Shuna Sun

Fluorimetric determination of ascorbic acid with o-phenylenediamine

A simple and sensitive fluorimetric method for the determination of ascorbic acid (AA) is described. The method is based on the condensation reaction between AA and o-phenylenediamine (OPDA) in the absence of the oxidant. The fluorescence intensity is measured at excitation and emission wavelengths of 360 and 430 nm, respectively. Under optimum condition, a linear relationship is obtained between the fluorescence intensity and the concentration of AA in the range of 0.05-40 mug ml(-1). The detection limit is 0.006 mug ml(-1), which is obviously lower than that of other fluorimetric methods reported.

Progress of Spectral Probes for Nucleic Acids

Abstract Spectral probes have been widely used for the structural and quantitative study of nucleic acids. Traditional probes including absorption-type, fluorescent, and chemiluminescent probes continue to be developed. Of them, near infrared (NIR) dyes, ruthenium(II), and rare earth complexes are especially suitable for the investigation and determination of biomacromolecules including nucleic acids, so their developments are rapid. Resonance light scattering and molecular beacon are recently developed sensitive probes of nucleic acids. They will become promising tools for studying and determining nucleic acids. This review summarizes recent developments in spectral probes for nucleic acids, and 148 references are quoted.

Study of the reaction between the nucleic acid and Y-BPMPHD-CTMAB complex and its analytical application.

The fluorescence quenching of the Y-BPMPHD-CTMAB by nucleic acids is reported. It is considered that the Y-BPMPHD-CTMAB can form a large complex with nucleic acid through the electrostatic attraction in the pH range of 4.2–6.8. Under optimal conditions, the difference of fluorescence intensity between the system without and with nucleic acids is proportional to the concentration of nucleic acids over the range of 4.5 × 10−8–1.2 × 10−5 g/mL for fsDNA and 3.2 × 10−8–3.0 × 10−5 g/mL for yRNA, respectively. The detection limits are 14.0 ng/mL for fsDNA and 21.0 ng/mL for yRNA. The method is applied for the determination of nucleic acids in actual sample, and the result obtained is satisfactory.

Enhanced Fluorescence of Eu‐Gd‐Oxolinic Acid‐CTMAB System and Its Application to the Determination of Europium (III) at Ultra‐Trace Amount

Abstract A fluorescence enhancement phenomenon in the europium‐oxolinic acid (OA)‐CTMAB fluorescence system was observed when Gd3+ was added. The fluorescence intensity of the systems was measured (λex = 345 nm, λem = 612 nm) at pH 7.25. Under optimum conditions, a linear relationship between the enhanced fluorescence intensity and the Eu3+ concentration in the range of 2.0 × 10−10 − 1.0 × 10−7 mol/l was observed. The detection limit of Eu3+ was 5.2 × 10−12 mol/l (S/N = 3). This method was used for the determination of trace amounts of europium in rare earth samples with satisfactory results.

Study on the Fluorescence System of Oxolinic Acid‐Tb(III) and the Determination of Oxolinic Acid

Abstract In Tris‐HCl buffer (pH=7.43), Tb3+ can react with oxolinic acid (OA) and form a 1:2 complex, which emits the intrinsic fluorescence of Tb3+. Based on this, a new fluorimetric method of determination of OA is developed. Under the optimum conditions, the enhanced fluorescence intensity of the system is proportional to the concentration of OA in the range of 1.5×10−7∼2.5×10−5mol/L, and the detection limit is 5.5×10−9 mol/L. Recovery test was also satisfactory. The experiments indicated that the luminescence mechanism was attributed to the M*–M luminescence.