Preferred Label : retention index;
Detailed label : retention index in column chromatography, I;
IUPAC definition : The retention index of a sample component is a number, obtained by interpolation (usually
logarithmic), relating the adjusted retention volume (time) or the retention factor
of the sample component to the adjusted retention volumes (times) of two standards
eluted before and after the peak of the sample component. In the Kováts index or Kováts
retention index used in gas chromatography, i n /i -alkanes serve as the standards
and logarithmic interpolation is utilized: \[I 100\left[\frac{\log _{10}X_{i}- \log
_{10}X_{z}}{\log _{10}X_{z 1}- \log _{10}X_{z}} z\right]\] where X refers to the adjusted
retention volumes or times, z is the number of carbon atoms of the i n /i -alkane
eluting before and z 1 is the number of carbon atoms of the i n /i -alkane eluting
after the peak of interest: \[V_{{R}z} {'} V_{{R}i} {'} V_{{R}(z 1)}\] The Kováts
(retention) index expresses the number of carbon atoms (multiplied by 100) of a hypothetical
normal alkane which would have an adjusted retention volume (time) identical to that
of the peak of interest when analysed under identical conditions. The Kováts retention
index is always measured under isothermal conditions. In the case of temperature-programmed
gas chromatography a similar value can be calculated utilizing direct numbers instead
of their logarithm. Since both the numerator and denominator contain the difference
of two values, here we can use the total retention volumes (times). Sometimes this
value is called the linear retention index. \[I {{T}} 100\left[\frac{t_{{R}i} {{T}}-
t_{{R}z} {{T}}}{t_{{R}(z 1)} {{T}}- t_{{R}z} {{T}}} z\right]\] where t R T refers
to the total retention times (chart distances) measured under the conditions of temperature
programming. The value of IT will usually differ from the value of I measured for
the same compound under isothermal conditions, using the same two phases.;
Origin ID : R05360;
See also
The retention index of a sample component is a number, obtained by interpolation (usually
logarithmic), relating the adjusted retention volume (time) or the retention factor
of the sample component to the adjusted retention volumes (times) of two standards
eluted before and after the peak of the sample component. In the Kováts index or Kováts
retention index used in gas chromatography, i n /i -alkanes serve as the standards
and logarithmic interpolation is utilized: \[I 100\left[\frac{\log _{10}X_{i}- \log
_{10}X_{z}}{\log _{10}X_{z 1}- \log _{10}X_{z}} z\right]\] where X refers to the adjusted
retention volumes or times, z is the number of carbon atoms of the i n /i -alkane
eluting before and z 1 is the number of carbon atoms of the i n /i -alkane eluting
after the peak of interest: \[V_{{R}z} {'} V_{{R}i} {'} V_{{R}(z 1)}\] The Kováts
(retention) index expresses the number of carbon atoms (multiplied by 100) of a hypothetical
normal alkane which would have an adjusted retention volume (time) identical to that
of the peak of interest when analysed under identical conditions. The Kováts retention
index is always measured under isothermal conditions. In the case of temperature-programmed
gas chromatography a similar value can be calculated utilizing direct numbers instead
of their logarithm. Since both the numerator and denominator contain the difference
of two values, here we can use the total retention volumes (times). Sometimes this
value is called the linear retention index. \[I {{T}} 100\left[\frac{t_{{R}i} {{T}}-
t_{{R}z} {{T}}}{t_{{R}(z 1)} {{T}}- t_{{R}z} {{T}}} z\right]\] where t R T refers
to the total retention times (chart distances) measured under the conditions of temperature
programming. The value of IT will usually differ from the value of I measured for
the same compound under isothermal conditions, using the same two phases.