ANALYTICAL METHODS USED FOR DETECTION OF PHYSICAL PROPERTY

[ DSC & X-RAY DIFFRACTION ]

Presented By

SOVAN KAYALM.PHARM(1ST SEM)

NETAJI SUBHAS CHANDRA BOSE INSTITUTE OF PHARMACY

DIFFERENTIAL SCANNING CALORIMETRY [DSC]

Calorimeter- Heat flow in sample

Differential calorimeter- Heat flow in sample vs reference as function of time

DSC: The Technique

• Differential scanning calorimetry (DSC) measures the temperature and

heat flows associated with transitions in materials as a function of time

and temperature in a controlled atmosphere.

• These measurements provide quantitative and qualitative information

about physical and chemical changes that involve endothermic or

exothermic processes or changes in heat capacity.

Diagram of a DSC apparatus

A DSC apparatus is built around A differential detector A signal amplifier A furnace A temperature controller A gas control device A data acquisition device

DSC measures:• Glass transitions• Melting and boiling points• Crystallization time and temperature• Percent crystallinity• Heats of fusion and reactions• Specific heat capacity• Oxidative/Thermal stability• Reaction kinetics• Purity

Control loupes in DSC:

Modes and Principles of operation:

Power Compensated DSC:Temperature differences between the sample and reference are ‘Compensated’ for by varying the heat required to keep both pans at the same temperature. The energy difference is plotted as a function of sample temperature.

Heat-flux DSC:

Heat flux DSC utilizes as a single furnace. Heat flow into both sample and reference material via an electrically heated constantan thermoelectric disk and is proportional to the difference in output of the two thermocouple junctions.

DSC Thermogram:

Operation Procedures:

Calibration of instrument

• Temperature, heat of reaction, heat capacity scale using high

purity standards (In, Sn, Bi, Pb, Au).

• Baseline correction for a given scan rate (1-40 K/min).

•Weight samples before (and maybe after) experiment.

Advantages:

• Rapidity of the determination

• Small sample masses

• Versatility

• Simplicity

• Applicable

• Study many types of chemical reactions

Disadvantages:

• Relative low accuracy and precision (5-10%)

• Not be used for overlapping reactions

• Need calibration over the entire temperature for DTA

X-RAY DIFFRACTION

X-RAY:

• An electromagnetive wave of high energy and very short wavelength (between ultraviolet light and gamma rays), which is able to pass through many materials opaque to light.

Energy: 100eV to 100KeVWavelength: 0.01 to 10 nanometer.

DIFFRACTION:

• The process by which a beam of light or other system of waves are spread out as a result of passing through a narrow aperture or across an edge, typically accompanied by interference between the wave forms produced.

X-RAY DIFFRACTION:

• A technique used to determine the atomic and molecular structure of a crystal, in which the crystalline atoms cause a beam of incident X-rays to diffract into many specific directions.• The atomic planes of a crystal cause an incident beam of X-rays to

interfere with one another as they leave the crystal. The phenomenon is called X-ray diffraction.• A stream of X-rays directed at a crystal diffract and scatter as they

encounter atoms. The scattered rays interfere with each other and produce spots of different intensities that can be recorded on film.

Experimental setup:

HOW DOES IT WORK:

HOW DIFFRACTION WORKS: SCHEMATIC

FACTORS THAT AFFECT XRD DATA:

Sample not powdered fine enough.

May not give all d-spacing data (not random enough).

Analysis too fast (degree/minutes).

May not give accurate peak data.

Mixture of minerals.

APPLICATION OF X-RAY DIFFRACTION:

Find structure to determine function of proteins.

Distinguish between different crystal structures with identical

compositions.

Study crystal deformation and stress properties.

Study of rapid Biological and Chemical processes.

Crystallographic applications.

X-RAY DIFFRACTION IS IMPORTANT FOR:

Solid-state physics

Biophysics

Medical physics

Chemistry and Biochemistry

THANK YOU