Ionization of airborne molecules:
Exhaled breath, headspace, and more.
real time analysis of metabolites in gas phase
High sensitivity instrumentation is able to detect Volatile Organic Compouns (VOCs) with concentrations as low as 1 ppt (one molecule of the analyte for every 1012 molecules of air). Ideally, with such a high sensitivity, one would expect very low volatility species (with vapor pressures as low as 10-12 Bar) to have become detectable.
However, only VOCs with substantial vapor pressures are routinely detected in real time. To a great extent, this is caused by poor handling of low volatility species.
SUPER SESI has been developed to fill this gap.
- SUPER SESI is an ionizer optimized for the analysis of low volatility molecules in the gas phase
- It builds upon the high ionization efficiency of Sencondary Electro-Spray Ionization (SESI)
- It is compatible with high performance commercial mass spectrometers*
- Due to its focus on low volatility species, SUPER SESI detects larger molecules, more relevant from a biological standpoint
*SUPER SESI has been optimized Thermo and Sciex Instruments. More information about SUPER SESI for Sciex here. We are constantly working to expand the compatibility of SUPER SESI. If you have access to other instruments and would like to integrate SUPER SESI, please let us know and we will inform how we can accelerate these developments.
Detecting low volatility species
Low volatility species are present at very low concentrations. Detecting them requires very good Limits of Detection.
SUPER SESI accomplishes this by:
- Improving the ionization efficiency: generating more ions for a given amount of sample.
- Harnessing the power of the best mass spectrometers in the market: best ionization + best ion analysis = best results.
- Improving background levels: low volatility species tend to condensate in the ionizer. Handling them properly is essential.
- Cleaning: ideally, the system should not get contaminated, but the truth is that contamination happens. SUPER SESI automates some cleaning procedures, and facilitates deep cleaning.
- Maintaining a stable electrospray without fragmentation: this greatly simplifies the structure of the resulting data.
- superior Ionization efficiency -
- SESI is inherently very efficient. By operating at atmospheric pressure, the ions and the vapors of interest are very concentrated. Also, coulombic repulsion and dilution of new formed ions is much lower than at reduced pressures.
- SUPER SESI has been carefully designed to optimize the ionization efficiency. For a given sample, a better ionization efficiency means more ions being transferred to the mass spectrometer.
> Click on improving ionization efficiency to learn more.
- tailored for the best mass spectrometers in the market -
- The performances of High Resolution Mass Spectrometry (HRMS) are orders of magnitude better than conventional mass spectrometers
- SUPER SESI harness the power of the best mass spectrometers to combine the best ionization efficiency and the best ion sensitivity and separation capacity of the mass spectrometer
As the sensitivity of an analyzer is improved, the number of different species that can be detected in a sample becomes greater, and differentiating them becomes a bigger challenge. For this reason, differentiating all species that can be detected with SUPER SESI normally requires HRMS.
- Improved background levels -
For an ionized molecule to be detected, the signal produced by it has to stand out above the background signals of the instrument, which are produced by ions with the same mass as the molecule we are trying to detect.
Low volatility species tend to condensate onto walls and other surfaces. Improving the background levels is crucial to detect low volatility species.
SUPER SESI is designed to minimize background signals.
> Click on improving background levels to learn more.
- Cleaning -
Avoiding contamination maintains a low background level. Cleaning eliminates contamination if it happens.
SUPER SESI is designed facilitate cleaning:
- A flow of clean gas is automatically sweeping the ionizer and the sample line when no sample is introduced
- A built-in steam generator enables steam-desorption cleaning without stopping the electrospray
- If required, the chamber can be easily opened for cleaning
> Click on improving background levels to learn more.
- Simplified spectral analysis with no fragmentation -
SESI produces very little or undetectable fragmentation. This is because no high energies are required to generate the ions with the nano-electrospray.
Ion fragmentation would be harmful for two main reasons:
- Interpreting the spectra would be very difficult. Without a chromatographyc step, knowing whether an ion is representative of a legit molecule or a fragment of a larger molecule becomes very difficult, if not impossible.
- A spectrum with the original molecules plus a myriad of fragments would be extremely complex, and differentiating all ions and fragments would require a prohibitive resolving power.
SUPER SESI is designed to maintain a stable electrospray and prevent the formation of energetic discharges:
- The voltage drops if a corona discharge is formed
- The narrow capillaries used in SUPER SESI require lower voltages that are not sufficient to initiate a discharge
> Click on ionization mechanism to learn more.
Real time analysis
The sample gas is directly introduced in SUPER SESI.
- No sample preparation, & no chromatographic separation
- This results in an almost immediate response. The time of residence of the gas in the ionizer is ≈1 second*
The time resolution of SUPER SESI is approximately 1 second.
This is much faster than most metabolic processes.
*Due to memory effects, the time of residence of low volatility species might be longer. Signals may return to background levels more slowly.
Reliable, High quality data
Confounding variables lead to spurious correlations.
They appear as bio-markers, but they are not. Ibuprofen is a usual suspect. Higher levels of ibuprofen correlate with disease, but this doesn't mean that it is a reliable biomarker. People in pain take more pain-killers.
Other less obvious confounding variables might be lurking in other steps of a study
SUPER SESI is designed to analyze the sample right as it is produced.
- With no intermediate steps, the data only reflects the sample and the instrument background
- Between samples, instrument background is constantly measured
> Click on data quality to learn more.
Online Breath analysis
In the spectra below, orange is breath & purple is background.
In the spectra below, red is wine & green is background.