U-V VISIBLE SPECTROSCOPY

-

 U-V VISIBLE SPECTROSCOPY 

  • UV-Vis spectrum results from the interaction of EM radiation in the UV-Vis region with atoms and molecules.
  • The UV radiation region extends from 200nm to 400nm and the visible region extends from 500nm to 800nm.
  • Organic compounds, inorganic compounds, and coordination compounds fall in the UV-Vis spectrum.

THEORY

  • The absorption of radiation in the UV-Vis region of the spectrum is dependent on the electronic structure of the absorbing species. 
  • When a photon of a given wavelength interacts with a molecule it may cause a transition among the electronic energy levels if its energy matches with the difference in the energies of these levels.
  • A given electronic energy level has a number of vibrational energy levels in it and each of the vibrational energy levels has a number of rotational energy levels in it. So along with the electronic transition, vibrational and rotational transitions also occur simultaneously. So electronic spectrum appears broad.
  • Transitions involving π orbitals and lone pairs are identified using UV-Vis spectrometers.

INSTRUMENTATION 

  


The sample is irradiated with UV-Vis radiation from a source. Monochromatic radiation is employed at a time. The amount of radiation absorbed at each wavelength is measured.
Spectrum is the plot of wavelength or frequency versus intensity of absorption. 
Light absorbed is directly proportional to the concentration in the sample.
Location: United States

Comments

Post a Comment

Popular posts from this blog

GLASS ELECTRODE

-
Image
 GLASS ELECTRODE It is a secondary reference electrode that produces a constant and reproducible electrode potential. It is an ion-selective electrode used with other reference electrodes to generate a potential difference. Construction It is made up of a special glass of relatively low melting point and high electrical conductivity, in the form of a sealed glass tube filled with 0.1M HCl, a platinum wire is inserted into it, to make electrical contact. The glass electrode is represented as Pt| 0.1M HCl | Glass | H+    The H+ ion concentration inside the electrode is constant. When the electrode is immersed into a solution of unknown H+, it becomes sensitive to the outside concentration in the solution. Such a sensitivity arises because of the difference between the H+ ion concentration inside and outside.       The electrode potential of the glass rod is : EG = EG0 + 0.0591 log [ H+ ]     EG = EG0 - 0.0591 pH  The glass electrode is used as the internal reference electrode for th
Read more

COLUMN CHROMATORGAPHY

-
Image
 COLUMN CHROMATOGRAPHY It is a technique in which the stationary phase is solid or a liquid supported by a solid. When a column is used as the adsorbent it is called adsorption column chromatography. When the solid column is acting only as a support to the liquid adsorbent then it is called partition column chromatography. SEPARATION The selection of solvent is based on the nature of the components in the mixture. Adsorption depends upon the nature of the solvent and the adsorbent.  The rate at which the components of a mixture are separated depends upon the activity of the adsorbent and the polarity of the solvent. If the activity of the adsorbent is very high and polarity is low, then separation is low but gives good separation. If the activity of the adsorbent is low and the polarity of the solvent is high, then the separation is rapid but gives poor separation PROCEDURE A proper adsorbent is selected and made a slurry with a suitable liquid and placed in a suitable tube which is pl
Read more

HIGH PERFORMANCE LIQUID CHROMATOGRAPHY

-
Image
 HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY It is a method used for the separation, purification, and identification of various nonvolatile high molecular weight organic compounds and natural products like cholesterol, terpenoids. ADVANTAGES High-speed separation Excellent column separation Solvent consumption is minimum Sensitive and accurate Separation can be done at an ambient temperature. PRINCIPLE The components of the mixture are separated depending upon the extent of adsorption and partition on the stationary phase and the rate at which the component is carried by the mobile phase. The mobile phase is liquid and the stationary phase can be solid or liquid. INSTRUMENTATION Solvent reservoirs are used to collect the different solvents. Pressure pump to apply pressure  Sample injector to give the mixture which is to be separated in the analytical column Regulator to adjust the flow rate Guard column to remove the particulate matter and contaminants from the solvent. The analytical colu
Read more