Kovat's retention index

Kovat's retention index or simply Kovat's index is a method of quantifying the relative elution times of compounds in gas chromatography in such a way as to help positively identify the components of a mixture. The method takes advantage of the linear relationship between the values of $$log (t_r')$$ and the number of carbon atoms in a molecule. The value of Kovat's index is usually represented by I in mathematical expressions. It's applicability is restricted to organic compounds. The Kovat's index is given by the equation

$$I = 100 \times \left [ n + ( N - n ) \frac{log (t_{r (unknown)} ') - log (t_{r (n)} ')}{log (t_{r (N)} ') - log (t_{r (n)} ')} \right ] $$

Where;

$$I =$$ Kovat's retention index,

$$n =$$ the number of carbon atoms in the smaller alkane,

$$N =$$ the number of carbon atoms in the larger alkane,

$$t_r' =$$ the adjusted retention time.

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