Liquid marbles as microreactors for qualitative and quantitative inorganic analyses

Abstract: Conventional qualitative analysis of ions from inorganic salts and acid–base and redox titrations require relatively large volumes of solution and hence require more reagent and generate relatively large amount of waste. Liquid marbles can be used to cut down the volume of solution and by extension the amount of reagent and volume of waste generated. Liquid marbles were used for qualitative analysis of ions from inorganic salt solutions and acid–base and redox titrations. This was compared with the conventional methods which require milliliters of solution. Fumed silica or fluorinated sericite clay particles of varying degrees of hydrophobicity were used to prepare the marbles. A drop of a test reagent was then placed on the marble, merging with it and initiating a chemical reaction. The characteristic reactions between a salt solution and a test reagent in the marbles were observed provided the reaction was clearly marked by a color change. Concentrations, calculated from the volume at the end-point, compared closely (p ≤ 0.05) with the known ones as well as those calculated from the bulk titration method that requires milliliters of solution. This indicates that the liquid marble method which rather requires microliters of solutions is reliable. These findings are especially important in microfluidics which utilizes microliters of solutions. Graphic abstract: [Figure not available: see fulltext.]