Types of Standards
Reference standards are of two type’s a. Primary standards and b. secondary standards.
Reference standards are of two type’s a. Primary standards and b. secondary standards.
Primary Reference standards or primary standards:
Primary standards are the chemical substances which are accepted without reference to other standards.
Primary standards are the chemical substances which are accepted without reference to other standards.
Primary standard may be obtained from the USP/NF or EP or BP and other official sources or prepared by the manufacturer if there is no official source to obtain material (In-house products).
Secondary reference standards or working standards:
A working standard is a standard that is qualified against and used instead of the reference standard. There are generally used for regular analysis of drug substances.
A working standard is a standard that is qualified against and used instead of the reference standard. There are generally used for regular analysis of drug substances.
Manufacturing of Reference standards:
The manufacturing process of references standards can be different from the final processing of the drug substance.It is most widely acceptable practice in the industry.
The manufacturing process of references standards can be different from the final processing of the drug substance.It is most widely acceptable practice in the industry.
Generally purification methods such as distillation, crystallization or extraction are used where as Prepaprative HPLC used only for rare or expensive products.
In all cases, the analytical procedure (purity and assay) used for characterization must be validated.
Characterization of Primary or working standards:
The characterization of primary standards or working standards generally involves the elucidation of chemical structure by IR, UV, H'-NMR, C13-NMR, XRD, Mass spectroscopy and elemental Analysis etc.
The characterization of primary standards or working standards generally involves the elucidation of chemical structure by IR, UV, H'-NMR, C13-NMR, XRD, Mass spectroscopy and elemental Analysis etc.
Purity/Potency Determination
The degree of potency is to be established by chromatographic validated method.
If the monograph contains only one method for assay (without purity determination), it is preferable to use a stability indicating method of the drug substance for purity determination.
If no drying is required, the assay and the water determination may be analyzed individually and the assay recorded "as is". The assay refers to the declared amount, and the figure is to be used in calculating the results of the assay.
The degree of potency is to be established by chromatographic validated method.
If the monograph contains only one method for assay (without purity determination), it is preferable to use a stability indicating method of the drug substance for purity determination.
If no drying is required, the assay and the water determination may be analyzed individually and the assay recorded "as is". The assay refers to the declared amount, and the figure is to be used in calculating the results of the assay.
The standard potency is calculated as follows:
%Potency = %Assay-(%water+% residual solvents)
Drying
Working standards are to be dried in accordance with the labeling of the same Pharmacopeial or primary standard.
Working standards are to be dried in accordance with the labeling of the same Pharmacopeial or primary standard.
If a standard requires drying, the required amount must be transferred to a clean weighing bottle for drying. The weighing bottle must be protected from light during use. Dried standards must not be returned to the original bottle in order to avoid any possible contamination of the stock. After drying, place the standard into the desiccator to equilibrate before assaying.
Retest or Expiration dating:
The retest or expirations dating for primary reference standards can be obtained from the official source. In case of in-house reference standards retest date can be assigned by the stability and sensitivity of drug substance.
The retest or expirations dating for primary reference standards can be obtained from the official source. In case of in-house reference standards retest date can be assigned by the stability and sensitivity of drug substance.
In case of secondary standards, usually one year is the retest period. This parameter always depends on the stability of the drug substance.
Storage of Standards:
Working standards are stored in the same manner as indicated by the official source or stability of the standard and are stored in amber glass containers, protected from light, heat and moisture.
Working standards should be kept at ambient conditions in an amber dissector cabinet, unless otherwise specified by the individual monograph and if the standard that require storage in a "cold" or "dry" place are to be stored in a refrigerator at 2-8°C.
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