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www.thinkSRS.com Temperature Calibration Methods Background Before OptiMlet is put into operation for the first time, it must be calibrated using appropriate reference substances with melting points that are known exactly. In addition, the OptiMelt temperature calibration must be checked, and readjusted if necessary, every six months (minimum) to maintain the instrument within its factory-certified accuracy specifications. A fresh calibration of the OptiMelt must be performed every 6 months. Analytical quality control (QC) Laboratories, are required to test their melting point instrumentation on a regular basis, against Certified Reference Standards (CRSs), to determine the acceptability of their instruments according to specific QC requirements set forth by Local, National and International Standards and Pharmacopoeia Laboratories. Temperature Calibration Methodology Most modern melting point instruments include temperature calibration hardware and procedures to adjust their temperature readings. The calibration methodologies applied by commercial instruments can be divided into three main categories: Method 1. Using a Calibration Bath The thermometer is removed from the heating block and immersed in a liquid bath with a well known temperature (i.e. ice bath) . The temperature readings are adjusted to match the temperature of the bath. The thermometer is then reinserted into the heating block. Method 2. Using a Reference Thermocouple and Electronic Thermometer. A calibrated thermocouple or Pt/RTD thermometer is inserted into one of the sample slots of the heating block. The melting point aparatus is preheated to a fixed Start temperature. Once the requested Start temperature becomes stable, the readings from the calibrated thermometer are used to correct the temperature display of the instrument. Method 3. Calibration with a Melting Point Standard Stanford Research Systems Phone: (408) 744-9040 www.thinkSRS.com The melting point(s) of one or more CRSs are measured and then compared with their certified values. If the two sets of numbers (i.e. measured vs. expected) deviate from one another beyond the accuracy of the instrument the temperature scale is readjusted accordingly. The aging of Pt/RTD resistor thermometers has been well documented in the engineering and scientific literatures and has been identified as the leading cause for loss of accuracy in most modern Melting Point (MP) instrumentation. Calibration methods relying on the use of reference thermometers or calibration baths (Methods 1 & 2), though adequate for checking the temperature accuracy of the block's thermometer by its