Synthesis of 1,5-bis(4,6-dichloro-1,3,5-triazinylamino)naphthalene and its application to spectrofluorimetric determination of aniline.

A new fluorescent reagent 1,5-bis(4,6-dichloro-1,3,5-triazinylamino)naphthalene (DTAN) was synthesized. The optimum conditions of fluorescent reaction of this reagent with aniline (PA) were also investigated. Based on this reaction, a new spectrofluorimetric method was developed for the determination of aniline. The fluorescent intensity was directly proportional to the concentration of aniline in the ranges 0.05-2.0 microg mL(-1) and 2.0-50 microg mL(-1) with the detection limits of 34 ng mL(-1) and 90 ng mL(-1). This method is simple, practical and can afford good precision and accuracy and can be successfully applied to assess aniline in water samples. A possible mechanism of the change of fluorescence intensity introduced by putting the aniline into the system is also discussed.

Spectrofluorimetric determination of dopamine using 1,5-bis(4,6-dicholro-1,3,5-triazinylamino) naphthalene.

A new fluorescent reagent, 1,5-bis(4,6-dichloro-1,3,5-triazinylamino)naphthalene, containing two active chlorines, was synthesized by a one-step reaction. Under the optimum conditions for the determination of dopamine, the enhanced fluorescence intensity is proportional to the dopamine concentration. The fluorescence intensity was measured at lambda(ex/em) = 400/460 nm, with and without dopamine. The linear range and detection limit for the determination of dopamine were 1.0 x 10(-7) mol/L-5.0 x 10(-5) mol/L and 4.0 x 10(-8) mol/L. This method is simple, practical, can afford good precision and accuracy and can be successfully applied to assess dopamine in injections and human serum samples.

Highly sensitive spectrofluorometric determination of trace amounts of mercury with a new fluorescent reagent, 2-hydroxy-1-naphthaldehydene-8-aminoquinoline.

A new fluorescent reagent, 2-hydroxy-1-naphthaldehydene-8-aminoquinoline (HNAAQ), was synthesized. The fluorescent reaction of this reagent with mercury was also studied. Based on this chelation, a highly sensitive spectrofluorometric method was developed for the determination of trace amounts of mercury in a water-ethanol (5 + 1, v/v) medium at pH 8.0. Under these conditions, the Hg-HNAAQ complex has excitation and emission maxima at 406 and 445 nm, respectively. The linear range of the method is from 0 to 16 microg L(-1) and the detection limit is 0.056 microg L(-1) of mercury. The interference of other ions was studied. In order to enhance the selectivity in the determination of mercury by the present method, we also applied the separation of mercury by distillation. Thus, the selectivity of the method could be increased remarkably. The procedure can be easily performed, and affords good precision and accuracy. This method has been successfully applied to the determination of mercury in waste water and prawns.

Lysozyme-enhanced europium(III)-metacycline luminescence and its application to the determination of metacycline.

A new spectrofluorometric method is described for the determination of metacycline (MC), based on modified enzyme-amplified lanthanide luminescence. Under the optimum conditions, Eu3+-MC forms a ternary complex with lysozyme in close proximity. Then lysozyme can remarkably enhance the characteristic fluorescence intensity of Eu3+ at 612 nm in metacycline-Eu3+ binary complex. The enhanced fluorescence intensity is in proportion to the concentration of MC. The limit of detection is 1.6 x 10(-8) mol L(-1), with a linear range from 6.2 x 10(-6) to 1.7 x 10(-5) mol L(-1). Interferences of other coexisting substances were studied. The developed method was successfully applied to the determination of MC in serum and urine samples. The mechanism of fluorescence enhancement was also studied.

Enzyme-amplified lanthanide luminescence based on complexation reaction--a new technique for the determination of doxycycline.

A new spectrofluorimetric method is described for the determination of doxycycline, based on modified enzyme-amplified lanthanide luminescence. Under the optimum conditions, Eu(3+)-doxycycline forms a ternary complex with lysozyme in close proximity and lysozyme can remarkably enhance the characteristic fluorescence intensity of Eu(3+) at 612nm in doxycycline-Eu(3+) binary complex. The enhanced fluorescence intensity is in proportion to the concentration of doxycycline. The limit of detection is 1.28 x 10(-8) moll(-1), with a linear range from 1.7 x 10(-7) to 1.7 x 10(-6) moll(-1). Interferences of other coexisting substances were studied. The developed method was successfully applied to the determination of doxycycline in serum, urine and real samples. The mechanism of fluorescence enhancement was also studied.

Study of the interactions between tetracycline analogues and lysozyme.

The interactions between tetracycline analogues (oxytetracycline, doxycycline, methacycline) and lysozyme (LYSO) were studied by using UV-visible absorption and spectrofluorimetric method. Tetracycline analogues can make LYSO's fluorescence quenching. The quenching mechanism is static quenching. Absorption spectrum and quenching constant all support this conclusion. The binding constants of tetracycline analogues with LYSO were obtained at various temperatures. According to the Förster nonradiative energy transfer theory, we can get the distances of donators and acceptors. We also determined the main acting force between them is electrostatic gravitation according to the thermodynamic parameter.

[Spectrophotomatric determination of antioxidative activity of extractives of Chinese traditional medicine by supercritical fluid CO2 extraction technology].

Applying supercritical CO2 fluid extraction technology, flavonoids were extracted from Chinese traditional medicine asarum heterotropoides, atractylodes macrocephala, and rheum palmatun. Using the method of autoxidation pyrogallol (known as 325 nm method), the superoxide radical scavenging effect of the extraction was carried out in the buffer solution of HCl-tris (pH 8.2). With spectrophotometry, hydroxyl radical created by the system Co2+ + H2O2 in the reaction like Fenton reaction was eliminated by alizarin violet as the color developing agent in the buffer solution HCl-tris (pH 9.0) and the reaction condition was investigated. Result showed that these extractions are elimination agent for these radicals. Asarum heterotropoides is the best of the three.

Study of the interaction between daunorubicin and human serum albumin, and the determination of daunorubicin in blood serum samples.

The interactions between daunorubicin and human serum albumin (HSA) were studied using the spectrofluorimetric method. The binding constants of daunorubicin with HSA were obtained at different temperatures. The effects of various metal ions on the binding constants of daunorubicin with HSA were also studied. The optimum conditions of fluorometric determination of daunorubicin were studied and the developed method was successfully applied to the determination of daunorubicin in serum samples.

[Studies on the interaction mode between polymyxin B sulfate and DNA with EB as a fluorescence probe].

The interaction between polymyxin B sulfate and ct-DNA was studied with ethidium bromide (EB) probe by UV spectroscopy, fluorescence spectroscopy, fluorescent polarization etc. The phenomena of hyperchromism effect and fluorescence quenching proved that polymyxin B sulfate in buffer solution at pH 7.4 can intercalate into the base pairs of ct-DNA. This interaction can cause conformational change of ct-DNA double helix. This interaction can be inhibited in the presence of high concentration of ions. At the same time, PB can combine with the phosphate group of ct-DNA by non-characteristic static force. In this paper, the interaction of PB and ct-DNA was made further discussion.