Sodium and potassium in rock and soil materials are generally estimated by

Solution (By Examveda Team)

The correct answer is B: Flame photometry
* Flame photometry is a technique specifically designed to measure the concentration of certain elements, like sodium (Na) and potassium (K), based on their emission of light when introduced into a flame.

* Here's why the other options are less suitable:
* UV-Visible spectrophotometry: This technique measures how much UV or visible light a substance absorbs. It's good for identifying and quantifying organic molecules, but not ideal for directly measuring sodium or potassium in a complex matrix like rock or soil.
* HPLC (High-Performance Liquid Chromatography): This is a separation technique. It separates different components in a liquid mixture. While it can be coupled with detectors that could measure sodium and potassium, it's not the primary or most efficient method for just measuring those elements.
* Colorimetry: This method measures the absorbance of light by a colored solution to determine the concentration of a substance. While some reactions can be developed that produce colored compounds from sodium or potassium, it's generally more complex and less accurate than flame photometry for direct measurement of these elements.

So, because Flame photometry directly measures the light emitted by sodium and potassium when heated in a flame, it's the most appropriate technique for estimating their concentration in rock and soil samples.