The ranked list contains 40 assignees drawn from 103 records in scope, with the leader alone holding 16 records. The top five combined account for 43.7% of all records, and the top ten reach 67.0%, which means the field is concentrated among a small group of established filers with a long tail of single- or double-filing entrants below them. This concentration pattern matters for competitive tracking: watching the leading handful covers most of the active claim space, while freedom-to-operate searches benefit more from checking the long tail for narrow, blocking claims.

Filing activity peaked at 12 records in 2020 and fell to 5 by 2021, continuing down to 0 by 2024 — a -100% change over that three-year span. Part of this apparent decline is real: fewer new filings were made in this specific problem space after 2020. But publication lags actual filing by roughly 18 months, so 2025 and 2026 counts in the dataset are still incomplete and should not yet be read as confirming a continued drop. A clearer read on 2025-2026 activity will only be available once those years finish publishing.

US5174872A claims a heavy metal-free buffer composition — built from a borate compound and an alkalinity adjusting compound — used to dilute and buffer a test sample while reducing interferent effects in ion-selective electrode assays, particularly for carbonate ion measurement in blood serum, plasma, urine or cerebrospinal fluid. It is one of the more heavily cited records in this landscape, which signals it has been treated as a reference point by later filers rather than that it necessarily still blocks new work. Anyone designing a buffer or dilution approach for carbonate or related ion assays should read its claims directly rather than relying on the abstract, since the specific compound classes and metal-free limitation define the actual scope.