ELECTRONIC SUPPLEMENTARY MATERIAL
SOILS, SEC 2 • GLOBAL CHANGE, ENVIRON RISK ASSESS, SUSTAINABLE LAND USE • RESEARCH
ARTICLE
Degradation study of mesotrione and other triketone herbicides on soils and sediments
Hanna Barchanska • Aleksandra Kluza • Karolina Krajczewska • Joanna Maj
Received: 17 February 2015 / Accepted: 16 June 2015
© Springer-Verlag 2015
Responsible editor: Hailong Wang
H. Barchanska () • A. Kluza • K. Krajczewska • J. Maj
Department of Inorganic, Analytical Chemistry and Electrochemistry, Faculty of Chemistry, Silesian University
of Technology, B.Krzywoustego 6 Str, 44-100 Gliwice, Poland
e-mail: hanna.barchanska@polsl.pl
() Corresponding author:
Tel. +48 32 237 28 18
Fax. +46 32 237 12 05
e-mail: hanna.barchanska@polsl.pl
I
Analytical performance and extraction procedures
Analytical performance
Chromatography was run using a LiChroCART 125-3 Purospher STAR RP-18e, 5μm column
with appropriate precolumn. The injected sample volume was 20 µl. The mobile phase
consisted of 0.05% trifluoroacetic acid in water (A) and acetonitrile (B), in the following
gradient program: t=0 min: 100%A, flow 0.7 ml/min; t=28 min: 60%A, 40%B, flow 0.7
ml/min; t= 35 min: 30%A, 70%B, flow 1.0 ml/min.
Quantification was performed using the internal standard method. A six point calibration
curves prepared in blank matrix extracts were analyzed in triplicate. Linearity was assumed
when the regression coefficient was greater than 0.99 with RSD lower than 15%, value
established according to the concentration range used in the calibration curve. The
instrumental limits of detection (LOD) were calculated by a signal-to-noise ratio of three,
using the lowest concentration standard. Limits of quantification (LOQ) were computed as
three times of LOD. The analytical wavelengths used for quantitative analysis, and retention
times of analytes, and detailed parameters of calibration curves are presented in Table 3.
Extraction procedures
Extraction of triketones and their degradation products from soil and sediment samples was
carried out in three stages. The first one (I STAGE) included solid-liquid extraction (SLE).
Soil and sediment samples (10g) spiked with standards (5µg/g, prepared according to section
2.2.2 Samples fortification) were mixed with solvent (30 ml) and shaken for 30 min.
Methanol, acetonitrile, and the mixture of acetonitrile: methanol (1:1, v/v) were applied, to
select the solvent that provided the highest recoveries of all analytes. Next, the extracts were
II
filtered. Since all of them contained matrix compounds, which hindered the chromatographic
analysis, therefore, another step of extracts purification was necessary.
According to literature (Barchanska et al. 2012; Chaabane et al., 2005; Chaabane et al.,
2008;), liquid-liquid extraction (LEE) is recommended for soil samples to remove the humic
acids from the extract (II STAGE). Therefore the extract obtained in the first step was
extracted with dichloromethane (2x5 ml). After phase separation, the organic layer was
evaporated to dryness, and the residue was dissolved in 0.1 M HCl (5 ml), whereas, the water
phase was discarded. To concentrate the extracts and to remove the traces of matrix
compounds, the solid-phase extraction (SPE) was applied.
The third step of analytes extraction from soil and sediments was SPE (III STAGE). To
establish the SPE conditions providing the separation of analytes and matrix compounds, and
at the same time, the highest recovery rates of all analytes, the following sorbents were
applied: silica gel modified with octadecyl carbon chains (C18), copolymer styrenedivinylobenzene (SDB) and copolymer N-vinylpyrrolidone-divinylbenzene (HLB). In all
cases, the sorbents were conditioned with 3 ml of water and 3 ml of methanol (flow rate 1
ml/min). Next, the extracts obtained in STAGE II were transferred onto sorbents (the flow
rate 1 ml/min).
To select a solvent, which provided the highest analytes elution from the sorbents, methanol
(5 ml), methanol (2 ml), followed by 4% acetic acid in acetonitrile (3 ml), as well as methanol
(2 ml), followed by ethyl acetate (2 ml) and 4% acetic acid in acetonitrile (3 ml) were applied.
In all cases the flow rate was 0.5 ml/min. After elution, the solvents were evaporated to
dryness and the residue was dissolved in 0.5 ml of methanol before chromatographic analyses.
The highest recoveries of all analytes from both soil and sediment samples, as well as
sufficient clean-up of the extracts were obtained according to the following procedure:
III
I STAGE–SLE: acetonitrile;
II STAGE–LLE: dichloromethane;
III STAGE–SPE: sorbent: SDB; elution solvents: ethanol, ethyl acetate and 4% acetic acid in
acetonitrile.
The recoveries with SD of all analytes are presented in Table 3.
An exemplary chromatogram of the extract of Soil 2 spiked with standards (5µg/g) is presented in Fig. 1SM.
Fig. 1SM Chromatogram of spiked Soil 2 (λ=230 nm)
IV