Reference Standards

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How To Read Reference Standards Listings

When you access any listing of Reference Standards through the alphabetical listing, search or PDF catalogs, you'll find some or all of the columns of information listed below. Here's what the columns mean:

Catalog Number: Catalog number currently assigned to each Reference Standard and Authentic Substance. Please include this number in your orders.

Description: Product description as designated in USP–NF, the product label, and/or the Drug Enforcement Administration Control Schedule, as applicable. The quantity of material per container follows the name in parentheses (all materials are in single containers unless otherwise specified).

Current Lot: Current lot designation of each official item being distributed as of the date of this catalog. If the current lot is blank, the item is not in distribution.

Purity Values: Assigned purity value as it appears on the product label. Code interpretations for the basis of purity assignments are as follows:

Basis Code	Interpretation
(ai)	as is
(dr)	dried
(an)	anhydrous
(fb)	free base
(ig)	ignited

Change Code: Codes that identify any change in USP Reference Standards status or information since the previous official USP Catalog. Code interpretations are as follows:

Change Code	Interpretation
1	New Reference Standard
2	New lot
3	Change in package size or description
4	Correction of typographical error
5	New catalog number — use for all orders
6	Previous lot no longer official; only current lot to be used
7	Valid use date of previous lot extended
8	Change in catalog number and/or name, see cross-reference section
9	Discontinued

Previous Lot/Valid Use Date: Lot designations for recent lots no longer being distributed. The date in parentheses indicates the month (last day of the month) through which that lot was valid as an official USP Reference Standard (e.g. "F-1 (06/00)" means lot F-1 is no longer being distributed, but was considered official through June 30, 2000).

CAS Number: Chemical Abstracts Service number, when available, for USP Reference Standards and Authentic Substances. In case of mixtures, typically, the CAS number of the analyte of interest is listed.

Price: List price of the Reference Standard.

What are Certified Reference Materials (CRMs)?

CRMs represent the next generation of exceptional quality Reference Standards from USP. They have undergone additional metrologically–based testing and statistical analysis to meet both USP's stringent criteria and guidelines established by the International Organization for Standardization (ISO).

CRM Features and Applications

• Special class of USP Reference Standard (RS)
• Metrologically–based testing and statistical analysis
• Accompanied by a special Certificate of Analysis that complies with ISO Guide 31 data:
• Certified property value
• Uncertainty value
• Expiration date/period of validity
• Traceable to an accurate realization of the unit in which the property value is expressed
• Trueness and traceability of CRM measurement system helps with consistency and comparability of measurement data among labs and over time
• Data can be used for calibration, validating processes, comparison, and value assignment
• Values meet ISO 17025 documentation requirement for testing labs
• USP CRM program meets the requirements of ISO 17025 and ISO Guide 34 for RMP