TLC-MALDI

One novel approach in the off-Une planar separation method coupled with DIOS is the use of SiNWs as a platform for the separation of molecules [48]. The capabiUty of a SiNW to separate a sample mixture lies in its high surface-to-volume ratio and in the differences in analyte-surface interactions. When combined with an ability to support laser desorption/ionization MS, chromatographic 

On-hne high-performance TLC (HPTLC) MALDI-FT-MS at elevated pressures was described in the direct analysis of gangliosides from TLC plates using soHd matrices [176]. Gangliosides are glycosphingolipids that contain one or more siahc 

A report from Kostiainen and coworkers utihzing ultra-TLC (UTLC) separations coupled with MALDI appears to offer significant improvement over high- performance TLC approaches. The fabrication of monolithic sUica UTLC plates provides a 10- to 100-fold greater sensitivity than HPTLC, a lower sample consumption, and a faster separation. Some caveats include less resolving power due to shorter elution distances (2 cm versus 5 cm) and a smaller overall adsorption surface area available for analytes. This method has been successfully applied to the analysis, purity estimates and qualitative idenhficahon components of crude mixtures of compounds synthesized via combinatorial chemistry [178]. Although at present TLC-MALDI analysis remains only semi-quanhtative in nature, its primary utQity as a qualitative tool for mixture separation and structural identification is currently on the rise. 

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If no references for the degradation products or impurities are available in the laboratory, the sample should be exposed to stress conditions such as heat (50-80 °C), ultraviolet light (2000 lux), acid and base (0.1-1 M HC1 and NaOH), and oxidant (3% H2O2). After incubation in the allotted time, the purity and identity of the analyte peak/spot should be proved by using DAD or MS detection (for LC), MS (for GC), or in situ UV-Vis measurement using a densitometry or TLC-MALDI MS (for TLC). 

Cleave a small sample and analyse (TLC, MALDI-TOF). Repeat... 

Methods relying on MALDI require application of an extraction solvent to the layer to move sample to the layer surface followed by co-crystallization with a MALDI matrix material. TLC-MALDI direct coupling methodologies use one of three methods of layer... 

Ivleva VB, Sapp LM, O Connor PB, Costello CE. Ganglioside analysis by TLC-MALDI-oTOF MS. J Am Soc Mass Spectrom 2005 16 1552-1560. 

Figure 5.17. Hybrid TLC-MALDI plate for coupling with TOF-MS. (From ref. 107.)...

J. T. Mehl and D. M. Hercules, Direct TLC-MALDI coupling using hybrid plate. Anal. Chem. 72, 68-73 (2000). 

For the detailed analysis of complex mixtures, a previous separation of the sample into the individual lipid classes is required, however, in the same manner as if a LC/MS process was being used. For this purpose, combined TLC/MALDI may be employed because, when the sample is dispersed in a solid matrix (i.e., the silica gel), it can easily be combined with a MALDl ion source. Thus, MALDI-M S can be expected to become a true alternative to currently established methods of lipid analysis. 

Subsequent to the determination of parent ion molecular weights, further structural information is obtained by MS/MS. The TLC-MALDI DataViewer enables to manually select zones by pick a peak and to complete the acquisition of MS/MS spectra within a few seconds The picked spectrum is opened in flex-Analysis and the precursor ion of interest is selected for MS/MS. In FlexControl, these selected precursor ions are MS/MS analyzed automatically. 

Schtlrenberg, M., Euchs, B., Bischoff, A., SiiB, R., Suckau, D., Schiller, J., Morlock, G. (2009) High-performance TLC-MALDI. In 18th International Mass Spectrometry Conference IMSC 2009, Bremen, Poster PMM-386. 

Crecelius, A., Clench,M.R.,Richards, D.S.,Parr, V. (2004) Quantitative determination of Piroxicam by TLC-MALDI TOP MS. Journal of Pharmaceutical and Biomedical Analysis, 35, 31-39. 

FIGURE 1.1 MTP TLC-MALDI adapter target for 50 x 75 mm TLC silica gel aluminum plates. After TLC separation and matrix coating, the plate is ready for MALDI analysis. (Adapted from Bruker Daltonics, Billerica, MA.)... 

Bradykinin was used as an analyte in the investigation and optimization of the TLC-MALDI coupling protocol. In this protocol, a matrix solution (a-cyano-4-hydroxycinnamic acid) was deposited onto a stainless steel or polyester plate. The resolved TLC plate was sprayed with extraction solvent and placed into a solvent-saturated atmosphere. Afterward, the stainless steel or polyester plate was placed face-to-face with the dampened TLC plate and pressed. The pressing step puts pressure on the stationary phase, forcing solvent toward the top surface of the TLC plate and the matrix layer and also transfers the matrix to the top of the TLC plate. After removal of the stainless steel or polyester plate, the matrix remains on the TLC plate cocrystallized with analyte. The TLC plate is then analyzed in a MALDI mass spectrometer. According to the discussed paper, the parameters of the TLC-MALDI coupling protocol, particularly for the extraction solvent selection, extraction time and pressure have been investigated and optimized [25]. 

A mixture of l-pahnitoyl-2-linoleoyl-OT-phosphatidylcholine (PLPC) and 1-palmitoyl-2-linoleoyl-OT-phosphatidylethanolamine (PLPE) was oxidized under the influence of atmospheric oxygen and characterized by TLC-MALDI. TLC separation was... 

Bischoff, A., Fibisch, M., Fuchs, B., Siiss, R., Schiirenberg, M., Suckau, D., and Schiller, J. 2011. A simple TLC-MALDI method to monitor oxidation products of phosphatidylcholines and -ethanolamines. Acta Chromatogr, 23 365-375. 

Leriche, E.D., Hubert-Ronx, M., Grossel, M.C., Lange, C.M., Afonso, C., and Loutelier-Bourhis, C. 2014. Direct TLC/MALDI-MS coupling for modified polyamidoamine dendrimers analyses. Ana/. Chim. Acta, SOS 144—150. 

Our focus will be exclusively on TLC/MALDI MS because (in our opinion) this coupling approach provides many advantages over other MS techniques [17]. Those advantages are as follows ... 

In a nutshell, the deposition of the MALDI matrix onto the TLC plate is a very important step of successful TLC/MALDI measurements [27]. There are different... 

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