Frequently Asked Questions

What does FAIMS mean?

FAIMS stands for Field Asymmetric Ion Mobility Spectrometry, which is also sometimes referred to as Differential Mobility Spectrometry (DMS). Owlstone’s dime-sized chemical sensor uses FAIMS to detect a wide range of airborne chemical agents that may be present in extremely small quantities.

How does FAIMS work?

FAIMS utilises an oscillating electric field to separate different gaseous analyte ions based on their differing ion mobilities. Gaseous analytes for detection by Owlstone’s FAIMS technology undergo three processes; ionisation, filtration and detection. The gas under analysis is introduced into the ionisation region where its constituent molecules gain either a positive of negative charge. The analyte ions are then filtered and separated as they pass between pairs of plates in an asymmetric oscillating radio frequency electric field. The ions become separated depending on their differing mobilities in the RF field. A varying compensation voltage (CV) is applied to the RF waveform that allows ions with different mobilities to be steered towards a detector, generating spectra of ion current as a function of CV. Separate spectra are obtained for positive and negative ions. The separation of ions can be enhanced by increasing the amplitude of the applied RF waveform. For more information on Owlstone's FAIMS technology check out our technology page.

What kind of samples can I analyze WITH Lonestar?

Lonestar can be used to sample and monitor ambient air or can be used to analyze liquid and solid samples based on the volatile species they generate.

How do I analyze samples with Lonestar?

When monitoring ambient air, sampling can simply consist of directing a flow of air into Lonestar. When analysing liquid or solid samples a headspace sampling technique is used. The sample is placed in a sealed vessel and and a flow of clean carrier gas is passed through the headspace of the vessel. Volatile chemical species released from the solid or liquid sample are then transported by the carrier gas to the Lonestar unit for analysis. Sometimes it is necessary to carefully heat and/or stir samples in order to volatilize particular analytes. To simplify this process, Owlstone supply the ATLAS at line sampling module that allows precise temperature control and stirring of samples under a flow of carrier gas. For both ambient and headspace sampling it is sometimes necessary to introduce a split flow to dilute the sample flow with a dry or humidified carrier gas to prevent detector saturation. For more information on the theory of headspace sampling have a look at this user guide

What gases can I detect using Lonestar?

Lonestar is able to detect a wide range of analytes from a variety of backgrounds (a non-exhaustive list of examples is available here). We understand that every customer’s needs are different so we are always happy to discuss what you want from Lonestar, so feel free to contact us to discuss your specific analytical requirements.

How do I get a sample into the headspace?

Often simply putting a flow through the headspace of a sample provides enough analyzable material to generate FAIMS spectra. However, sometimes less volatile species require a sample to be heated and/or stirred to encourage volatilization. Owlstone have made this process easy by providing the ATLAS at line sampling module for Lonestar. ATLAS combines a temperature controlled sample container, glass coated sampling lines, and a magnetic stirrer. The ATLAS module ensures repeatable sampling with the minimum of fuss. For more information on the theory of headspace sampling have a look at this user guide

How reliable is headspace sampling?

When temperature and humidity are carefully maintained headspace sampling is a repeatable and reliable technique. Ideal, controlled sampling conditions are ensured when using Lonestar’s ATLAS sampling module (see above),

What is the limit of detection? How sensitive is FAIMS?

The exact limit of detection possible for particular analytes is dependent upon the physical characteristics of the species in question as well as the chemical background from which they need to be detected. Typically Lonestar can detect chemical species in the gas phase at concentrations in the part per trillion (ppt) - part per billion (ppb) range.

What ionization techniques do Owlstone use?

Ionization is a crucial step in the FAIMS analytical process as it has a significant effect on the response observed for different analytes. Depending upon the application, Owlstone either use a nickel-63 beta radiation source, corona discharge from a metal pin or a UV lamp for ionization. Nickel-63 and corona discharge both generate high energy electrons which indirectly ionize analyte molecules prior to detection, whereas a UV lamp produces photons which directly ionize analyte molecules.

What effect does humidity have on detection?

Humidity has a direct effect on the differential mobility of certain chemicals, by increasing or decreasing the collision cross section of the ion within the respective low/high field regions. The addition and subtraction of water molecules to and from analyte ions is referred to as clustering and de-clustering. Increased humidity increases the number of water molecules involved in a cluster formed in the ionisation region. When this cluster experiences the high field in between the electrodes, the water molecules are forced away from the cluster reducing its size. As the low field regime returns so do the water molecules to the cluster, thus increasing the ion’s size and giving the ion a larger differential mobility. Varying the humidity allows better separation between certain analytes.

What effect does temperature have on detection?

At higher temperatures, the collisional cross sections of gaseous ions in the sensor increases. So changing the temperature affects ion mobility by altering the number of collisions they undergo. Tuning the instrumental temperature can improve the separation of different chemical species in the FAIMS spectra of a sample.

What effect does pressure have on detection?

Raising the internal pressure of the Lonestar unit effectively increases the density of the gas in the FAIMS sensor chip. Higher density gas in the sensor results in the analyte ions undergoing more collisions before detection, resulting in increased separation.

How do I build a rule for Lonestar to detect a certain species?

Programming Lonestar to detect a specific contaminant is simple using Owlstone’s EasySpec Rule builder software. Using a FAIMS spectrum for the species in question users can quickly and easily define the location of peaks associated with that species. Lonestar can then quickly detect whether samples contain the species in question. To find out more take a look at the EasySpec Quickstart guide and EasySpec user manual.

How do I build an application?

Owlstone’s EasySpec Application builder lets users combine a set of rules for different compounds and adjust individual tolerances and set logic so that Lonestar can raise the alarm if it detects the presence or an increase in the presence of specific chemicals. To find out more take a look at the EasySpec Quickstart guide and EasySpec user manual.

How portable is Lonestar?

Due to the inherently small size of Owlstone’s FAIMS chip based chemical sensor, Lonestar is a lightweight and easily portable device that can be operated at the point of need.

What do I need to run Lonestar?

When using Lonestar for headspace sampling, a clean supply of carrier gas is required. Take a look at our recommended gas Line supply schematic to find out more.

How reliable is FAIMS/Lonestar?

Unlike other separation techniques such as column chromatography, FAIMS does not require any ‘active surfaces’ with which to separate different chemical species. For example, during a gas chromatography column’s lifetime its separation efficiency will change causing drift in its calibration, which will eventually result in it requiring replacement. The new column will have subtly different characteristics to the previous column potentially invalidating the existing calibrations. As the Owlstone FAIMS sensor at the heart of Lonestar does not rely on an active surface for separation it experiences very little calibration drift over time and does not require regular replacement. This saves time, money and hassle and reduces the requirement for regular maintenance by skilled personnel.

How selective is FAIMS?

Analysis of a known gaseous chemical species using FAIMS provides information rich 3D spectrum which can be used as a chemical ‘fingerprint’ to identify that chemical in real samples. The unique nature of each chemical’s FAIMS fingerprint ensures a high degree of instrument selectivity. In cases where there is some overlap in the chemical fingerprint of different species, the humidity, temperature and pressure can all be varied independently in order to increase the separation between the two (or more) responses.

What consumables are required for Lonestar?

Lonestar only requires replacement particulate filters and gas scrubbers to clean the air intake prior to headspace sampling. These are inexpensive and available from any laboratory supplies company.

Can Lonestar identify unknowns?

FAIMS alone can not be used to for instance identify the structure or molecular mass of an unknown chemical species. Chemical species visible in FAIMS spectra can be identified when using FAIMS in conjunction with a mass spectrometer.

Can Lonestar be trained for different chemicals?

Lonestar can be easily trained to recognise the unique FAIMS fingerprints of different chemical species. Lonestar users can use Owlstone’s Easyspec software suite to customise Lonestar’s detection criteria for different chemicals.

What are the main interferents?

Interference is rarely an issue when using Lonestar as the FAIMS technique it uses provides analysis at a range of different electric field strengths. This means that even if an interferent obscures the response from the desired analyte at one field strength, clear peak separation will probably be visible at a higher field. This combined with control over Lonestar’s temperature, humidity and pressure settings ensures that even similar chemical species can be easily distinguished.

Can you give examples of where Lonestar has been used before?

Lonestar has been used in a wide range of applications across the oil, food, drink, water and pharmaceutical sectors. These range from the validation of clean in place processes, to the detection of methanol and other chemical in crude oil. Visit our application pages for specific information, case studies and technical whitepapers.