Instant Notes: Analytical Chemistry

series of n-alkanes, defines an index for each alkane as 100 ¥the number of

carbon atomsfor any column at any temperature, i.e. n-pentaneis 500 , n-

octaneis 800 etc. The retention index of any other solute, relative to the n-

alkane scale, is calculated or read from a graph of log(retention time) against

D5 – Gas chromatography: procedures and applications 153

Carrier gas

Automatic

switching

system

Desorption oven

(for thermal

desorption mode)

Backflush

vent

Purge

vessel

Cryostat

Fused silica cold trap

inside tubular heater

Purge/desorb vent

Capillary column

Liquid N 2 or CO 2

coolant

(a)

12

3

4

5

6

7

8

9

Time (min)

(b)

Fig. 3. Combined headspace sampling, thermal desorption and purge and trap injection

system with example headspace chromatogram. (a) Injection system; (b) Headspace

chromatogram. Detection of solvents in blood sample by headspace analysis as part of an

industrial hygiene study. Sample held at 60°C. Column UCON LB 550, 25 m, at 40°C.

Produced from D.W. Grant, Capillary Gas Chromatography, 1996. © John Wiley & Sons Ltd.

Reproduced with permission.

Peak identification

1. diethyl ether


2. hexane


3. acetone


4. dichloromethane


5. methyl ethyl ketone


6. ethanol


7. benzene


8. methyl isobutyl ketone


9. toluene