High performance thin layer chromatography with eluents containing SDS aided by UV- and Raman spectroscopy

Area of Science:

• Analytical Chemistry
• Chromatography
• Spectroscopy

Background:

• Non-polar silica gel plates are commonly used in chromatography.
• Sodium dodecyl sulphate (SDS) is a surfactant with potential applications in modifying chromatographic stationary phases.
• Raman spectroscopy offers insights into molecular interactions and structural changes.

Purpose of the Study:

• To investigate the modification of silica gel plates using aqueous-organic solvent with SDS.
• To explore the application of Raman spectroscopy in analyzing SDS-modified sorbents and drug-SDS complexes.
• To develop and optimize a thin-layer chromatography (TLC) method for the separation and quantitative analysis of neurodegenerative drugs using SDS-modified RP-18 W plates.

Main Methods:

• Modification of RP-18 W silica gel plates with sodium dodecyl sulphate (SDS) in aqueous-organic solvent.
• Analysis of sorbent modification and carbamazepine-SDS complexes using Raman spectroscopy.
• Thin-layer chromatography (TLC) for the separation of neurodegenerative drugs (sulpiride, olanzapine, carbamazepine, trazodone, clomipramine, pridinol).
• Determination of critical micelle concentration (CMC) of SDS using conductometry and spectrophotometry.
• Optimization of mobile phase composition and evaluation of chromatographic parameters (tailing factor, asymmetry factor, separation efficiency).
• Quantitative analysis using LOD and LOQ determination and application to pharmaceutical preparations.

Main Results:

• Raman spectroscopy confirmed changes in the silica gel sorbent upon SDS modification and provided insights into carbamazepine-SDS complex formation.
• The developed TLC method enabled the separation of a mixture containing six neurodegenerative drugs.
• Critical micelle concentration of SDS was determined, confirming micellar formation.
• Chromatographic parameters like tailing and asymmetry factors were improved for most compounds, with values close to 1.0.
• Separation efficiency was measured, with the height of the theoretical plate varying from 39 to 73 μm.
• Optimized method demonstrated good sensitivity for quantitative analysis, with LOD values ranging from 0.22 to 1.67 μg/spot and LOQ values from 0.66 to 5.07 μg/spot.
• The method was successfully applied to the quantitative analysis of drugs in pharmaceutical preparations.

Conclusions:

• The modification of RP-18 W TLC plates with SDS is a viable strategy for enhancing the separation of neurodegenerative drugs.
• The combined use of TLC, Raman spectroscopy, and conductometry provides a comprehensive approach for analyzing chromatographic systems.
• This novel method offers improved or comparable analytical performance for certain compounds compared to existing methods.
• The developed method opens new avenues for the quantitative analysis of drugs in pharmaceutical formulations.