Flow injection spectrofluorimetric determination of cystine and cysteine

A relatively simple and sensitive procedure with spectrofluorimetric detection was developed for the determination of cystine and cysteine by flow injection system with sequential determination. This method is based on the reduction of Tl(III) with cysteine in acidic media, producing a fluorescence reagent, TlCl3(2-) (λex = 227 nm, λem = 419 nm). Before injection, the sample solution was divided into two streams. The first stream was treated with Cd reduction column and then joined with the carrier to react with Tl(III) at pH 5.0 and then passed through a 100 cm reaction coil to the flow cell of the spectrofluorimeter, where the fluorescence intensity was measured (λex = 227 nm, λem = 419 nm). This signal is related to cystine and cysteine concentrations. The second stream of sample solution was injected directly into the carrier stream to react with the reagents and then passed through the reaction coil and detector for measuring the fluorescence intensity. The signal in this step is related only to cysteine. Thus, the cystine content was determined directly from difference of the two signals. Cystine and cysteine can be determined in the range of 0.10 to 5.50 µmol L-1 and 0.20 to 8.0 µmol L-1, respectively, at a rate of 20 samples per hour. The limit of detection (3s/k) was 0.10 µmol L-1 for both analytes. The relative standard deviations for ten replicates determination of 4.0 and 3.5 µmol L-1 cystine or cysteine were 1.1% and 1.8%, respectively. The influence of potential interfering substances was studied. The proposed method was successfully applied to the sequential determination of both analytes in pharmaceutical samples

Study on the interaction between morin-bi(III) complex and DNA with the use of methylene blue dye as a fluorophor probe

Based on our investigation, although both morin-Bi(III) complex and morin can bind to DNA, the nature of the binding was found to be different for each of them. In the presence and absence of the DNA, the morin-Bi(III) complex shows different spectral characteristics which agree with those observed for other intercalators. In this work, the interaction of morin-Bi(III) complex with calf thymus DNA was investigated with the use of methylene blue (MB) dye as a spectral probe and application of UV-Vis spectrophotometry, fluorescence spectroscopy and cyclic voltammetry. The 2:1 morin-Bi(III) complex ratio was calculated by UV-Vis spectroscopy (mole ratio method). The fluorescence signal of Bi(III)-morin complex is increased with DNA addition whereas the fluorescence signal of Morin is decreased with DNA addition. The fluorescence signal of the DNA-complex is quenched by addition of MB which confirms the displacement of the complex with MB. Cyclic voltammetry studies confirm the intercalation reaction. The results showed that only morin-Bi(III) complex can intercalate into the double helix of the DNA. The apparent binding constant of morin-Bi(III) complex with DNA is found to be 2.8 × 10(4) L mol-1, while morin binds in a non-intercalation mode

Thionine-functionalized graphene oxide nanosheet as an efficient electrocatalyst for NADH oxidation and H2O2 reduction

Thionine-functionalized graphene oxide (Th-GO) has been successfully prepared for use as an efficient electrocatalyst in the electrochemical detection of hydrogen peroxide and nicotinamide adenine dinucleotide (NADH), and subsequently characterized by FT-IR spectroscopy, X-ray diffraction, transmission and scanning electron microscopy, and electrochemical methods. Electrochemical studies reveal that the carbon paste electrode modified with Th-GO decreases the working potentials to 0.24 V and 0.00 V towards oxidation of NADH and reduction of H2O2, respectively. Two linear ranges of 2.0–200 µmol L–1 and 200–500 µmol L–1 and a detection limit of 0.43 µmol L–1 have been obtained for NADH analysis. These quantitative data for H2O2 determination are 2.0–3500 µmol L–1 and 1.3 µmol L–1 respectively. Th-GO/CPE shows satisfactory results in terms of repeatability, reproducibility, and selectivity towards NADH and H2O2 analysis in both buffer and real sample

Ruthenium oxide-carbon-based nanofiller-reinforced conducting polymer nanocomposites and their supercapacitor applications.

In this review article, we have presented for the first time the new applications of supercapacitor technologies and working principles of the family of RuO2-carbon-based nanofiller-reinforced conducting polymer nanocomposites. Our review focuses on pseudocapacitors and symmetric and asymmetric supercapacitors. Over the last years, the supercapacitors as a new technology in energy storage systems have attracted more and more attention. They have some unique characteristics such as fast charge/discharge capability, high energy and power densities, and long stability. However, the need for economic, compatible, and easy synthesis materials for supercapacitors have led to the development of RuO2-carbon-based nanofiller-reinforced conducting polymer nanocomposites with RuO2. Therefore, the aim of this manuscript was to review RuO2-carbon-based nanofiller-reinforced conducting polymer nanocomposites with RuO2 over the last 17 years

Flow injection spectrophotometric determination of ultra trace amounts of selenium(IV)

105-107A flow injection spectrophotometric method has been described for determination of selenium(IV). The method is based on the catalytic effect of Se(IV) on the reduction of gallocyanine by sulphide. The decrease in absorbance of gallocyanine at 620 nm is proportional to the Se(IV) concentration in the range 2.5- 500 ng/mI with a limit of detection of 1.0 ng/mI. The relative standard deviation for ten replicate measurements of 50 ng/mI of Se(IV) is 1.5%. Interference due to various ions has been studied

Spectrophotometric flow injection determination of thiocyanate

344-346A spectrophotometric flow injection procedure is described for the determination of thiocyanate in aqueous medium over the range of 0.005-1.800µg/ml, The effect of reagent concentration, reagent flow rates, sample volume, length of the reaction coil and temperature are reported. The limit of detection is 0.62 ng/ml of thiocyanate. Thiocyanate can be determined at a rate of 40 ± 5 samples/h. The relative standard deviation for ten replicate analysis of 0.060.µg/ml of thiocyanate is 1.3%. The system has been applied for the determination of thiocyanate in water, synthetic sample, and biological fluids