Primary Standard:
- Definition: A primary standard is a highly purified compound that can be used to prepare a standard solution for analytical purposes. It is typically used in titrations to determine the concentration of a substance in a sample.
- Purity: Primary standards are of exceptionally high purity, often exceeding 99.99%. They undergo rigorous purification processes to eliminate impurities and ensure accurate and precise measurements.
- Stability: Primary standards are chemically stable and do not undergo significant changes in their composition over time. This stability is crucial for accurate and reproducible measurements.
- Availability: Primary standards are usually not readily available and may require specialized sources or synthesis procedures to obtain them. They are often established by official organizations or institutes to ensure consistency and reliability in analytical measurements.
Secondary Standard:
- Definition: A secondary standard is a substance that is used as a reference or comparison to a primary standard. It is typically prepared from a primary standard by dilution or by chemical reactions to establish its concentration.
- Purity: While secondary standards are still of high purity, they may not reach the same level of purity as primary standards. However, their purity is sufficient for most analytical applications.
- Stability: Secondary standards are generally stable but may be less stable compared to primary standards. They may exhibit slight degradation or changes in concentration over time, but these changes are within acceptable limits for routine measurements.
- Availability: Secondary standards are more readily available compared to primary standards. They can be purchased from commercial suppliers or prepared in the laboratory using appropriate procedures.
