StationaryPhases
43
Irregularmicro-
packed column
Classical packed
columns
Regularmicro-
packed columns
Tube i.d.
(d,)
[mm]
0.3-0.5
≥
2
0.3-1.5
Particle size
(d,)
mm 0.05-0.15
0.12-0.30
0.04-0.3
d
p
/d
c
0.04-0.10
0.07-0.25
0.25-0.5
sample capacit
y
μ
g
5-20
>1000
1-10
h
(mm)
0.4-1.2
>0.5
0.15-0.40
L
,m
1.8 (6 ft)
4.5 (15 ft)
4.5 (15 ft)
Preferred
applications
Short columns
permit high-speed
analyses coupled
techniqueswith
MS.
Simple separation
problems; trace
analysis; coupled
techniqueswith
spectrometr
y
Multi-component
analysis; high-
resolution coupled
techniquewithMS;
trace anal
y
sis
Table 6. Geometrical characteristics forpacked columns andmicro-packed columns
Micro-packed columns are suitable for the analysis of multi-component mixtures and trace
constituents, especially when coupling with mass spectrometry, thus allowing quickly
analyses.
7. Operationcolumn
Several parameters can be used to evaluate the operation of a column and to obtain
information about a specific system. An ideal gas chromatographic column is considered to
havehigh resolvingpower, high speedof operation andhigh capacity.
ColumnEfficiency
Two methods are available for expressing the efficiency of a column in terms of HETP
(height equivalent to a theoretical plate): measurement of the peakwidth (1) at the baseline,
N=16(V
R
/w
b
)
2
and the peakwidth at half the peak height (2), N=5.54(VR/w
k
)
2
, whereN is
the height equivalent to theoretical plate (HETP) and w has the significance from the
graphic below (Figure 2).
Fig. 2.Methods for expressing the efficiencyof a column in terms ofHETP
