Colorimetric Assay for 4-Phenylthiosemicarbazide Detection in Environmental Samples Based on Prussian Blue Nanoparticles Formation Ion

In this research, a fast colorimetric method for the detection of 4-phenylthiosemicarbazid (4-PTSC) in environmental samples, is reported for the first time. Semicarbazide compounds have been used as pesticides or fungicides in agriculture and for chemical synthesis in industrial processes. With this method, one or the total amount of Semicarbazide in real samples can be detected within 6-7 min. For this purpose, 4-PTSC was determined and can be used as a representative of the Semicarbazide family. The assay principle is based on the oxidation of 4-phenylthiosemicarbazid (as reducing agent) with Ferric ions in the presence of ferricyanide ion and triton X-100 as a stabilizer, as well as the formation of Prussian Blue Nanoparticles (PBNPs). These nanoparticles exhibit a strong UV-Vis extinction band at 700 nm with high absorption coefficient (3.0× 104 M-1 cm-1 at 700 nm). A UV-Vis spectrophotometer is used to monitor changes in the absorption intensity of PBNPs. A change in the color of the solution can be easily observed by naked eyes, in the presence of sub-ppm levels of 4-PTSC, which is directly related to the 4-PTSC concentration. TEM images showed an average diameter of 30 nm. The effect of several reaction variables on the formation rate of PBNPs was studied. Beer's law was obeyed in the concentration range of 0.20-3.20 μg/mL. The detection limit was found to be 0.10 μg/mL. This method was successfully applied for the determination of 4-PTSC in different environmental samples. Interfering species with reducing properties are not commonly present in environmental samples. Hence, this optical assay is simple and has acceptable selectivity.