Usage of Reference Standard Working Standard the Complete Guidelines


Reference standards are authentic substances approved by the reference standard approving authority as a preferred method for use. Comparison Standards are described as individual monographs and methods of analysis. The purpose of this is to define the procedure for preparation, standardization, and usage of a working standard.


Wherever possible this reference standard shall be used including those for which impurities are not available. Remember the same can be gotten from chemical research laboratories, drug substance manufacturers, a contract giver or an in-house references standard at the manufacturing facility.



There are certain precautions that have to be taken like using a clean and dry amber coloured vial for storage of working standards. All reference standards or impurity standards have to be stored as per the storage condition mentioned in MSDS from the supplier. Remember before usage, the temperature of the vials must reach room temperature. In the case that potency of the working standard is found more than 100.0% during the standardization, as a policy cut off the potency of the working standard will be considered as 100.0%.


Maintenance of Reference Standard

According to pharmaceutical standards, reference substances or standards are authentic purified chemicals supplied by the official pharmacopoeia commission. These are generally used for comparison to determine the purity of the test specimen. In case the reference standard isn’t available in the pharmacopeial catalog, the manufacturer shall be asked for their reference standard or working standard with a certificate of analysis. As reference standards are usually available only in small quantities, working standards can be prepared to act as a substitute, these are prepared from approved raw materials and validated against authentic reference standards or substances.


All standardized records of working standards shall be maintained in a QC laboratory. The Inventory and consumption of reference standards shall be maintained as per Annexure – VI, the validity of reference standards shall be verified on a quarterly basis, and before preparation for a working standard.


Now, in case the reference standard is found to be consumed or expired during verification, then the indent for procurement of a fresh lot shall be initiated by the Manager Q.C.


Preparation of Working Standard

Select any approved batch, the quality attributes of the selected batch will be reviewed critically with special emphasis on its assay and related substances. This batch shall have reviewed according to pharmaceutical standards and the selected batch shall have maximum assay/purity and the lowest related substance.


Analyse the selected batch against the reference standard using logbook as per Annexure – VI and follow the stipulated control procedure which includes Description, Identification, Moisture Content, Assay, Perform Assay, and Moisture Content Analysis in triplicate.  The QC manager shall allocate the material abbreviation and assign a unique number to each working standard as below.




WS – denotes the working standard

‘/ ‘- denotes the slash

XXXX – denotes the four-letter abbreviation for the material 

YY – denotes the year of preparation of working standard

01 – denotes the serial number of working standards.              


A typical example of Paracetamol working standard shall be as below:




The details of results in the record analysis sheet are to be entered and calculated with the purity of the working standard, post which it is to be transferred to clean amber coloured vials, sealed and labelled as per Annexure – V. Fifteen vials of 2gm should be prepared and another 20gm working standard should be stored in the vial. Prepare a list of working standards to identify the due date for preparation and in case of any absence of API or CRS working standards received from the manufacturer should be used for respective analysis.


Storage and Expiry Working Standards

All working standards are to be stored under refrigeration, in case a specific storage condition is mentioned then the material should be stored according to that. All working standards shall be brought to ambient temperature before use and the details to be recorded in the usage log book as per Annexure – I. The expiry period for the working standard is one year from the day or preparation, and for a vial is one month, expiry period should not exceed the retest period of the selected API batch.



Expired working or reference standards should not be used. Instead, they should be discarded immediately in a proper way.


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