On-line detection of mesogenic azoxybenzenes by combined liquid chromatography and Raman spectrometry

Abstract

16) Fales, H. M.; Lukkainen, T. Anal. Chem. 1965, 37, 955. (17) Burgett, C. A.; Smlth, 01. H.; Bente, H. B.

Surface-enhanced resonance Raman spectroscopy of liquid chromatographic analytes on thin-layer chromatographic plates

“…The parameters that were optimized in order to maximize the signal intensity and preserve the LC peak shapes were (1) the time delays during deposition of the analyte to the TLC plate, (2) the total flow rate of the mobile phase and the 12 " The laser power on the sample was 100 mW with the intensity monitored at the 1593-cm"1 band of the dye. 6 The standard deviations are given in parentheses.…”

“…One method to overcome this inefficiency is the use of a laser with an emission line in resonance with an electronic transition of the analyte molecule; i.e., resonance Raman spectroscopy (RRS). DOrazio and Schimpf (1) reported the RRS detection of LC-separated azoxybenzenes. Sensitivities in the millimolar range were attained.…”

“…Surface-enhanced resonance Raman spectroscopy (SERRS) is employed as the detection method in this study for the interrogation of LC analytes which have been transferred onto a thin-layer chromatography (TLC) plate. The coupling of LC to TLC with SERRS analysis offers several unique advantages such as the following: (1) The isolation of the LC analytes on a TLC plate allows the acquisition of complete SERRS spectra with conventional scanning spectrometers which would be otherwise difficult in a flowing LC liquid. (2) The properties of analytes in the adsorbed state may differ and have desirable spectroscopic features from that in solution.…”

Online Liquid Chromatography–Raman Spectroscopy Using the Vertical Flow Method

“…The resonance effect intensifies the Raman signal. The resonance effect occurs when the excitation wavelength matches the electronic absorption band of chromophores; the LOD is reportedly 15–50 ng mL –1 of polycyclic aromatic hydrocarbons and 2 × 10 –5 mol L –1 of azoxybenzenes . Surface-enhanced Raman scattering (SERS) also intensifies the signal of molecular vibration.…”

“…The resonance effect occurs when the excitation wavelength matches the electronic absorption band of chromophores; the LOD is reportedly 15−50 ng mL −1 of polycyclic aromatic hydrocarbons 11 and 2 × 10 −5 mol L −1 of azoxybenzenes. 12 Surface-enhanced Raman scattering (SERS) also intensifies the signal of molecular vibration. The LC-SERS method has markedly improved the sensitivity of the analyses of purine bases, for example, LOD of 0.2−0.3 ng L −1 , 13 and 100−500 pmol.…”