In DART-MS the sample is ionized at atmospheric pressure at the entrance of an LC/MS-type mass spectrometer, and the ions immediately enters the MS.
The sample molecules are ionized by bombardment of exited He-atoms, via the ionization of water molecules in the air and subsequent proton transfer to the sample molecules, the result is a soft chemical ionization of the sample molecules.
The DART ion source is an alternative to electrospray or APCI, and gives a possibility for direct analysis without a preceeding LC system.
When using DART for the ionisation of the sample, the sample composition (or rather, the molar weights represented in the sample) is directly shown in few seconds.
This is the main asset of the system, the really fast data collection, typically in few seconds.
The system is therefore well suited for screening of a high number of samples /day or for the synthesis lab test of intermediates.
The primary advantage is the really short analysis time and the possibility to analyze almost all types of polar/non polar molecules.
On the –SVP (see below) the temperature on the beam can be adjusted, and large molecules analyzed.
The system may be further expanded with the BioChromato IonRocket, where the sample temperature may be ramped from room temperature till 600°C.
This module therefore also allows the sample to be analyzed under oxidative pyrolytic conditions.
With analysis using internal standard, a precision of 2-3% RSD is often possible.
For inhomogenous samples, or when an external standard is emplued, a somewhat larger RSD of typically 5-10% must be expected.
As there is no chromatographic separation in the system, the choice of MS is determining the selectivity of the entire system.
For single quad systems, the natural limit is Molecular fragments with the same unit MW.
On MS/MS systems, possibly combined with high res MS, the system enables quantitation and structural elucidation in complicated matrices
somewhat depending on the MS in question, the typical detection limit is in the low picogram range. It is therefore also suited for the screening of almost all types of unwanted compounds, from pesticides to “Forensics”.
The possible DART sources couples to almost all types of LC/MS mass spectrometers.
DART is administered by a simple web-based software, built into the DART controller.
This means that no installation of a software package is necessary, and there are no syncronization necessary between the DART and the mass spectrometer.
There exist two different models of the DART:
This model is based on direct ionization of sample deposited on single-use grid mounted on a cardboard.
What you get is a standardized set-up, where the sample-on-the-grid, liquid or powder, is inserted in the beam-line.
After few seconds the analysis is performed and the card discarded. If customer wishes, the sample may also be introduced directly in the beam line. Sample exchange is done manually.
The DART OS can be combined with the SVP-45A, where the beam line is angled 45° in regard to the sample material.
The DART OS may also be comnbined with the Swap thermal desorber (see below).
This model adds somewhat more flexibility to the analysis.
SVP may be added different types of modules, to take full advantage of the fast analysis..
SVP has automation built into the system, and has a range of modules to be positioned into the beam line.
Depending on the module 10 to 384 samples may be processed in series, thereby taking full advantage of the short analysis time.
Transmission scanning: (Classical DART SVP)
Quickstrip:This module holds a 12 position card, where the mesh is scanned and data collected. As a further development of this, the:
X-Z Scanner, Scanner holds 96 metal net positions, again with a scanning of each position in few seconds. This module is especially designed for the fast analysis of many samples in a well-defined matrix. The net has the same geometry as 96 or 384 micro titer/deepwell plates, and therefore sample addition may be performed with automation robots.
12 Dip-it holder: This is tiny pipette tips which may be dipped into a matrix and positioned in a special holder. Again these tips are scanned and the results are shown.
24-pin sampler: with the 24 pin sampler a single row from 384 position plates may be analyzed automatically. The module may also be used for multi-sampling of semi solid samples and thus be used for variation studies
Reflection scanning: DART SVP-45A, mounted in a 45° angle to the sample material, the module angle may also be reduced to 0° and thus used for ordinary transmission scanning.
Tablet carrier: This module holds 12 tablets and enables surface scanning of these
TLC holder: With this module individual components on a TLC plate may be analyzed directly by the MS.
Forceps module: With this holder any (minor) object may be fixed in the beamline
Swab holder: This device holds standard TSA swabs and desorbs these while the beam carries the desorbed and ionized components into the MS. The Swab device is usually used in a unified package together with the Waters QDa mass spectrometer and the PIMISA software which holds a specific database on drugs and explosives against which the scanned data are compared. This system enables fast analysis in airports/ emergency management areas/at borders, and gives almost immediate answers on drugs and explosives.
With this module the temperature of the sample may be further increased up till 600°C.
The sample is placed in a small sample container directly under the beam line.
The container may be heat-programmed, from room temperature till the desired maximum. This results in a timewise desorption of the sample.
Furthermore, this device gives the possibility for analysis of large molecules and/or pyrolysis of samples, which only with difficulties is possible with conventional DART modules.
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