Abstract High concentrations of heavy metals in urban watersheds can offer harmful effects to human health and have contributed to environmental contamination. The present work aims to evaluate the total concentration of Zn (Zinc), Mg (Magnesium), Lead (Pb), Cr (Chromium), Manganese (Mn) and Ni (Nickel) analyzed according to FAAS - Flame Atomic Absorption Spectrometry, in samples of the aquatic macrophyte Egeria densa present in the urban stretch of the Cascavel River watershed, Guarapuava, PR; and specific objectives to identify the potential sources of contamination by heavy metals and to obtain physical parameters of the water. The elements zinc, magnesium, manganese and lead showed higher potential emissions upstream, a fact associated with the proximity of the industrial zone of Guarapuava. It is likely that the increase in electrical conductivity values at the upstream points is related to the discharge of domestic effluents. The decrease of conductivity and total dissolved solids in the sample points occurs downstream, corresponding to the lower topography of the study area and the end of the urban stretch of the Cascavel River basin. Despite the concentrations of heavy metals being considered critical, the plant showed efficiency in bioaccumulation of these chemical elements, being an effective tool for research and environmental assessment, and aquatic macrophytes can be the basis for biomonitoring studies of urban environments impacted by heavy metals.

Abstract Objective To establish a method for the simultaneous determination of four sulfonamides residues in prawn, including sulfadiazine, sulfathiazole, sulfamerazine and sulfamethazine, by ultrasound-assisted matrix solid phase dispersion extraction coupled with pre - column derivation high performance liquid chromatography(HPLC). Methods Through the optimization of extraction conditions, ethyl acetate was selected as the extraction agent and florisil as the solid dispersion agent, and the sulfonamides in prawn were extracted with the method ultrasound-assisted matrix solid phase dispersion. The sulfonamides were pre-column derived by fluorescamine and detected by HPLC-fluorescence method. Results All sulfonamides showed good linearity in the concentration range of 2-100μg/L, with the correlation coefficient>0.999. The limit of detection and limit of quantification was 0.5 and 2μg/kg, respectively. The spike recoveries of blank prawn samples were 84.4%-93.9% at two levels of 2 and 20μg/kg, with the relative standard deviation( n =3)less than 7.7%. Conclusion The method is simple, time-consuming and high precision, which meets the requirements of residue analysis.

Abstract A fast and simple approach to directly determine sio2. Al2O3. Fe. Mgo. Cao. K2O. Mn. Tio2. P and Zn in manganese ores samples by X-ray fluorescence spectrometer(XRF) was developed. This method used a glass fuse piece technique with Li2 B4 O7. Libo2 and lif(Mass ratio:45:10:5) as the flux, NH4 NO3 as the oxidant, libr as the stripping agent. Several experimental parameters were optimized, and the analytical figures of merit were evaluated. The components in the certified reference material of GBW07261~GBW07266 were determined by the proposed method. The relative standard deviation(RSD, n = 12) was less than 2%. The accuracy test was conducted with synthetic samples. The results were consistent with the certified values.

Abstract Based on biomass (taro leaf). Iron was prepared by hydrothermal method with ammonium ferric sulfate dodecahydrate and urea as raw materials. Nitrogen Co doped carbon dots (Fe, N-CDs) were characterized by transmission electron microscopy and X-ray photoelectron spectroscopy. The Fe, N-CDs not only has peroxidase like activity, but also can produce strong fluorescence emission at 450 nm. Using Fe, N-CDs and o-phenylenediamine (OPD) as probes, a dual signal colorimetric/ratio fluorescence method for the determination of hydrogen peroxide (H 2 O 2 ) was established. In the presence of H 2 O 2 , Fe, N-CDs catalyze the oxidation of OPD to yellow 2, 3-diaminophenazine (DAP), which has a characteristic absorption peak at 420 nm. Under the excitation of 360 nm wavelength light, DAP has strong fluorescence emission at 550 nm; DAP can quench the fluorescence of Fe and N-CDs at 450 nm due to the fluorescence internal filtering effect. Based on this, the absorbance of DAP at 420 nm ( A 420 ) and the fluorescence intensity ratio of DAP to Fe, N-CDs ( I 550 / I 450 ) can be used for the quantitative analysis of H 2 O 2 . Considering that glucose oxidase can catalyze the oxidation of glucose to H 2 O 2 , a colorimetric/ratio fluorescence dual signal glucose determination method was further developed. Under the conditions of pH=5.4, temperature 40℃, 1.75 mmol/L OPD and reaction time 25 min, when the glucose concentration is in the range of 1.0~100μmol/L, the values of A 420 and I 550 / I 450 have a good linear relationship with the concentration, and the detection limits of the method are respectively 0.8 (colorimetry) and 0.6 μmol/L (ratio fluorescence). The method was successfully applied to the determination of glucose in human serum.

Abstract Graphene quantum dots (GQDS) with uniform particle size were successfully prepared by a simple in-situ electrolytic graphite rod method at a certain current density, and nafion/GQDS modified glassy carbon electrodes (nafion/GQDS/GCE) were constructed. Anodic stripping voltammetry and differential pulse voltammetry were applied to heavy metal Pb(Ⅱ) respectively. Electrochemical detection of CD(Ⅱ) and chloramphenicol. The results showed that the dissolution current of Pb (Ⅱ) and CD(Ⅱ) increased with the increase of their concentration, and showed a good linear relationship. The linear range of Pb (Ⅱ) was 4.82×10 -8 ~9.65×10 -7 mol/L ( R 2 =0.9923), CD (Ⅱ) linear range is 1.07×10 -7 ~1.96×10 -6 mol/L ( R 2 =0.9912), the detection limits of Pb (Ⅱ) and CD (Ⅱ) are 1.61×10 -8 mol/L and 3.57×10 -8 mol/L respectively. The nafion/GQDs/GCE has obvious electrocatalytic reduction effect on chloramphenicol. The electrocatalytic mechanism is an irreversible reaction involving 6 Electrons, and the electron transfer rate constant KS is 105.4s -1 . The catalytic reduction current of chloramphenicol at the modified electrode is 5.00×10 -7 ~2.50×There is a good linear relationship in the range of 10 -3 mol/L, and the detection limit (S/N=3) is 1.67×10 -7 mol/L. The nafion/GQDs/GCE also has good anti-interference performance. Stability and reproducibility, and satisfactory results were obtained for the detection of actual samples.