Direct analysis in real time
The DART ionization process can produce positive or negative ions depending on the potential applied to the exit electrode.
This ionization can occur for species desorbed directly from surfaces such as bank notes, tablets, bodily fluids (blood, saliva and urine), polymers, glass, plant leaves, fruits & vegetables, clothing, and living organisms.
DART is applied for rapid analysis of a wide variety of samples at atmospheric pressure and in the open laboratory environment.
[1] DART resulted from conversations between Laramee and Cody about the development of an atmospheric pressure ion source to replace the radioactive sources in handheld chemical weapons detectors.DART was developed in late 2002 to early 2003 by Cody and Laramee as a new atmospheric pressure ionization process,[2] and a US patent application was filed in April 2003.
DESI and DART are considered as pioneer techniques in the field of ambient ionization,[4] since they operate in the open laboratory environment and do not require sample pretreatment.
[5][6] In contrast to the liquid spray used by DESI, the ionizing gas from the DART ion source contains a dry stream containing excited state species.
As the gas (M) enters the ion source, an electric potential in the range of +1 to +5 kV is applied to generate a glow discharge.
Ion/electron recombination leads to the formation of long-lived excited-state neutral atoms or molecules (metastable species, M*) in the flowing afterglow region.
The heated stream of gaseous metastable species passes through a porous exit electrode that is biased to a positive or negative potential in the range 0 to 530V.
[7] Once the metastable carrier gas atoms (M*) released from the source, they initiate Penning ionization of nitrogen, atmospheric water and other gaseous species.
[9] The stream of protonated water clusters acts as a secondary ionizing species[10] and generates analytes ions by chemical ionization mechanisms at atmospheric pressure.
To accelerate sample release from the surface, the DART gas stream is usually heated to temperature in the range 100-500 °C and this operation can be employed for temperature-dependent analysis.
[1][7] In forensic science, DART is used for analysis of explosives, warfare agents, drugs, inks and sexual assault evidence.
[17][18] In clinical and pharmaceutical sector, DART is utilized for body fluid analysis such as blood, plasma, urine etc.
[22] In the manufacturing industry, to determine the deposition and release of a fragrance on surfaces such as fabric and hair and dyes in textiles, DART is often utilized.
