OptiMelt Automated Melting Point System - Stanford Research ...

58 Melting Point Determination Chapter 3Tips• The dependence of the clear point on the sample height and capillary geometry iswhy it is so important to calibrate your OptiMelt using capillaries and loadingtechniques identical to those applied during routine determinations.• The SRS OptiMelt can automatically detect and record the onset and clear points of asample. User adjustable thresholds are available to match the visual and automaticvalues for both points.• A large majority of pure organic compounds melt neatly within a range of 1.25±5 ºCor melt with decomposition over a narrow range of temperature (~2 ºC) at heatingrates about 1 ºC/min. Many organic compounds, melt with decomposition over aconsiderable range of temp: amino acids, salts of acids, salts of amines,carbohydrates, etc.• Impure substances (i.e. mixtures) melt over a larger temperature range.Melting Point ReportA complete melting point Report should include enough information to make it possiblefor somebody else to reproduce the determination and compare results. Very usefulreporting guidelines, compatible with modern GLP requirements, were set forth by Carterand Carter (J. Chem. Ed., 72 (1995) 647) and are listed here:• Report all instrument settings, especially heating rate, so they can be duplicated orreasonable adjustments made.• Report onset and clear point temperatures to the nearest 0.1 °C (or at least 0.5 °C) forroutine melting point ranges.• Report onset, meniscus and clear point to nearest 0.1 °C for important melting pointranges, such as those of new compounds.• If a single temperature is to be reported as the melting point (not recommended)specify whether it represents the meniscus or clear point.• Use well known melting point standards (i.e. certified reference standards) forcalibration. The quality of your measurements are only as good as the quality of thestandards used for calibration.TipsA Report is automatically generated by the OptiMelt system at the end of each analysis.The report includes all manual and automated records collected throughout the test, aswell as all setup and calibration information required for proper certification of theresults. Touch the Report button on the Melt Screen at any time to access the last eightReports stored within your OptiMelt system.OptiMelt Automated Melting Point System