Optimization of complexing membranes for platinum analysis in water at part per trillion levels by X-ray fluorescence

Background: Platinum is a critical metal, especially in medicine and catalysis. Its concentration in aquatic ecosystems may gradually affect aquatic animals due to its ability to bioaccumulate. Additionally, the recycling of platinum has become crucial, so new extraction methods are needed. In recent years, there has been increasing interest in environmental studies based on X-Ray Fluorescence, due to the requirements of green chemistry. Complexing membranes have been used for platinum analysis in combination with X-ray Fluorescence, although with a relatively high detection limit. Results: Several optimizations were introduced to achieve a significantly improved detection limit and repeatability. Self-supported membranes were used for the first time and proved to be highly effective in binding platinum from aqueous solutions. An extensive search was conducted to identify an appropriate chemical element to serve as an internal standard; osmium met many of the necessary criteria and was successfully used as an internal standard, leading to a remarkable improvement in the method's precision. The effect of various elements present in natural waters was examined, and no interferences were observed. The method gave equally reliable results in all types of water, including seawater. Through substantial optimization procedures, a minimum detection limit up of 37 ng L- 1 was achieved with a 1000 s irradiation time. The potential aging of the membrane was investigated, showing that the membrane does not deteriorate for at least one month when stored at refrigeration temperature. Significance: The newly introduced self-supported complexing membranes improved the platinum detection limit by more than 100-fold, enabling, for the first time, platinum analysis at low ng L-1 concentration levels using Xray Fluorescence. This method can be used to various types of natural waters, including seawater with nearcomplete recovery from the aquatic matrix. This research may also contribute to improving the minimum detection limits of the method for other trace elements besides platinum.