Chromatographia 67 (3-4), 315-313 (2008). Investigation of two different chromatographic substrates and one interface for coupling surface-enhanced Raman spectroscopy (SERS) with TLC. A chromatographic thin layer, specially produced for RS measurements, and a monolithic silica thin layer were used. A typical TLC plate with a modified aluminium backplate foil on one side was used as an interface. As test analytes three biologically active diterpenes (gibberellic acid, abietic acid, and kaurenoic acid) were applied directly onto the surface, followed by the addition of silver colloid and measurements by SERS. The strongest signal (excitation at 514.5 nm) was obtained for gibberellic acid using a Raman treated thin layer where the enhancement factor value was determined to be 102. No useful SERS signals were observed when the monolithic silica layer was used. Similar SERS spectra on modified aluminium backplate were obtained for abietic acid and gibberellic acid and no SERS spectrum was obtained for kaurenoic acid.

Anal. Chem. 76, 479-482 (2004). Coupling of a rotation preparative layer chromatography system on-line with mass spectrometry using a simple plumbing scheme and a self-aspirating heated nebulizer probe of a corona discharge atmospheric pressure chemical ionization (APCI) source. The self-aspiration of the heated nebulizer delivers approx. 20 µL/min of the 3.0 mL/min eluate stream to the mass spectrometer, eliminating the need for an external pump in the system. The viability of the coupling is demonstrated with a three-dye mixture composed of fat red 7B, solvent green 3, and solvent blue 35 separated and eluted from a silica gel-coated rotor using toluene. The real-time characterization of the dyes eluting from the rotor is illustrated in positive ion full-scan mode. Other self-aspirating ion source systems including atmospheric pressure photoionization, electrospray ionization, and inductively coupled plasma ionization, for example, might be configured and used in a similar manner coupled to the chromatograph to expand the types of analytes that could be ionized, detected, and characterized effectively.

Rapid Commun. Mass Spectrom. 24, 1032-1038 (2010) HPTLC of glycosphingolipids (GSLs) on silica gel with chloroform - methanol - water 120:70:17. The plate was overlaid with GSL-specific bacteria, and the microbes were detected with primary antibodies and appropriate alkaline phosphatase labeled secondary antibodies, and by in situ MS analysis of bacteria-specific GSL receptors. The thin-layer chromatography infrared matrix-assisted laser desorption/ionization orthogonal time-of-flight mass spectrometry (TLC/IR-MALDI-o-TOF-MS) method represents one of the most powerful approaches for the detection of GSL receptors of microorganisms.

CBS 110, 2-4 (2013). HPTLC of caffeic acid, chlorogenic acid, and rutin hydrate on silica gel (prewashed with methanol and dried under vacuum at 50 °C for 30 min) with formic acid - ethyl acetate - water - methyl ethyl ketone 5:30:6:18 with chamber saturation for 5 min over a developing distance of 5 cm. Detection under UV 254 nm. Elution of substance zones with TLC-MS Interface using methanol and a flow-rate of 0.3 mL/min for 6 min. Evaporation of methanol under nitrogen, residue taken up with methanol-d4. Subsequent off-line quantitative 1H-NMR spectroscopic analysis of the residue, acquisition time 30 min. Linearity for all substances was confirmed in the range of 10 - 80 µg/mL. Recoveries were in the range of 100.5 % for chlorogenic acid and up to 103.4 % for caffeic acid, with precisions under 3.9 % (%RSD, n=3).

J. Planar Chromatogr. 28, 190-204 (2015). The analysis of multiple pesticide residues in environmental samples is often impossible in a single-step process. Comprehensive 2D planar chromatography on mono and bilayers, coupled-layer chromatography, combination of multidimensional planar chromatographic techniques, hyphenated methods are proved to be suitable.

J. of Chromatogr. A 1415, 155-160 (2015). Presentation of a technique for direct analysis of raw samples by TLC coupled with electrospray ionization mass spectrometry (ESI-MS) instead of conventional MS analysis, which for raw samples commonly requires time-consuming and laborious sample pretreatment and separation using HPLC or GC. The analytes of interest could be extracted, ionized and detected by ESI-MS with much reduced matrix interference because the interfering compounds were retained by the sorbent material of the TLC plate. Demonstration by applying in direct analysis of samples containing common interfering compounds, e.g. salts and detergents. Rapid detection and quantification of target analytes in raw samples showed that the TLC-ESI-MS method was simple, rapid, efficient and could be effectively applied in offline and online separation and detection of different components in raw samples, e.g. plant extracts.

J. Chromatogr. A 1462, 134-145 (2016). Development of simple method for the separation of different colored pigment formulations used in the printing materials on food packaging to control the quality and safety of the package. HPTLC on silica gel by automated multiple development with a 9-step gradient based on ethyl acetate, methanol and water, and ending with toluene. Good resolution of differently soluble constituents of the pigment formulation like additives and coating materials. The results obtained by multi-detection allowed a first assignment of the differently detectable bands to particular chemical substance classes, enabled the comparison of different commercially available pigment batches and revealed substantial variations in the composition of the batches. Characterization of single unknown pigment constituents by HPTLC-MS and HPTLC combined with ATR-FTIR. The new HPTLC method for routine quality control for incoming pigment batches and monitoring of internal pigment production processes secures a consistent pigment composition, resulting in consistent ink quality. Hyphenation of HPTLC with the Aliivibrio fischeri bioassay revealed information on the toxicological potential of different pigment compounds which helps guarantee consumer safety, especially in regard to readily permeable pigment components.

J. Sep. Sci. 42, 415-430 (2019). Review of the application of TLC hyphenated with mass spectrometry for the analysis of low-molecular-mass solutes. Different monolithic layers and their main applications were also described, including plates with thin inorganic layers, composite silica/organic polymer layers and porous polymeric monolithic layers (thermally initiated and prepared by photopolymerization). Methods of detection in TLC-MS systems were also described as indirect and direct mass spectrometric analyses.