Will my application work?

Billy Boyle -

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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