It might surprise you but already since the Middle Ages, people are interested in the smell of a person’s breath. In those days it must have been quite a challenge to investigate but as early as those days diseases like diabetes (associated with a sweet, acetone odor) and liver failure ( a fish-like smell) were diagnosed upon one’s breath. I will not discuss the treatments during those years; let’s say that much has improved since the Middle Ages. For example, nowadays, we use Ion Mobility Spectrometers (IMS) to measure Volatile Organic Compound (VOC).
At the beginning of the 21st century, research studies show that dogs are able to detect cancer by smell. The dogs are trained to detect different kinds of cancer in exhaled breath of human patients, as they can smell with a sensitivity of parts per trillion (ppt). To give an example: the scent of one cc of blood, diluted in 20 Olympic sized swimming pools can still be detected by the dog.
It was concluded that dogs are probably discriminating between breath samples based on a specific breath odor but it is still unknown what odor or mix of compounds dogs detect. The detection of cancer by trained dogs seems to be obvious when you think about it, but it requires a lot of training of the dogs and it is still unknown why not all cases of cancer are detected.
Volatile Organic Compound (VOC)
This is the reason that researchers have started to develop analyzers that can do the dog’s job. In the last few years it was discovered that Volatile Organic Compounds (VOC) can be distinctive biomarkers in the diagnosis of human diseases. Volatility is the tendency of a substance to evaporate, therefore Volatile Organic Compounds are organic compounds that will easily evaporate or sublimate at room temperature.
The exhaled human breath contains a few thousand volatile organic compounds and the composition of the VOCs is used in breath biopsy to serve as a biomarker to test for diseases such as lung cancer.
An increasingly popular analytical technique to measure VOC’s is Ion Mobility Spectrometry (IMS). This technique is ideal for analysis in medical applications since the analysis is fast, not affected by humidity, highly sensitive, and operates at ambient pressures. This makes the technique very suitable for portable or Point of Care application.
Ion Mobility Spectrometry (IMS)
The Ion Mobility Spectrometer operating principle is based on the drift, or time-of-flight, of ions that are formed in the reactant section. The ions travel, supported by an electric field, through the drift tube where they encounter a drift gas (N2 or Air). The shape and the charge number of the ion will make it easier or harder to flow through the drift gas which will cause a separation of the ions in the sample and after detection give an IMS-spectrum as shown in Figure 1.
Figure 1 : Ion Mobility Spectrometer with spectrum
Mass Flow Controllers
To deliver the gases to the drift tube, Bronkhorst has the knowledge and experience to supply the right products. Our products address the specifications that are important for controlling the gases in Ion Mobility Spectrometry such as:
- small instrument size
- fast response
- good reliability
- low power and
- low cost of ownership. Our MEMS (Micro Electro Mechanical Systems) based instruments, such as the IQ+FLOW thermal flow meters, are very suitable for Ion Mobility Spectrometry.
IQ+FLOW thermal flow meter
- Are you interested to read more about mass spectrometry (MS) and how mass flow controllers and evaporation is used for Electrospray Ion source, check our blog ‘A closer Ion them’.
- Check our success story using IQ+ gas flow meters and pressure controllers for a gas chromatography application.
- If you have questions or ideas on Ion Mobility Spectrometry other analytical applications that involve controlling of gas or liquid, feel free to contact us.