Transcript Chapter 7
Chapter 7 Instrumental Analysis Spring 2011 I. Introduction • There are 6 optical spectroscopic methods that we are going to study in general II. Components of optical spectroscopy • All spectroscopic instruments contain 5 general components III. Sources of radiation • The source must have sufficient power and be stable for reasonable periods • As such there are 2 general types of sources A. Continuum Source • Use in absorption and fluorescence spectroscopy B. Line Sources • Emit a limited number of lines used in atomic absorption and fluorescence spectroscopy • http://youtu.be/y3SBSbsdiYg Types of LASERs Medium Wavelength Ruby Crystal (Cr3+) 694.3 nm Nd:YAG (neodymium in yttrium aluminum garnet) 1064 nm and 532 nm He/Ne 632.8 nm Ar+ 514.5 nm or 488.0 nm N2 337.1 nm Dye Laser (organic compounds that fluoresce in UV/Vis/IR range Use a monochrometer to select wavelength Diode Varies IV. Sample Container • Required for all spectroscopy – except emission V. Wavelength Selector • Passes limited narrow band of wavelengths • 2 types of wavelength selectors: A. Interference Filter B. Monochromators • Allows variation of wavelength continuously over a considerable range http://youtu.be/1pIjSuK23RM VI. Detectors • Several ideal properties • Photon transducers vs. Thermal transducers A. Photon transducers • Photomultiplier tube http://youtu.be/9FpYiB7gCP8 B. Photodiodes • Silicon Diodes http://youtu.be/W6QUEq0nUH8 Photodiode array B. Heat Detector • Thermocouple • Pyroelectric transducer VII. Signal Processor • Photon counting – Used for fluorescence, Raman • Fiber Optics – Used for UV-Vis and IR