Development of an ultrasensitive molecularly imprinted poly-(ortho-phenylenediamine) based sensor for the determination of melamine adulteration in milk and infant formula.

A sensitive molecularly imprinted poly-(ortho-phenylenediamine) electrochemical sensor was fabricated for selective melamine detection in milk and infant formula. The pencil graphite electrode (PGE) was modified by deposition of Au nanoparticles and reduced graphene oxide (RGO) on its surface. The fabrication of the electrode in various stages was monitored using cyclic voltammetry. The immobilized RGO, MIP, and gold nanoparticles on the PGE surface were morphologically characterized by field-emission scanning electron microscopy (FESEM). Under the optimized conditions, the linear range and the limit of detection (LOD) were 10-17-10-8 M and 2.64 × 10-16 M (S/N = 3), respectively. The prepared sensor exhibited a good reproducibility and repeatability response. The recovery range of melamine-spiked milk and infant formula was 92.7%-103.9% and 93.5%-105.8%, respectively. The sensor could apply successfully for melamine determination in milk and infant formula samples.

Chemical composition of essential oils in Zataria multiflora Boiss. from different parts of Iran and their radical scavenging and antimicrobial activity.

The objective of the study was to characterize the chemical constituents, antioxidant and antibacterial properties of five ecotypes of Zataria multiflora Boiss. essential oil with respect to main phytogeographic grown towns in Iran. Our investigation showed that the plants had essential oil yield ranging from 1.59+/-0.86% to 0.99+/-0.29% v/w. There were qualitative similarities among the oils from different origins, whereas the amounts of some components were varied. From different samples, 34, 34, 32, 29 and 53 various compounds were identified, representing 98.32%, 97.77%, 99.5%, 98.38% and 96.54% of total oils, respectively. The highest oxygenated monoterpens value in this study stood at 72.99%. Moreover, thymol, a phenolic compound of oxygenated monoterpens, was the most abundant component in GC/MS ranging from 27.05% to 64.87%. In the DPPH antioxidant assay, all samples exhibited a remarkable activity with a higher degree of IC(50)=19.7+/-0.7 microg/ml almost similar to BHT (18.1+/-0.4 microg/ml). Escherichia coli O157:H7 was the most resistant and Candida tropicalis was the most vulnerable organisms with MICs of 16 and 0.062 mg/ml, respectively. In conclusion, it seemed that geographical variation might have influenced the oil compounds either quantitatively or qualitatively.