No abstract

In this work, an electroenzymatic methodology based on two coupled enzymatic activities (glycerokinase and glycerol-3-phosphate oxidase) was developed using an oxygen Clark-type electrode for the determination of free and total glycerol in biodiesel samples. The enzymatic conversion of glycerol consumes oxygen, which is measured amperometrically in a Clark-type electrode and correlated with the concentration of glycerol in the sample. The electroenzymatic method proposed showed a good linear correlation coefficient (R ¼ 0.9990) with a linear response in the concentration range of 6.25 Â 10 À5 to 6.25 Â 10 À4 % (w/v) and limits of detection and quantification at 1.0 Â 10 À5 % and 3.0 Â 10 À5 % (w/v), respectively. Good correlations were found between the results obtained in this work and those by the gas chromatography technique (R ¼ 0.9994). The proposed method was shown to be promising for the analysis of glycerol in biodiesel samples, with a simple and inexpensive methodology compared with the gas chromatography technique.

The aim of this study was to obtain ionic quantification in periradicular medium after diffusion tests of the solution used inside root canals during the electrochemical dissolution of endodontic file fragments and the NiTi-containing dissolution product via an apical foramen. Thirty single-rooted extracted human teeth had root canals prepared and were attached to Eppendorf tubes filled with sterile saline. The samples were divided into 3 groups (n = 10) according to the solution used inside the root canal during the diffusion tests: Group 1: [NaF 12 g/L + NaCl 1 g/L]; Group 2: [NaF 12 g/L + NaCl 1 g/L + NiTi 0.50 g/L]; Group 3: [NaF 6 g/L + NaCl 0.5 g/L + NiTi 0.25 g/L]. The sample in each Eppendorf tube was then analyzed to assay the ionic quantification in periradicular medium. The groups were compared in relation to ionic quantifications (Kruskal-Wallis and Dunn's tests, p ≤ 0.05). Group 2 showed significantly higher F -, Ni and Ti quantities than groups 1 and 3 (p < 0.05). Group 3 showed significantly higher Ti and Ni quantities than group 1, where no measurable quantities of Ti and Ni were observed (p < 0.05). The conclusions were that a 50% dilution of the NiTi-containing dissolution product resulted in significantly lower F -, Ni and Ti quantities compared to the undiluted product. The quantifications observed here suggest that irrigation is recommendable during the electrochemical dissolution process to reduce the resultant ion concentrations in both the root canal and the periradicular medium.