Synthesis, characterization and thermal behavior on solid tartrates of light trivalent lanthanides
Solid state Ln–L compounds, where Ln stands for light trivalent lanthanides (L–Gd) and L is tartrate, have been synthesized. Thermogravimetry and differential thermal analysis (TG/DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, elemental analysis and complexometry were used to characterize and to study the thermal behaviour of these compounds. The results led to information about the composition, dehydration and thermal decomposition of the isolated compounds.
Concentração de ácido tartárico dos vinhos da serra gaúcha
Due to the importance of tartaric acid in the composition and quality of wines, this work aimed to determine its concentration in wines from the highlands in Rio Grande do Sul, Brazil. A total of 288 samples of the red wines Isabella, Cabernet Sauvignon, Cabernet Franc, and Merlot and of the white wines Chardonnay, Italic Riesling and White Muscat were analysed by HPLC. Results showed that the average concentration of tartaric acid in Isabella (5.0g L-1) was significantly higher than in other wines; the concentration of the tartaric acid in Italic Riesling (3.1g L-1) wine was similar to the Chardonnay (2.6g L-1) but significantly higher than the concentrations found in the wines of Cabernet Sauvignon (2.2g L-1), Cabernet Franc (2.3g L-1), Merlot (2.4g L-1) and White Muscat (2.2g L-1).
An Ultrasensitive Analytical Method Based on Chemiluminescence Sensing Electrochemical Parallel Catalytic Reaction Event
An ultrasensitive electrochemiluminescence (ECL) method on the combination of electrochemical parallel catalytic reaction and chemiluminesence signal sensing was proposed for improving ECL analytical characteristics using vanadate(V) as a representative. Vanadate(V) could be electrochemically reduced to generate vanadate(II) which could be chemically oxidized by potassium periodate to regenerate vanadate(V) and give parallel catalytic wave effect. Then, the reduced product of potassium periodate could react with butyl-rhodamine B to emit a sensitive chemiluminescence signal. The chemiluminescence intensity was correlative with vanadate(V) concentration. The investigation on the electrochemical reaction rate constant (k0) confirmed that the speed of electrochemical reaction was faster than that of the subsequent chemiluminescence reaction. The possibility of the combination of electrochemical parallel catalytic reaction with chemiluminescence signal sensing was proved. The similar ECL behaviors could be observed at zirconia nanowires-Nafion modified electrode. Because of the separation and enrichment effect of the modified electrode on vanadate(V), the selectivity and sensitivity was further improved greatly. Based on these findings, a new concept on the combination of electrochemical parallel catalytic reaction and chemiluminesence signal sensing was proposed and an ultrasensitive ECL method for the determination of vanadate(V) was developed at zirconia nanowires-Nafion modified electrode. Under the optimum experimental conditions, the ECL intensity was linear with the concentration of vanadate(V) in the range of 2.0×10−12 mol/L–2.0×10−10 mol/L. The detection limit was 8.0×10−13 mol/L, which was more than 6 orders of magnitude lower than that observed by electrochemical current transduction for electrochemical parallel catalytic reaction at zirconia nanowires-Nafion modified electrode.