Fluorescence characterization of acid-base interaction and mobility at Chromatographic interfaces

Uhl, S.; Rempfer, K.; Egelhaaf, Hans‐Joachim; Lehr, B.; Oelkrug, D.

doi:10.1016/0003-2670(94)00624-u

Cited by 7 publications

(3 citation statements)

References 28 publications

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“…Indeed, the formation of singlet excited ANH + has been reported in not-pretreated alumina. 27 It has been reported that the excited-state pK a of acridine is 10.35, 28 much larger than for its ground state (pK a ) 5.45). This large change in pK a has been explained as resulting from the acquisition of a higher electron density by the nitrogen heteroatom in the excited state than in the ground state, facilitating the proton addition reaction.…”

Section: B Steady-state Emission Spectramentioning

confidence: 98%

“…The authors suggested that the acidity of the alumina was higher when physiadsorbed water was removed, resulting in higher yields of formation of protonated acridines than on the unactivated surfaces . The adsorption and emission spectra of acridine on silica gel pretreated at different temperatures ( T a ) provided evidence of the presence of protonated acridines at low T a (100 or 180 °C), and a larger yeld of neutral acridine species at higher T a (300−800 °C). ,− In addition, the formation of singlet excited protonated acridine has been reported on silica. ,,, These studies have demonstrated that the type of the acridine species produced on the inorganic solids depends on the acidic properties of the substrate and its water content.…”

Section: Introductionmentioning

confidence: 99%

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Characterization of Acridine Species Adsorbed on (NH₄)₂SO₄, SiO₂, Al₂O₃, and MgO by Steady-State and Time-Resolved Fluorescence and Diffuse Reflectance Techniques

2005

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The ground- and excited-state species of acridine adsorbed on (NH(4))(2)SO(4), SiO(2), Al(2)O(3), and MgO surfaces were investigated in order to determine the precursor species and electronic states responsible for acridine photodegradation on particles serving as models of atmospheric particulate matter. The species present on each solid surface were characterized by comparing the steady-state absorption and fluorescence spectra, time-resolved fluorescence, and absorption measurements on acridine in solution with those corresponding to adsorbed acridine. On silica, the ground-state species present were hydrogen-bonded, neutral, and protonated, while on alumina hydrogen-bonded and neutral species were identified. A comparison of the protonated acridine absorption and emission intensities on silica and alumina with those observed for acridine in acidic water demonstrated that the emission on the surfaces is higher than expected. This was interpreted as resulting from photoprotolytic reactions on silica and alumina. For acridine adsorbed on ammonium sulfate, protonated acridine was the only adsorbed species identified. Since, at a similar ground-state absorbance, the fluorescence intensity of acridine on ammonium sulfate was smaller than for acridine in acidic water, the quenching of the excited state or a rapid photochemical reaction with the surface was proposed. On magnesium oxide, the presence of neutral and hydrogen-bonded acridine species were characterized from the two-component analysis of the fluorescence, the triplet-triplet absorption decay curves, and the time-resolved emission spectra at different time delays. As demonstrated in these studies, acridine adsorbed species and their decay pathways depend on the acidic properties of these models of atmospheric particulate matter. In addition, a comparison of the photodegradation rates of acridine on the different solids tested is presented and discussed in terms of the nature of the species and their decay pathways.

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Section: B Steady-state Emission Spectramentioning

confidence: 98%

Section: Introductionmentioning

confidence: 99%

Characterization of Acridine Species Adsorbed on (NH₄)₂SO₄, SiO₂, Al₂O₃, and MgO by Steady-State and Time-Resolved Fluorescence and Diffuse Reflectance Techniques

2005

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“…The practical usefulness of the RP-HPLC technique, however, seems to distract the chromatographer's attention from the theoretical problems that are left unsolved . For example, stationary phase stability and the relation between molecular stationary phase structure and chromatographic retention mechanism are still topics of discussion among stationary phase researchers. − Especially residual silanol functionalities, which remain at the silica surface after derivatization with alkylsilanes, have been the subject of investigation. − Apart from the solvophobic interactions between solutes and the nonpolar octadecyl phase, also the silanophilic interactions with residual silanols had to be taken into account to explain the observed chromatographic separation characteristics of silica-based alkylsilane phases.…”

Section: Introductionmentioning

confidence: 99%

Fundamental Study of Residual Silanol Populations on Alkylsilane-Derivatized Silica Surfaces

et al. 1996

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Two commercially available reversed phases for high-performance liquid chromatography (one dimethyl-n-octadecylsilane phase and one di-isobutyl-n-octadecylsilane phase) and the native silica substrate were subjected to deuterium exchange in a mobile phase-like medium of acetonitrile and deuterium oxide (90/10, v/v). 29Si cross-polarization magic-angle-spinning (CP MAS) NMR was used to obtain information on the amounts and relaxation behavior of the internal silanols of the silica substrate, and the residual silanols of the alkylsilane-derivatized phases. Consequences for the correlation of silanol 29Si CP MAS NMR data and chromatography are discussed. Detection of deuterated silanol (SiOD) signals in 29Si CP MAS NMR of deuterium-exchanged phases depends on a transfer of magnetization (cross-polarization) from silane protons to silanol silicon atoms. It is concluded that a large portion of the residual silanol NMR signal of the phases stems from internal silanols and from silanols that are spatially very close to an alkylsilane attachment site. The former are considered chromatographically irrelevant while the latter are assumed to be inaccessible for analytes during the chromatographic separation process for reasons of steric constraints. One bulky di-isobutyl-n-octadecylsilane is capable of cross-polarizing proton magnetization to 0.8 residual surface silanols, whereas this is only 0.3 for the conventional octadecylsilane with dimethyl side groups. However, the lower surface concentration of bulky alkylsilanes leaves more space for free, unhindered silanols. The most important factor determining the relaxation behavior of the residual silanol NMR signal is the mobility of the octadecylsilane side chains, bulky silanes having the larger mobility quenching effect on residual silanols.

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Synthesis, Fluorescence Properties, and Head-to-Tail Regioselectivity in the Photodimerization of a Donor–Acceptor-Substituted Anthracene

Ihmels

1999

Eur. J. Org. Chem.

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The novel 2,6‐donor–acceptor‐substituted anthracene, namely 6‐methoxy‐2‐anthracene carboxylic acid (7), was synthesized. The emission of this compound exhibits significant solvatochromism. The fluorescence band position and intensity are also remarkably sensitive to H+. Irradiation of the anthracene 7 in solution yields the syn and anti head‐to‐tail dimers exclusively. A synergistic electronic effect between the donor and acceptor substituents is proposed to operate on the photophysical and photochemical properties of anthracene 7.

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Fluorescence characterization of acid-base interaction and mobility at Chromatographic interfaces

Cited by 7 publications

References 28 publications

Characterization of Acridine Species Adsorbed on (NH₄)₂SO₄, SiO₂, Al₂O₃, and MgO by Steady-State and Time-Resolved Fluorescence and Diffuse Reflectance Techniques

Characterization of Acridine Species Adsorbed on (NH₄)₂SO₄, SiO₂, Al₂O₃, and MgO by Steady-State and Time-Resolved Fluorescence and Diffuse Reflectance Techniques

Fundamental Study of Residual Silanol Populations on Alkylsilane-Derivatized Silica Surfaces

Synthesis, Fluorescence Properties, and Head-to-Tail Regioselectivity in the Photodimerization of a Donor–Acceptor-Substituted Anthracene

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Fluorescence characterization of acid-base interaction and mobility at Chromatographic interfaces

Cited by 7 publications

References 28 publications

Characterization of Acridine Species Adsorbed on (NH4)2SO4, SiO2, Al2O3, and MgO by Steady-State and Time-Resolved Fluorescence and Diffuse Reflectance Techniques

Characterization of Acridine Species Adsorbed on (NH4)2SO4, SiO2, Al2O3, and MgO by Steady-State and Time-Resolved Fluorescence and Diffuse Reflectance Techniques

Fundamental Study of Residual Silanol Populations on Alkylsilane-Derivatized Silica Surfaces

Synthesis, Fluorescence Properties, and Head-to-Tail Regioselectivity in the Photodimerization of a Donor–Acceptor-Substituted Anthracene

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Characterization of Acridine Species Adsorbed on (NH₄)₂SO₄, SiO₂, Al₂O₃, and MgO by Steady-State and Time-Resolved Fluorescence and Diffuse Reflectance Techniques

Characterization of Acridine Species Adsorbed on (NH₄)₂SO₄, SiO₂, Al₂O₃, and MgO by Steady-State and Time-Resolved Fluorescence and Diffuse Reflectance Techniques