OptiMelt Automated Melting Point System - Stanford Research ...

More documents

Recommendations

Info

50 Melting Point Determination Chapter 3Instrument SetupAlong with proper sample preparation, careful selection of the instrumentsettings is also essential for accurate and reproducible melting pointdeterminations.The modern trend in melting point instrumentation is towards small aluminum ovens. Atypical oven can hold three capillaries and the thermal mass around the three tubes is veryclose so that deviations as small as 0.02 to 0.1ºC (temperature dependent) are keptbetween the three tubes during a melt.The main advantage of a small metal oven is the lack of an overshoot that lets you parkthe unit at a start temperature
Chapter 3 Melting Point Determination 51Correct selection of the Start temperature, ramp Rate and Stop temperature is absolutelyessential to prevent inaccuracies due to a heat increase in the sample that is incorrect ortoo fast.Start TemperatureOptiMelt range: 30 °C – 400 °CThis is the temperature at which the sample capillaries are introduced into the heatingstand, and serves as the starting temperature for the heating ramp. The Start temperatureis usually programmed 5-10 °C below the expected melting point of the substance.NoteThe Start Temperature must be at least 10 °C above ambient temperature to assure properstabilization of the oven.Ramp RateOptiMelt range: 0.1 – 20 °C/min, 0.1 °C/min stepsThis is the fixed rate of temperature rise between the Start and Stop temperatures for theheating ramp. User adjustable ramp Rates are standard in modern automated meltingpoint instrumentation.The ramp Rate/min is the most important instrumental parameter affectingthe accuracy of melting points.Since the melting point temperature is not measured directly within the substance, butrather outside the capillary tube (i.e. inside the heating stand) the results are dependent onthe heating rate. The temperature in a pure melting substance remains constant until thesample has completely melted. However, this takes a finite amount of time and the oventemperature continues to increase according to the heating rate chosen (i.e. thermal lag).The temperature displayed does not correspond to the exact temperature in the meltingsubstance but to that of the oven. Consequently, higher values are obtained where thedifference between the measured melting point and the true melting temperature isgreater the more rapid the rise in oven temperature. These heating rate dependenttemperatures are referred to as “according to pharmacopeia”. Some melting pointinstruments (such as the SRS OptiMelt) can compensate for the oven ramp rate andprovide corrections for the temperature readings obtained according to pharmacopeia sothat the “true thermodynamic” melting point of a pure substance can be reported.Misuse of fast ramp rates is the main cause of inaccuracies in melting pointmeasurements.The factory default setting is 1 °C/min. Ramp rates up to 2 °C/min are reasonable forroutine determinations. Higher rates are only recommended for quick determinations onsubstances with unknown melting points. Purity determination and precisionmeasurements are performed at a maximum heating rate of ~0.5 °C/min, though therecommendation is to stay at 0.1-0.2 °C/min whenever feasible. Samples that start todecompose at temperatures below their melting point, are typically analyzed at ramp ratesOptiMelt Automated Melting Point System
Page 4 and 5:
iiSafety and Preparation For Use•
Page 6 and 7:
ivSafety and Preparation For UseOpt
Page 8 and 9:
viContentsMelting Point Range 57Mel
Page 10 and 11:
viiiFront Panel OverviewReady LEDA
Page 12 and 13:
xBack Panel OverviewPrinterOptiMelt
Page 14 and 15: xiiSpecificationsOptiMelt Automated
Page 16 and 17: 2 Getting Started Chapter 1• Repl
Page 18 and 19: 4 Getting Started Chapter 1Ceramic
Page 20 and 21: 6 Getting Started Chapter 1Principl
Page 22 and 23: 8 Getting Started Chapter 1Quick St
Page 24 and 25: 10 Getting Started Chapter 18. Preh
Page 26 and 27: 12 Getting Started Chapter 1Touch t
Page 28 and 29: 14 Getting Started Chapter 1If none
Page 30 and 31: 16 Getting Started Chapter 1• Tou
Page 32 and 33: 18 Getting Started Chapter 1OptiMel
Page 34 and 35: 20 Displays and Menus Chapter 2Nume
Page 36: 22 Melt Screen Chapter 2Melt Screen
Page 39 and 40: Chapter 2 Melt Screen 25Touch the T
Page 41 and 42: Chapter 2 Melt Screen 27Select Newe
Page 43 and 44: Chapter 2 Melt Screen 29Select Came
Page 45 and 46: Chapter 2 Melt Screen 31Options Men
Page 47 and 48: Chapter 2 Melt Screen 33The thermod
Page 49 and 50: Chapter 2 Timer Screen 35ResetTouch
Page 51 and 52: Chapter 2 T Meter Screen 37Alarm Lo
Page 53 and 54: Chapter 2 System Screen 39System Sc
Page 55 and 56: Chapter 2 System Screen 41The Print
Page 57 and 58: Chapter 2 System Screen 43Screen Me
Page 59 and 60: Melting Point Determination 45Chapt
Page 61 and 62: Chapter 3 Melting Point Determinati
Page 63: Chapter 3 Melting Point Determinati
Page 77 and 78: Maintenance and Calibration 63Chapt
Page 79 and 80: Chapter 4 Maintenance and Calibrati
Page 91 and 92: Pharmacopeia vs. Thermodynamic Melt
Page 93 and 94: Appendix A Pharmacopeia vs. Thermod
Page 99 and 100: Melting Point Certified Reference S
Page 101 and 102: Appendix B Melting Point Certified
Page 103 and 104: Appendix B Melting Point Certified
Page 105 and 106: Using Melt Graphs 91Appendix CUsing
Page 107 and 108: Appendix C Using Melt Graphs 93The
Page 109 and 110: OptiMelt Remote Programming 95Appen
Page 111 and 112: Appendix D OptiMelt Remote Programm
Page 113 and 114: Appendix D OptiMelt Remote Programm
Page 115 and 116:
Appendix D OptiMelt Remote Programm
Page 117 and 118:
Page 119 and 120:
Page 121 and 122:
Page 123:
show all

OptiMelt Automated Melting Point System - Stanford Research ...

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?