Laser Diode Thermal Desorption (LDTD)


The LDTD ion source is a disruptive high throughput technology invented and patented by Phytronix Technologies (Canada), and distributed in the US by Overbrook Scientific.


The LDTD makes use of a laser diode to thermally desorb a dried sample into gas phase, and by transporting the neutral species through Atmospheric Pressure Chemical Ionization (APCI) using compressed air, the LDTD achieves a very fast and efficient sample introduction into a tandem mass spectrometer (LC-MS/MS) in less than 10 seconds.  It is a direct sample introduction source that does not require chromatographic separations prior to detection via tandem mass spectrometry.  A  technology that is superior to anything on the market.



“We have used the Phytronix LDTD sources for several years, and have reported out over a 1,000,000 combined tests on LDTD/MS-MS instruments, and of course have submitted many proficiency samples with never an error…. it made a 16 hour run by LC decrease to a 15 minute run for 96 samples, and greatly decreased sample volumes required, so fewer QNS samples ….” — Toxicology Lab


We encourage your questions about the LDTD ion source. For more answers to your questions, contact us.

Q 1: How does the LDTD deal with Ionic suppression?

A: The fundamental characteristics of solvent free APCI allows limited to no Ionic suppression effect up to the corona discharge capacity which differs from the physical interactions with ESI.

Q 2: How does the LDTD deal with interferences?

A: As the LDTD vaporizes the sample in a few second desorption, many molecules ionize at the same time. Nevertheless, as the ionization is exempt of ionic suppression, interferences are reduced to a minimum by the fundamental aspect of the LDTD of solvent free APCI.

Q 3: Without chromatographic separation how do I get specificity?

A: In LC-MS/MS, the main part of the specificity relies on MS/MS which is dependent on the parent mass and the daughter ions. A probability of 2×10-7 or lower is considered as sufficient. Chromatography represents 10-1 in the total statistic. The technique by its nature, has to separate compounds to avoid ionic suppression. LDTD uses the MRM transitions to achieve specificity. It also includes separation of the volatile/non-volatile molecules in which there is no ionic suppression to contend with. Almost all the molecules using the LDTD reach the minimum probability for specific analysis in a regulatory environment.

Q 4: How will the LDTD affect my sample prep?

A: The LDTD requires little deviation from your existing sample prep methods. Techniques such as protein precipitation, liquid-liquid extraction and solid phase extraction (SPE) are generally used. Minimal adjustments to preparation volume may be needed.

Q 5: What instruments can be configured with the LDTD?

A: Most OEM LC/MS/MS are suitable for LDTD.