87667-33-2Relevant academic research and scientific papers
Combined Surface-Enhanced and Resonance-Raman Scattering from the Aspartic Acid Derivative of Methyl Orange on Colloidal Silver
Sliman, O.,Lepp, A.,Kerker, M.
, p. 5319 - 5325 (1983)
By selecting a chromophore, dabsyl (N-4-dimethylaminoazobenzene-4'-sulfonyl) aspartate (DABS-ASP), whose absorption spectrum overlaps with the surface-enhanced Raman scattering (SERS) excitation profile for colloidal silver sols, we have found it possible to study the triple combination of resonant Raman scattering (RRS) of the DABS-ASP in solution and both the combined RRS-SERS (SERRS) and the SERS of DABS-ASP adsorbed on the colloidal silver particles.The SERRS and SERS spectra were distinctly different from each other.The measured surface enhancements were in excess of 103.This is less than the values of the order of 105 measured earlier for citrate on these silver sols.Just as for citrate, the excitation profiles peaked at about 500 nm whereas the main absorption band was in the region of 400 nm, a disparity from our electrodynamic model for SERS.
Center-of-mass iso-energetic collision-induced decomposition in tandem triple quadrupole mass spectrometry
Rubino, Federico Maria
, (2020)
Two scan modes of the triple quadrupole tandem mass spectrometer, namely Collision Induced Dissociation Precursor Ion scan and Neutral Loss scan, allow selectively pinpointing, in a complex mixture, compounds that feature specific chemical groups, which yield characteristic fragment ions or are lost as distinctive neutral fragments. This feature of the triple quadrupole tandem mass spectrometer allows the non-target screening of mixtures for classes of components. The effective (center-of-mass) energy to achieve specific fragmentation depends on the inter-quadrupole voltage (laboratory-frame collision energy) and on the masses of the precursor molecular ion and of the collision gas, through a non-linear relationship. Thus, in a class of homologous compounds, precursor ions activated at the same laboratory-frame collision energy face different center-of-mass collision energy, and therefore the same fragmentation channel operates with different degrees of efficiency. This article reports a linear equation to calculate the laboratory-frame collision energy necessary to operate Collision-Induced Dissociation at the same center-of-mass energy on closely related compounds with different molecular mass. A routine triple quadrupole tandem mass spectrometer can operate this novel feature (iso-energetic collision-induced dissociation scan; i-CID) to analyze mixtures of endogenous metabolites by Precursor Ion and Neutral Loss scans. The latter experiment also entails the hitherto unprecedented synchronized scanning of all three quadrupoles of the triple quadrupole tandem mass spectrometer. To exemplify the application of this technique, this article shows two proof-of-principle approaches to the determination of biological mixtures, one by Precursor Ion analysis on alpha amino acid derivatized with a popular chromophore, and the other on modified nucleosides with a Neutral Fragment Loss scan.
