UNITY-xr Markes International
The most versatile and powerful thermal desorption unit.
UNITY-xr™ is an industry-leading analytical TD instrument for the simultaneous analysis of VOCs, SVOCs and thermally labile compounds collected onto sorbent tubes.
In contrast to other thermal desorption units, UNITY-xr quantitatively re-collects samples for re-analysis or storage, enhancing sample security. UNITY-xr also features an electrically cooled cold trap, dispensing with the expense and inconvenience of liquid cryogen.
UNITY-xr is perfect for any laboratory needing a versatile thermal desorber for all their TD applications.
Product benefits:
- With quantitative sample re-collection for repeat analysis, UNITY-xr offers simple method/data validation and overcomes the ‘one-shot’ limitation of other systems.
- Analyse the widest possible range of VOCs and SVOCs in a single run, including reactive and thermally labile species.
- Reduce running costs by avoiding the need for cryogen.
- Enhance productivity with the world’s most versatile thermal desorber – UNITY-xr offers unmatched analytical performance for the widest range of TD applications.
- Additional modules allow automation of multiple tubes, canisters and on-line samples – making UNITY-xr the perfect platform for expansion as the needs of your lab grow.
- You’re using a desorber that complies with key standards such as US EPA Method TO-17.
Features:
- Quantitative sample re-collection of all the split flows enables repeat analysis of critical samples and easy method validation.
- An inert, optimised flow path allows quantitative recovery of C2 to C44, including reactive and thermally labile species... from percent to sub-ppt concentrations.
- As well analysing 3½″ standard TD tubes, the UNITY-xr facilitates analysis of on-line, canister and bag samples through the modular addition of versatile accessories.
- Rapid operation of the electrically-cooled focusing trap reduces costs and ensures fast sample throughput.
- Method-compliance is aided by tube- and leak-testing, water management, and addition of internal standards.
- Samples are easily tracked with barcoded tubes and RFID TubeTAGs.
- Compatible with all major makes of GC and GC–MS.
| Desorption tubes |
| The automated desorber must be compatible with industry standard 3.5-inch (89 mm) x ¼-inch (6.4 mm) O.D. tubes for compliance with standard methods e.g. ASTM D 6196, EN ISO 16017, ISO 16000-6, EN 14662-4, US EPA Method TO-17, NIOSH 2549 and the UK MDHS series. |
| The automated desorber must be compatible with RFID tagged tubes |
| The tubes must be compatible with standard Swagelok-type ¼-inch long-term brass storage caps fitted with combined PTFE ferrules as specified in standard methods. |
| Sample tubes must be compatible with axial diffusive sampling as per standard methods (EN ISO 16017-2, EN 14662-4 and ASTM D 6196). |
| Tubes should be orientated horizontally throughout TD operation to prevent particles dropping into tube seals and to prevent samples shifting within the tube during direct desorption of materials. |
| Carrier gas must only be allowed to pass through the middle of the tube and not around the outside of the tube during the analysis process – to minimise contamination. |
| Focusing trap |
| The system must feature 2-stage desorption using an electrically-cooled packed cold trap capable of cooling to sub-zero temperatures as specified in US EPA Method TO-17 and other standards. |
| It should be possible to pack the electrically-cooled cold trap with up to four sorbent beds to a total length of 60 mm to match the sorbent bed length found in industry standard sample tubes. |
| Desorption of the focusing trap must take place in a backflush mode i.e. analytes must enter the trap from one end and be desorbed from the same end to facilitate simultaneous analysis of volatiles and semi- volatiles. |
| The system should offer rapid heating (>60°C/sec) of the focusing trap to optimise chromatographic resolution and analytical sensitivity. |
| Optional, slower, programmed heating options should also be available for the focusing trap to ensure compatibility with very reactive components |
| The focusing trap must feature a narrow / restricted I.D. (<1 mm I.D.) at the inlet / outlet end to the cold trap to optimise linear gas velocity and minimise band width after trap desorption. |
| The dimensions, sorbent mass and heating rate of the focusing trap plus the design of the sample flow path downstream of the focusing trap should facilitate splitless operation even with high resolution capillary GC / GC-MS operating at flow rates of 2 mL/min or below. |
| The flow of dry gas required for purging the cold trap area to prevent build-up of ice during system operation, should be less than 100 ml/min to minimise gas consumption and operator intervention. |
| Sample Flow Path |
| The desorber must feature a totally inert flow path (constructed, for example, using SilcosteelÒ, quartz or fused silica components) the flow path must contain no uncoated metal fittings. |
| The sample flow path inside the desorber must feature uniform heating and minimal volume / length / I.D., particularly post focusing trap, to ensure high linear gas velocity and no band dispersion as components are transferred to the capillary column or fused silica retention gap. |
| It must be possible to set the flow path at temperatures below 100°C to prevent degradation of heat sensitive compounds. It must also be possible to set the flow path at temperatures which allow quantitative recovery of low volatility compounds, including n-C40 |
| After primary (tube) desorption, the desorber must isolate the cooling sample tube from the flow path to prevent contaminants desorbing late from the primary tube from passing into the focusing trap after secondary (trap) desorption has begun. Isolation of the primary tube should involve some sort of appropriate heated, inert valve |
| At no stage during sample analysis must the sample flow path be opened to atmosphere or air (and associated contaminants) will get into the system |
| Once the desorber has initiated a run, all parts of the desorption sequence – leak testing, purging, tube desorption, trap desorption and starting the GC run – should be automatic, to allow unattended operation. |
| The desorber must connect directly to the analytical column or to a heated uncoated, deactivated fused-silica capillary retention gap, without passing through a GC injector |
| Sample split capabilities |
| It should be possible to split both during primary (tube) desorption (inlet splitting) and secondary (trap) desorption (outlet splitting) – in order to obtain overall split ratios in excess of 1000:1 for analysis of high concentration samples. |
| The flow path to the sample split point(s) must be inert and uniformly heated |
| The system must allow the user to select for the sample split flow to be on during instrument standby to minimise air ingress for MS and ECD installations. |
| The system must allow manual, quantitative re-collection of both the inlet and outlet split effluent on a single re-collection tube such that the entire unanalysed portion of the sample, from any single or double split method, is re-collected. The re-collected sample is needed for repeat analysis, sample archiving and method / data validation in compliance with ASTM 6196. |
| There must be easy access to the split re-collection tube without need to tighten and undo screw fittings. Software must also allow carrier gas to be isolated from the split line such that access to the re-collection tube does not cause a temporary leak. |
| It must be possible to automate split re-collection – this upgrade should be possible at any point during the lifetime of the system |
| Analytical sequence |
| As required by relevant standard methods such as US EPA Method TO-17, the analytical sequence must include an ambient temperature, no-flow leak test of each tube prior to analysis, to ensure data integrity. |
| Any tube which fails the leak test must remain intact and unanalysed, maintaining sample integrity until the fault is diagnosed and the sample can be successfully analysed. |
| The analytical sequence must also include an ambient temperature carrier gas purge of each tube to eliminate O2 prior to analysis. Any air purged from the system must be directed away from the analytical GC(MS) system. This is in order to minimise interference – e.g. column oxidation or high air / water background on MS. |
| The system must offer the option of an elevated temperature tube purge during standard 2-stage tube desorption for selective elimination of water and unwanted volatiles prior to analysis. |
| The desorption oven should heat from near ambient during primary (tube) desorption to minimise risk of split discrimination from samples with high solvent or water content |
| The system should facilitate the sequencing of multiple desorptions of a single tube at different temperatures for automating the TD method development process |
