Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
DETECTORS USED IN UV-VIS, IR AND MASS SPECTROSCOPY Presented by Dr. A. Suneetha Dept. of Pharm. Analysis Hindu College of Pharmacy DEFINITION: Detector is defined as the device that identifies and records the signals produced by the sample components. An ideal detector has: • Adequate sensitivity – range 10-18 to 10-15 g analyte/sec • Good stability and reproducibility • Good linearity A temperature range from room temperature to at least 4000C. A short response time that is independent of flow rate. High reliability and ease of use. Nondestructive of sample. DETECTORS USED IN UV-VIS SPECTROSCOPY Detectors used in UV-Visible Spectroscopy mainly includes: Barrier layer cell or photo voltaic cell Photo tubes or photo emissive cells Photo multiplier tubes and Photo diode array detector Photo voltaic cell: Also known as barrier layer cell A: Iron base plate B: Bi-layer selenium C: Thin layer of silver D: Glass E: Plastic case ADVANTAGES: Simple in design and does not require any external power supply. Cheapest and inexpensive of all UV detectors DISADVANTAGES: Amplification of the detector is not possible. Lesser response of the detector with light other than blue and red light. Photo emissive cells: Also known as Photo tubes. ADVANTAGES: • Better sensitivity than photovoltaic cell. • Amplification of the signal is possible. PHOTO MULTIPLIER TUBES: ADVANTAGES: ► PMT are extremely sensitive i.e., can detect very weak signals even 200 times than that could be done using photovoltaic cell. ► Extremely fast in response. Photodiode array detector: Advantages: The wavelength need not be selected, but the detector detects the responses of all the compounds. Resolves the problem of peak purity. Excellent sensitivity. DETECTORS USED IN IR SPECTROSCOPY Detectors used in IR-spectroscopy mainly includes: Bolometers Thermocouple Thermisters Golay cell Photo conductivity cell Semiconductor detectors Pyroelectric detectors and Fourier transform systems. BOLOMETERS: . ADVANTAGE: Bolometers have considerable fast response time(4 milli sec). Thermocouple: Disadvantage: Response time is slow compared to bolometers(60 milli sec). Golay cell: Merits: • Used for wide wavelength range. • Linearity in response is seen. Demerits: • More expensive and bulky. Fourier transform system: Merits: Increasing in sensitivity and accuracy can be achieved. The sample is not subjected to thermal effects. DETECTORS USED IN MASS SPECTROSCOPY Detectors used in mass spectroscopy mainly includes: Faraday cup detector Electron multiplier detector and Photographic detector Faraday cup detector: Electron multiplier detector: Photographic detection: Photographic detection is used effectively for high resolution in double focusing spectrometers References: • Instrumental methods of chemical analysis-by Gurudeep, R.Chatwal, Sham k. Anand. • Text book of pharmaceutical analysis-by S.Ravi Shankar • Instrumental Methods Of Chemical analysis-by B.K.Sharma • wikipedia