Leaching of chromium from chromium contaminated soil: Speciation study and geochemical modeling

Distribution of chromium between soil and leachate was monitored. A natural process of percolating rainwater through the soil was simulated in the laboratory conditions and studied with column leaching extraction. Migration of chromium in the soil is conditioned by the level of chromium soil contamination, the soil organic matter content, and rainwater acidity. Chromium (III) and chromium(VI) were determined by spectrophotometric method with diphenilcarbazide in acidic media. Comparing the results of chromium speciation in leachate obtained by experimental model systems and geochemical modelling calculations using Visual MINTEQ model, a correlation was observed regarding the influence of the tested parameters. Leachate solutions showed that the concentration of Cr depended on the organic matter content. The influence of pH and soil organic matter content is in compliance after its definition through experimental and theoretical way. The computer model - Stockholm Humic Model used to evaluate the leaching results corresponded rather well with the measured values

Evaluation of method for phthalate extraction from milk related to milk dilution ratio

Liquid-liquid extraction techniques were compared coupled with gas chromatography-mass spectrometry (GC-MS), for the extraction and the determination of four phthalates: dimethyl phthalate (DMP), di-n-butyl phthalate (DBP), benzyl butyl phthalate (BBP) and di-(2-ethylhexyl) phthalate (DEHP) in six different kinds of milk-based samples. Extraction factors: sample preparation, organic solvent type and volume, salt effect, agitation and the extraction time were optimized. The ion of base peaks (m/z 149 for DBP, BBP and DEHP and m/z 163 for DMP) for investigated phthalates were selected for the screening studies. The acquisition was performed at the selected ion monitoring mode. The MSD response for GC-MS phthalate calibration standards was linear between 0.25 and 2.50 μg mL-1 with calculated LODs between 0.01 μg mL-1 to 0.04 μg mL-1 and LOQs of 0.05 μg mL-1 to 0.12 μg mL-1, while repeatability was between 1.7 % to 4.9 % RSD. The study demonstrated an increase of the recovery of less polar phthalates in matrix milk standards by matrix dilution. Recovery for hydrophilic phthalates, like DMP, was not changed by matrix dilution and it was continuously low for the investigated method. Two spiking levels were tested for influence of matrix dilution on phthalate recovery, showed the same trend. [Projekat Ministarstva nauke Republike Srbije, br. 31060

Electrospray ionization mass spectrometry combined with the ultra high performance liquid chromatography in the analysis of in vitro formation of chlorophyll complexes with copper and zinc

The aim of this work was to give more accurate insight in the interaction of major photosynthesis pigment, chlorophyll (Chl), with copper (II) and zinc (II) in solution by flow injection analysis with electrospray ionization mass spectrometry (FIA-ESI-MS) method, as well as combined with ultra high performance liquid chromatography with DAD detection (UHPLC-DAD). These interactions may potentially, but not necessarily lead to formation of Cu-Chl and Zn-Chl complexes of two different types, which has a lot of - at least - disfunctional implications in plant world. The results based on analysis of full-scan and MS/MS spectra - with or without the UHPLC chromatograms - confirm formation of “central type” Cu-Chl complex, and “central type” Zn-Chl complex as well, along with a proof for formation of “peripheral” Zn-Chl complex, the latter one originating from a very week coordinative interaction at the edge of Chl structure. The used techniques appeared to be an efficient and reliable tool for studying formation and stability of heavy metals complexes with chlorophyll, at least in vitro, with a considerable possibility for assessment of real bio-environmental behavior. [Projekat Ministarstva nauke Republike Srbije, br. TR-34012 i br. OI-172044

Determination of di(2-ethylhexyl) phthalate in plastic medical devices

The presence of DEHP in dialysis and infusion sets for peritoneal dialysis and parenteral nutrition, which are made of PVC and other plastic polymeric materials, were investigated. Phthalate determination was carried out by gas chromatography - mass spectrometry method (GC-MS). The results showed that the peritoneal dialysis set (bag and tubing) made of PVC contains DEHP in significant amount, about 31 - 34%. Solution for peritoneal dialysis which was stored in the investigated PVC bag, contains low amount of DEHP, about 3.72 μg dm-3. Infusion bottles which are made of LDPE, also contain DEHP but in lower amount than PVC bags. LDPE bottle for packaging physiological saline solution (0.9% NaCl) showed higher amount of DEHP than LDPE bottle for packaging Ringer’s solution. In contrast, solution stored in bottle with lower DEHP level, i.e. Ringer’s solution contained about three times higher concentration of DEHP than physiological saline solution stored in bottle with higher DEHP level. Concentrations of DEHP in Ringer’s solution and physiological saline solution are 17.30 and 5.83 μg dm-3, respectively. The obtained values are under estimated upper-bound dose of DEHP received by adult patients undergoing procedures of peritoneal dialysis and parenteral nutrition. [Projekat Ministarstva nauke Republike Srbije, III 41018