A sensitive hydrophilic interaction liquid chromatography/electrospray ionization mass spectrometry (HILIC/ESI-MS/MS) method was developed for determination of selected aliphatic (i.e. malonic, ...succinic, glutaric, adipic, pimelic, suberic, azelaic, maleic, fumaric, glycolic and pyruvic acid), alicyclic (i.e. cis-pinonic and pinic acid) and aromatic (i.e. trimesic, phthalic acid and its isomers) carboxylic acids. Analytes were separated on an amide column using a gradient elution with a 10
mM constant ionic strength mobile phase containing acetonitrile and aqueous ammonium acetate buffer (pH 5.0). The influence of the buffer type, pH, polar modifier and temperature on analyte retention under HILIC was studied. Static sonication-assisted solvent extraction was optimized for sample preparation prior to analysis. The recoveries obtained were higher than 90% for most analytes. The method was proven to be sensitive with limits of detection ranged from 0.03 to 16.0
μg/L in selected reaction monitoring mode (SRM). The repeatability and intermediate precision of the method, expressed as RSD (%) of the peak area ratio between analytes and their internal standards were generally lower than 5%. The method was successfully applied for determination of the studied acids in samples of ambient aerosol particles. A big advantage of the new method is also its ability to detect and separate the isobaric compounds of the selected carboxylic acids. Our results demonstrate that the method is specific and sensitive for the determination of a wider range of polar carboxylic acids at low concentrations in complex samples of aerosol particles.
Chromium, cadmium and lead were determined in different fractions of the winemaking process such as in grape, pressed pomace, must deposit, deposit of lees, must and wine. Grape, pressed pomace, must ...deposit and deposit of lees were digested by a high-pressure microwave-assisted digestion system with a mixture of nitric acid and hydrogen peroxide, while for must and wine no special treatment was required. The temperature programs of the graphite furnace were optimised and different matrix modifiers were applied: Mg(NO3)2, NaVO3 for Cr and NH4H2PO4, Pd(NO3)2 for Pb and Cd determinations. Mg(NO3)2 and NaVO3 thermally stabilized Cr and enabled the increase of pyrolysis temperatures up to 1500 degrees C. NH4H2PO4 and Pd(NO3)2 are suitable modifiers for Pb and allowed pyrolysis temperatures up to 800 degrees C in grape, pressed pomace and wine samples, 1100 degrees C in must samples and 1200 degrees C in deposit of lees. The non-specific background absorption of NH4H2PO4 was 1.5-2 orders of magnitude higher than that of the Pd(NO3)2.
The applicability of nitric acid, palladium nitrate and a mixture of palladium and magnesium nitrate as matrix modifiers was estimated for the accurate and reproducible determination of cadmium (Cd), ...lead (Pb) and arsenic (As) in sediments of the Sava River by electrothermal atomic absorption spectrometry, ETAAS. Decomposition of the samples was done in a closed vessel microwave-assisted digestion system using nitric, hydrochloric and hydrofluoric acids, followed by the addition of boric acid to convert the fluorides into soluble complexes. The parameters for the determination of Cd, Pb and As in sediments were optimized for each individual element and for each matrix modifier. In addition, two sediment reference materials were also analyzed. In determination of Cd and Pb, nitric acid was found to be the most appropriate matrix modifier. The accurate and reliable determination of Cd and Pb in sediments was possible also in the presence of boric acid. The use of a mixture of palladium and magnesium nitrate efficiently compensated for matrix effects and enabled the accurate and reliable determination of As in the sediments. Quantification of Cd and As was performed by calibration using acid matched standard solutions, while the standard addition method was applied for the quantification of Pb. The repeatability of the analytical procedure for the determination of Cd, Pb and As in sediments was ?5 % for Cd, ?4 % for Pb and ?2 % for As. The LOD values of the analytical procedure were found to be 0.05 mg/kg for Cd and 0.25 mg/kg for Pb and As, while the LOQ values were 0.16 mg/kg for Cd and 0.83 mg/kg for Pb and As. Finally, Cd, Pb and As were successfully determined in sediments of the Sava River in Slovenia.
Primenljivost azotne kiseline, paladijum-nitrata i smese paladijum- i magnezijum-nitrata kao modifikatora matrice ocenjena je u slucaju pouzdanog i reproduktivnog odredjivanja kadmijuma, olova i arsena iz naslaga reke Save elektrotermickom atomskom apsorpcionom spektrometrijom, ETAAS. Uzorci su razgradjeni u zatvorenom mikrotalasnom digestoru pomocu azotne, hlorovodonicne i fluorovodonicne kiseline, uz naknadno dodavanje borne kiseline, cime su fluoridi prevedeni u rastvorne komplekse. Parametri odredjivanja Cd, Pb i As u naslagama optimizovani su za svaki element i svaki modifikator matrice ponaosob. Takodje su analizirana dva referentna materijala naslaga. Azotna kiselina se pokazala kao najpogodniji modifikator matrice za odredjivanje Cd i Pb. Tacno i pouzdano odredjivanje Cd i Pb iz naslaga bilo je moguce i u prisustvu borne kiseline. Uticaj matrice je uspesno kompenzovan upotrebom smese paladijum- i magnezijum-nitrata, sto je omogucilo tacno i pouzdano odredjivanje As iz naslaga. Kvantitativno odredjivanje Cd i As uradjeno je pomocu kalibracije standardim rastvorima za kiselu sredinu, dok je za kvantitativno odredjivanje Pb primenjena standardna metoda adicije. Reproduktivnost analiticke procedure za odredjivanje Cd, Pb i As iz naslaga iznosila je ?5, ?4 i ?2 %, redom. LOD vrednosti analiticke procedure iznosile su 0,05 mg/kg za Cd i 0,25 mg/kg za Pb i As, dok su LOQ vrednosti iznosile 0,16 mg/kg za Cd i 0,83 mg/kg za Pb i As. Na kraju, Cd, Pb i As su uspesno odredjeni iz naslaga reke Save duz toka kroz Sloveniju.
Volatile organic compounds (VOCs) play an important role in different photochemical processes in the troposphere. In order to predict their impact on ozone formation processes a detailed knowledge ...about their abundance in the atmosphere as well as their reaction rate constants is required. The QSPR models were developed for the prediction of reaction rate constants of volatile unsaturated hydrocarbons. The chemical structure was encoded by constitutional and topological indices. Multiple linear regression models using CODESSA software was developed with the RMS(CV) error of 0.119 log units. The chemical structure was encoded by six topological indices. Additionally, a regression model using a variable connectivity index was developed. It provided worse cross-validation results with an RMS(CV) error of 0.16 log units, but enabled a structural interpretation of the obtained model. We differentiated between three classes of carbon atoms: sp2-hybridized, non-allylic sp3-hybridized and allylic sp3-hybridized. The structural interpretation of the developed model shows that most probably the most important mechanisms are the addition to multiple bonds and the hydrogen atom abstraction at allylic sites.
A well-balanced incubation saline is necessary for permeability experiments with the rat jejunal tissue in the diffusion chambers. At the same time the investigated substance must be chemically ...stable and sufficiently soluble in this incubation saline. To investigate whether the absence of some ions in incubation salines influences the tissue viability and integrity or the diffusional characteristics of the epithelial membrane the electrical parameters were monitored and the permeability of fluorescein and acyclovir was evaluated during the experiments in side-by-side diffusion chambers. Our results show that the tissue integrity and viability are seriously impaired when Ca
2+ and Mg
2+-free conditions are applied on both sides of the diffusion chambers, but not when only mucosal or only serosal side is Ca
2+ and Mg
2+-free. Bicarbonate-free incubation salines can also alter the measured apparent permeability coefficients even though the tissue viability and integrity do not change. This change in the apparent permeability is most likely due to a change in the pH of the mucosal surface and can be prevented if the buffer capacity of the incubation saline is increased.
Medicinal plants accumulate heavy metals from contaminated soil, and their consumption can cause poisoning. Our objective was to determine the levels of Pb, Cd, Zn, Cu, Fe, and Mn in four medicinal ...plant species (Achillea millefolium, Hypericum perforatum, Plantago lanceolata, and Urtica dioica) and their native soil, all sampled at a former smelter. The highest soil Cd, Pb, and Zn levels surpassed the maximum allowed limit 75-fold, 48-fold, and 14-fold, respectively. Their soil levels correlated with those in the plants, but this was not the case with Cu, Fe, and Mn. Heavy metal accumulation seems to depend on the plant species, yet even so, medicinal herbs should be cultivated and gathered only from controlled (uncontaminated) areas. Polluted areas should be monitored on a regular basis, while further research should investigate the connection between the heavy metal levels in the soil, their levels available for plants, and the levels extractable from plants.
•Functioning of the in situ prepared antimony film electrode (SbFE).•Cyclic and anodic stripping voltammetry study of SbFE.•Stripping performance of SbFE in HNO3 and five other acids.•Cleaning and ...initializing the electrode surface for memory free functioning of SbFE.•Drinking and surface water analysis on Pb, Cd and Zn.
New insights into the functioning, i.e. electrochemical behaviour and analytical performance, of in situ prepared antimony film electrodes (SbFEs) under square-wave anodic stripping (SW-ASV) and cyclic (CV) voltammetry conditions are presented by studying several key operational parameters using Pb(II), Cd(II) and Zn(II) as model analyte ions. Five different carbon- and metal-based substrate transducer electrodes revealed a clear advantage of the former ones while the concentration of the precursor Sb(III) ion exhibited a distinct influence on the ASV functioning of the SbFE. Among six acids examined as potential supporting electrolytes the HNO3 was demonstrated to yield nearly identical results in conducting ASV experiments with SbFE as so far almost exclusively used HCl. This is extremely important as HNO3 is commonly employed acidifying agent in trace metal analysis, especially in elemental mass spectrometry measurements. By carrying out a systematic CV and ASV investigation using a medium exchange protocol, we confirmed the formation of poorly soluble oxidized Sb species at the substrate electrode surface at the end of each stripping step, i.e. at the potentials beyond the anodic dissolution of the antimony film. Hence, the significance of the cleaning and initializing the surface of a substrate electrode after accomplishing a stripping step was thoroughly studied in order to find conditions for a complete removal of the adhered Sb-oxides and thus to assure a memory-free functioning of the in situ prepared SbFE. Finally, the practical analytical application of the proposed ASV method was successfully tested and evaluated by measuring the three metal analytes in ground (tap) and surface (river) water samples acidified with HNO3. Our results approved the appropriateness of the SbFE and the proposed method for measuring low μgL−1 levels of some toxic metals, particularly taking into account the possibility of on-field testing and the use of low cost instrumentation.
Certain types of samples contain chloride in concentrations that are too high to accurately determine other anions by ion chromatography without any pretreatment. One of the most widely used ...approaches for such samples is matrix elimination using disposable cartridges containing a cation-exchange resin in the Ag
+ form. The efficiency and characteristics of the commercially available cartridge for Cl
− removal were tested by the on-line connection of the cartridge effluent to an inductively coupled plasma mass spectrometer. Displacement efficiency of Ag
+ ions and loading capacity of the cartridges were studied at different flow-rates. Significant amounts of silver were detected in the effluent, which were attributed to colloidal AgCl as well as dissolved Ag
+ ions. Because silver ions can cause irreversible damage to the analytical column, an Ag cartridge followed by an on line filter (pore size 0.22 μm) and cartridge in the H
3O
+ form were proposed for improvement of this sample pretreatment technique for chloride removal.
The purpose of this work was the development of a method for the determination of Se compounds in leaves of plants. Water-soluble Se compounds were extracted from samples by water. Enzymatic ...hydrolysis with the non-specific enzyme protease XIV was used for the release of Se compounds bound to proteins. Separation of Se species was made by ion exchange chromatography, using an anion exchange column for Se
IV, Se
VI and selenomethionine (SeMet), and a cation exchange column for selenomethylselenocysteine (SeMeSeCys) and selenocystine (SeCys
2). Columns were connected “on line” to a hydride generation atomic fluorescence spectrometer (HG-AFS) using a UV lamp between the separation and detection system. The repeatability of the results obtained by the developed method was under 15% (R.S.D.) for all Se species; the detection limit was 2–10
ng Se/g of supernatant. The accuracy was checked by comparison with some literature data for reference materials since there were no suitable certified reference materials available. The method was used for the determination of Se compounds in chicory (
Cichorium intybus L.) leaves from plants which were cultivated aeroponically with elevated concentrations of Na
2SeO
4 for different periods. Se accumulated efficiently in chicory leaves; up to 480
μg/g after 41 days of exposure, mostly (64%) as Se
VI, i.e. in the form of Se added. Beside inorganic Se, in the extracts from enzyme hydrolysis we also found SeMet (4.2–8.4%) and SeMeSeCys (<DL−0.7%). Some unidentified peaks were also observed in the chromatograms of plant extracts.
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