For dissolved metals analysis by atomic absorption spectroscopy, filtration through a 0.45 μm membrane before acidifying is recommended because:

For dissolved metals analysis by atomic absorption spectroscopy, filtration through a 0.45 μm membrane before acidifying is recommended because:

• A. True
• B. False
• C. It should be filtered after acidification
• D. It is optional

Answer: (A)

Measuring dissolved metals means capturing only what is truly in solution, defined by what passes through a 0.45 μm filter. Filtering first removes suspended solids that could carry metals or clog the instrument, ensuring metals bound to particles aren’t counted as dissolved. Filtering after acidification could release metals from particulates or change how metals interact with the filter, biasing the result. After filtration, acidifying stabilizes the dissolved metals, prevents precipitation and adsorption to container walls, and preserves them for accurate AAS measurement. Because the goal is to quantify the truly dissolved fraction, this order is recommended, so the statement is true. The filtration step is necessary to define the dissolved fraction, not optional.

Measuring dissolved metals means capturing only what is truly in solution, defined by what passes through a 0.45 μm filter. Filtering first removes suspended solids that could carry metals or clog the instrument, ensuring metals bound to particles aren’t counted as dissolved. Filtering after acidification could release metals from particulates or change how metals interact with the filter, biasing the result. After filtration, acidifying stabilizes the dissolved metals, prevents precipitation and adsorption to container walls, and preserves them for accurate AAS measurement. Because the goal is to quantify the truly dissolved fraction, this order is recommended, so the statement is true. The filtration step is necessary to define the dissolved fraction, not optional.