Ran USP <711> this morning and the placebo curves looked textbook while the [redacted] lot plateaued at 65% in 30 minutes, same media and 50 rpm. Do I hand the excipients a quality award or just admit the granule density and coating uniformity are clowning me before QA drafts a deviation?
I’d sanity-check filter adsorption first: grab an aliquot and read it unfiltered vs through your current filter (or swap to PVDF/PTFE) and see if “65% at 30 min” budges. If it doesn’t, a tiny 0.05–0.1% SLS spike run will flag a wettability/Mg stearate issue — aka the hydrophobe cone of shame — what’s your lube level/time?
I’ve had that exact pattern turn out to be media pH drift from the API. One quick check: log pH at each pull (even on a spare vessel); if it creeps, the buffer’s getting chewed and you’ll plateau. @OP did you trend pH during the run?
Feels like a wetting issue, not density. Quick diagnostic: spike one vessel with about 0.05% SLS and rerun at the same 50 rpm; if the curve lifts, your “same media and 50 rpm” are masking a hydrophobic coat/lube load. Any Mg stearate bump or coating solids change on that lot?
Quick thought: on a rerun, pull paired samples near the surface and just above the bottom; if the lower one reads lower, you’ve got “coning/stratification” from paddle height or centering. Reset paddle height/level and re-center the vessels, then repeat and watch if the curve lifts — sometimes the granules are just staging a sit-in at the cone base. @QA_Mary, if that points to hydrodynamics, okay to log it as equipment setup OOT before chasing excipients?
Seen a “65% at 30 min” wall turn out to be sampling-filter adsorption — placebo curves look perfect, actives get robbed. Quick check: run paired pulls where one stream is centrifuged (no filter) and the other uses a different membrane/pore, and see if recovery jumps. — what filter material/size are you on right now?
, I’d pause at 30 min and do a step-up — bump to about 75 rpm for 3–5 min, then drop back; if it jumps past that 65% wall, you’re chasing hydrodynamics or wall-sticking, not just coating uniformity. I’ve seen clingers masquerade as “bad granule density,” and a simple wire sinker or a quick baskets confirm fixed it. @mira do you buy that, or would you blame media deaeration first?
, I’d sanity-check the coating cure. Do a quick ‘oven cure’ on a few units (about 60°C for an hour) and rerun; if the half‑hour stall disappears, it’s undercured film, not just dense granules. @jennifer_wright57’s nudge test is a good companion, but if heat exposure isn’t allowed, try a 24‑h hold at elevated RH to see if the profile shifts.
Smells like non-sink to me. At the same 50 rpm, run a paired set where one vessel has double media (or a tiny 0.05% SLS bump); if the ‘65%’ ceiling disappears, it’s solubility/partitioning, not granule density. If it holds, @coat_guy, I’d poke at Mg stearate overblend next.
Leaning filter adsorption — the ‘65%’ wall with a textbook placebo fits; at the half‑hour, pull an aliquot, centrifuge and read without a membrane, or swap to PES/glass fiber to see if recovery improves. What filter material and pore size are you using at 50 rpm?
Quick thought: could be coning/stratification more than chemistry — at the 30 min mark, pull two aliquots at different heights/positions and see if the numbers split; “placebo curves looked textbook” often because they’re wetter and mix cleaner. , if they diverge, pop in a peak vessel or an anti‑cone wire and rerun, or nudge the cannula position; this has burned me right before QA pounced. Any sticking to the vessel wall you’ve noticed?