production of selected secondary metabolites in transformed ...

Fig. 1: Scheme of the hydride generation aparature coupled with the heated molybdenum-foil
trap system and simple hydrogen diffusion flame atomic absorption system.
The implementation of the electrothermal trapping/vaporisation (ETV) device in the
instrumental arrangement is shown in Fig. 1. Only a very simple atomiser based on
a miniature hydrogen diffusion flame was used for atomic absorption spectrometry detection
in trapping experiments. The flame was supported by the gas mixture of hydrogen and argon
at a flow rate of 215 ml min -1 and 800 ml min -1 , respectively. The injection capillary, made of
a wide bore quartz GC–capillary (8 cm × 0.53 mm id), was inserted through the narrow hole,
drilled in the axis of the boron nitride body. The tip of the capillary was precisely positioned
by means of an adjusting screw made of PEEK. A laboratory made pulse-width modulation
power supply was used for heating the molybdenum strip. It was based on a high power
MOS-FET transistor and a car battery (12 V, 60 Ah). The power supply was controlled by
a PC by using software created in Visual Basic ver.3. In trapping experiments, the actual
temperature of the heated central part of the molybdenum strip was simultaneously measured
by pyrometers.
A laboratory made flow injection hydride generation system is depicted also in Fig. 1. The
peristaltic pump (model 72624–71, Ismatec, Switzerland) was fitted with Tygon tubes. The
generation system was based on 3-channel peristaltic pump, PTFE-reaction loop and gasliquid
separator with a forced outlet for liquid phase and with a PTFE-filter in an outlet for
gaseous phase. The flow rates were 1.1, 3.6 and 5.0 ml min -1 for 0.5% m/v NaBH4 solution,
sample solution in 1 mol l -1 HCl and waste solution, respectively. The sample channel was
equipped with a Knauer (Berlin, Germany) 6–port injection valve made of PEEK with
a 100 μl sampling loop for performing flow injection of the sample solution. Argon was
introduced in two channels, upstream of the reaction loop as reaction gas and into the gas–
liquid separator as stripping gas at a flow rate of 55 ml min -1 and 10 ml min -1 , respectively.
Sborník soutěže Studentské tvůrčí činnosti Student 2006 a doktorské soutěže O cenu děkana 2005 a 2006
Sekce DSP 2006, strana 207