An optimised extraction and cleanup method for the analysis of pesticide in natural water samples is presented. Sixteen pesticides of different polarity and from the different chemical classes (organophosphates, triazines, benzimidazoles, carbamates, carbamides, neonicotinoides, methylureas, phenylureas and benzohydrazides), most frequently used in Serbia, were selected for the analysis. Liquid-phase microextraction in a single hollow fibre (HF-LPME) has been applied for sample preparation. The concentrations of pesticides were determined using HPLC-MS/MS method with electrospray ionisation. The extraction behaviour and selection of the experimental conditions was predicted based on log D and pK(a) values of targeted pesticides, which were calculated applying the computer software ACD/Labs PhysChem Suite v12. The influence of the donor pH and concentration of pesticides, organic phase composition as well as the extraction time on the extraction efficiency was investigated. Optimum extraction conditions were evaluated with respect to the investigated parameters of the extraction. The extraction method was validated for 10 out of 16 studied pesticides. Linear range of the pesticides was 0.1-5 microg L(-1) with the correlation coefficient from 0.991 to 0.9998, and the relative standard deviation for three standard measurements was between 0.2 and 11.8%. The limits of detections ranged from 0.026 to 0.237 microg L(-1) and the limits of quantifications from 0.094 to 0.793 microg L(-1). The optimised two-phase HF-LPME method was successfully applied for determination of moderately polar as well low-polar pesticides in the environmental water samples.
The removal of Pb(II),
Cd(II), Cu(II), and Zn(II) from aqueous
solutions using (un)modified Serbian interstratified montmorillonite/kaolinite
clay as an adsorbent was investigated. The clay was modified by mechanochemical
activation for different time periods. X-ray diffraction patterns
and particle size distributions were used to characterize the samples.
Batch adsorption studies were conducted to optimize various conditions.
The adsorption equilibrium was established within 60 min, and the
maximum adsorption occurred in the pH range of 4.5–6.5. The
milled clays exhibited greater equilibrium adsorption capacities (q
e) for all of the metals than the raw clay.
A difference in q
e values for clays milled
for 2 and 19 h could be observed only for initial concentrations (C
i) of ≥100 mg dm–3.
This was related to the amorphization (i.e., exfoliation) of 19-h-milled
clay particles. The adsorption equilibrium data of heavy metals on
both raw and modified clays fit the Langmuir equation, although there
were changes in the microstructure of the clay. The mechanochemical
treatment of the clay reduced the amount of adsorbent necessary to
achieve a highly efficient removal of heavy metals by a factor of
5. Thus, the mechanochemically treated interstratified clay can be
considered as an efficient adsorbent for the simultaneous removal
of divalent heavy metals.
Transport behaviour of Lu(III) across a polypropylene hollow fibre-supported liquid membrane containing di(2-ethylhexyl)phosphoric acid (DEHPA) in dihexyl ether as a carrier has been studied. The donor phase was LuCl(3) in the buffer solution consisting of 0.2 M sodium acetate at pH 2.5-5.0. A miniaturised system with a single hollow fibre has been operated in a batch mode. The concentration of Lu(III) was determined by indirect voltammetric method using Zn-EDTA complex. The effect of pH and volume of the donor phase, DEHPA concentration in the organic (liquid membrane) phase, the time of extraction and the content of the acceptor phase on the Lu(III) extraction and stripping behaviour was investigated. The results were discussed in terms of the pertraction and removal efficiency, the memory effect and the mean flux of Lu(III). The optimal conditions for the removal of (177)Lu(III) from labelled (177)Lu-radiopharmaceuticals were discussed and identified. The removal efficiency of Lu(III) greater than 99% was achieved at pH of the donor phase between 3.5 and 5.0 using DEHPA concentration in the organic phase of 0.47 M and the ratio of the donor to the acceptor phase of 182.
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