Instant Notes: Analytical Chemistry

are specific interactions with a solute, e.g. on a nonpolar stationary phase,

t-butyl alcohol (bp 82.6∞C) elutes before cyclohexane (bp 80.8∞C) because

the latter, being nonpolar itself, dissolves better in the stationary phase.

However, on a polar stationary phase with hydroxy groups, the elution order

is reversed because the alcohol can H-bond to it.

Selections of stationary phases are given in Tables 3 and 4.

144 Section D – Separation techniques

036912

Time (min)

15 18 21 24

1

2

3

4

5

6

7

8

9

10

Inject

0

1234

6

7

(^89)
10
12
11
40 min
13
14
15
16
17
Peak indentification

1. pyridine


2. 2,4,5-trimethyloxazole


3. 3-methylpyridine


4. 1-pentanol


5. ethylheptanoate


6. 1-hexanol


7. 1-heptanol


8. linaloate


9. 1-octanol


10. 1-nonanol


11. citronellol


12. 1-decanol


13. 3-acetylpyridine


14. anisaldehyde


15. cinnamaldehyde


16. d-decalactone


17. anisylalcohol

5

Fig. 4. Examples of gas chromatographic separations on capillary and packed columns. (a) Packed column separation
of mixed hydrocarbons; (b) capillary column separation of some flavor compounds. Reproduced from D.W. Grant,
Capillary Gas Chromatography, 1996. © John Wiley & Sons Ltd. Reproduced with permission.

(a) Peak indentification

1. isopentane


2. n-pentane


3. cyclopentane


4. 3-methylpentane


5. n-hexane


6. 2,4-dimethylpentane


7. benzene


8. cyclohexane


9. 3-methylhexane


10. n-heptane

(b)