Frequently Asked Questions: Reference Standards
- What information do I need when ordering from outside of the United States?
- Why has USP changed the lot number format of USP Reference Standards?
- Why is USP not requiring annual recertification of the USP Near IR System Suitability Reference Standard (Catalog No. 1457844)?
- How do I reliably remove powdered material from the vial?
- Why is the catalog number on my Reference Standard different than others, and will that affect its compendial use?
- How do USP Units convert to International Units?
- What guidance does USP provide related to secondary reference standards?
- Does USP issue Certificates of Analysis (COAs) for USP Reference Standards?
- Where can I find the Safety Data Sheet (SDS) for a USP Reference Standard?
- Are Safety Data Sheets (SDSs) available in different formats and languages?
- Is the Safety Data Sheet (SDS) available on the website the most up-to-date version?
- Why does the Safety Data Sheet (SDS) of a particular USP Reference Standard not meet the U.S. Occupational Health and Safety Administration (OSHA) standard (HazCom2012) requirements that went into effect on May 25, 2012?
- Is the information on the Safety Data Sheet (SDS) of a USP Reference Standard obtained in USP laboratories?
- Does USP provide chromatograms and IR spectra for USP Reference Standards?
- Where can I find specific test results for a USP Reference Standard?
- Where can I find the purity/potency value of a USP Reference Standard?
- How is the labeled value of a USP Reference Standard calculated?
- Why has the basis of the labeled value changed from one lot to another?
- Do USP Reference Standard labels meet the requirements put into law by the U.S. Occupational Health and Safety Administration (OSHA) HazCom2012 standards?
- Why is a USP Reference Standard over-labeled?
- What does “AS” stand for on the label of a USP Reference Standard?
- Are USP Reference Standards suitable for use as drugs, medical devices or diagnostic purposes?
- Are USP Reference Standards suitable for applications not specified in the USP-NF publication and other USP compendia?
- Do USP Reference Standards require any special preparation before use?
- What is the storage condition for a USP Reference Standard?
- Can USP Reference Standards be stored after opening for future use?
- Why is the storage condition of a USP Reference Standard different from the storage condition provided in a USP compendial monograph?
- Can a USP Reference Standard be stored at a different temperature other than what is provided on the label?
- Is a USP Reference Standard still suitable for use if a temperature excursion occurs?
- Do USP Reference Standards require special shipping?
- What happens if a new USP Reference Standard that is specified in a new USP compendial monograph is not yet available for purchase?
- What happens if a USP Reference Standard is on back order?
- Are the impurities listed in a table of a specific USP compendial monograph available from USP?
- What is USP’s policy on Product Recalls and Withdrawals?
- How do I determine if a USP Reference Standard is still valid for use or has expired?
Technical Data Sheets
Labeled Value (Purity/Potency)
Uses and Applications
Shipping and Storage
Availability and Validity
Special instructions for orders from outside of the United States can be found on our Purchasing/Customer Support page.
The new lot numbering format allows for many more lot numbers of a given item, while maintaining the same number of characters (7) as the previous numbering format.
Why is USP not requiring annual recertification of the USP Near IR System Suitability Reference Standard (Catalog No. 1457844)?
The USP Near IR System Suitability Reference Standard does not require recertification because of a combination of the component material, a proprietary housing and seal, and USP's commitment to a Continued Suitability for Use Program. For more details, please view our official statement.
Please see Tips for Effective Retrieval of Powder from Vials .
Why is the catalog number on my Reference Standard different than others, and will that affect its compendial use?
USP changed the numbering system for all USP Reference Standard catalog numbers. A “1” was added as the first digit to the existing catalog number. If there was punctuation in the previous number, such as a hyphen, it was removed. All catalog numbers are now 7 digits in length. There are still lots that were labeled prior to this change in distribution, so the catalog number on the label will be the previous number. Whether the catalog number printed on the USP RS label is from the old or new numbering system, it has no bearing on the potency, stability, or suitability for use of the USP RS. USP monitors items in our inventory on a regular basis in the Continued Suitability for Use Program. The following chart shows the new numbering system.
Item Old Item No. New Item No. Acetaminophen (400 mg) 00300-9 1003009 Brompheniramine Maleate (125 mg)
USP Endotoxin Units are identical to International Units. Please click here to read USP’s statement on the Heparin Potency Unit Assignment and Harmonization with the International Standard for Unfractionated Heparin. Relationships for other USP units must be determined on a case–by–case basis. Please refer to the USP compendial monograph of a specific material for further information.
USP’s Reference Standards are considered primary standards, except for certain biological USP Reference Standards with units of activity that are established against and traceable to the World Health Organization International Standards. USP does not develop secondary reference standards against its own primary reference standards. USP does not provide guidance on the qualification or use of such secondary reference standards. For questions about the use of primary vs. secondary reference standards and implications for compliance, users are advised to consult with the regulatory authority where their products are marketed for guidance.
USP does not provide COAs. USP does provide USP Certificates for most USP Reference Standards (RS). USP Certificates do not completely describe the test results obtained during evaluation. Rather, they are issued to provide customers with information such as a hard copy of the USP RS label text, molecular information, typical chromatograms (limited cases), and additional use/handling information that may not be contained on the RS label. USP Certificates for current & previous lots, when available, can be viewed on our web site by clicking on the catalog number for an item in our downloadable USP Catalog or by clicking on the Product name in the online store. If there is not a link to view the USP Certificate for a specific lot number, then a USP Certificate is not available for that lot. Read USP's policy statement on USP Certificates.
SDSs are not available in additional formats and languages. It is the responsibility of the importer to provide SDSs in the required format, if different.
The SDS's posted on our web site are the most recently updated versions. The U.S. OSHA Hazard Communication Standard does not specify a specific time frame beyond which SDS information is to be considered unacceptable. [See, 29 Code of Federal Regulations § 1910.1200(g)(5)]
Why does the Safety Data Sheet (SDS) of a particular USP Reference Standard not meet the U.S. Occupational Health and Safety Administration (OSHA) standard (HazCom2012) requirements that went into effect on May 25, 2012?
OSHA published the HazCom2012 requirements to bring U.S. SDSs in line with the Globally Harmonized System of Classification and Labeling of Chemicals (GHS). USP is currently revising its SDSs to comply with these new OSHA regulations. The regulatory deadline for implementation is June 1, 2015.
Is the information on the Safety Data Sheet (SDS) of a USP Reference Standard obtained in USP laboratories?
Testing is not required for a safety evaluation or an SDS by the U.S. Occupational Health and Safety Administration (OSHA). USP relies on published and supplier data in conformance with OSHA regulations. USP Reference Standards are intended only for use in their associated USP compendial applications. Any use beyond these applications is the responsibility of the user. USP Reference Standards are not intended for human and animal use.
There are a limited number of USP Reference Standards that have an available Typical Chromatogram. If provided, the Typical Chromatogram is included in the USP Certificate. Details that are not included on the chromatogram are confidential and not available. IR spectra are not available for USP Reference Standards.
All information required for official uses of a USP Reference Standard may be found on the label and, when available, in the USP Certificate. Monographs or other USP standards that have specified particular USP Reference Standards to be suitable for use may also provide additional information or directions for use. Due to legal and scientific reasons, test results and data that are not included in these sources cannot be shared. (Read our Document Disclosure Policy)
In most cases, the assigned value can be found on the label of a USP Reference Standard. If a value is not provided on the label or accompanying documentation and the Reference Standard has a quantitative USP compendial application, a value of 100.0% is used. This applies only to USP Reference Standards intended for quantitative use in USP compendial procedures. The purity value is not applicable for qualitative uses. Please refer to a USP Reference Standard’s USP compendial application(s) to determine if the RS is used qualitatively and/or quantitatively. The downloadable USP Catalog also contains the labeled values for the current lot of most quantitative USP Reference Standards.
The method of choice in computing the assigned value of a USP Reference Standard is a mass balance analysis using independently determined components such as moisture, solvent residues, inorganic residues, chromatographic impurities and ion content. The mass balance equation used is confidential and cannot be shared due to legal and scientific reasons. The assay results against a previous lot or against another validated standard and the results of the functional group analysis are for confirmatory purposes only.
USP uses the mass balance approach as this provides a more precise determination of the assigned value than assaying versus a previous lot. The assaying versus a previous lot approach inherently causes greater variability and less precision due to the variability of the previous lot being incorporated into the overall variability of the lot under evaluation. The mass balance approach also results in higher accuracy.
Exceptions to the mass balance approach include many biological Reference Standards, especially those which define the Unit of Activity. A label value is not assigned to Reference Standards having only qualitative USP compendial uses.
Labeled values, including their basis, are lot specific and may change from one lot to another. For the convenience of our customer, USP is labeling a USP Reference Standard "as is" whenever possible. It is the preferred option and is selected whenever valid data indicates that the volatiles content is constant over time. The change to "as is" will not affect the USP compendial use of a USP Reference Standard.
Do USP Reference Standard labels meet the requirements put into law by the U.S. Occupational Health and Safety Administration (OSHA) HazCom2012 standards?
USP is currently transitioning to revised label formats to meet the labeling requirements of the HazCom2012 standard. The required label elements are signal words, hazard statements, precautionary statements & pictograms, product identifier, and supplier identification. All elements except the precautionary statements will be visible on the outside label of a USP Reference Standard vial. The precautionary statements can be found under the wrap label. During this transition, you may receive units in both the old label format and the new label format. The regulatory deadline for implementation is June 1, 2015. By this date, all USP Reference Standards will be shipped using the new label format only.
Select USP Reference Standards have a wrap label with all label elements required by HazCom2012 placed over the original labels. The updated wrap label includes the same information as the label in the old format with the addition of precautionary statements & pictograms, and the updated language for signal words and hazard statements. These items will include a statement on the label indicating that they are intentionally over-labeled. Please refer to FAQ #18 for more details about the new label format.
AS stands for Authentic Substance. Authentic Substances were developed by USP as a service primarily to analytical, clinical, pharmaceutical, and research laboratories. Such substances may be used for identification, method development, evaluation of method performance, or other applications as found suitable and validated by the user. AS Reference Standards do not have USP applications in monographs or other compendial standards. All available information can be found on the label of the AS Reference Standard. No additional data is publicly available.
USP Reference Standards are intended for test and assay use only as directed by USP compendia; they are not intended for use in humans or animals as drugs or medical devices. View USP's policy statement on the storage and usage of Reference Standards.
Are USP Reference Standards suitable for applications not specified in the USP-NF publication and other USP compendia?
USP Reference Standards are intended only for use in analytical or laboratory applications as specified in USP compendia. It may be possible to use a USP Reference Standard in other compendial or quality assessment applications however it is the responsibility of the user to determine the suitability of the USP Reference Standard for other non-specified purposes.
Any specific instructions for use may be provided in the compendial monograph, the label of the USP Reference Standard and/or on its USP Certificate, if available. Some lots can be used as–is but others may require drying before use or a correction with a concurrent moisture or Loss on Drying determination. Additional information on special preparation requirements for USP Reference Standards may be found in General Chapter <11> USP Reference Standards and the USP Reference Standard’s associated USP compendial methods. See Use and Storage for more details.
The storage condition for an unopened USP Reference Standard can typically be found on the container label. Storage conditions are no longer provided in the Safety Data Sheets (SDSs). Instead, the SDS refers users to the USP Reference Standard label. Storage conditions are lot–specific and may change from one lot to another. If no specific directions or limitations are provided on the USP Reference Standard label, the conditions of storage shall include storage at room temperature and protection from moisture, light, freezing, and excessive heat. Refer to General Chapter <659> Packaging and Storage Requirements in the USP-NF publication for definitions of storage and handling terms. See Use and Storage for more details.
USP generally provides enough material for multiple preparations. Any unused portions remaining after the container has been opened should be carefully stored in accordance with prudent laboratory procedures. Many variables are outside of the control of USP. Therefore, USP makes no warranties concerning the continued suitability of previously opened Reference Standards. Decisions concerning the proper use of previously opened Reference Standards are the responsibility of the user. View USP's policy statement on the storage and usage of Reference Standards.
Why is the storage condition of a USP Reference Standard different from the storage condition provided in a USP compendial monograph?
The storage condition of a USP Reference Standard is determined based on the recommendation from the material’s supplier/manufacturer. Data obtained during the collaborative study of a lot and historic data are also considered. The provided storage condition of a USP Reference Standard is intended to preserve the integrity of the Reference Standard for the duration of its use as an RS. The storage condition in a USP compendial monograph is based on the recommendation of the monograph’s sponsor. The storage condition provided in a monograph is for the article of commerce.
Can a USP Reference Standard be stored at a different temperature other than what is provided on the label?
The provided storage condition is also how USP stores the specific item. As Continued Suitability for Use (CSU) testing is performed on the item stored as per its label, we do not have data to support the continued suitability of the item stored at an alternate storage condition. For this reason, we are unable to comment on the storage of a USP Reference Standard at an alternate temperature. It is the responsibility of the user to determine if a material remains suitable for use when handled differently than the provided instructions.
USP does not comment on storage deviations and the potential effect of temperature excursions on the USP Reference Standard material. The user should consult their own internal policies & SOPs and use their best scientific judgment to make the decision on whether or not to use the material(s).
The storage condition of a USP Reference Standard is intended to preserve the integrity of the material for the duration of its use as an RS. USP Reference Standards are not customarily shipped on ice or under refrigerated conditions. Shipping conditions are determined based on the stability information for individual USP Reference Standards and transit times. If scientific evidence suggests the need to ship a USP Reference Standard on ice or dry ice, USP will do so. For these items, a statement that a cold shipment is required will be included in the Product Description [e.g. Endotoxin (10,000 USP Endotoxin Units) (COLD SHIPMENT REQUIRED)]. View USP's policy statement on the shipping conditions of USP Reference Standards.
Shipping on ice or dry ice is available for all USP Reference Standards on request and for an extra charge - Call USP Customer Service at 1–800–227–8772 (U.S. and Canada), +1–301–881–0666, or 00–800–4875–5555 (Select Europe) for details.
What happens if a new USP Reference Standard that is specified in a new USP compendial monograph is not yet available for purchase?
As per Section 5.80 of the General Notices in the USP-NF publication, if any new USP or NF written standard requires the use of a new USP Reference Standard that is not yet available, that portion of the standard containing the requirement shall not be official until the specified USP reference material is available.
To learn when a new USP Reference Standard becomes available for the first time, use the New Reference Standards Release Notification Service. This service is not available for the release of back-ordered items or lot changeovers. To receive a monthly list of lot changeovers, please subscribe to our free monthly Email Notice.
The availability of USP Reference Standards is generally better than 99 percent. USP strives to plan ahead to replace depleted lots in a timely manner. However, despite our best efforts, some USP Reference Standards might occasionally be out of stock temporarily. Contact your USP Account Manager or Reference Standards Technical Service (email@example.com) to find out when the specific USP Reference Standard you are looking for might become available again. You can also frequently check the product listings on USP's online store which are updated on a daily basis or sign up for our free monthly Email Notice which will keep you informed about USP Reference Standards that become available.
You can place an order for USP Reference Standards that are currently out of stock. Products that become available within 30 days of your order will be shipped to you automatically. If the product becomes available after 30 days, USP will send you a Notice of Availability to get your confirmation before shipping the order.
All USP Reference Standards that are required to carry out the tests or methods within a specific monograph will be provided in a list at the beginning or end of a monograph. The Reference Standards are written as "USP <name> RS." Other chemicals, reagents, impurities, etc. that are listed in the monograph are not available as USP Reference Standards.
If a product is determined by USP to no longer meet the compendial requirements, USP will notify customers who purchased the product in the last 12 months that it is being recalled or withdrawn. USP recommends referring to the online store and Daily Listings prior to using a USP Reference Standard to make sure the specific lot is valid for use. These sources are updated on a daily basis.
Current lots of USP Reference Standards do not have valid use dates (expiration dates). As long as a lot is listed as being the “current lot,” it is valid and suitable for use. Once a current lot is depleted, it becomes the “previous lot.” At this time a valid use date is assigned, which is typically a year from the date of depletion. The last day of the indicated month represents the expiration date for the specified lot (e.g., "05/14" means the lot was considered official through May 31, 2014).
The downloadable USP Reference Standards Catalog and online store are updated daily. USP recommends referring to one of these sources prior to using a USP Reference Standard to make sure the lot is valid for use. It is the responsibility of the user to ascertain that a particular lot of a USP Reference Standard has official status either as a "Current Lot" or as a "Previous Lot" within the valid use date. View USP's policy statement on expiration dating of Reference Standards.