[Study on the inclusion behavior of p-sulphonatocalix[4]arene with acridine by spectrofluorometric titrations].

p-sulphonatocalix[4] arene (1) was prepared according to the literature, and spectrofluorometric titrations were performed to investigate the inclusion behavior of (1) and acridine in citrate buffer solution (pH 5.92, 0.1 mol x L(-1)) at different temperatures. It was found that in definite concentration range, the emission peak of acridine exhibited a slight red shift and th fluorescence intensity decreased when (1) was added. They form stable host-guest complex, and the stoichiometry of the inclusion complex is 1 : 1. The stability constants of the inclusion complex at 15.0 degrees C, 20.0, 25.0 and 30.0 degrees C were determined as 3.08 x 10(5), 4.45 x 10(4), 2.58 x 10(4) and 8.90 x 10(3), respectively. The thermodynamic parameters of inclusion process, deltaG, deltaH and deltaS, were determined. The experimental results indicated that the inclusion process was an exothermic and enthalpy-driven process. It was found that the stability constants descended when temperature rose. The most probable pattern of the inclusion complex between (1) and acridine was proposed as: acridine partially goes into the cavity of (1), and the protonated N atom and the negatively charged sulphonyl group bond firmly owing to strong electrostatic interaction. With the main contribution of electrostatic interaction and the assistance of Van de Waals and hydrophobic interaction, the host and the guest molecules form 1 : 1 supramolecular complex.

[Highly sensitive spectrofluorimetric determination of trace amounts of nitrite with N-(1-naphthyl) ethylenediamine].

A simple and sensitive fluorescence quenching method for the determination of trace nitrite was developed. The method is based on the reaction of NED with nitrite in acidic medium to form a new compound, which has weak fluorescence. The linear range was 1.07-214.0 microg x L(-1) with a 3sigma detection limit of 0.069 microg x L(-1) under the optimum experimental conditions. This proposed method has been applied to the determination of trace amounts of NO2- in tap water and lake water without extraction.

[Spectrum studies and application of the reaction system phenanthroline-EBT-H2O2].

A kinetic spectrophotometric method for the determination of trace phenanthroline was proposed. The method is based on the inhibition of phenanthroline to the discoloring reaction of EBT oxidized by hydrogen peroxide in the dilute acetic acid solution. At the same time, the kinetic parameters were studied in detail. Under optimum experimental conditions, the linear range is 0.003-0.08 mg x L(-1), and the detection limit is 4.0 microg x L(-1). The method is simple, rapid, and easy to operate. The method was applied to the determination of trace phenanthroline in water samples with satisfactory results.

[Highly sensitive spectrofluorimetric determination of trace amounts of chromium (VI) with mono[6-o-(4-aminobenzoic acid)]-beta-cyclodextrin].

A novel fluorescence probe, mono[6-o-(4-aminobenzoic acid)]-beta-cyclodextrin(ACD), was synthesized, and a new sensitive fluorescence identification reaction was studied based on the reaction of Cr2O7(2-) with compound ACD in NaAc-HAc buffer medium at pH 4.90. Under optimal conditions the determination limit was 1.26 microg x L(-1). The linear range was 5.20-1040 microg x L(-1). This method has been applied to the determination of trace amounts of chromium (VI) in electroplating liquor, electroplating waste water with satisfactory results.