What method is primarily used to determine Total Dissolved Solids (TDS) in water samples?

The method primarily used to determine Total Dissolved Solids (TDS) in water samples is evaporation and drying to constant weight. This technique involves taking a known volume of the water sample and evaporating it completely, leaving behind the solid residues that represent the dissolved solids. After the evaporation, the remaining solids are weighed, and the weight represents the TDS concentration in the sample. This approach provides a direct measurement of the total mass of dissolved substances in the water, making it a reliable method for assessing TDS.

Conductivity measurement is often employed as an indirect method for estimating TDS since the conductivity of a solution is influenced by the concentration of dissolved ions. However, it does not directly quantify TDS and requires calibration against known standards for accuracy. Therefore, while conductivity is relevant in assessing water quality, it is not the primary method for determining TDS compared to the direct weight measurement achieved through evaporation and drying.