In this work, a new method for the simultaneous determination of tryptophan (Trp) and tyrosine (Tyr) in milk has been reported. Trp and Tyr are essential amino acids in human nutrition, but their electrochemical signal overlapped. For solve this problem, we developed modified Screen Printed Carbon Electrode (SPCE) with Graphene Oxide-COOH/Chitosan (GO-COOH/Chitosan) electro-deposition. The morphology and electrochemical performance of modified electrode were characterized by scanning electron microscopy, energy dispersive spectrometry, FT-IR, electrochemical impedance spectroscopy and cyclic voltammetry. The electrochemical simultaneous determination of Trp and Tyr has been investigated by using differential pulse voltammetry. The carboxylic acid functionalized GO modified SPCE was utilized to catalyze the oxidation of Trp and Tyr. Compared with SPCE/GO/Chitosan and SPCE/Chitosan sensor, the new sensor has enhanced sensitivity, low detection limit and high selectivity. In addition, the SPCE/GO-COOH-Chitosan sensor enhanced separation of the oxidation peak of Tyr and Trp and showed a remarkable increase in peak current for electroactive compounds, thus, it can be used for simultaneous voltammetric determination. Under the optimized experimental conditions, a linear correlation between oxidation peak current and concentration of Tyr and Trp in the ranges 0.1-60 µM and 0.4-40 µM with a detection limit of 0.05 µM (S/N = 3) and 0.1 µM (S/N = 3) were achieved, respectively. Finally, the proposed electrochemical sensor was applied for quantification of Tyr and Trp in milk samples, where standard solutions were spiked to the milk samples and recoveries were obtained.

Vegetables are the main source of nitrate food contamination. More than 80% of nitrates are consumed by humans through vegetables. The present study was conducted to investigate the contamination of nitrite and nitrate vegetables in Iran. In this systematic overview we reviewed all internal and external databases for relevant articles. According to different studies, contamination was detected in different types of vegetables in different regions of Iran. Articles that examined nitrite values above the standard limit were not reported. Due to nitrate contamination in vegetables in some cities of Iran and the effects of this nitrogen combination on human health, it is necessary to find a solution in this regard.

Background & objectives: In recent years, iron nanoparticles have been successfully used to remove water pollutants. Fecal coliform is one of the parameters that reduces water quality and its removal is essential. The aim of the present study is using nanoscale zerovalent iron particles to enhance the usual sand filters in removal of fecal coliform of groundwater in Ilam city. Methods: Water samples were collected from several active wells in Ilam city. The parameters of hardness, probable and fecal coliforms were measured. Afterward, samples of fecal coliform contaminated-water were passed through filters with different values of zerovalent iron nanoparticles (0.5-3 gr) and parameters were remeasured. Results: The results of this study showed that by increase of iron nanoparticles, the removal efficiency of coliform was increased, so that, in most samples, by increasing the iron nanoparticles to 3 gr, the coliform content reached to zero. The degree of hardness was initially reduced when the amount of iron nanoparticles increased, but over time, the reduction trend was halted. Conclusion: In general, the results indicate that not only zero-valent iron nanoparticles are capable enough to remove microbial contamination from water, but also they can be used to completely purify the groundwater and also to reduce other contaminants including chemical pollutants to a permissible threshold, especially in small regions where complex water treatment plants may not be available.