Is the $250 test the same as USP monograph testing?
No. Psyllium hemicellulose (Plantago ovata husk) does not fit the standard $250 identity, purity and quantity test, so it is tested to the USP Psyllium Hemicellulose monograph. Pricing is quoted.
Why can't psyllium be tested by HPLC like other compounds?
Psyllium hemicellulose is an arabinoxylan polysaccharide, not a single molecule, so it has no HPLC purity peak. Its content is measured as soluble fiber by digestion and weighing.
What is swell volume?
Swell volume is how much the powder expands in water. It is a quick identity and quality check, since diluted or wrong material swells less.