Three-phase solvent bar micro-extraction as an approach to silver ultra-traces speciation in estuarine water samples

• 3-phase solvent bar micro-extraction simplifies 3 phase HFLPME of metals.
• Selective pre-concentration of Ag+ permits estimating Ag speciation.
• 3-phase solvent bar micro-extraction is a green tool for silver speciation.

Silver ion inputs into the environment due to human activities have been increased in the last years because it has been used as a bactericide with application in medical, homecare and self-care products. In addition, it is toxic at low concentration for aquatic organisms. In estuarine waters, salinity and dissolved organic matter (DOM) regulate Ag+ concentration by the formation of complexes as AgCln(n-1)− and Ag-DOM.Difficulties of Ag+ analysis in estuaries are associated to its low concentration level and interferences of sample matrix. Liquid and solid phase extraction methods have been used for speciation of silver in waters; however, miniaturized methods that offer a better environmental profile are desirable. Hollow fiber liquid phase micro-extraction (HFLPME) allows obtaining higher pre-concentration factors with a reduction of waste generation. Notwithstanding, some operational improvements are needed to permit their use as a routine method that can be afforded using a configuration of three-phase solvent bar micro-extraction (3PSBME).In this work, tri-isobutylphosphine sulphide (TIBPS) has been used as an extractant for Ag+ pre-concentration in estuarine waters by 3PSBME. Under optimized conditions, Ag+ has been pre-concentrated 60 times and the method presents a limit of detection of 1.53 ng L−1. To evaluate which Ag species is transported by TIBPS, Cl− and DOM have been added to synthetic samples. As a result, a decrease in Ag pre-concentration efficiency after additions has been observed and quantified. Results showed that Ag+ is selectively transported by TIBPS from estuarine water samples after comparison of the results with those obtained by the reference method of liquid extraction with APDC/DDDC.

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