2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P64 OPTIMALIZATION OF SPME METhOD
FOR SPICE CONTENTuAL SubSTANCES
DETERMINATION
MICHAELA STOUPALOVá, MILADA VáVROVá,
HAnA PLESKAČOVá, LUDMILA MRAVCOVá and
VLADIMíR VEČEREK
University of Veterinary and Pharmaceutical Sciences Brno,
Faculty of Veterinary Hygiene and Ecology
Palackého 1–3, 612 42 Brno, Czech Republic
stoupalovam@vfu.cz
Introduction
The SPME method can be used to extract analytes from
different matrices. It has been employed in the isolation of
analytes from the air, food, water, and other matrices 1 . The
SPME method has a number of major advantages such as fast
rate, high sensitivity and good accuracy; the detection limit
regularly achieved for the above-mentioned matrices ranges
in ng kg –1 . First published in 1989, the SPME method is now
a well established extraction method whose application has
been assessed and documented 2 .
The analyses of organic, fragrant, and flavouring components
as well as sample preparation are usually started
with the concentration of an analyte. If one considers a time
demand, the passive SPME sampling technique is the quickest,
with sample preparation not exceeding 30 minutes 3 .
The consistency of the results and the reliability of detection
with SPME as well as repeatability and reproducibility
are influenced by a number of factors, like polymer polarity
and the thickness of a polymer layer (stationary phase) on
the surface of a fibre, the sampling method, the pH, the ionic
strength of a solution, sample temperature, agitation, etc.
Experimental
The objective of this paper was the optimization of solid
phase microextraction (SPME) method, which is used for
determination of the essential oils in spice. Analytes were
analysed by GC/MS.
S P M E
The SPME method was investigated with different
fibers (polydimethylsiloxane – 100 μm thickness and polydimethylksiloxayne-divinylbenzene
– 65 μm), extraction time
(1; 2; 5; 10; 15; 20; 30; 40 and 60 minutes), extraction temperature
(30; 40 and 50 °C) and incubation of sample (0; 5;
10; 15; 20 minutes).
G C / M S
The determination itself was performed using the
GC 6890n (Agilent Technologies, USA) with a massspectrometric
detector 5973n MSD (Agilent Technologies,
USA); for separation HP-5MS capillary column was used
(30 m × 0.25 mm × 0.25 μm). The injector temperature was
270 °C, the ion source temperature was 230 °C and the
Transfer Line temperature was 250 °C. The temperature
s461
programme was 45 °C for period of 2 minutes, 5 °C min –1
to 200 °C, 200 °C for period of 2 minutes; the total analysis
time was 35 minutes. The flow-rate of the carrier gas (He)
was constant, 1 ml min –1 .
Results
The aim hereof was to optimise the SPME method for
determination of the essential oils in spice. We monitored
influence of the stationary phase on the sorption of monitored
analytes. We carried out comparison of two PDMS fibres
(100 μm) and PDMS-DVB (65 μm). The results obtained are
stated in Fig. 1. From it follows that the PDMS-DVB fibre
(65 μm) shows higher sorption effectivity for all the monitored
pesticides.
Fig. 1. Influence of the fibre type on response of detectors for
the monitored analytes
Also the influence of temperature on sorption of the target
compounds was monitored. The following temperatures
were tested: 30, 40 and 50 °C. Lower-molecular-weight terpenes
were shown to have the best responses at a temperature
of 30 °C while for the medium-molecular-weight terpenes
(around 150 g mol –1 ), the effect of different temperature on
the adsorption of analytes wasn’t so strong. Terpenes with the
highest molecular weight (204 g mol –1 ) exhibited the highest
response at a temperature of 50 °C. On the basis of the results
and literature data, the sorption value at 30 °C was selected.
Various sorption times were measured (1; 2; 5; 10; 15;
20; 30; 40, and 60 minutes) at temperature of 30 °C. The time
of 15 minutes seems to be suitable for both the sensitivity and
a good repeatability.
This study also investigated the effect of sample conditioning
before analyte sorption. The conditions of analysis
Fig. 2. Influence of the incubation time on response of detectors
for the monitored analytes