Gonca Tosun

Simple time-saving method for iron determination based on fluorescence quenching of an azaflavanon-3-ol compound.

A simple and time-saving spectrofluorometric method developed using an azaflavanon-3-ol compound was used for the determination of iron in various food samples. Nitric acid and hydrogen peroxide were used for digestion of samples in a closed microwave system. The method was validated by analyzing two certified reference materials (CRM-SA-C Sandy Soil C and Mixed Polish Herbs INCT-MPH-2). Measurements were carried out using a modified standard addition method. The standard addition graph was linear until 21.6 mg/L in the determination of iron(III). Detection and quantification limits were 0.81 and 2.4 mg/L, respectively. Satisfactory accuracy was obtained for spinach, dill, mint, purslane, rocket, red lentils, dry beans, and two iron medicinal tablets. High recoveries were found for streamwater samples fortified at three different concentrations. The method is simple, time-saving, cost-effective, and suitable for the determination of the iron content of foods.

Antimicrobial activity and a comparative essential oil analysis of Centaurea pulcherrima Willd. var. pulcherrima extracted by hydrodistillation and microwave distillation.

The essential oils of Centaurea pulcherrima Willd. var. pulcherrima (Asteraceae) were isolated by hydrodistillation (HD) and a microwave distillation (MD), than characterised by GC-FID and GC-MS. A total of 58 and 57 compounds were identified, constituting over 93.7%, and 91.6% of volatile oil composition of C. pulcherrima var. pulcherrima, respectively. Sesquiterpene hydrocarbons were shown to be the main group of constituents (HD: 42.4% versus MD: 51.5%). The major component of the oils of C. pulcherrima var. pulcherrima was germacrene D (HD, 17.8% versus MD, 23.2%). The antimicrobial activity of the isolated essential oils of the plant was also investigated, and they showed good antibacterial activity against to tested Gram-positive bacteria, especially to M. smegmatis and a yeast-like fungus C. albicans.

Effect of increased exposure times on amount of residual monomer released from single-step self-etch adhesives

Background The aim of this study was to evaluate the effect of increased exposure times on the amount of residual Bis-GMA, TEGDMA, HEMA and UDMA released from single-step self-etch adhesive systems. Methods Two adhesive systems were used. The adhesives were applied to bovine dentin surface according to the manufacturers instructions and were polymerized using an LED curing unit for 10, 20 and 40 seconds (n = 5). After polymerization, the specimens were stored in 75% ethanol-water solution (6 mL). Residual monomers (Bis-GMA, TEGDMA, UDMA and HEMA) that were eluted from the adhesives (after 10 minutes, 1 hour, 1 day, 7 days and 30 days) were analyzed by high-performance liquid chromatography (HPLC). The data were analyzed using 1-way analysis of variance and Tukey HSD tests. Results Among the time periods, the highest amount of released residual monomers from adhesives was observed in the 10th minute. There were statistically significant differences regarding released Bis-GMA, UDMA, HEMA and TEGDMA between the adhesive systems (p<0.05). There were no significant differences among the 10, 20 and 40 second polymerization times according to their effect on residual monomer release from adhesives (p>0.05). Conclusions Increasing the polymerization time did not have an effect on residual monomer release from single-step self-etch adhesives.

Farklı polimerizasyon sürelerinin adeziv sistemlerden salınan artık monomer miktarına etkisi

OBJECTIVE: The aim of this study was to evaluate the amount of residual monomer released from three different adhesive systems polymerized with four different exposure times. MATERIALS AND METHOD: The adhesives were applied onto dentin surfaces (length of an edge of 7 mm and 0.9 mm thickness) according to the manufacturer instructions, and polymerized using light curing unit (LED) for 10, 20, 40 and 60 seconds, respectively (n=5). After polymerization, each specimen was immediately immersed in lightproof glass bottle containing 75% ethanol and 25% deionized water at 37 o C. During the period of immersion, samples were removed from the bottles at 10 min, 1 h., 24 h., 7 d. and 30 d. by using micro-pipette. Residual monomers (Bis-GMA, UDMA) eluted from adhesives were analyzed with HPLC. The results were analyzed with one-way analysis of variance and Tukey HSD test. RESULTS: There was residual monomer release at all time periods. It was observed that the increase in the polymerization time did not have an effect on residual monomer release except for Clearfil S3 Bond (Bis-GMA) and Clearfil Photo Bond (UDMA) groups. CONCLUSION: Longer exposure times than those recommended by the manufacturers may decrease residual monomer release from some of the adhesives.