d. Sample handling: Collect samples in clean, acid-rinsed bottles, preferably plastic, and
examine them as soon as possible after collection. If only soluble aluminum is to be determined,
filter a portion of sample through a 0.45-µm membrane filter; discard first 50 mL of filtrate and
use succeeding filtrate for the determination. Do not use filter paper, absorbent cotton, or glass
wool for filtering any solution that is to be tested for aluminum, because they will remove most
of the soluble aluminum.