Stanford Research Systems www.thinksrs.com-AutomatedMP free download

File name www.thinksrs.com-AutomatedMP.pdf

www.thinkSRS.com Automated MP Determinations Application Note #5 Introduction OptiMelt was specifically designed to detect and determine melting points with completely unattended operation. What sets this instrument apart from its competition is its reliance on a "built-in digital camera" and sophisticated Digital Image Processing (DIP) to detect and determine melting points. Figure 1. View of the OptiMelt's heating chamber. A built-in camera faces the samples; a digital image processor calculates melting points and melting ranges. A very important advantage of the OptiMelt system is its capability to determine melting points automatically while simultaneously visualizing the samples. If required, the capillaries can be viewed at any time, and the melting points can be determined visually. The choice between a time-consuming visual determination and a faster blind automated method is eliminated. Visualization is important for colored or problematic samples, for chemists trying to reproduce published visual observations, and for synthetic chemists generating new, intermediate or exotic compounds. Stanford Research Systems Phone: (408) 744-9040 Automated MP Determinations www.thinkSRS.com Figure 2. OptiMelt offers the option to determine melting points automatically while simultaneously visualizing the samples. Automation offers significant time saving advantages for routine determinations of melting points in production, research and educational settings. This application note describes the automation capabilities of OptiMelt and compares its Digital Imaging approach to the more primitive optical transmission and reflection methodologies used by its competitors. Automation Techniques Most modern automated melting point measurement instruments rely on changes in optical properties of the solid samples during the heating ramp to detect and estimate melting points and ranges. The three optical techniques used to automatically detect melting point transitions are: 1) Transmission, 2) Reflection, 3) Digital Imaging. Stanford Research Systems Phone: (408) 744-9040 Automated MP Determinations www.thinkSRS.com Figure 3. Schematic representation of the transmission method. The principle of operation of the transmission method is simple. The capillary tube standing in a heating block is illuminated from the front with a source of IR light (i.e. LED). A small light channel, drilled into the metal block (directly behind the capillary slot), optically connects the emitter to a photodiode located behind the heater block. A solid sample effectively blocks all light from getting to the photodetector (i.e. 0 % transmission). During the heating process, the light intensity measured by the photocell increases. At a certain transmittance