A flow injection biosensor system for highly sensitive detection of 2,4,6-trichlorophenol based on preoxidation by ceric sulfate

A flow injection biosensor system was proposed for the highly sensitive detection of 2,4,6-trichlorophenol (2,4,6-TCP). The system is based on the preoxidation by ceric sulfate to the corresponding benzoquinone (2,6-dichloro-1,4-benzoquinone: 2,6-DC-1,4-BQ), which was characterized using cyclic voltammetry, hydrodynamic voltammetry, and UV-vis spectrophotometry. The laccase-based biosensor used in this analytical system responded sensitively to 2,4,6-TCP after the preoxidation by ceric sulfate. The response could be based on the bioelectrocatalytic recycling of oxidation product (2,6-DC-1,4-BQ) between laccase membrane and the electrode, because the oxidation product (2,6-DC-1,4-BQ) of 2,4,6-TCP was an electrochemically reversible redox species. The signal current was linearly related to the 2,4,6-TCP concentrations in a dynamic range of 2 nM - 2 microM; the slope and the y-intercept of the straight line were 1150 nA microM(-1) and 0.88 nA, respectively. The detection limit was 1.2 nM (S/N = 3) for a 20 microl injection. Among a variety of chlorophenols and some phenolic compounds, the only interferent was 2,4-dichlorophenol.

Fluorescent molecular sensory system based on bis pyrene-modified gamma-cyclodextrin dimer for steroids and endocrine disruptors

A gamma-cyclodextrin dimer modified with two pyrene moieties, 6-(2-pyrenebutylate-aminoethyl)pyrenebutylate-amino-6-deoxy-bis-gamma-cyclodextrin, has been synthesized in the presence of N,N'-dicyclohexycarbodiimide from gamma-cyciodextrin dimer linked with ethylenediamine at an upper rim. The sensing ability and binding property of the titled dimer were investigated for bile acids and endocrine disruptors. This cyclodextrin dimer showed both monomer and excimer fluorescence; the guest-induced emissions were observed as increases or decreases depending on the guest. The values deltaI(m)/I0(m) and deltaI(ex)/I0(ex), where I0(m) and I(m) are fluorescence intensities of monomer emission in the absence and presence of a guest and I0(ex) and I(ex) are those of excimer emission and deltaI(m) and deltaI(ex) were I(m) - I0(m) and I(ex) - I0(ex), respectively, were used as a parameter of sensitivity. This host exhibited highly sensitive molecular recognition ability for bile acids and endocrine disruptors, in which the sensing parameters obtained from monomer emission were plus or minus values, whereas the parameters obtained as excimer emission were minus ones. The behavior of the appended moieties of the host during a host-guest complexation was studied by induced circular dichroism (ICD) and fluorescence spectra. The ICD intensities of the titled dimer were decreased upon an addition of a guest. The guest-induced variations in the fluorescence and ICD intensity suggest that the appended moieties move by altering the spatial relationship in the hydrophobic space between two linked cyclodextrins.