CALIBRATION CURVE
          • Calibration curve, also called standard curve, is 
           a general method for determining the 
           concentration of a substance in unknown 
           sample by comparing the unknown to a set of 
           standard samples of known concentration.
                 CALIBRATION CURVE
          • The curve prepared from a series of dilutions 
           from standard solutions of a certain substance 
          • Used as a reference curve to obtain the 
           concentration of unknown samples of that 
           substance.
               SPECTROPHOTOMETRY 
          • Spectrophotometry is a method to measure 
           how much a chemical substance absorbs light, 
           by measuring the intensity of light, as a beam 
           of light passes through sample solution. 
          • The basic principle behind this method is that : 
           “Each compound absorbs or transmits light 
           over a certain range of wavelength”
               SPECTROPHOTOMETRY
         • The light absorbed by the sample is directly 
          proportional to the concentration of sample in 
          the solution.  As concentration increases , 
          absorption increases exponentially.
                    HOW IT WORKS ?
           •  When light goes through the substance some 
            of it is reflected & the rest is partially absorbed 
            and partially transmitted. 
           • Spectrophotometric method of analysis is 
            usually concerned with measurement of the 
            amount of light absorbed.