In the below table is a range of user requirement specifications for an application and in terms of FAIMS is this a difficult spec point to reach
|
User requirement Spec |
Easy Spec |
Difficult Spec |
|
Number of target chemicals |
1 target: The detection problem / compromise of selectivity and sensitivity are limited to the target chemical and the background. |
>1 target: The detection problem / compromise of selectivity and sensitivity are increase with each additional target chemical as well as background. |
|
Type of detection |
Qualitative: Is the chemical present |
Quantitation: Requires FAIMS calibration and effort required doubles with each additional target chemicals. |
|
Limit of detection |
High: Can be exploited to minimize background effects with the addition of dilutant flows such as makeup and splits. Risk of competitive Ionisation and background interferents reduced. Target chemical proton / electron affinity not as important |
Low: Limiting the use of makeup flows and splits. Risk of competitive Ionisation and background interferents increased Analyte proton / electron affinity important |
|
Proton affinity of target chemical |
High: Results in a high sensor sensitivity which can be exploited to minimize background effects with the addition of makeup flows and splits. Ionisation interferents from background reduced Would lower obtainable LOD |
Low: Sensor sensitivity decreases limiting the use of makeup flows and splits. Ionisation interferents from background increased Would raise obtainable LOD |
|
Calibration / detection range |
1-2orders of magnitude: Typical dynamic range for the LNS device, before saturation occurs |
<2 orders of magnitude: Large detection range would mean the co-development of > 1 method with different flow settings to cover the complete range and avoid saturation |
|
Accuracy |
>20%: |
>20%: |
|
Precision |
>10%: |
<10%: |
|
Simultaneous detection of target chemicals |
No: Detection problem can be treated as a 1 target chemical detection. |
Yes: The detection problem / compromise of selectivity and sensitivity are increase with each additional target chemical |
|
Volatility of target chemical |
High: Higher sample sensitivity Increase in LOD Decrease in memory effects Decrease in response time |
Low: lower sample sensitivity Reduced LOD Increase in memory effects Increase in response time |
|
Number of chemicals in background matrix |
Low: The detection problem / compromise of selectivity and sensitivity is decreases with less chemicals |
High: The detection problem / compromise of selectivity and sensitivity are increase with each additional chemical |
|
Proton affinity of chemicals in background matrix |
Low: Reduces the risk of competitive ionisation Increases obtainable LOD |
High: Increases the risk of competitive ionisation Decreases obtainable LOD |
|
Volatility of chemicals in background matrix |
Low: Reduces the risk of competitive ionisation and background interference of the target chemical |
High: Increases the risk of competitive ionisation and interference of the target chemical |
|
Response Time |
High: Can take more averages which increase the signal to noise ratio, lowering the obtainable LOD |
Low: Can take less averages which decreases the signal to noise ratio, increasing the obtainable LOD |
The following link is a useful tool in determining the likelihood of your application being successful. http://www.owlstonenanotech.com/faims/nickel-affinity-video
With this tool, you can enter the class of analyte you are interested in detecting (an example analyte and proton affinity are displayed) followed by up to two background components which may affect the ionisation of your analyte of interest. The dial then gives you a likelihood of your analyte being detected in the background mixture.
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