Separation of the tin finding forms and determination of the organotin compounds total content in natural waters of different salinity

Abstract

In the current paper, the possibility of separating inorganic and organic forms of tin occurrences has been considered and the features of determining the total content of organotin compounds (OTC) in waters with different salinities by ICP-spectrometry with hydride generation were studied. Various approaches to the separation of the chemical forms of tin by liquid-liquid extraction with various solvents, as well as by precipitation with fluorides, iodides, aqueous solutions of ammonia and iron (III) chloride at analyte concentrations at the MPC level for fishery reservoirs, have been examined. The separation of the chemical forms of tin due to the taking out the OTC by liquid-liquid extraction turned out to be inefficient because of the incomplete extraction of analytes and partial extraction (up to 15%) of the inorganic form of tin into the organic phase. Precipitation of inorganic and organic forms of tin using fluorides, iodides, ammonia, and iron (III) chloride also turned out to be inefficient. This was due to the low content of analytes, at which their quantitative precipitation was difficult. Under the conditions of high-level mineralization of sea waters, it was also unlikely that a competing reaction of changing the chloride environment to fluoride or iodide one would occur. Separation of the chemical forms of tin was achieved using the solid phase sorption. The Diapak C18 silica gel sorbent selectively extracted the organic form of tin from waters with different salinity under the optimized conditions. The optimized conditions for separating the chemical forms of tin made it possible to develop a method for determining the total content of OTC in natural waters with different salinity from the difference between the total content of the analyte and the inorganic form of tin. To determine the total content of the analyte, microwave mineralization of the water sample was carried out; the concentration of the inorganic form of tin was determined after its solid-phase separation from organotin compounds. The lower limits of analyte concentrations determined were 0.03 and 0.05 μg/dm3 for the ICP-MS and ICP-AES methods, respectively, which made it possible to separately determine the OTC during the ecoanalytical monitoring at the level below the MPC.