Quantitative inkjet application on self-printed, binder-free HPTLC layers for submicromole-scaled analytical 1H NMR spectroscopy

• Published in: Analytica chimica acta 2019-12, Vol.1087, p.131-139
• Main Authors: Yüce, Imanuel, Mayr, Milena, Morlock, Gertrud E.
• Format: Article
• Language: English
• Subjects: Background signals; Binder-free analytical chromatography plates; Nuclear magnetic resonance spectroscopy; Planar chromatography; Structure elucidation; Submicromole-scaled analytical spectroscopy
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2019.08.013

High-performance thin-layer chromatography (HPTLC) combined with 1H nuclear magnetic resonance (NMR) spectroscopy has only been demonstrated over a small spectral range so far. The self-printing of chromatographic plates with a modified 3D slurry printer allowed the operator to influence the composition of the adsorbent slurry and thus the purity of the adsorbent layer. The combination of such self-printed, binder-free HPTLC plates with inkjet-driven sample application made possible submicromole-scaled analytical 1H NMR spectroscopy. This was proven using pure HPTLC adsorbents. For comparison, commercial silica gel HPTLC plates were purified by pre-development with solvents for spectroscopy, whereas commercial silica gel HPTLC particles were self-printed on the glass plate after purification under solvent pressure in a recycled HPLC cartridge. Evaluating the signals from different treatments, seven background signals disappeared in the proton spectra and three were reduced to a minimum by use of pre-developed commercial HPTLC plates. In the case of the self-printed, binder-free HPTLC plates made of purified adsorbent, most of the spectral background signals were reduced to a minimum, thus these spectra showed the highest cleanness and most pure analyte proton spectra. For the first time, the full 1H NMR spectroscopy range was made available after an HPTLC separation. This proof of principle opens the avenue for submicromole-scaled analytical 1H NMR spectroscopy. [Display omitted] •Reduced background signals, useful for structure elucidation at analytical scale.•Full 1H NMR spectroscopy range (small molecule range) available after HPTLC separation.•Suitable HPTLC plate quality for submicromole-scaled analytical 1H NMR spectroscopy.•Clean 1H NMR spectra obtained after separation on inkjet-printed binder-free HPTLC plate.•Orthogonal cleaning procedures utilized to proof quality of self-printed vs. commercial plates.