CEI-MS-07 — worked example

§6Worked example

§6.1Worked example — why the small-volume limit is per container, not per millilitre

1. A 2 mL reconstituted solution gives light-obscuration counts of 2 850 particles ≥ 10 µm and 180 ≥ 25 µm per millilitre.
2. Per container: 2 850 × 2 = 5 700 particles ≥ 10 µm and 180 × 2 = 360 ≥ 25 µm.
3. Both fall below the small-volume limits of 6 000 and 600 per container, so the preparation complies.
4. Now reconstitute the identical vial with 5 mL instead. If the particle burden is intrinsic to the solid and not to the diluent, the total count per container is unchanged at roughly 5 700, but the per-millilitre count falls to 1 140.
5. A laboratory reporting a per-millilitre figure against a per-container limit would record the 5 mL preparation as five times better than the 2 mL one, when they contain the same particles. The limit is stated per container precisely because that is the quantity administered, and the Institute records mis-stated units as one of the recurring errors in submitted data.

§6.2Illustrative mass balance

References cited on this page

References are numbered in order of first citation in this document. Each superscript in the text links to its entry below.

1. United States Pharmacopeial Convention. General Chapter ⟨788⟩ Particulate Matter in Injections. United States Pharmacopeia — National Formulary (USP–NF) 2024;USP 2024 Issue 1. identifier not held by the Institute
2. United States Pharmacopeial Convention. General Chapter ⟨1225⟩ Validation of Compendial Procedures. United States Pharmacopeia — National Formulary (USP–NF) 2024;USP 2024 Issue 1. identifier not held by the Institute

Identifiers are reproduced only where the Institute holds them. Where a digital object identifier or PubMed identifier is not shown, the Institute has recorded the journal and year and has not constructed an identifier.