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In-process control during chemical synthesis of ergoline psychedelics by HPTLC

Introduction

HPTLC is a powerful technique enabling high sample throughput capacity, short analysis time, and low operating costs. Our case study demonstrates a rapid way of in-process control during chemical synthesis.


Challenge

Commonly used chromatographic techniques require a time- and cost-intensive sample preparation step. In many cases HPTLC allows one to analyze several samples side-by-side with little to no sample preparation. The progress of a reaction during a chemical synthesis and of purification can easily be monitored by comparing samples on the same plate side-by-side.


Description of the procedure & documentation

All samples are directly applied from each step of the chemical synthesis without sample preparation on an HPTLC plate (silica gel 60 F254). The visionCATS method file is opened and executed, creating a new analysis file. In this visionCATS analysis file the sequence table is completed (Vial ID, description of samples and references, and selection of the rack position of each vial). An image of the clean plate under UV 254 nm is captured with the TLC Visualizer. The samples and standards are applied bandwise onto the HPTLC plate using the Automatic TLC Sampler 4 (ATS 4), which guarantees precise and reliable application. Then the HPTLC plate is developed using the Automatic Developing Chamber 2 (ADC 2) allowing for reproducibility between plates. For visualization the plate is documented with the TLC Visualizer under UV 254 nm and UV 366 nm. Spectra from 200 to 500 nm are recorded with the TLC Scanner 4 and visionCATS. The purified product zone of interest is eluted with the TLC-MS Interface 2 and confirmed by HPTLC-MS.


Synthesis of ergoline psychedelics: In a first step the lysergic acid (LysS) is produced with ergotamine as the starting material. Then the formation of the amide takes place, with e.g. LSP (Lysergic acid 3-pentyl amide) as finished product.


Images of the results: Chromatogram under UV 254 and UV 366 nm, UV spectra and mass spectra of LSP (finished product)

 

Track Sample
Track 1 LSD (reference)
Track 2 Digest of the lysergic acid from ergotamine
Track 3 Purified lysergic acid (starting material for the chemical synthesis)
Track 4 Crude synthesis product (LSP and side products)
Track 5 First column purification step
Track 6 Second column purification step
Track 7 Purified LSP (finished product)

Image Comparison of the different purified ergoline psychedelics: LSD (Lysergic acid diethylamide, LSZ (Lysergic acid 2,4-dimethylazetidide) and LSM (N-Morpholinyllysergamide) are synthesized and purified in the same way as LSP. The purified products are shown below.

 

Track Sample
Track 1 LSD (reference), UV 254 nm
Track 2 LSD (reference), UV 366 nm
Track 3 LSZ*, UV 254 nm
Track 4 LSZ*, UV 366 nm
Track 5 LSM, UV 254 nm
Track 6 LSM, UV 366 nm
Track 7 LSP, UV 254 nm
Track 8 LSP, UV 366 nm

 
*two product zones due to the formation of the isomers


Benefits of using modern HPTLC for the analysis of drugs

  • HPTLC is suitable as a high throughput and low cost technique for the analysis of drugs.
  • HPTLC is used for determination of purity and for stability studies (shelf life).
  • HPTLC allows the separation of several samples in parallel on one plate and is therefore excellently suited for process monitoring.
  • HPTLC visualizes the similarities and differences between samples at a glance on a plate (e.g. to monitor up- and downscaling processes) and by using the software visionCATS to even compare between plates created years apart.
  • HPTLC-MS is a fast way for substance confirmation.
 
 
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