Q 1 : How does the LDTD work?
A: The LDTD is a high efficiency thermal desorption sample introduction technique followed by solvent free APCI.
Q 2: What is the LDTD throughput?
A: The LDTD can achieve complete analysis in less than 9 seconds.
Q 3: 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 4: What is the efficiency of the LDTD-APCI ionization?
A: Chemists expect lower molecular coverage for ionization using APCI. They refer to LC-APCI with solvent in which the analyte represents a tiny fraction of the molecules in the gas phase (1/106). In LDTD, the reactant is protonated water, H3O+, that is the ideal proton donor. Charges are transferred to the analyte up to the maximum capacity of the corona discharge. A successful ionization rate of 96% for various small molecules has been observed in a drug discovery environment.
Q 5: 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 6: 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 7: Does LDTD work for isomers?
A; Specificity in LDTD does not separate the isomers with reliance only on MS/MS. It is also possible to achieve separation with derivatization, the extraction method or an Ion Mobility spectrometer.
Q 8: Which type of molecules work with the LDTD?
A; Small molecules with mass <1500 are suitable for the LDTD.
Q 9: 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 10: What instruments can be configured with the LDTD?
A: Most OEM LC/MS/MS are suitable for LDTD.
Q 11: What consumables are required for the LDTD?
A: The only consumables required are proprietary 96 or 384 well plates, the LazWell.
Q 12: How are the LDTD plates spotted?
A: The LazWell plates can be either hand spotted and have also been designed to be fully compatible with existing automated liquid handler workstations.
Q 13: How robust is the LDTD and how do we get service?
A: The LDTD requires periodic cleaning every 10,000 to 30,000 samples analyzed. Routine maintenance can be performed by the client and onsite service can be provided by authorized factory trained personnel (like Overbrook Scientific).
Q 14: These Q&A raise additional questions. How can I learn more answers for my lab?
A: Contact Overbrook Scientific, the only independent distributor of LDTD ion source in the U.S. –
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