2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
P63 PuRIFICATION PROCESS INFLuENCE ON
ThE PAh DETERMINATION IN REAL SOIL
SAMPLES
MICHAELA STOUPALOVá, MILADA VáVROVá,
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 analytical procedure usually consists of several partial
steps: the isolation of analytes, extract purification, and
the concentration of monitored analytes 1 . environmental
analysis currently tends to use such analytical procedures to
allow the reliable and fast determination of monitored substances
at the lowest possible costs. In the field of sample preparation,
attention is devoted particularly to the combination
of methods which enable the selective extraction of analytes
followed by their concentration. The accuracy and precision
of measurement in particular are monitored in the instrumental
end-point as they are closely linked to the selectivity and
sensitivity of analytical instruments. A special emphasis is
laid on the confirmation techniques which should prove the
results obtained using a typical method and reduce the risk of
false-positive and false-negative results 2,3 .
Polycyclic aromatic hydrocarbons (PAHs) are formed
in the incomplete combustion of organic matter, for example
during combustion of fossil fuel or wood, in running engines
of motor vehicles, during fire and during free incineration of
biomass or municipal waste 4 . They are also produced naturally,
for example in active volcanoes.
Individual PAHs differ significantly by their properties
which define their potential risks. They are characterized by
great variability in terms of toxic, physicochemical and chemical
properties that may affect the environment. They produce
different effects on individual species and the link
between toxicity of individual PAHs and their structure
is currently being investigated 5 .
Experimental
The effect of the purification procedure on the content of
analytes was investigated in samples of soil. The isolation of
PAHs from soil was performed using microwave extraction.
Samples were purified using column chromatography. HPLC
was used as final analytical method.
e x t r a c t i o n
The isolation of PAHs from soil was performed using
microwave extraction. The extraction step lasted 25 minutes,
at a temperature of 120 °C and an input of 1,200 W, by using
20 ml of a hexane/acetone (1 : 1) mixture. Microwave extraction
provided two sets of samples; each set was subsequently
subjected to a different purification method.
s459
P u r i f i c a t i o n
We monitored influence of the purification process on
the determination of monitored analytes. We carried out comparison
of two purification process.
Purification 1: Samples were cleaned-up using column
chromatography on a silica column (5 g). The sample was
applied on the top of the column; 10 ml of hexane were
applied on the top of the column prior to the complete adsorption
of the sample on the column, followed by elution with
5 ml of an eluting mixture consisting of hexane : dichloromethane
(1 : 1) and finally with 10 ml of the same mixture. The
last fraction was collected.
Purification 2: The samples in the second set were purified
using column chromatography on a column with silica
gel (4 g) and florisil (4 g). The sample was applied directly
on the prepared column. The column was washed with 60 ml
of a hexane : dichloromethane (1 : 1) mixture prior to the complete
adsorption of the sample into the sorbent. The whole
eluate was collected.
H P L C
The determination itself was performed using the HPLC
Agilent 1100 Series with a DAD and FLD detectors. The
HPLC determination was carried out under following conditions:
gradient elution (A = 60 % water/40 % acetonitrile;
B = 100 % acetonitrile); 0 min A, 30 min B, 40 min. B, 42
min A For separation SUPELCOSIL LC-PAH column was
used (25 cm × 2.1 mm × 5 µm). The flow-rate of the mobile
phase was constant, 0.4 ml min –1 , temperature 30 °C. FLD
settings were: 0–17.4 min λ ex = 260 nm, λ em = 350 nm;
17.4–42 min λ ex = 260 nm, λ em = 420 nm. DAD setting was:
λ = 225 nm.
Results
The main aim of this work was to investigate the effect
of the purification process on the content of monitored PAHs
in the real samples of soil. For better clarity, the results are
provided in graphs and expressed in percentage; for assessment,
the values determined in the first set of samples (purification
on silica) were chosen as 100 % for assessment purposes.
The results are presented in Figs. 1.–3. for individual
samples of soil.
It follows from Fig. 1. that both purification techniques
provided comparable results. Fig. 2. shows the results for
Fig. 1. Influence of a purification procedure – soil A