Overview
The Universal Vaping Machine (UVM) generates aerosol under precisely controlled puff parameters — volume, duration, frequency, and flow profile — and exhausts it through a standard Luer-lock port. That exhaust port accepts a variety of capture apparatus, from disposable filter cartridges to multi-stage impinger trains, enabling researchers to collect the aerosol for downstream chemical analysis. This application note covers the most common capture methods, filter selection criteria, extraction protocols, and analytical workflows used with the UVM in emissions testing laboratories.
Whether the goal is regulatory compliance testing, product development screening, or academic toxicology research, the same general workflow applies: generate aerosol under a defined puff regimen, capture it quantitatively, extract the analytes of interest, and submit the extract to the appropriate instrument. The UVM automates the generation and capture steps, freeing the analyst to focus on chemistry.
Capture Methods
The choice of capture method depends on the analyte class, the required collection efficiency, and any regulatory or protocol constraints. Four primary approaches are used with the UVM.
1. PTFE Fiber Cartridge Filters (Gram)
Gram's disposable PTFE fiber cartridge filters are designed specifically for inline aerosol capture with the UVM. Each cartridge contains approximately 0.75 g of 4 μm diameter amorphous silica/PTFE fibers packed into a standard 10 mL syringe barrel. The cartridge threads directly onto the UVM's exhaust port via a Luer-lock connection, requiring no adapters or additional hardware.
Capture efficiency is approximately 96–97% by mass under standard puffing conditions. The pressure drop across a fresh cartridge is low — roughly 273 Pa at a flow rate of 70 mL over a 3-second puff — so the filter does not meaningfully alter the draw resistance experienced by the product under test. Importantly, PTFE fiber cartridges retain significantly higher condensate levels before saturation than Cambridge filter pads, making them well suited for extended collection runs of 50–100+ puffs without filter replacement.
Recovery is straightforward: after collection, the cartridge is placed in a centrifuge tube and rinsed with a small volume of solvent (typically 5–10 mL of methanol, acetone, or another solvent appropriate for the target analyte). The fibrous matrix releases trapped particulate matter readily, yielding high analyte recovery rates on a single rinse.
2. Cambridge Filter Pads (CFP)
Cambridge filter pads are the traditional industry-standard capture medium for smoking and vaping machine studies. The most common format is the 47 mm glass fiber disc (Whatman EPM 2000 or equivalent). CFPs are widely specified in regulatory test methods including ISO 20768, Health Canada T-115, and CORESTA Recommended Methods.
CFPs offer excellent particle retention efficiency for single-puff or short-run collections. However, their flat-disc geometry means they saturate more quickly than packed-fiber cartridges when exposed to high-condensate aerosols typical of modern vape products. For extended collection runs, multiple filter changes may be required. The UVM's disposable flow path supports inline CFP holders for labs that require this format.
3. Gas Impinger Tubes
For volatile and semi-volatile compounds that may pass through particulate filters, gas impinger tubes filled with liquid solvent can be placed downstream of the filter or used as the primary collection device. Common solvents include DNPH-acidified acetonitrile (for carbonyls), methanol, and dilute acid solutions. Multi-stage impinger trains allow simultaneous collection of multiple analyte classes in a single run.
4. Direct Exposure Systems
The UVM's exhaust port can also feed directly into biological exposure apparatus, including air–liquid interface (ALI) cell culture exposure chambers and rodent nose-cone inhalation systems. In these configurations the aerosol is not captured for chemical analysis but instead delivered to living cells or organisms for toxicological assessment. The UVM provides the same puff-to-puff consistency and parameter logging regardless of whether the downstream apparatus is a filter, an impinger, or an exposure chamber.
PTFE Filter vs. Cambridge Filter Pad
Both capture methods are effective, but they differ in several practical respects that influence method selection.
Gram's PTFE fiber cartridges capture more aerosol mass before reaching saturation, offer higher recovery rates on solvent rinse, and integrate seamlessly with the UVM's disposable Luer-lock flow path — no adapters, holders, or O-rings required. They are the preferred choice for routine emissions testing, extended multi-puff collections, and any protocol where maximum analyte recovery is important.
Cambridge filter pads remain the standard specified in many legacy regulatory methods. If a specific regulatory submission requires CFP-based collection (as some FDA PMTA guidance documents and CORESTA methods do), then CFPs should be used to ensure method compliance. In practice, many labs run both formats side by side during method development, then select the capture medium that best fits their submission requirements.
Typical Collection Protocol (Using PTFE Filter)
The following protocol outlines a standard gravimetric and chemical collection run using the PTFE fiber cartridge filter. Adjust solvent, puff count, and analytical endpoint as needed for your specific study.
- Weigh the filter. Record the pre-test mass of the PTFE cartridge on an analytical balance with 0.1 mg precision. Allow the cartridge to equilibrate in the weighing room for at least 30 minutes prior to weighing.
- Install the filter inline. Connect the cartridge to the UVM exhaust port via the Luer-lock fitting. Seat the product under test in the appropriate adapter on the inlet side.
- Program the puff regimen. Configure puff volume, duration, interval, and total puff count in the UVM software. A common starting point is the CORESTA Recommended Method No. 81 profile: 55 mL puff volume, 3-second duration, 30-second interval.
- Run the collection. Start the automated run. The UVM will execute the programmed regimen unattended, logging per-puff pressure drop and vapor density throughout.
- Weigh the filter after collection. Remove the cartridge and re-weigh on the same analytical balance. The mass difference equals total particulate matter (TPM) collected.
- Extract for chemical analysis. Place the cartridge in a 50 mL centrifuge tube. Add 5–10 mL of the appropriate solvent (acetone for gravimetric residue analysis, methanol for nicotine, DNPH-acetonitrile for carbonyls, or dilute nitric acid for metals). Vortex or sonicate to ensure complete contact with the fiber matrix.
- Centrifuge and concentrate. Centrifuge at 3000 rpm for 5 minutes to separate fibers from the extract. Transfer the supernatant to a clean vial. Evaporate or concentrate under nitrogen if the analyte requires it.
- Submit for instrumental analysis. Transfer the prepared extract to the appropriate analytical instrument (see below).
Common Analytical Targets
The following table summarizes the most frequently requested analyte classes, the recommended analytical technique, and key target compounds.
Heavy Metals
Technique: ICP-MS (inductively coupled plasma mass spectrometry) after acid digestion of the filter extract. Targets: lead (Pb), cadmium (Cd), chromium (Cr), nickel (Ni), and arsenic (As). Heavy metals testing is increasingly required by state cannabis regulators and is a component of FDA PMTA submissions for ENDS products. The UVM's inert, stainless-steel-free flow path minimizes background metal contamination.
Carbonyls
Technique: HPLC (high-performance liquid chromatography) after DNPH (2,4-dinitrophenylhydrazine) derivatization. Targets: formaldehyde, acetaldehyde, acrolein, crotonaldehyde, and other low-molecular-weight aldehydes and ketones. Carbonyl collection typically uses a DNPH-coated silica cartridge or DNPH solution in an impinger downstream of the particulate filter.
Volatile Organic Compounds (VOCs)
Technique: GC-MS (gas chromatography–mass spectrometry). Targets vary by study but commonly include benzene, toluene, 1,3-butadiene, and acrylonitrile. VOC collection may use sorbent tubes (Tenax, activated charcoal) or direct gas-phase sampling from the UVM exhaust.
Nicotine
Technique: LC-MS/MS (liquid chromatography tandem mass spectrometry) or GC-FID (gas chromatography with flame ionization detection). Nicotine is readily extracted from the PTFE cartridge with methanol. Deuterated nicotine (nicotine-d4) is commonly used as an internal standard.
Gravimetric (TPM)
Technique: Analytical balance (0.1 mg precision). No extraction or instrumental analysis required — simply weigh the filter before and after collection. TPM is the most basic emissions metric and is often reported alongside chemical-specific results. See also the companion application note on Aerosol Mass Output (Gravimetric).
Multi-Puff Collection for Trace Analysis
Many analytes of regulatory interest — heavy metals, carbonyls, certain VOCs — are present in vape emissions at very low concentrations (ng to low-μg per puff). To accumulate sufficient analyte mass for reliable quantitation above the instrument's limit of detection, it is common to collect over 50–100 or more puffs per sample.
The UVM is purpose-built for this workflow. Once programmed, it runs the entire collection unattended, maintaining consistent puff parameters from the first puff to the last. Multi-hour collection runs of 200+ puffs are routine. The PTFE fiber cartridge's high saturation capacity means a single filter can handle extended runs without replacement, simplifying sample preparation and reducing the risk of analyte loss during filter changes.
Data Integration
One of the UVM's key advantages over manual collection methods is its ability to log physical puff data alongside the chemical collection. Every run records per-puff pressure drop and per-puff vapor density (via the integrated IR sensor), producing a time-series dataset that is automatically correlated with the chemical sample.
This means researchers can answer questions that pure chemical analysis cannot: Did the aerosol output change over the course of the collection? Did pressure drop increase (indicating clogging)? Was the product producing consistent vapor on every puff, or did output decline as the reservoir emptied? These physical metrics add context to the chemical results and can explain unexpected variation between replicates.
All data exports in CSV format for easy import into LIMS, Excel, or statistical software.