The RTube is perfect for collecting Exhaled Breath Condensate from humans. As a bonus, Volatile Organic Compounds (VOC’s) which are readily soluble in water can also be easily collected in the RTube as they will naturally dissolve into the condensate.
But what about VOC’s that are not readily soluble in water?
Dr. Martin et. al. performed several experiments in which he used the RTube, not as a condensate collector, but as a human interface to an SPME fiber. SPME (Solid Phase MicroExtraction) is a widely-used technique particularly well suited for analyzing compounds using GC/MS. In their paper, they used the RTube as kind of a Lego building block to put together a hybrid VOC collector:
“…A new procedure, exhaled breath vapor (EBV) collection, involving the active sampling and preconcentration of a breath sample with a SPME fiber fitted inside a modified commercial breath-collection device, the RTube, is described…It is demonstrated herein that this active SPME breath-sampling device provides advantages in the forms of faster sample collection and data analysis, apparatus portability and avoidance of power or cooling requirements, and performance for sample collection in a contaminated environment…”
Of course, we were paying attention, and realized that designing a custom adapter could help others perform the same type of testing with the RTube. Furthermore, we found that the RTube, even when fitted with the SPME adapter and SPME Field Sampler, could still collect breath condensate and be used normally by simply sliding a chilled cooling sleeve over the assembly shown in the photo. This opens the possibility of collecting a wide variety of compounds from a single patient sitting which would not be possible with any other method. Consider the example of collecting breath cytokines, performing pH analysis, measuring levels of 8-isoprostane, and monitoring a series of VOC’s all in the same 10-minute period while your study subject simply breathes. This could provide great flexibility to your protocol without adding time, cost or complexity.
- SPME (Solid Phase Microextraction) improves sampling of non-water-soluable VOC’s (Volatile Organic Compounds) compared to EBC (Exhaled Breath Condensate) alone
- Adapter allows RTube™ and Supelco® Field Sampler to be used together as an optimized instrument for collecting exhaled biomarkers derived from multiple full tidal breaths
- RTube provides an ideal human interface for the Supelco® SPME Field Sampler, and can subsequently or simultaneously be used to collect EBC from the same patient
- Unique venting design allows exhalate to pass through the RTube™ normally – with our without the Supeloco® mated and with or without a cooling sleeve
We do offer the adapter shown in the photo, although it is not shown in our price list, and invite you to contact us with any questions about this technique. To date only two groups have actually done this, and as we have not seen their publications yet, we can only offer our forward sensibilities along with the data in the paper referenced above.
To try this, you will need the following:
- Reusable SPME Adapter by Respiratory Research part number 3009 ($65). This is made of white Delrin and can be cleaned using most common processes.
- Reusable SPME Field SAMPLER by Supelco part number 504831 (also shown in photo above).
- SPME Fiber (various part numbers depending on application. Please consult Supelco)
We have added links to two useful documents below:
IMPORTANT FOOTNOTE: The RTube fitted with SPME will collect VOC’s from multiple full breaths containing air from all airway compartments. These biomarkers will therefore be non-specific to a particular breath or airway compartment. This is in contrast to the RTubeVOC which specifically collects only End Tidal Air from the deep lung compartment of a single breath. In a separate blog post we will show how to interface the RTubeVOC with a GC/MS using a septum inlet instead of the Universal Needle Interface shown in the product video. Please contact us with any questions about these techniques.