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发表于 2021-4-2 08:48:01
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<922> Water Activity
Type of Posting: General Announcement
Posting Date: 30–Mar–2018
Input Deadline: 30–Apr–2018
Expert Committee: General Chapters—Physical Analysis
Proposed new title: <922> Water Activity
Suggested audience: Suppliers and manufactures of excipients, drug substances, drug products, veterinary products, regulatory agencies, and manufacturers of water activity instruments
Estimated proposal PF: Pharmacopeial Forum 44(6) [Nov.–Dec. 2018]
Background and objective(s):
Water activity (Aw) refers to the effective concentration of pure water in a raw material or product. When water is strongly bound to a solute or surface, it does not contribute to the water activity. Measurements of water activity are made by allowing a sample to equilibrate with the moisture in the headspace above the sample and then measuring the equilibrium relative humidity (ERH) of the headspace. At equilibrium, the ERH is also a measure of the Aw in the formulation. Water activity meters measure the relative humidity with a moisture-dependent resistor or capacitor or may use psychometry (wet bulb temperature) or dew point depression. Regardless of the principle of measurement, water activity meters can be calibrated and qualified using the same saturated salt reference solutions. This chapter will outline the recommended methods to qualify, calibrate, and use water activity meters to accurately measure the water activity of raw materials and products.
Description of scope and application: This new general chapter is intended to provide guidance for performing measurements of water activity (Aw). The general chapter will specify methods for qualification of instruments, calibration of instruments, methods for performing water activity measurements, and reporting of results.
Preliminary outline:
Introduction
Background
Application of Water Activity Measurements
Types of Water Activity Meters
Electronic Hygrometer
Resistance hygrometer
Capacitive hygrometer
Psychrometric (wet bulb temperature)
Dew Point
Chilled-mirror hygrometer
Thermocouple
Hair hygrometer
Freezing-point depression sensor
Near infrared spectrometry
Operation and Calibration of Water Activity Meters
Standard Saturated Salt Solutions
Calibration of Water Activity Meters
Dew Point Hygrometer
Electronic Hygrometer
Near Infrared spectrometry
Precision/Repeatability Assessment (Performance Qualification)
Measurement of Water Activity
Sample Preparation
Calibration Check
Measurement Procedure
Reporting Results
Assay Verification and Validation
Troubleshooting
Dew Point Hygrometer
Electronic Hygrometer
Near Infrared spectrometry
Glossary
References
Anticipated proposed design phase activities: The general chapter will be developed by a Joint Subcommittee with representation from General Chapters—Physical Analysis, General Chapters—Microbiology, and the Non-botanical Dietary Supplements Expert Committees. In addition, the Joint Subcommittee will assess the impact of the new general chapter on the existing General Chapter <1112> Microbiological Attributes Of Nonsterile Pharmaceutical Products—Application Of Water Activity Determination and work with the General Chapters—Microbiology EC to update <1112> to align with this new general chapter.
Anticipated implementation timing: Routine
Contact: Antonio Hernandez-Cardoso, M.Sc., Senior Scientific Liaison, (301-816-8308),AHC@usp.org). |
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