PREFICS - Pre concentrator with Fast Integrated Chromatographic Separation
Over the past few years Kore has been developing fast chromatographic separation/interface technology for key mass spectrometry products, with an emphasis on high sensitivity, high specificity and versatile sample introduction for real-world samples. Analyte is first flushed from one of various quick-swap inlet modules onto a thermoelectrically cooled trap. This allows subsequent splitless introduction onto a short GC column in a custom designed, miniature and fast oven. A typical semi-volatile analysis, including pre-concentration and chromatography might typically take just five minutes, yielding detection limits in the picogram range.
Prefics is conceived to be a 'universal front end' separator of complex chemical mixtures that could be joined to any suitable detection technique. Results shown below were taken with Prefics connected to a PTR-TOF-MS, but any mass spectrometer or indeed other detection technique could be considered.
- Quick change inlet modules to suit a variety of sampling methods.
- Splitless analysis for highest sensitivity.
- Fast thermoelectric-cooled trap with wide temperature range (-2°C to >200°C) .
- Small, fast (2 - 3 min), lightweight, low power consumption, custom GC oven.
- Flexible output conditions - relatively easy change for wide range of output pressure.
- User customisable sampling-sequence scripting with macro record/playback.
- Manual control for method development.
- Simple interface (USB) to Windows compatible controlling computer (Windows XP or later).
Quick swap inlet modules
The front end of PREFICS consists of a platform with mounting lugs and a simple to use, hot inlet coupling (Ultratorr) that can be released/sealed by hand. Services are provided on an adjacent panel, consisting of low voltage power, a simple 3-wire data-bus and a quick-fit low dead-volume carrier gas connection. These features allow a very quick change of inlet module to suit the application. Three modules have been designed, built and tested to date:
- A swab desorber for card mounted, felted, PTFE swabs (Can also be used as stand-alone fast thermal desorber).
- A trap tube interface with fast load mechanism, which accepts standard off-the-shelf desorber tubes.
- A solid phase micro extraction interface (SPME).
This data was taken during a quick pre-delivery check of Prefics with an unoptimised PTRMS. A rather well used swab (PTFE felt in a card holder) was employed, with no special pre-treatment. Therefore as a check, it was first run without any deliberate dosing. For the second run the swab was dosed with 20ng each of DNT and TNT.
Single ion chromatograms for 183amu, protonated DNT (green = dirty blank; red = spiked )
Single ion chromatograms for 228amu, protonated TNT (green = dirty blank; red = spiked )
Single ion Chromatograms (SIC) for the protonated DNT at 183amu and protonated TNT at 228 amu are shown above for the blank and dosed runs. There would appear to be small residues on the swab in the blank run, presumably from earlier experiments. The swab was very dirty before the first run so there are plenty of other compounds in the full data-set for the blank run. It should be noted that the times indicated include 60s of trap back-flush before the start of the GC oven program.
The software also allows us to extract a baseline-subtracted mass spectrum for the each of the chromatographic peaks shown above. In both cases the spectra are very simple because they are dominated by the protonated parent molecule. The reactor conditions were rather vigorous in this run so smaller electron impact like fragment peaks can be seen at 165 amu (DNT) and 210 amu (TNT). Reactor conditions can be adjusted to make these peaks very small, if desired, but they can also provide additional confirmation of compound identity.
Baseline subtracted mass spectrum for DNT chromatographic peak
Baseline subtracted mass spectrum for TNT chromatographic peak
Analyte is presented to the separator unit on a PTFE swab and is desorbed into a focussing trap for sample pre-concentration before a second desorption onto the front of the GC column. Preliminary experiments coupling the separator unit to Kore's PTR-TOF-MS and analysing organochloride pesticides show very clear chromatographic peaks for the four structural isomers of BHC (lindane), Heptachlor, Aldrin and Heptachlor epoxide.
The elution times axis for these compounds is marked in seconds; chromatographic peak widths for the BHC compounds range from 1 to 3 seconds. The total experiment time from sample introduction to detection of the first BHC compounds was ~230s, with 90s of this being the contribution of the sample loading, focussing and desorbing and the remaining ~140s being the elution time through the GC column. 20ng of each pesticide sample was introduced via a sample swab in this experiment.
Kore Technology Ltd would like to acknowledge the fact that the PREFICS technology was largely developed with funding from the UK Ministry of Defence.
Last updated: 10:37 30/01/2014
© Kore Technology Limited 2013