified temperature between 10 - 200 °C. The gas flow, containing the headspace sample gas, passes an adsorbent that collects the headspace sample gas.
The adsorbent is usually made of Tenax TA material. Now, the adsorbent is transported to the inlet of a gas chromatograph. While the adsorbent is heated between 20 - 350°C, a controlled Helium or Nitrogen gas flow passes the adsorbent to release the headspace sample gas into the inlet of the gas chromatograph. The gas chromatograph does its job to analyse the sample. Different signal peaks in time show the different components and their concentration.
IQ+FLOW gas flow meters and pressure controllers
For flow instruments, a number of specifications are important in headspace sampling and gas chromatography in general. The IQ+FLOW product line addresses these specifications with small instrument size, fast response, good repeatability, low power, low cost of ownership and the excellent support that you can expect from Bronkhorst.
For more information about gas chromatography in combination with IQ+FLOW flow and pressure meters and controller have a look at our application note ‘Gas Chromatography'.
The future of MEMS technology
Bronkhorst is committed to look ahead and find applications that can be enhanced with MEMS chip technology. Feel free to contact us for questions. We will keep you informed!
Read more about MEMS technology in our blog 'Miniaturization to the extreme: micro-coriolis mass flow sensor'