What might be used to measure TDS in water using a gravimetric method?

The gravimetric method for measuring Total Dissolved Solids (TDS) in water involves evaluating the mass of solid residues left after evaporating a water sample. This procedure begins with taking a known volume of water, filtering it to remove suspended solids, and then evaporating the filtrate to completely dry the residual salts. After evaporation, the residual solids are weighed. The weight of these solids, when related back to the volume of the original water sample, gives a direct measurement of TDS in the water.

This method is highly accurate and provides a direct measurement as it focuses purely on the mass of dissolved substances that remain after the water has been eliminated, making it a reliable technique for quantifying TDS levels in environmental and analytical contexts. Other methods, such as UV spectrophotometry or calorimetry, do not measure solids directly and often focus on specific types of solutes or rely on chemical reactions that do not quantify TDS as a total measurement. Conductivity tests, while useful for estimating TDS, do not provide a direct mass measurement and rely on assumptions about the relationship between conductivity and dissolved solids, which can vary with the type of solutes present.