2. ENVIRONMENTAL ChEMISTRy & TEChNOLOGy 2.1. Lectures

Chem. Listy, 102, s265–s1311 (2008) Environmental Chemistry & Technology
Table III
Comparison of efficiency of extraction by Pn-ICP-OES to
XRF analysis
Element Efficiency [%]
Cr 63
ni 82
Cu 80
Zn 102
Pb 96
metals by Pn-ICP-OES. The results as a sum of the five
extraction steps were compared with those obtained after
total decomposition and by XRF spectrometry. Efficiency
of soil extracts to pressed pellets together with correlation
coefficients are presented in Table III. The best efficienty of
extraction can be observed for lead and zinc. Efficiency of
extraction depends on the binding to minerals with different
solubility. Low efficiency of chromium can be explained by
binding to poorly soluble chromspinels and chromite 12,13 .
The soil samples were analysed to evaluate the possibility
of quantitative elemental analysis by laser ablation. The
results for LA-ICP-MS were compared with the results of
XRF as a method representing another type of direct analysis
and with the results of solution analysis by ICP-OES as an
ordinary method. In the case of Cr, slightly lower concentration
values were yielded for the total decomposition using
Pn-ICP-OES than for both direct analysis methods, which
can be caused by the incomplete decomposition of Cr in acids
(Fig. 2.).
Fig. 2. Comparison of LA-ICP-MS and PN-ICP-OES after total
decomposition results for Cr as a barely leachable element
The calibration was performed using spiked sample pellets.
The soil with a low content of elements of interest was
spiked with seven concentration levels to obtain a calibrated
range from 24 to 965 mg kg –1 . The calibration curves were
fitted by a computer program WinStat. All calibration plots
were linear over the whole concentration range. Intercepts of
the regression lines were tested by t-test and were statistically
insignificant (t a < t 0.05;n-2 ) for all studied elements. Correla-
s315
Table IV
Comparison of CRM GBW07407 soil analysis results by
LA-ICP-MS and certified values; the uncertainty intervals
are calculated on a 95 % confidence level
Method [mg kg–1 ] LA-ICP-MS Certified value
Cr 432 ± 28 410 ± 23
ni 269 ± 27 276 ± 15
Cu 84 ± 8 97 ± 6
Zn 139 ± 15 142 ± 11
Pb 15 ± 3 14 ± 3
tion coefficient r values were in the range of 0.997–0.999.
Calibration line for copper with scandium as internal standard
is presented in Fig. 3.
Repeatability of ablation was described as RSD % which
was calculated from three measurements of ablation signal on
the different locations of each pellet. The RSD values did not
exceed 8%.
The accuracy of the method was confirmed by analysis
of three CRM soils. Results of CRM GBW 7407 by LA-ICP-
MS and certified values are given in Table IV.
Fig. 3. Calibration graph for Cu with internal standardization
by Sc
Conclusions
Monitoring of the heavy metals in agricultural soils is gaining
the importance because these elements can be accumulated
by plants and thus enter the food chain. To obtain total
elemental content of Cr, ni, Cu, Zn, Pb the decomposition
with HF and HClO 4 by ICP-OES was used. The sequential
extraction procedure providing more information than total
concentration determination was used to study bioavailability
of metals. Methods of total decomposition are very lengthy
and sometimes even not fully efficient therefore direct
methods are more convenient in such a case. XRF analysis
of soil pellets prepared with a wax binder and LA-ICP-MS
of perfectly homogenized pellets using sol-gel method represented
the direct methods.
The results of direct methods were compared with those
obtained by Pn-ICP-OES. A satisfactory agreement was