Device for Raman Difference Spectroscopy

Abstract

A new layout of a versatile Raman difference setup is presented. The new device combines the advantages of the rotating cell for exploitation of the resonance Raman enhancement and the high precision of Raman difference spectroscopy together with the multiplex advantages and very high quantum efficiency offered by a CCD detector. While Raman difference spectroscopy is the most accurate method for the detection of very small band shifts, the method requires the strict prevention of any environmental perturbation of one of the two spectra, which are used for the difference spectra calculation. The presented device satisfies this requirement by implementing a double-beam layout, where the simultaneously detected Raman signals of two sample cells are combined within a Y-fiber bundle and imaged together onto the CCD detector. The accuracy of the new apparatus in detecting frequency shifts and minor sample components is greatly increased compared to conventional Raman spectroscopy as shown by studying binary mixtures of CHCl3 and CCl4. Hereby it was possible to resolve a formerly undetected shift of <0.02 cm(-1) of the CCl4 band at 218 cm(-1). The new RDS setup has a very versatile design. The device can take advantage of the high sensitivity and selectivity of the resonance Raman enhancement applying excitation wavelengths from the UV to NIR and can be used for a variety of samples with only minor changes in the optical arrangement. The new device will be of utmost importance for a fast, gentle, sensitive, selective, and precise investigation of biomolecules and their interactions. Some first results are shown concerning the interaction of the antimalarial chloroquine with hematin in a hydrous environment.

Attenuated Total Reflection Infrared Difference Spectroscopy (ATR-IRDS) for Quantitative Reaction Monitoring

“…In principle, this method is a common tool in the field of vibrational spectroscopy, for example, to visualize tiny changes in the shape or position of spectral lines for studying intermolecular interactions. 16 In such an application, two Raman or IR spectra, recorded under slightly different conditions, are subtracted from each other and the difference spectrum reveals line shifts, for instance. We utilize this approach in a different way taking advantage of the fact that there are no strong intermolecular interactions taking place in the mixtures under investigation that would result in line shifts or line shape changes as would be the case in mixtures of polar solvents.…”

Recent advances in nano-photonic techniques for pharmaceutical drug monitoring with emphasis on Raman spectroscopy

“…In SERS, various advances were achieved for TDM [52,75,76,79,81,83,84,97] of antibiotics [41,75] and anti-cancer drugs [32,35,38,81,130]. Innovative SERS substrates [82,84] represent a breakthrough towards clinical application as they overcome difficulties related to proteins in body fluids.…”

“…Thanks to recent advances in instrumentation, portable devices [28][29][30][31][32] are available and applied on-site, e.g. for drug sensing [33][34][35][36][37][38][39] in forensics [28,29,31,40] and in the pharmaceutical industry [32]. For example, transmission Raman-based methods enable at-line or on-line analysis of bulk content of tablets [41][42][43] or active pharmaceutical ingredients (APIs) of other solid dosage forms [44].…”

Highly Sensitive Detection of the Antibiotic Ciprofloxacin by Means of Fiber Enhanced Raman Spectroscopy

“…Raman spectroscopy is an arising technique [15][16][17][18][19][20][21][22][23], which is based on the vibrations of molecules [24][25][26][27][28] and provides high chemical selectivity [29][30][31][32]. This direct method is non-destructive and can be applied for quantitative measurements [33][34][35][36][37].…”