Chemistry Reference
In-Depth Information
Table 10.2
Column inner diameter and pump flow rate of different
types of LC.
LC type
Column inner diameter
Pump flow rate
traditional LC
<10 mm; >1 mm
>1 ml min
−1
microbore LC
1 mm ~ 500
μ
m
100 ~ 500
μ
l min
−1
capillary LC
100 ~ 500
μ
m
1 ~ 25
μ
l min
−1
nano LC
<100
μ
m
<1
μ
l min
−1
(a)
(b)
(c)
(d)
Figure 10.3
The cartoon diagram of the band broadening versus LC tubing diameter and column at the same
stationary phase: tubing diameter and column, (a > (b) > (c) > (d). The analyte concentration is the same and
peak dispersion easily occurs in the tubing with a broad inner diameter.
traditional LC is diluted by mobile phase and band broadening easily occurs. This phenomenon could be
avoided when the tubing of LC system is shrunk. For low rate of the mobile phase and narrow tubing of the
LC system, peak dispersion (or peak spreading) in this condition is small. Microbore LC is suitable for
developing the low dispersion LC (LDLC). The relationship between the band broadening and the diameter
of LC tubing is shown in Figure 10.3.
Theoretically, the peak of sample in microbore LC is sharper than traditional LC and the sensitivity is
increased obviously at the same concentration. Microbore LC is the fast and simple way to reduce organic
waste from traditional LC. There are many areas using microbore LC as the analytical system, such as drug
(or drug-like compound) analysis [61-69], protein or peptide analysis [70-78], inorganic analysis [79-88],
hormone analysis [89-100], neurotransmitter analysis [101-112] and toxin analysis [113-116].
10.3.2
Capillary Liquid Chromatography (capillary LC)
Capillary LC is a good strategy to reduce organic waste effectively. Capillary LC is derived from microbore
LC, but the tubing and flow rate of capillary LC are all narrowed down. Sometimes it is difficult to distinguish
between microbore LC and capillary LC. The pump flow rate of capillary LC generally is about 1 ~ 25
l min
−1
.
Capillary LC has two major designs: capillary flow pump and traditional LC pump coupled with a splitter. The
later is a traditional LC system; its flow rate at microliter level is generated by a flow rate controller or a splitter
or both. A capillary flow pump could generate the exact flow rate at microliter level; this kind of pump is
expensive. Because of the low detected volume, the commercial detector of capillary LC is UV, photo diode
array (PDA) and mass spectrometry (see Figure 10.4).
μ
