ABSTRACT
This work proposes a highly specific method of Cr6+ determination based on the double reactions of two metals, Co2+ with dithizone to form a (DTZ)-Co2+ complex, and the replacement of Co2+ in the formed complex with Cr6+. The fast degradation of DTZ in solution in wet analysis was overcome by preparing dithizone functionalized polyurethane nanofibers that were electrospun into a membrane (DTZ/PU-NF) and a microwell plate film (DTZ/PU-MPF). For comparison, the performance of diphenylcarbazide (DPC), a currently used complexing agent for Cr6+, was also investigated. Colour changes were detected as red-green-blue values. The DTZ/PU-NF was smooth, with an average diameter of 384.09 nm and no bead appeared. A dense network structure was formed. The best formulation of DTZ, PU and Co2+ was also applied as a microwell plate film. In the presence of Cr6+, the colour of DTZ-Co2+ changed from red to magenta. Among the three studied methods, the colorimetric DTZ-Co2+/PU-NF presented the best results. Its linearity range was 0.001-1.0 mg L-1, with a regression equation of Cr6+ = -0.189 + (0.0056 × red) + (0.0086 × green) - (0.0129 × blue), R 2 of 0.990. The limit of detection was 0.001 mg L-1 and the precision was 1.7%. The applicability of DTZ/PU-NF was validated for Cr6+ in vegetable oils with recoveries of 89.5-116.8%. The sensitivity of DTZ/PU-NF was ten times higher than that of DTZ/PU-MPF. The methods based on DTZ-Co2+/PU-NF and DTZ-Co2+/PU-MPF proved to be highly selective, rapid, user-friendly, simple and reliable.
ABSTRACT
While versatile application of plastics has generated huge benefits in our life, the 'plastic end-of-life' comes with downsides of emerging concern is plastic particles within all parts of environments. Plastics are highly resistant to degradation and sustain in the environment for a prolonged period resulting in easy access of microplastics into human food chain. Microplastic exposure to humans is caused by foods of both animal and plant origin, food additives, drinks, and plastic food packaging. Living organisms can accumulate microplastics in cells and tissues which results in threats of chronic biological effects and potential health hazards for humans including body gastrointestinal disorders, immunity, respiratory problem, cancer, infertility, and alteration in chromosomes. Because of the threat of microplastics on human health, it is essential to ensure food safety as well as control plastic use with strict regulation of proper management. This study aims to enlighten future research into the core component of microplastics, their exposure to human food, prevention to human food chain, and biological reactions in human body. Finally, it is recommended to consider the presence of microplastics in different foods, as most of the existing research mainly focused on sea foods. And it is important to study the mechanism of toxicity with pathways in the human body based on the different types, shapes, and sizes of plastic particles.
