u-CTE: Sampling technology for fast screening of toxic organic chemicals from products & raw materials
Micro-Chamber/Thermal Extractor options
The Micro-Chamber/Thermal Extractor is available in two versions:
- Six-chamber (44 mL capacity). Temperature range: ambient to 120ºC. Available with or without toggle valves. The toggle valve option allows gas flow to unused microchambers to be turned off, minimising gas consumption.
- Four-chamber (114 mL capacity) Temperature range: ambient to 250ºC.
Both versions of the μ-CTE comply with standard methods for emissions screening using micro-scale chambers e.g. draft ISO standard 12219-3. The higher temperature unit can also be used for analysis of semi-volatile emissions as described in draft ISO standard 16000-25. All chambers are constructed from inertcoated stainless steel and are compatible with reactive chemicals.
In-house quality control of product/material emissions
Correlation with conventional emission test chamber/cell data
It is possible to use the μ-CTE for standard 3-day emissions testing of homogeneous samples per standard reference methods. However, the primary purpose of Markes’ μ-CTE is to screen emissions of materials soon after production. Several independent comparative studies have shown that μ-CTE emissions data, obtained within a few minutes of sample preparation, correlate with those from longer-term small-chamber reference methods1–4. This means micro-chambers can be used to monitor chemical emissions as part of routine QC.
To support this, micro-chamber technology is now the subject of extensive method development for rapid emissions screening within key standards agencies5–8.
- T. Schripp, B. Nachtwey, J. Toelke, T. Salthammer, E. Uhde, M. Wensing and M. Bahadir (2007), Analytical and Bioanalytical Chemistry, 387(5), 1907–1919.
PARD Report: Correlation between the VDA 276 test and micro-chamber testing. Issued by WMG, University of Warwick, UK
M. Lore, E. Goelen, et al. (2010), HEMICPD Report, published by the Belgian Science Policy, Reference D/2010/1191/12
M. Kim (Kangwon National University, Korea) (2010), Presentation to ISO TC146 SC6 WG13 (Document # N0087)
ASTM D7706, Standard practice for micro-scale test chambers for rapid assessment of vapour-phase organic compounds (VOC) emitted by materials
ISO DIS 12219-3, Draft standard for screening car trim component emissions using micro-chambers
VDI 2083-17 (proposed ISO), Clean room technology – Compatibility with required clean lines class and surface clean lines
Screening VOC emissions from textile floor coverings (GUT carpet label)
Three modes of operation
Micro-Chamber/Thermal Extractor operation
When the μ-CTE unit has reached its set temperature, the individual micro-chambers containing correctly-positioned samples are placed into the unit and the lids are sealed. A controlled flow of air or inert gas is passed through all chambers simultaneously. After an equilibration period (typically 20–30 minutes), conditioned sorbent tubes or DNPH cartridges (formaldehyde analysis) are attached to each micro-chamber to begin the vapour sampling process. As the pure air or gas passes over the surface or around the bulk sample, vapours are swept from the material, out of the micro-chamber and onto the attached sorbent tube.
No pump required
Unique technology (UK patent application 0501928.6) maintains a constant flow of air or gas through each micro-chamber regardless of sampling tube impedance or whether a sampling tube is attached. No pump or mass flow controller is required. This makes the system fundamentally easy to use and ideal for routine operation by manufacturing industry.
Multi-tube format compatible
The Micro-Chamber/Thermal Extractor is compatible with the following:
- (S)VOC: Industry standard (89 mm long x 6.4 mm O.D.) sorbent tubes and 6 mm O.D. sorbent tubes.
- Formaldehyde: DNPH cartridges with a 4 mm ‘luer’ outlet.
Enhanced recovery of SVOCs
Efficient heating of all micro-chamber components (sample pans, chamber lids, air/gas supply tubing, etc.) prevents surface adsorption/condensation and sample-to-sample carryover. Internal surfaces coming into contact with sample vapours comprise inert coated stainless steel to minimise sink effects and accommodate thermally labile species. Micro-chambers are readily removed from the μ-CTE for easy cleaning.
Orientation of the air/gas inlet at right angles to the emitting sample surface maximises turbulence and eliminates areas of still or low-flow air/gas. Surface air velocities are roughly uniform across the sample surface and range from approximately 0.5 cm/s at 50 mL/min inlet gas flow to approximately 5 cm/s at 350 mL/min.
Micro-Chamber/Thermal Extractor units can be operated at ambient temperature or elevated temperatures. Each unit can be temperature controlled within 1ºC to a maximum of 120ºC or 250ºC for the six- and four-chamber units respectively.
In the case of testing emissions from building materials/products, moderate temperatures (i.e. 30–60ºC) are used to boost sensitivity and compensate for the relatively small sample size without affecting the correlation with data from conventional chambers/cells at ambient temperature. Typical equilibration times range from 20–30 minutes for VOCs, with subsequent vapour sampling (15–20 minutes) at 50 mL/min. These conditions allow four or six samples to be processed every hour.
Formaldehyde monitoring, e.g. per ISO 16000-3 or ASTM D5197, typically requires much larger volumes of vapour to be sampled (e.g. 250 mL/min for 2–4 hours) and may require humidification of the inlet gas supply. Throughput in this case is therefore four or six samples every 2–4 hours. The μ-CTE can also be operated at higher temperatures and flow rates for extended periods, for example when testing the emission of semi-volatile ‘fogging’ compounds from car trim materials or electronic components.
Offline analysis of trapped vapours
After vapour sampling, trapped organic vapours undergo analysis by thermal desorption (TD)–GC(MS), per standard methods ISO 16000-6, ISO/EN 16017-1, ASTM D6196, etc. Alternative analysers, for example systems combining TD with process MS or enose detectors, may also be applicable in some cases. The analytical process is carried out offline, allowing a fresh set of samples to be introduced to the μ-CTE while analysis of the previous set is on-going. Offline operation also allows chemical analysis by third party laboratories if preferred.
Key performance criteria
Blank profile and sink effects
Blank profiles from μ-CTE units show low/sub-ng quantities of individual VOCs, and low levels of total VOC (TVOC) background, even at elevated temperatures. This satisfies the most stringent requirements of relevant standard methods.
Markes Micro-Chamber/Thermal Extractor units are used extensively for testing VOC and SVOC emissions from construction products and car trim components.
A wide range of construction materials and car trim components have been successfully analysed using the μ-CTE.
They include adhesives, wood-based panels, laminate and resilient flooring materials, polyurethane foam, pvc, textiles, plasterboard, timber and carpeting. Semi-volatile emissions can also be evaluated in two steps as described in ISO 16000-25.
In addition to these mainstream applications, the Micro-Chamber/Thermal Extractor has also proved popular for testing emissions and hazardous chemicals in many consumer goods. Key examples include phthalates in toys and solvents in printed circuit boards.
The μ-CTE also provides an adaptable and robust general-purpose sample preparation device, allowing aroma profiling, emissions testing and VOC/SVOC content analysis for a wide range of samples and materials:
- Tobacco profiling
- Aroma profiling of fresh and prepared foods – cheese, potato crisps, etc.
- Aroma profiling of consumer goods (e.g. shampoo)
- Characterising the vapour profile of biological samples; animal waste products, plant material, GM foods, etc.
- Residual solvents in packaging materials
- Effectiveness of coatings to protect buildings and surfaces against chemical attack
While many of these Micro-Chamber/Thermal Extractor applications employ dry air/gas, there has been rising interest in the use of humidified air/gas. This allows the closer simulation of conditions used in some reference tests, and in real-life scenarios more generally.
It also improves the recoveries of some less volatile polar compounds.
The Humidifier Accessory meets this demand by supplying the Micro-Chamber/Thermal Extractor with air/gas at up to 50% relative humidity at room temperature, improving its value as a tool for emissions testing, routine quality assurance and advanced research.
The Humidifier Accessory includes:
- Humidifier assembly, comprising:
- Bottle humidifier.
- Rotameter (for control of flow rate).
- Single regulator pneumatics accessory (U-GAS03) to control air/gas supply pressure
- Hygrometer (for humidity measurement).
- Humidity measurement test chamber.