Page 280 - Multidimensional Chromatography

Biomedical and Pharmaceutical Applications 275

(b)

Internal standard
(a)

Broxaterol

0 2 4 6 0 2 4 6 8 10
x Time (min)
Time (min)
Figure 11.9 (a) LC trace of human plasma with 0.1 g/ml broxaterol, where ‘x’ indicates
the cut introduced into the GC run; (b) chromatogram of human plasma with 0.1 ng/ml
broxaterol and 5 ng/ml internal standard. Reprinted from Journal of High Resolution
Chromatography and Chronatographical Communication, 11, V. Gianesello et al.,
‘Determination of broxaterol in plasma by coupled HPLC–GC,’ pp 99–102, 1988, with
permission from Wiley-VCH.

lites. The LC eluent consisted of ethyl ether/methanol/diethylamine (91.5 : 8 : 0.5,
vol/vol) at a flow-rate of 400 l/min and a fraction of 500 l was transferred to the
GC unit through a loop-type interface. Ghys et al. (122) have used the same set-up
for the coupling of micro-SEC and GC. The interesting aspect of a micro LC column
of 320 m i.d. with a flow-rate of about 1 l/min is that a relatively large fraction
can be introduced into the GC unit. For the analysis of steroid esters in a pharmaceu-
tical formulation, a volume of only 4 l THF was transferred to the GC system.
Figure 11.10 shows the potential of this system. The heart-cut chromatogram of the
sample is very similar to the chromatogram of a standard solution of the steroid
esters.