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preface to fifteenth edition

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PRACTICAL LABORATORY INFORMATION 11.27<br />

Now the overall effects due <strong>to</strong> hydrogen bonding, dipole moment, acid-base properties, and<br />

molecular configuration can be expressed as<br />

I ax by cz du es<br />

where x I for benzene (the column headed “1” in Table 11.13, intermolecular forces typical of<br />

aromatics and olefins), y I for 1-butanol (the column headed “2” in Table 11.13, electron<br />

attraction typical of alcohols, nitriles, acids, and nitro and alkyl monochlorides, dichlorides and<br />

trichlorides), z I for 2-pentanone (the column headed “3” in Table 11.13, electron repulsion<br />

typical of ke<strong>to</strong>nes, ethers, aldehydes, esters, epoxides, and dimethylamino derivatives), u I for<br />

1-nitropropane (the column headed “4” in Table 11.13, typical of nitro and nitrile derivatives), and<br />

s I for pyridine (or dioxane) (the column headed “5” in Table 11.13).<br />

11.4.2 Chroma<strong>to</strong>graphic Behavior of Solutes<br />

11.4.2.1 Retention Behavior. On a chroma<strong>to</strong>gram the distance on the time axis from the point<br />

of sample injection <strong>to</strong> the peak of an eluted component is called the uncorrected retention time t R .<br />

The corresponding retention volume is the product of retention time and flow rate, expressed as<br />

volume of mobile phase per unit time:<br />

V tF R R c<br />

The average linear velocity u of the mobile phase in terms of the column length L and the average<br />

linear velocity of eluent t M (which is measured by the transit time of a nonretained solute) is<br />

L<br />

u <br />

tM<br />

The adjusted retention time t R is given by<br />

tt t<br />

R R M<br />

When the mobile phase is a gas, a compressibility fac<strong>to</strong>r j must be applied <strong>to</strong> the adjusted retention<br />

volume <strong>to</strong> give the net retention volume:<br />

VN<br />

jV <br />

R<br />

The compressibility fac<strong>to</strong>r is expressed by<br />

3[(P /P )<br />

2<br />

i o 1]<br />

j <br />

3<br />

2[(P /P ) 1]<br />

i<br />

o<br />

where P i is the carrier gas pressure at the column inlet and P o that at the outlet.

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