OptiMelt Automated Melting Point System - Stanford Research ...

48 Melting Point Determination Chapter 3If your sample is hygroscopic, or sublimates at high temperatures, the open end of thecapillary tube must be sealed by heating. Hygroscopic samples must be stored in adessicator between tests, this is particularly critical in humid environments or duringrainy days.The sample tubes are loaded into the OptiMelt by inserting them into one of the sampleposition slots located on top of the instrument. Up to three samples can be accommodatedby the heating block simultaneously. Loading three capillaries with the same substanceand melting them at the same time and averaging their melting points provides the fastestand simplest way to improve the repeatability and accuracy of melting pointdeterminations.Figure 29. Loading capillaries into OptiMelt.Tips• Most pharmacopeias list recommended drying procedures for melting point samplesand certified reference standards.• Make sure the OptiMelt is plugged in and set to a Start temperature below theexpected melting point of the sample(s) before placing any capillaries into the sampleslots.• Use the same batch of capillaries for calibration and for high accuracy measurementsto assure the repeatability of results. NOT ALL CAPILLARIES ARE MADEEQUAL!• The standard OptiMelt package includes a vial of precision melting point capillariesspecifically designed to (1) fit the OptiMelt heating stand and (2) provide the mostuniform and repeatable results. Replacement capillaries can be purchased directlyfrom SRS (SRS Part# O100MPC).• Never force a capillary into the heating block! Once the capillary is inserted into asample hole, it should literally drop down to the bottom of the stand.OptiMelt Automated Melting Point System