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Laser diode thermal desorption

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Laser diode thermal desorption (LDTD) is an ionization technique that is coupled to mass spectrometry to analyze samples with atmospheric pressure chemical ionization (APCI). It uses a laser to thermally desorb analytes that are deposited on a stainless steel sheet sample holder, called LazWell.[1] The coupling of LDTD and APCI is considered to be a soft-ionization technique.[2] With LDTD-APCI, it is possible to analyze samples in forensics,[3] pharmaceuticals,[4] environment,[5] food[6] and clinical studies.[7] LDTD is suitable for small molecules[7] between 0 and 1200 Da and some peptides such as cyclosporine.[8]

Luxon Ion Source installed on a Shimadzu mass spectrometer

History

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In 2005, a patent was filed by Phytronix Technologies Inc., from Quebec, Canada, for the LDTD ion source for mass spectrometry.[9] In 2016, the Luxon Ion Source, based on the same technology, was put on the market.[10]

Principle of operation

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Schematic of the LDTD technology

An aliquot of the sample preparation between 1 and 10 μL is deposited with a pipette into the well of a metal sample holder and dried with a temperature between room temperature and 40 degrees Celsius.[11] After the sample is completely dried, the sample holder is inserted into the ion source. Compared with desorption electrospray ionization (DESI), direct analysis in real time (DART) and matrix-assisted laser desorption/ionization (MALDI), where the droplets, gas or laser come into direct contact with the sample, LDTD relies on heat transfer through a metal surface.[12] An infrared laser diode array (980 nm) is collimated to heat the back of the sample holder causing the desorption of the molecules.[13] The gas-phase neutral molecules are then transported through a transfer tube, which is pneumatically and sequentially inserted into each well,[11] with a carrier gas into a corona discharge region to undergo an atmospheric pressure ionization.[3] The ions enter the mass spectrometer through the inlet to be measured by the detector. This whole process takes between 0.7 and 10 seconds depending on the laser pattern and the method created by the user.[14] The carrier gas used is compressed air which contains a concentration of water between 3 and 1800 ppm to be able to efficiently protonate the molecules.[11]

Adding to the mass spectrometer's software-controlled parameters, three other parameters can be varied to achieve a higher sensibility or reproducibility: the carrier gas flow, the laser power and the laser gradient.[15][16] An important part of the analysis is also the sample preparation. The most common sample preparation methods used with LDTD are liquid-liquid extraction (LLE),[3] protein precipitation,[8] solid phase extraction (SPE)[17] or a dilution.

 
Typical laser pattern used with LDTD

Ionization mechanism

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Since LDTD is always coupled to APCI, the same ionization mechanism happens. The main difference is that no solvent or mobile phase is available and the protons come from the water content of the carrier gas. A water concentration between 3 and 1800 ppm is recommended.

The ionization can be done in negative[8] or positive[18] mode.

In some applications, such as the analysis of tacrolimus in whole blood, ammonium hydroxide is added to the carrier gas to modify the ionization process.[17]

Sample holder

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The sample holders that can be inserted in LDTD ion sources are named LazWell and are specially designed 96, 384[19] or 1536-well plates.[20] Different coatings can be applied[21] depending on the molecules being analyzed. The hexagonal well shape is designed to concentrate the sample in the path of the laser for an optimal desorption.[11]

Advantages

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Since no solvent or mobile phase carries the sample, this technique is characterized by a highly efficient protonation[12] and a strong resistance to ionic suppression.[19] This and the fact that no needle touches the samples adds the benefit of eliminating carry over between the different wells of the plate.[4] The technology is also a good alternative for the traditional LC-MS users since the results give a similar peak shape as in liquid chromatography and it significantly reduces the analysis time.[22] It also uses low volumes of samples, which is an asset in applications where the available sample volume is limited or difficult to acquire.[23] In addition, it is deemed to be an environmentally friendly alternative to LC-MS/MS.[19]

The ion sources, LDTD and Luxon Ion Source, can be attached to different mass spectrometers with its adapted source housing, available for multiple manufacturers, such as triple quadrupole,[7] time-of-flight,[24] and orbitrap[25] mass spectrometers.

On the downside, since no chromatographic separation is done, interferences coming from isobaric compounds may occur in heavily charged matrices. Differential ion mobility spectrometry-mass spectrometry (DMS-MS) or high-resolution mass spectrometry (HRMS) can be used in tandem with LDTD to eliminate these interferences.[26]

Disadvantages

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While it only requires a small volume of sample, this technique results in a destruction of that sample.[27] The manual sample placing required can cause a variation in results achieved.[27] Care must be taken when designing methods within an experiment using this technology as the lack of chromatography can cause the inability to analyze isomers. [27]

References

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  1. ^ Wu, Jin; Hughes, Christopher S.; Picard, Pierre; Letarte, Sylvain; Gaudreault, Mireille; Lévesque, Jean-François; Nicoll-Griffith, Deborah A.; Bateman, Kevin P. (June 2007). "High-Throughput Cytochrome P450 Inhibition Assays Using Laser Diode Thermal Desorption-Atmospheric Pressure Chemical Ionization-Tandem Mass Spectrometry". Analytical Chemistry. 79 (12): 4657–4665. doi:10.1021/ac070221o. ISSN 0003-2700. PMID 17497828.
  2. ^ Borik, A.; Vojs Stanova, A.; Kodesova, R.; Brooks, B. W.; Grabicova, K.; Novakova, P.; Grabic, R. (2020-02-01). "Ultrafast laser diode thermal desorption method for analysis of representative pharmaceuticals in soil leachate samples". Talanta. 208: 120382. doi:10.1016/j.talanta.2019.120382. ISSN 0039-9140. PMID 31816693. S2CID 203936286.
  3. ^ a b c Bynum, Nichole D.; Moore, Katherine N.; Grabenauer, Megan (2014-10-01). "Evaluation of Laser Diode Thermal Desorption–Tandem Mass Spectrometry (LDTD–MS-MS) in Forensic Toxicology". Journal of Analytical Toxicology. 38 (8): 528–535. doi:10.1093/jat/bku084. ISSN 0146-4760. PMID 25217542.
  4. ^ a b Heudi, Olivier; Barteau, Samuel; Picard, Pierre; Tremblay, Patrice; Picard, Franck; Kretz, Olivier (2011-04-05). "Laser diode thermal desorption–positive mode atmospheric pressure chemical ionization tandem mass spectrometry for the ultra-fast quantification of a pharmaceutical compound in human plasma". Journal of Pharmaceutical and Biomedical Analysis. 54 (5): 1088–1095. doi:10.1016/j.jpba.2010.11.025. ISSN 0731-7085. PMID 21156343.
  5. ^ Mohapatra, D. P.; Brar, S. K.; Tyagi, R. D.; Picard, P.; Surampalli, R. Y. (2012-09-15). "Carbamazepine in municipal wastewater and wastewater sludge: Ultrafast quantification by laser diode thermal desorption-atmospheric pressure chemical ionization coupled with tandem mass spectrometry". Talanta. 99: 247–255. doi:10.1016/j.talanta.2012.05.047. ISSN 0039-9140. PMID 22967548.
  6. ^ Andersen, Wendy C.; VanSickle, Michael; Storey, Joseph; Sheldon, Virginia; Lohne, Jack; Turnipseed, Sherri B.; Thomas, Terri; Madson, Mark (2019-11-02). "Fast analysis of caffeinated beverages using laser diode thermal desorption mass spectrometry (LDTD-MS/MS)". Food Additives & Contaminants: Part A. 36 (11): 1616–1625. doi:10.1080/19440049.2019.1658904. ISSN 1944-0049. PMID 31479386. S2CID 201829502.
  7. ^ a b c Lanshoeft, Christian; Heudi, Olivier; Leuthold, Luc Alexis; Schlotterbeck, Götz; Elbast, Walid; Picard, Franck; Kretz, Olivier (2014-09-01). "Laser diode thermal desorption atmospheric pressure chemical ionization tandem mass spectrometry applied for the ultra-fast quantitative analysis of BKM120 in human plasma". Analytical and Bioanalytical Chemistry. 406 (22): 5413–5423. doi:10.1007/s00216-014-7966-6. ISSN 1618-2650. PMID 24958346. S2CID 2923544.
  8. ^ a b c Jourdil, Jean-François; Picard, Pierre; Meunier, Cécile; Auger, Serge; Stanke-Labesque, Françoise (2013-12-17). "Ultra-fast cyclosporin A quantitation in whole blood by Laser Diode Thermal Desorption – Tandem Mass Spectrometry; comparison with High Performance Liquid Chromatography–Tandem Mass Spectrometry". Analytica Chimica Acta. 805: 80–86. doi:10.1016/j.aca.2013.10.051. ISSN 0003-2670. PMID 24296146.
  9. ^ US 7321116, Picard, Pierre; Lessard, Denis & L'Heureux, André et al., "Ionization source for mass spectrometer", published 2008-01-22, assigned to Phytronix Technologies Inc. 
  10. ^ "Phytronix Technologies Launches the Fastest Process in Mass Spectrometry with the Luxon Ion Source at ASMS2016". www.businesswire.com. 2016-06-06. Retrieved 2020-07-28.
  11. ^ a b c d Fayad, Paul B.; Prévost, Michèle; Sauvé, Sébastien (2010-01-15). "Laser Diode Thermal Desorption/Atmospheric Pressure Chemical Ionization Tandem Mass Spectrometry Analysis of Selected Steroid Hormones in Wastewater: Method Optimization and Application". Analytical Chemistry. 82 (2): 639–645. doi:10.1021/ac902074x. ISSN 0003-2700. PMID 20000768.
  12. ^ a b Segura, Pedro A.; Tremblay, Patrice; Picard, Pierre; Gagnon, Christian; Sauvé, Sébastien (2010-02-10). "High-Throughput Quantitation of Seven Sulfonamide Residues in Dairy Milk using Laser Diode Thermal Desorption-Negative Mode Atmospheric Pressure Chemical Ionization Tandem Mass Spectrometry". Journal of Agricultural and Food Chemistry. 58 (3): 1442–1446. doi:10.1021/jf903362v. ISSN 0021-8561. PMID 20078066.
  13. ^ Advanced Mass Spectrometry for Food Safety and Quality. Elsevier. 2015-05-08. ISBN 978-0-444-63392-7.
  14. ^ Haarhoff, Zuzana; Wagner, Andrew; Picard, Pierre; Drexler, Dieter M.; Zvyaga, Tatyana; Shou, Wilson (February 2016). "Coupling Laser Diode Thermal Desorption with Acoustic Sample Deposition to Improve Throughput of Mass Spectrometry-Based Screening". Journal of Biomolecular Screening. 21 (2): 165–175. doi:10.1177/1087057115607184. ISSN 1552-454X. PMID 26420787. S2CID 45076552.
  15. ^ Lohne, Jack J.; Andersen, Wendy C.; Clark, Susan B.; Turnipseed, Sherri B.; Madson, Mark R. (2012). "Laser diode thermal desorption mass spectrometry for the analysis of quinolone antibiotic residues in aquacultured seafood". Rapid Communications in Mass Spectrometry. 26 (24): 2854–2864. Bibcode:2012RCMS...26.2854L. doi:10.1002/rcm.6414. ISSN 1097-0231. PMID 23136016.
  16. ^ Berkel, Gary J. Van; Pasilis, Sofie P.; Ovchinnikova, Olga (2008). "Established and emerging atmospheric pressure surface sampling/ionization techniques for mass spectrometry". Journal of Mass Spectrometry. 43 (9): 1161–1180. Bibcode:2008JMSp...43.1161V. doi:10.1002/jms.1440. ISSN 1096-9888. PMID 18671242.
  17. ^ a b Merrigan, Stephen D.; Johnson-Davis, Kamisha L. (2019-05-01). "A 6 Second Analytical Method for Quantitation of Tacrolimus in Whole Blood by Use of Laser Diode Thermal Desorption Tandem Mass Spectrometry". The Journal of Applied Laboratory Medicine. 3 (6): 965–973. doi:10.1373/jalm.2018.027243. ISSN 2576-9456. PMID 31639688.
  18. ^ Daldoul, Insaf; Auger, Serge; Picard, Pierre; Nohair, Bendaoud; Kaliaguine, Serge (2016). "Effect of temperature Ramp on hydrocarbon desorption profiles from zeolite ZSM-12". The Canadian Journal of Chemical Engineering. 94 (5): 931–937. doi:10.1002/cjce.22467. ISSN 1939-019X.
  19. ^ a b c Swales, John G.; Temesi, David G.; Denn, Mark; Murphy, Keeley (June 2012). "Determination of paracetamol in mouse, rat and dog plasma samples by laser diode thermal desorption--APCI-MS/MS". Bioanalysis. 4 (11): 1327–1335. doi:10.4155/bio.12.68. ISSN 1757-6199. PMID 22720651.
  20. ^ "News | Changing the Game in High-Throughput Screening". Phytronix. 2018-08-01. Retrieved 2020-07-30.
  21. ^ Dion‐Fortier, Annick; Gravel, Alexia; Guérette, Cassandra; Chevillot, Fanny; Blais, Sonia; Auger, Serge; Picard, Pierre; Segura, Pedro A. (2019). "Signal enhancement in laser diode thermal desorption-triple quadrupole mass spectrometry analysis using microwell surface coatings". Journal of Mass Spectrometry. 54 (2): 167–177. Bibcode:2019JMSp...54..167D. doi:10.1002/jms.4328. ISSN 1096-9888. PMID 30600862. S2CID 58666707.
  22. ^ "Growing Pains in LC-MS/MS Testing | AACC.org". www.aacc.org. Retrieved 2020-07-28.
  23. ^ Borik, Adam; Staňová, Andrea Vojs; Brooks, Bryan W.; Grabicová, Kateřina; Randák, Tomáš; Grabic, Roman (2020-07-01). "Determination of citalopram in fish brain tissue: benefits of coupling laser diode thermal desorption with low- and high-resolution mass spectrometry". Analytical and Bioanalytical Chemistry. 412 (18): 4353–4361. doi:10.1007/s00216-020-02672-y. ISSN 1618-2650. PMID 32372276. S2CID 218512949.
  24. ^ "The Evaluation of Laser Diode Thermal Desorption ((LDTD) for High Throughput Analysis of Controlled Substances and Toxicology in Forensic Sciences". National Institute of Justice. Retrieved 2020-07-30.
  25. ^ Hecht, Elizabeth S.; Scigelova, Michaela; Eliuk, Shannon; Makarov, Alexander (2019), "Fundamentals and Advances of Orbitrap Mass Spectrometry", Encyclopedia of Analytical Chemistry, American Cancer Society, pp. 1–40, doi:10.1002/9780470027318.a9309.pub2, ISBN 978-0-470-02731-8
  26. ^ Flanagan, Robert J.; Cuypers, Eva; Maurer, Hans H.; Whelpton, Robin (2020-05-21). Fundamentals of Analytical Toxicology: Clinical and Forensic. John Wiley & Sons. ISBN 978-1-119-12236-4.
  27. ^ a b c Bynum, Nichole D.; Grabenauer, Megan; Moore, Katherine N. (April 2014). "The Evaluation of Laser Diode Thermal Desorption (LDTD) for High Throughput Analysis of Controlled Substances and Toxicology in Forensic Sciences" (PDF). Office of Justice Programs.
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