Embodiments of the disclosed invention provide devices and methods for buffering fluid samples to enable accurate concentration measurements of analytes by salinity-sensitive or pH-sensitive sensors. The buffering capabilities of the device include the ability to control the salinity and pH of a fluid sample, specifically, through the management of solutes such as salts, H+, other ions, and other solutes, that are found in sweat, biofluids, or other fluids. The purpose of such control is to enhance particular fluid sensing device applications by improving detectability of the targeted analyte, or improving performance of analyte sensors. Some embodiments also include components to enable sample concentration to enhance the measurement of low-concentration solutes found in the fluid.