Multi-element analysis based on an automated on-line microcolumn separation/preconcentration system using a novel sol-gel thiocyanatopropyl-functionalized silica sorbent prior to ICP-AES for environmental water samples

A sol-gel thiocyanatopropyl-functionalized silica sorbent was synthesized and employed for an automated on-line microcolumn preconcentration platform as a front-end to inductively coupled plasma atomic emission spectroscopy (ICP-AES) for the simultaneous determination of Cd(II), Pb(II), Cu(II), Cr(III), Co(II), Ni(II), Zn(II), Mn(II), Hg(II), and V(II). The developed system is based on an easy-to-repack microcolumn construction integrated into a flow injection manifold coupled directly to ICP-AES’s nebulizer. After on-line extraction/preconcentration of the target analyte onto the surface of the sorbent, successive elution with 1.0 mol L−1 HNO3 was performed. All main chemical and hydrodynamic factors affecting the effectiveness of the system were thoroughly investigated and optimized. Under optimized experimental conditions, for 60 s preconcentration time, the enhancement factor achieved for the target analytes was between 31 to 53. The limits of detection varied in the range of 0.05 to 0.24 μg L−1, while the limits of quantification ranged from 0.17 to 0.79 μg L−1. The precision of the method was expressed in terms of relative standard deviation (RSD%) and was less than 7.9%. Furthermore, good method accuracy was observed by analyzing three certified reference materials. The proposed method was also successfully employed for the analysis of environmental water samples

Polyurethane composite adsorbent using solid phase extraction method for preconcentration of metal ion from aqueous solution

Polyurethane composite adsorbent polymeric material was prepared and investigated for selected solid-phase extraction for metal ions, prior to its determination by inductively coupled plasma optical emission spectrometry. The surface characterisation was done using Fourier transform infrared spectroscopy. The separation and preconcentration conditions of the analytes investigated includes influence of pH, sample loading flow rate, elution flow rate, type and concentration of eluents. The optimum pH for the highest efficient recoveries for all metal ions, which ranged from 70 to 85 %, is pH 7. The metal ions were quantitatively eluted with 5 mL of 2 mol/L HNO3. Common coexisting ions did not interfere with the separation. The percentage recovery of the metal ions ranged between 70 and 89 %, while the results for the limit of detection and limit of quantification ranged from 0.249 to 0.256 and 0.831 to 0.855, respectively. The experimental tests showed good preconcentration results of trace levels of metal ions using synthesised polyurethane polymer adsorbent composite

Diapause as escape strategy to exposure to toxicants: response of Brachionus calyciforus to arsenic

Invertebrate organisms commonly respond to environmental fluctuation by entering diapause. Production of diapause in monogonont rotifers involves a previous switch from asexual to partial sexual reproduction. Although zooplankton have been used in ecotoxicological assays, often their true vulnerability to toxicants is underestimated by not incorporating the sexual phase. We experimentally analyzed traits involved in sexual reproduction and diapause in the cyclically parthenogenetic freshwater rotifer, Brachionus calyciflorus, exposed to arsenic, a metalloid naturally found in high concentrations in desert zones, focusing on the effectiveness of diapause as an escape response in the face of an adverse condition. Addition of sublethal concentrations of arsenic modified the pattern of diapause observed in the rotifer: investment in diapause with arsenic addition peaked earlier and higher than in non-toxicant conditions, which suggests that sexual investment could be enhanced in highly stressed environmental conditions by increased responsiveness to stimulation. Nevertheless, eggs produced in large amount with arsenic, were mostly low quality, and healthy-looking eggs had lower hatching success, therefore it is unclear whether this pattern is optimum in an environment with arsenic, or if rather arsenic presence in water bodies disturbs the optimal allocation of offspring entering diapause. We observed high accumulation of arsenic in organisms exposed to constant concentration after several generations, which suggests that arsenic may be accumulated transgenerationally. The sexual phase in rotifers may be more sensitive to environmental conditions than the asexual one, therefore diapause attributes should be considered in ecotoxicological assessment because of its ecological and evolutionary implications on lakes biodiversity

On-line solid phase extraction system using PTFE packed column for the flame atomic absorption spectrometric determination of copper in water samples

Abstract A new flow injection on-line adsorption preconcentration system adapted to flame atomic absorption spectrometry (FAAS) for copper determination at the mg l − 1 level was developed. Polytetrafluoroethylene (PTFE) turnings packed in a mini-column were used as sorbent material. The copper ammonium pyrrolidine dithiocarbamate (APDC) complex was sorbed on the PTFE turnings, from which it could be eluted on-line instantly by isobutyl methyl ketone (IBMK) into the flame at a flow rate of 2.3 ml min − 1 . The system was optimized and offered good performance characteristics with practically unlimited life time, greater flow rates and improved flexibility, as compared with other sorbent materials and the knotted reactor preconcentration systems. With 1 min preconcentration time, and a sample frequency of 40 h − 1 , the enhancement factor was 340, which could be further improved by increasing the preconcentration time. The detection limit was c L = 0.05 mg l − 1 , and the precision was 1.5%, at the 2.0 mg l − 1 Cu level. The method has been applied successfully to the analysis of potable, river and seawater, and its accuracy was tested by the analysis of certified reference materials and by recovery measurements on spiked samples. No significant interferences exist from other substances usually occurring in natural water

Selective stopped-flow injection spectrophotometric determination of palladium(II) in hydrogenation and automobile exhaust gas converter catalysts

Abstract A stopped-flow injection spectrophotometric method is reported for the determination of palladium(II), using 2,2 -dipyridyl-2-pyridylhydrazone (DPPH) as a colour forming reagent. The absorbance of the Pd(II)-DPPH complex was monitored at 540 nm, at pH≈0.3. The various chemical and physical parameters were optimized and a study of interfering ions was also carried out. The calibration graph has two linear parts, first in the range 0-25 mg l −1 (s r =0.44%, r=0.9999) with a detection limit of c L =0.084 mg l −1 and the second in the range 25-60 mg l −1 (s r =1.6%, r=0.9996). In both cases the sampling rate was 30 injections per hour. The method is very selective because the strongly acidic medium used prevented the formation of complexes of the reagent with other ions. The method was successfully applied to the determination of palladium in hydrogenation and automobile exhaust gas converters catalysts. The relative standard deviation of the mean values and the recovery ranged between 0.6 and 1.6% and 97.0-102.6%, respectively

Determination of Metals in Walnut Oils by Means of an Optimized and Validated ICP-AES Method in Conventional and Organic Farming Type Samples

Agricultural products are indispensable for equilibrated diets since they discharge minerals and several bioactive constituents. Considering the increasing demand for organic products, research has been conducted over recent years to investigate whether organically grown food products are chemically different compared to those produced with conventional farming. In this work, a novel inductively coupled plasma atomic emission spectrometric method was developed and validated for the determination of nutrient and toxic elements in walnut oils produced with conventional and organic farming. The method presented good linearity (r2 > 0.9990) for each element at the selected emission line. The limits of detection and limits of quantification ranged between 0.09 μg g−1 to 2.43 μg g−1 and 0.28 μg g−1 to 8.1 μg g−1, respectively. Method accuracy and was assessed by analyzing the certified reference materials BCR 278-R and spiked walnut oil samples. The determined metals were quantified, and the results were analyzed by Student’s t-test to investigate the differences in the elemental profile of the walnut oils according to type of farming (conventional or organic)