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This study investigates the effects of problem-based learning (PBL) on students' academic achievements in studying ‘Electrochemistry’ within a course on Analytical Chemistry. The research was of a pretest–posttest control group quasi-experimental design and it was conducted with second year students in the Chemistry Teaching Program at the Faculty of Education at Dokuz Eylul University. The topic was taught with PBL in the experimental group and with expository teaching strategies in the control group. The ‘Chemistry achievement test (CAT)’ was applied as the pre-test and post-test in both groups. Post-test scores from the CAT demonstrated that there was a significant difference between the academic achievements of the two groups in favour of the experimental group (U= 8.500,p< 0.05). After using PBL for a period, eleven open-ended questions related to the topic were asked to both groups. The results of these questions were categorized and the scores obtained from the categories were evaluated using content analysis. The results of the scores obtained from the open-ended questions showed that the students in the experimental group were able to make statements containing fewer misconceptions and also had a better understanding of this topic when compared to the students in the control group (U= 2.500,p< 0.05). The correlation between the scores in the CAT post-test and the scores obtained from the open-ended questions of the experimental and control groups was also examined. The Spearman correlation coefficients were found to be 0.907 and 0.595 for the experimental and the control group, respectively. This finding indicated that there was a positive and very high level of statistically significant correlation between the scores in the CAT post-test and the scores obtained from the open-ended questions of the students in the experimental group. Therefore this finding also supports the conclusion that the students in the experimental group were better able to understand the topic and its structure compared to the students in the control group. At the end of the application, the results of semi-structured interviews carried out showed that students in the experimental group had positive opinions regarding PBL.

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A selective dopamine determination using a nafion-coated clinoptilolite-modified carbon paste electrode in the presence of ascorbic acid was studied. Both cyclic voltammetry (CV) and differential pulse anodic stripping voltammetry (DPASV) were used for measurements of dopamine. To improve the selectivity of the clinoptilolite-modified carbon paste electrode in presence of a high concentration of ascorbic acid, the electrode surface was coated with nafion membrane. Experimental parameters affecting the determination of dopamine, including the clinoptilolite ratio, nafion membrane thickness, preconcentration time, preconcentration solution pH, stripping solution pH and interferences are discussed. The developed sensor has a wide linear range, a low detection limit, and good stability and reproducibility. The sensor offers a good alternative to existing analytical methods for dopamine, permits a relatively short analysis time, and is simple, selective and inexpensive.

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