Gz Chen

Derivative constant-energy synchronous fluorescence for simultaneous analysis of polynuclear aromatic hydrocarbon mixtures

Abstract Derivative constant-energy synchronous luminescence spectrometry (DCESLS) was evaluated using four-component mixtures of fluorene, carbazole, anthracene and perylene. The results show the effectiveness of DCESLS for the identification and determination of polynuclear aromatic hydrocarbons.

Determination of thiamine (vitamin B1) by in situ sensitized photochemical spectrofluorimetry

Abstract An in situ photochemical spectrofluorimetric flow-injection method for the determination of thiamine (vitamin B 1 ) is proposed. It is based on the conversion of thiamine in alkaline medium into an intensively fluorescent compound. The photochemical reaction is sensitized by acetone. The determination can be carried out by measuring the fluorescence intensity when the fluorescent signal reaches its maximum or at a fixed time. The calibration graph was linear up to 10.0 μg ml −1 thiamine ( r = 0.9996), the limit of detection was 0.46 ng ml −1 thiamine and the relative standard deviation was 1.5% for 50.0 ng ml −1 thiamine ( n = 6). The kinetic behaviour of the reaction and the effects of some experimental conditions were investigated and are discussed in detail. The mechanism of the sensitization of acetone was examined. Its application to vitamin B 1 tablets and injections was found to be satisfactory. By use of a selection valve and combination with a synchronous fluorescence technique, vitamin B 1 , B 2 and B 6 in pharmaceuticals were simultaneously determined.

Study of room-temperature phosphorescence of 1-bromonaphthalene in sodium dodecylbenzene sulfonate and beta-cyclodextrin solution

Abstract Intense room-temperature phosphorescence (RTP) of 1-bromo-naphthalene (1-BrN) was studied in aerated aqueous solutions containing sodium dodecylbenzene sulfonate (SDBS) and β-cyclodextrin (β-CD). It has been found that considerably enhanced RTP arises from the formation of the 1:1:1/SDBS:1-BrN:β-CD ternary inclusion complex in premicellar solutions. The spectral and structural analyses of molecules indicate that the phenyl ring of SDBS is included in the apolar cavity of β-CD and the polar head group and a part of hydrocarbon chain located outside the cavity. Surface tension of the solutions demonstrates that the presence of micelles results in serious phosphorescence quenching.

Study on total luminescence spectra. Application of the Monte-Carlo method to three-dimensional synchronous fluorescence spectrometry

Abstract Three-dimensional synchronous fluorescence spectrometry (TDSFS, a combination of synchronous fluorescence spectrometry and three-dimensional fluorescence spectrometry) is a new method which has been developed recently. The method has usually been used as an efficient tool to select the best Δλ value for synchronous fluorescence spectra. This paper studies the sensitivity of the method, which was not been done in the past. The total fluorescence intensity has been used instead of the conventional single point intensity, calculated by the Monte-Carlo method, as the experimental parameter to determine fluorescein and tryptophan. The sensitivity of the total fluorescence method is nearly one hundred times better than that of the single point method. The new method has been used to simultaneously determine naphthalene, pyrene and perylene successfully. The mechanism of the method has also been studied.

Room temperature phosphorescence study on supramolecular system of cyclodextrin/surfactants

THE microenvironmental properties of cyclodextrin/surfactants supramolecular system have been investigated with a variety of methods. Usually, a 1:1 stoichiometry of cyclodextrin/surfactant and noneffectiveness of cyclodextrin on the micellization behavior are reported

Sensitized room temperature phosphorescence of biacetyl in reversed micelles

Abstract The energy transfer between α-naphthylacetic acid (α-NAA) and biacetyl (BIAC) has been investigated in normal micelles of sodium dodecylsulfate (SDS) and reversed micelles of di-2-ethylhexylsodium sulfosuccinate (AOT). It has been observed that the sensitized room temperature phosphorescence intensity of BIAC in AOT reversed micelles is about 13 times greater than that in SDS normal micelles. Parameters that may influence the sensitized phosphorescence of BIAC, including the concentration of AOT, solubilized water and the concentrations of α-NAA and BIAC, have been examined. The absorption and luminescence spectra as well as microviscosity data are used to elucidate the factors that may affect the sensitized phosphorescence of BIAC. It is suggested that the sensitized phosphorescence of BIAC may be affected by two factors: the protective effect afforded by the micellar media and the Poisson distribution. At low W ([H 2 O]/[AOT]) values, no remarkable influence of water content on the sensitized phosphorescence of BIAC has been observed, and the sensitized phosphorescence of BIAC decreases with the increase of water content at W > 20.

Study on strongly polarized water in AOT reversed micelles by fluorescence probes and analytical application of AOT reversed micelles

Abstract The basicity of water in AOT (sodium bis(2-ethyl-1-hexyl)sulfosuccinate) reversed micelles has been investigated by tetracycline-Eu 3+ complex and tetracycline as fluorescence probes. The results obtained show that the variation in luminescence intensity and absorption spectra of the compounds together with a decrease in water content of the reversed micelles coincides with an increase in the pH value of the bulk water. It indicates that with a gradual decrease in the R ([H 2 O]/[AOT]) value water molecules become more polarized, like the hydroxide ion. The apparent pH in reversed micelles at R = 1.5–2.0 is ca. 9. The properties of the water pool in reversed micelles can be utilized for sensitive detection of tetracycline and analogues without addition of alkaline solutions. The detection limit is in the subnanogram range.

Sensitized room temperature phosphorescence of biacetyl in AOT reversed micelles-dodecylammonium α-naphthylacetate as energy donor

Abstract The energy transfer between dodecylammonium α-naphthylacetate (DA+NAA−) and biacetyl has been investigated in normal micelles of CTAC, SDS and reversed micelles of AOT. A surfactant with α-naphthylacetate counterion has been synthesized. Parameters that may influence the sensitized phosphorescence of biacetyl, including the concentration of AOT, solubilized water, and the concentration of DA+NAA− and biacetyl, have been examined. The absorption and luminescence spectra as well as polarization data are used to elucidate the factors that may affect the sensitized phosphorescence of biacetyl. It is suggested that the sensitized phosphorescence of biacetyl be affected by two factors, the protective effect afforded by micellar media and the Poisson distribution. Since the α-naphthylacetate moiety is associated with the DA+ surfactant, it is anchored to the head group in reversed micelles of AOT where biacetyl is solubilized. It has been observed that the RTP characterization of biacetyl sensitized by DA+NAA− with changing of AOT or W ([H 2 O] [AOT] ) in AOT reversed micelles is different from that sensitized by NAA. The remarkable influence of water content on the sensitized phosphorescence of biacetyl has been observed with the increase of water content. The detection limit of biacetyl by using DA+NAA− as the donor is about three times lower than that by using NAA as the donor. It indicates that DA + NAA− is a more efficient donor than NAA.

TOTAL INTEGRATION METHOD OF THREE-DIMENSIONAL FLUORESCENCE SPECTROMETRY

THREE-dimensional fluorescence spectrometry (TDFS) is a new technique of spectrofluorimetry that was developed two decades ago.Making use of the abundant information of