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TLC-MS Coupling

What is TLC-MS?

TLC- HPTLC-MS grade platesTLC-MS combines the ease and speed of thin-layer chromatography (TLC) with powerful on-line identification by mass spectrometry (MS). Enabled by the recent development of special interfaces and MS-grade plates for TLC and HPTLC, the coupling technique allows fast trace analysis with extremely low detection limits. This makes TLC-MS ideal for analytical use in a wide range of industries, such as pharmaceuticals, cosmetics, food and beverages.

TLC-MS Techniques

TLC-MS coupling can be performed using an elution-based, or desorption-based technique. Both methods are offline, and are commenced after the separation is completed and the plate dried. Sample transfer to the mass spectrometer is fast and typically takes less than one minute.

Elution-Based TLC-MS (Indirect MS Analysis)
The analyte on the TLC plate is first scraped, extracted, purified, and concentrated, then transferred in the liquid phase to the mass spectrometer’s ion source for further analysis.

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TLC-MS Apparatus by
Plate Express™ TLC-MS
by Advion
Desorption-Based TLC-MS (Direct MS Analysis)

The analyte is vaporized from the silica layer, and transferred to the mass spectrometer in the gas phase. Vaporization techniques include gas beam, ion bombardment, and MALDI (matrix-assisted laser desorption/ionization).
Working conditions: Desorption-based TLC-MS is conventionally performed under vacuum, however analysis under atmospheric pressure is also possible through the use of ambient mass spectrometry.

TLC-MS Benefits

Excellent Efficiency and Resolution
  • Silica gel matrix of MS-grade plates has considerably fewer impurities than standard plates
  • Detection limit of HPTLC-MS-grade plates is in the lower nanogram range
  • Targeted recording of mass spectra on zones or lines of interest is performed after development, thus ensuring high efficiency
  • Mass spectra are obtained quickly by direct sample access on TLC plates at room temperature
Flexible Choice of Mobile Phase
  • In contrast, standard LC-MS coupling using HPLC is not compatible with certain mobile phases (e.g. inorganic buffers)
Easy Method Transfer
  • Similar separation performance to standard TLC and HPTLC plates allows direct transfer of methods
High Sensitivity with Low Background
  • MS-grade plates are much cleaner than standard TLC or HPTLC plates, thus ensuring superior sensitivity with extremely lower background signals
  • MS-grade plates are packed in aluminum foil to prevent contamination

TLC-MS Application Examples

The following separations demonstrate the enhanced sensitivity and low background signal of TLC-MS plates over HPTLC plates.

MS background signal measurement using a standard HPTLC silica gel 60 F254 glass plate with mobile phase acetonitrile/water (95/5).

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MS background signal measurement using an MS-grade HPTLC silica gel 60 F254 glass plate with mobile phase acetonitrile/water (95/5). 

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TLC-MS Detection Methods

1. Visible Compounds
2. Derivatization of Non-Detectable Compounds
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Plates with visible substances can be directly extracted.
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Cover the extraction zone of the plate, then derivatize the remaining area and compare with R
f values, or mark the extraction zone.
3. UV-Active Compounds
a. Use Rf values or mark the zone before extraction.
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b. Use Rf values or mark the zone after extraction.
Merck:/Freestyle/LE-Lab-Essentials/Chromatography/LE-UV-active compounds on a TLC-MS plate after extraction-700x214-06062016.jpg 

Recommended TLC-MS Tutorials

Recommended Literature

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