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Analytica Chimica Acta (v.540, #1)
Determination of glyphosate and aminomethylphosphonic acid in natural water using the capillary electrophoresis combined with enrichment step by M. Corbera; M. Hidalgo; V. Salvadó; P.P. Wieczorek (pp. 3-7).
A previously elaborated capillary electrophoresis (CE) method used for the determination of glyphosate and aminomethylphosphonic acid (AMPA) was slightly modified in order to improve the sensitivity. However, detection limits attained (5μgmL−1 for glyphosate and 4μgmL−1 for AMPA) were still not satisfactory for analytical purposes, thus the addition of a preconcentration step before the CE analysis was proposed. AMBERLITE®IRA-900, a strong anion-exchange resin, was used to preconcentrate both analytes in environmental aqueous samples. The experimental conditions optimised in a previous work were readapted, by decreasing the eluent concentration due to CE limitations. Satisfactory results were attained when spiked ultrapure water was applied, with recoveries from 84 to 87% for glyphosate (R.S.D.<6%) and from 85 to 98% for AMPA (R.S.D.<5%). Enrichment factors up to 65 were achieved with this system, allowing the determination of 85ngmL−1 of glyphosate and 60ngmL−1 of AMPA. The extraction efficiency varied when four different natural water samples of varying conductivity were applied. Especially the strong dependence on ion concentration in samples on AMPA recovery was found. For glyphosate, good recoveries (86–99%) were obtained for samples of low and medium conductivity (0–800μS). The effect of sample salt content on extraction efficiency was studied and a linear relationship could be established for AMPA ( r2=0.996). An important improvement on recoveries was observed when lower volumes of sample were treated.A HPLC method with UV–vis detection and pre-column derivatisation with p-toluensulphonyl chloride was compared to the CE method. No significant differences in results were found when t- and F-statistical tests were applied.
Keywords: Glyphosate; Aminomethylphosphonic acid (AMPA); Capillary electrophoresis; HPLC; Anion-exchange resins; Environmental analysis
PTFE capillary trap as a tool to monitor non-ionic surfactants in the aquatic environment by Joanna Morchalo; Robert Rydlichowski; Andrzej Szymanski; Bogdan Wyrwas; Zenon Lukaszewski (pp. 9-15).
A method based on the separation of non-ionic surfactants (NS) in the PTFE capillary trap with final determination by the indirect adsorptive stripping tensammetry has been developed. The method is suitable for NS determination in river water, raw and treated sewage within the range of 2–10,000μgl−1. The sample volume varies between 0.1 and 50ml depending on NS concentration, and the time necessary for a single determination is approximately 15min. This is several orders of magnitude better than determination with the recommended BiAS method. In environmental samples, recoveries ranges from 81 to 95% and precision ranges from 3 to 10%.
Keywords: Non-ionic surfactant determination; Environmental samples; Indirect adsorptive stripping tensammetry; PTFE capillary trap
Optimisation of a pressurised liquid extraction method for haloanisoles in cork stoppers by J.L. Gómez-Ariza; T. García-Barrera; F. Lorenzo; A. Gustavo González (pp. 17-24).
Cork taint is a musty off-flavour in wines mainly caused by 2,4,6-trichloroanisole, but other haloanisoles can contribute. In this work, a method for the extraction of 2,4,6-trichloroanisole, 2,4,6-tribromoanisole and 2,6-dichloroanisole has been developed. The procedure involves the extraction of the haloanisoles from cork by pressurised liquid extraction and the analysis of the extracts by both GC–μECD and GC–MS–MS. A central composite design was used to investigate the dependence of the recoveries of the analytes on the temperature, percentage pentane–diethyl ether ratio and the extraction time. Experimental data were then processed by using the multiple regression analysis in order to calculate a mathematical model representing the relationship between factors and responses and to determine the best experimental conditions for PLE method. These conditions corresponded to a temperature of 176°C, an extraction time between 2.8 and 4min and an 80:20 pentane:diethyl ether ratio.
Keywords: Anisoles; ASE; GC–MS; Cork taint; Off-flavour; Wine; Musty
Application of a retention database to the identification of individual polychlorinated biphenyl congeners in Aroclors mixture using selected polychlorinated biphenyls as a reference series by Janina Lulek; Maurycy Opielewicz; Katarzyna Szyrwińska; Bartłomiej Milanowski (pp. 25-31).
The database of the relative retention times (RRTs) of polychlorinated biphenyls (PCBs) reported in literature was used to calculate the retention indices (RIs) of all 209 PCB congeners on temperature programmed capillary column Rtx-5. Calculation of retention indices was based on reference series of seven congeners (PCB IUPAC Nos. 18, 52, 101, 143, 185, 203 and 206) that exhibit linear relative retention time behaviour as a function of chlorine number. The calculated indices were compared to those determined in our laboratory as well as to those obtained by other authors. The proposed indices system was applied for identification individual congeners in mixture of Aroclors 1242:1254:1260, using only reference series of PCBs.
Keywords: Polychlorinated biphenyls (PCBs); Relative retention time database; Correlation analysis; Retention index system; Aroclors; Gas chromatography-low resolution mass spectrometry
Determination of operationally defined fractions of aluminium in reference materials and acid attacked environmental samples by Peter Matúš; Jana Kubová; Marek Bujdoš; Ján Medved’ (pp. 33-43).
The aim of the presented work is to evaluate the selectivity of the operationally defined procedures for the aluminium fractionation in the reference materials and the environmental samples affected by the mining activity. The combination of the sequential optimized BCR (European Commission Community Bureau of Reference) three-step, the single (H2O, CaCl2, Na2S2O4, NH4F, (NH4)2C2O4, HCl, NTA, EDTA, DTPA) and the solid phase chelating ion-exchange extraction procedures was performed for the aluminium fractionation in the samples. The amount of the reactive Al determined by the solid phase extraction on the chelating resin Iontosorb Salicyl is the most important operationally defined fraction of aluminium from the aspect of its negative effects on the environment. The available Al concentrations obtained from the different operationally defined fractionation methods were compared. The flame atomic absorption spectrometry was used for the aluminium quantification. The X-ray diffraction analyse of the samples was performed for the mineral composition determination.The precision, the repeatability and the accuracy for the all steps of the optimized BCR sequential extraction procedure were checked on six reference materials (SRM 2710, RSS SO-2, RSS SO-4, CRM SA-B, SRM RTH 912, CRM 025-050). The precision and the repeatability were very good with the R.S.D. values ≤11%. The fraction specific accuracy was excellent. The new indicative fractional Al values in the used reference materials are published.
Keywords: Fractionation; Speciation; Single; sequential and solid phase extraction; Ion-exchange; Iontosorb Salicyl; Reactive aluminium
New materials: analytical and environmental applications in ion chromatography by Corrado Sarzanini; Maria Concetta Bruzzoniti (pp. 45-53).
This review details ion chromatography developments and related applications, mainly in the field of environmental analysis, gained by the evolution in the science and technology for new stationary phases. Unconventional approaches to ion chromatographic separations are also outlined.
Keywords: Ion chromatography; New materials; Stationary phases; Environmental applications
Determination of propane chloroderivatives in environmental samples by Jerzy Gaca; Grażyna Wejnerowska (pp. 55-60).
Studies on determination of the semi-volatile halogenoorganic compounds (SVHCs) in the sewage samples have been carried out and a new method has been developed. Both the static (headspace) and dynamic (stripping with adsorption on solid phase) method of extraction into gaseous phase turned out to be the most efficient ones for determination of SVHCs in the rich environmental matrixes. In order to determine the low concentrations of SVHCs in the presence of high amounts of inorganic compounds and hardly volatile organic compounds (nitro compounds, dyes, fats and so on), the selective extraction and selection of the adequate parameters of the final analysis (GC-ECD) are required. The developed methods (headspace and stripping) of the semi-volatile compounds determination were subjected to a statistical evaluation by determining the precision of measurement (max. R.S.D.=6.02) and interval of uncertainty (max. ±6.31%). Application of the conventional extrapolative method for quantitative determination of analytes in the complex environmental matrixes gives the satisfying results.
Keywords: Water analysis; Semi-volatile halogenoorganic compounds; Static headspace gas chromatography; Stripping
Cadmium speciation in Arabidopsis thaliana as a strategy to study metal accumulation system in plants by Kasia Połeć-Pawlak; Rafał Ruzik; Krzysztof Abramski; Monika Ciurzyńska; Helena Gawrońska (pp. 61-70).
The strategy to identify cadmium deactivation mechanism in Arabidopsis thaliana has been developed using selective and sensitive hyphenated techniques. Cadmium concentrations, in main parts of the plant, were determined by ICP-MS and total amount was found as 0.43–0.44μgg−1 in leaves and 3.3–3.4μgg−1 in roots. Speciation of the metal complexes in cells was investigated by SEC–ICP-MS in order to estimate the accumulation process. Phytochelatins, desglycyl-phytochelatins and phytochelatins homologues lacking the N-terminal γ-linked glutamic acid were extracted from plant and were identified by RPLC–ESI-MS. Two-dimensional chromatography allowed to link the metal complexes separated by SEC with isoforms of phytochelatins analyzed by high resolution RPLC and confirm their significant responsibility for metal accumulation. The potential of the cadmium complexes speciation indicates that obtained results could be reliable source of knowledge to confirm the information coming from the well-known genomic sequence of Arabidopsis and to estimate the role of γ-glutamyl transpeptidase in metabolism of glutathione.
Keywords: Cadmium accumulation; Phytochelatins; Reversed phase liquid chromatography; Size exclusion chromatography; ICP-MS; Electrospray MS; Hyphenated techniques
Metabolomics of arsenic based on speciation studies by Kazuo T. Suzuki (pp. 71-76).
Biomedical research on arsenic can be divided into three steps, i.e., speciation of the entirety of arsenic in a biological system (metallome), examination of the metabolism of arsenic based on the speciation of metallome (metabolomics), and examination of the metallomics underlying the mechanism that triggers biological/physiological/toxicological effects based on the metabolomics. In the present communication, the metabolic pathway for inorganic arsenic, a known human carcinogen, was explained based on current results of speciation. In addition to the consecutive reduction and oxidative methylation reactions converting inorganic arsenicals to the major urinary metabolite dimethylarsinic acid, the role of the conjugation reaction involving glutathione resulting in excretion from the liver was discussed. Furthermore, sulfur-containing arsenicals (thioarsenicals) identified as new metabolites in the livers of rats were characterized chemically and metabolically.
Keywords: Metallomics; Metallo-metabolomics; Speciation; Metallome; Arsenic; Thioarsenical
Speciation of iron (II) and (III) by using solvent extraction and flame atomic absorption spectrometry by Mehmet Yaman; Gokçe Kaya (pp. 77-81).
A method for speciation, preconcentration and separation of Fe2+ and Fe3+ in different matrices was developed using solvent extraction and flame atomic absorption spectrometry. PAN as complexing reagent for Fe2+ and chloroform as organic solvent were used. The complex of Fe2+–PAN was extracted into chloroform phase in the pH range of 0.75–4.0 and Fe3+ remains in water phase in the pH range 0.75–1.25. The optimum conditions for maximum recovery of Fe2+ and minimum recovery of Fe3+ were determined as pH = 1, the stirring time of 20min, the PAN amount of 0.5mg and chloroform volume of 8mL. The developed method was applied to the determination of Fe2+ and Fe3+ in tea infusion, fruit juice, cola and pekmez. It is seen that there is high bioavailable iron (Fe2+) in pekmez. The developed method is sensitive, simple and need the shorter time in comparison with other similar studies.
Keywords: Iron (II) and (III); AAS; Extraction; Chloroform; PAN
The use of fast protein liquid chromatography with ICP-OES and ES–MS–MS detection for the determination of various forms of aluminium in the roots of Chinese cabbage by TjaÅ¡a Bantan-Polak; Bojan Mitrović; Radmila MilaÄ?iÄ? (pp. 83-89).
The distribution of aluminium (Al) species was investigated in the roots of Al-tolerant Chinese cabbage ( Brassica rapa L. ssp. pekinensis) by employing fast protein liquid chromatography (FPLC) with inductively coupled plasma optical emission spectrometry (ICP-OES) and electrospray tandem mass spectrometry (ES–MS–MS) detection. The cabbage was exposed to a nutrient solution that contained 10μgcm−3 of Al3+. The results demonstrated that after 24h of exposure, Al was quantitatively taken up by the cabbage and was distributed in different parts of the plant. 36±6% of total Al was located in the roots, while the remaining 64±10% was transferred to the leaves. It was found that in the roots Al was partially present in the root sap (15.5%), while the majority (84.5%) was accumulated in its apoplasmic compartments. It was further demonstrated that the proportion of Al that entered the symplasm formed a complex with organic acid. Speciation analysis by FPLC with ICP-OES detection and ES–MS–MS identification of the binding ligand indicated that Al-citrate complex was the prevailing species in the root sap.The results of the present study showed that both immobilization of Al in the apoplasmic compartments of the roots and transformation of Al3+ to Al-citrate are most likely responsible for the tolerance of Chinese cabbage ( B. rapa L. ssp. pekinensis) to the toxic effects of Al3+.
Keywords: Chinese cabbage (; Brassica rapa; L. ssp.; pekinensis; ); Aluminium speciation; Al-citrate; Fast protein liquid chromatography–inductively coupled plasma optical emission spectrometry; Electrospray tandem mass spectrometry
Pre-concentration and separation of vanadium on Amberlite IRA-904 resin functionalized with porphyrin ligands by Krystyna Pyrzyńska; Tomasz Wierzbicki (pp. 91-94).
Among several methods, enrichment techniques based on sorption onto chelating resins seem convenient, rapid and capable to achieve a high concentration factor. Amberlite IRA-904 resin modified with tetrakis ( p-carboxyphenyl) porphyrin (TCPP) was used to pre-concentrate vanadium species. Several parameters, such as sorption capacity of the chelating resin, pH for retention of V(IV) and V(V), volume of sample and eluent, were evaluated. Both vanadium species sorbed on TCPP-modified resin were eluted by use of 2M nitric acid and determined by atomic absorption spectrometry. The recovery values were >94% and pre-concentration factor of 110 was obtained. For speciation studies, CDTA was added to the sample for complexing vanadium(IV), which was not retained on the microcolumn. The proposed method was examined for reference standard material (TM-25.2) and river water sample.
Keywords: Vanadium; Pre-concentration; Speciation; Water analysis
High performance capillary electrophoresis method for determination of ibuprofen enantiomers in human serum and urine by Franciszek K. Główka; Marta Karaźniewicz (pp. 95-102).
A direct and stereospecific capillary zone electrophoresis (CZE) method for quantification ibuprofen enantiomers in biological matrices: human serum and urine, has been developed. Chiral separation of the enantiomers of ibuprofen and (+)- S-indobufen [(+)- S-INDB, internal standard, IS] was obtained in an uncoated silica capillary filled with a background electrolyte (BGE), consisted of heptakis 2,3,6-tri- O-methyl-β-cyclodextrin (TM-β-CD) in buffer of pH 5.0. The complete enantioselective analysis of ibuprofen and its 1-hydroxy metabolite confirmed appropriate specificity of the method. The electrophoretic parameters: electroosmotic ( μEOF) and electrophoretic ( μep) mobility and resolution factor ( Rs) were determined. Extraction procedures with organic solvent and solid phase extraction (SPE) with C18 stationary phase for isolation of enantiomers from biological fluids were compared. SPE method for further studies was chosen. Stereoselective extraction of IBP enantiomers from serum at basic pH has been discovered. Validation of the method was carried out. Calibration curves of ibuprofen enantiomers were linear in the range of 0.1–25.0μg/ml in serum and of 0.5–250.0μg/ml in urine. Recovery of both enantiomers from serum and urine amounted 74–86 and 90–98%, respectively. Intra- and inter-day measurement precision and accuracy were below 15%. Limits of detection for IBP enantiomers amounted 0.05 and 0.25μg/ml in samples of serum and urine, respectively. Limit of quantitation was also estimated. IBP enantiomers proved to be stable following three freeze and thaw cycles and during storage in autosampler at ambient temperature. The validated methods enable pharmacokinetic studies of enantiomers in both media. The elaborated HPCE method can be alternative to HPLC.
Keywords: Capillary electrophoresis; Chiral separation; Stereoselective extraction; Validation; Pharmacokinetic study; 1-Hydroxyibuprofen
Rapid simultaneous determination of alkylxanthines by CZE and its application in analysis of pharmaceuticals and food samples by Fiona Regan; Yuliya Shakalisava (pp. 103-110).
Capillary electrophoresis (CE) offers the possibility of fast, cheap and reproducible separations for pharmaceutical preparations. Alkylxanthines make up a family of compounds that are used in the treatment and prevention of bronchi asthma and chronic pulmonary disease. The group of analysed compounds include caffeine, dyphylline, theophylline, theobromine and enprofylline. This paper shows a simple capillary zone electrophoretic (CZE) method for separation of this group of xanthines. Using 20mM borate buffer at pH 9.4 as running buffer at 55°C it was possible to complete a total separation of a sample in 2min. Limits of detection in the range 1.9–2.5mgl−1 were achieved with %R.S.D. of 0.06–0.22% ( n=5). The technique is applied to a range of samples containing the analytes, including tablets and chocolate. Reproducibility (%R.S.D.) of the chocolate analysis technique by CZE was less than 4.5%.
Keywords: Capillary zone elctrophoresis; Fast separation; Alkylxanthines; Chocolate
Metabolic studies of methenolone acetate in horses by Emmie N.M. Ho; David K.K. Leung; Terence S.M. Wan; Nola H. Yu (pp. 111-119).
Methenolone acetate (17β-acetoxy-1-methyl-5α-androst-1-en-3-one), a synthetic anabolic steroid, is frequently abused in human sports. It is preferred for its therapeutic efficiency and lower hepatic toxicity compared with its 17α-alkylated analogs. As with other anabolic steroids, methenolone acetate may be used to enhance performance in racehorses. Metabolic studies on methenolone acetate have been reported for humans, whereas little is known about its metabolic fate in horses. This paper describes the investigation of in vitro and in vivo metabolism of methenolone acetate in racehorses.Studies on the in vitro biotransformation of methenolone acetate with horse liver microsomes were carried out. Methenolone (M1, 1-methyl-5α-androst-1-en-17β-ol-3-one) and seven other metabolites (M2–M8) were detected in vitro. They were 1-methyl-5α-androst-1-ene-3,17-dione (M2), 1-methyl-5α-androst-1-en-6-ol-3,17-dione (M3) and two stereoisomers of 1-methylen-5α-androstan-2-ol-3,17-dione (M4 and M5), 1-methyl-5α-androst-1-en-16-ol-3,17-dione (M6) and monohydroxylated 1-methyl-5α-androst-1-en-17-ol-3-one (M7 and M8). After oral administration of Primobolan® (80 tablets×5mg of methenolone acetate each) to two thoroughbred geldings, the parent steroid ester was not detected in the post-administration urine samples. However, seven metabolites, namely M1, M6–M8, two stereoisomers of M7 (M9 and M10) and 1-methyl-5α-androst-1-en-17α-ol-3-one (M11), could be detected. The metabolic pathway for methenolone acetate is postulated. This study has shown that metabolite M1 could be targeted for controlling the abuse of methenolone acetate in horses.
Keywords: Methenolone; Steroids; Metabolism; Horse
Chemometric approach in optimization of micellar liquid chromatographic separation of some halogenated phenols by F. Safa; M.R. Hadjmohammadi (pp. 121-126).
Simultaneous optimization of separation quality and analysis time of the micellar liquid chromatography of nine chlorophenol isomers was investigated. The effect on retention of three experimental parameters was studied using multivariate analysis. The factors studied were the concentration of sodium dodecyl sulfate, propanol content and pH of the mobile phase. The experiments were performed according to the face-centred cube central composite design and the inverse form of the experimental retention times for analytes were fitted to the polynomial models. The results of the analysis of variance showed that the models obtained explain greater than 99% of the variance observed in the chromatograms. Good predictive ability of the models was verified as high values of the statistics R2 and F were obtained for the linear relationship between predicted cross-validated and experimental values of the dependent variable. The study showed that the use of Pareto-optimality method, an approach from multi-criteria decision-making, allows the selection of the best possible combinations of separation and analysis time in micellar liquid chromatography of chlorophenols.
Keywords: Micellar liquid chromatography; Multi-criteria decision-making; Experimental design; Optimization; Multivariate analysis
Comparison of column properties in reversed-phase chromatography: monolithic, cholesterolic and mixed bonded stationary phases by Katarzyna Krupczyńska; Pavel Jandera; Bogusław Buszewski (pp. 127-137).
A commercial Chromolith C18 column and two new stationary phases with mixed ligands bonded on the Kromasil silica gel support, SG-MIX and SG-Chol, were characterized using simple tests based on the retention of non-polar, basic and acidic compounds. Polar and methylene selectivity tests in acetonitrile–water and methanol–water mobile phases revealed lower hydrophobicities of the SG-MIX and SG-Chol columns in comparison to the Chromolith column. The columns were further characterized using new test criteria – gradient oligomer capacity and isomeric selectivity and peak symmetry of naphthalene di-sulphonic acids in aqueous mobile phases. The cholesterolic column shows greater gradient oligomer selectivity for the separation of oligoethylene glycol samples than the SG-MIX and the Chromolith columns. Increased retention and peak tailing, but decreased isomeric selectivity for naphthalene-di-sulphonic acids was observed with the SG-MIX column, because of interactions with various polar bonded groups.
Keywords: Column characterization; Bonded phase; Selectivity; Naphthalene sulphonic acids; Oligoethylene glycols
Approaches to separation interfaces by Tetsuo Okada (pp. 139-145).
The interaction and separation of ions with zwitterionic layers are reviewed principally based on a series of the author's work. An electrostatic model has allowed us to discuss the chromatographic retention of ions on the zwitterionic stationary phase, and has revealed the ionic interaction occurring at the zwitterionic interface. Similar consideration is applicable to the ionic partition into zwitterionic micelles having the spherical dimension. In the electrostatic models, ion association and solvation changes of ions have been assumed to explain the selectivity in ion recognition. Both assumptions are applicable to polarizable large ions, whereas the former cannot account for the results obtained for small and well-hydrated ions (Cl− and Br−). A special X-ray absorption finestructure (XAFS) measurement, which allows selective access to ions interacting with surface monolayers, has been developed, and applied to ions attracted by a zwitterionic monolayer. The X-ray absorption spectra suggest that Zn2+ attracted by the zwitterionic monolayer is still hydrated. In contrast, the direct interaction of Br− has been confirmed, indicating that the electrostatic model involving either ion association or the solvation change of an ion does not properly explain the observed phenomena but both effects should be taken into consideration.
Keywords: Zwitterionic layers; Electrostatic interaction; X-ray absorption fine structure
Optical behaviour of pH detectors based on sol–gel technology by M. García-Heras; C. Gil; N. Carmona; J. Faber; K. Kromka; M.A. Villegas (pp. 147-152).
Acidity is an outstanding parameter that affect the correct preservation of most part of materials engaged in artworks and heritage objects. In spite of the new generation of advanced analytical devices, the conservation/heritage management sector claims for some kind of simple, robust and low-cost device to monitor environmental acidity wherever necessary. The purpose of this paper is to offer a suitable alternative for the estimation of environmental acidity by means of detectors to be used without electrodes, solutions, pH meters, wires or batteries.Doped sol–gel thin coatings have been used as transductors for producing pH detectors. The coatings consist of a partially densified polysiloxane network and an organic dye sensitive to pH changes. The siloxane network behaves as a host for immobilisation of the dye molecules, in such a way that chemical–optical properties of the dye are preserved as far as possible. The transductors were applied on common glass substrates by dipping. Further heat-treatment allows the coating partial densification.The optical response of the detectors was analysed by VIS absorption spectroscopy, since a change of colour took place when the detectors were submitted to different pH buffered solutions. With the aim to investigate their optical behaviour as a function of pH, several experimental measurements were undertaken: absorption intensity; maximum spectral wavelength; colour coordinates; colour purity percentages. Time response and memory effect were also studied. The detector operation conditions for monitoring environmental acidity both indoor and outdoor are discussed.
Keywords: Acidity detection; Sol–gel sensors; Optical absorption; Doped coatings; Environmental measurements
Spectrophotometric determination of dopamine in microliter scale using microfluidic system based on polymeric technology by Mariusz Mamiński; Małgorzata Olejniczak; Michał Chudy; Artur Dybko; Zbigniew Brzózka (pp. 153-157).
In this paper we report two simple and sensitive spectrophotometric procedures for the determination of dopamine in microfluidic system based on poly(dimethylsiloxane) (PDMS) technology and comparison of their interference-susceptibility. The analytical reactions and measurements were carried out at ambient temperature in a microreactor of total volume 6μl coupled with a spectrophotometric flow-through cuvette.
Keywords: Dopamine; Catecholoamines; Microsystem; PDMS; Optical detection
Fluoride-selective sensors based on polyurethane membranes doped with Zr(IV)-porphyrins by Å?ukasz Górski; Elżbieta Malinowska (pp. 159-165).
The feasibility of using Tecoflex polyurethane as a polymeric matrix for fluoride-selective membranes doped with Zr(IV)-octaethyl-(OEP) or Zr(IV)-tetraphenylporphyrins (TPP) is examined. Membranes containing cationic or anionic additives were prepared, with ionophore working according to neutral or charged carrier mechanism, respectively. Results are compared to those found previously using conventional poly(vinyl chloride) (PVC) as the membrane matrix. It was found that this polymer does not affect significantly the properties of these porphyrins, compared to poly(vinyl chloride) matrix. A dimer–monomer equilibrium determined recently to occur for Zr(IV)-porphyrins in PVC/ o-NPOE membranes containing lipophilic anionic additives is also observed to occur (via UV–vis spectrophotometry) in the PU matrix. However, the equilibrium constants for dimer–monomer reactions appear to be lower in PU membranes compared to PVC films, as determined from the degree of super-Nernstian responses towards fluoride as well as the anion concentration ranges required to break the dimer as determined spectroscopically. Due to reduced dimerization of Zr(IV)[OEP]Cl2 it was possible to obtain electrodes with PU/ o-NPOE/KTFPB membranes exhibiting only slightly super-Nernstian (−64.6mV/dec) response towards fluoride and response time ( t95<120s) faster than observed for PVC-based membranes. Good working parameters were also obtained for this metalloporphyrin in PU membrane that forces neutral carrier mechanism (PU/DOS/TDMACl): F− calibration slope −58.3mV/dec and response time t95<12s. Tested membranes were subsequently applied for construction of miniaturized silicon-based sensors. Better fluoride selectivity was observed for sensors with Zr(IV)[OEP]Cl2/PU/ o-NPOE/KTFPB membranes (logKF−,J−pot: ClO4− 0.7; Br− −1.9; NO3− −1.9; Cl− −3.1), compared to Zr(IV)[OEP]Cl2/PU/DOS/TDMACl matrix (logKF−,J−pot: ClO4− −0.8; Br− −1.3; NO3− −1.5; Cl− −2.1). However, latter composition was chosen to be better for flow measurement mode, as dimer formation can be totally prevented within this membrane. Sensors with Zr(IV)[OEP]Cl2/PU/DOS/TDMACl maintained their characteristics at least for 2 months.
Keywords: Fluoride-selective sensors; Polyurethane membranes; Zr(IV)-porphyrins
Planar potentiometric sensors based on Au and Ag microelectrodes and conducting polymers for flow-cell analysis by Renata Toczyłowska; Rafał Pokrop; Artur Dybko; Wojciech Wróblewski (pp. 167-172).
Back-side contact Au and Ag microelectrodes were used as transducers to construct planar all-solid-state electrodes suitable for flow-through analysis. The microsensors were based on plasticized PVC potassium-selective membranes containing ion-electron conducting polymer—polypyrrole doped with di(2-ethylhexyl) sulfosuccinate. The proposed technique allowed simple construction of microsensors in one step, by membrane solution casting directly on the surface of the planar metallic transducers. The performance of the microsensors based on Au and Ag transducers were determined and compared with planar sensors based on internal electrolyte immobilized in polyHEMA. The addition of the polypyrrole to the membrane composition did not influence on the selectivity, reproducibility and long-term stability of the microsensors but improved their standard potential stability in time in comparison with coated-wire type sensors. Moreover, all-solid-state microsensors based on Au transducers exhibited better signal stability than Ag based sensors.
Keywords: Ion-selective electrode; Miniaturised planar sensor; Solid-state sensors; Conducting polymers; Flow analysis
Kinetic method for determination of nanogram amounts of copper(II) by its catalytic effect on hexacynoferrate(III)–citric acid indicator reaction by Surendra Prasad (pp. 173-180).
This paper describes a highly sensitive, selective catalytic-kinetic-spectrophotometric method for the determination of copper(II) concentration as low as 6ngml−1. The method is based on the catalytic effect of copper(II) on the oxidation of citric acid by alkaline hexacyanoferrate(III). The reaction was followed by measuring the decrease in absorbance of hexacyanoferrate(III) at 420nm ( λmax of [Fe(CN)6]3−, ∈=1020dm3mol−1cm−1). The dependence of rate of the indicator reaction on the reaction variables has been studied and discussed to propose a suitable mechanism to get a relation between the reaction rate and [Cu2+]. A fixed time procedure has been used to obtain a linear calibration curve between the initial rate and lower [Cu2+] or log[Cu2+] in the range 1×10−7 to 4×10−4moll−1 (6.35–25,400ngml−1). The detection limit has been calculated to be 4ngml−1. The maximum average error is 3.5%. The effect of the presence of various cations, commonly associated with copper(II) and some anions has also been investigated and discussed. The proposed method is sensitive, accurate, rapid and inexpensive compared to other techniques available for determination of copper(II) in such a large range of concentration. The new method has been successfully applied for the determination of copper(II) in various samples.
Keywords: Kinetic determination of copper; Catalytic determination of copper; Copper determination; Catalytic reaction; Catalysed oxidation of citric acid; Hexacyanoferrate(III); Citric acid
Determination of creatinine in clinical samples based on flow-through microsystem by Ilona Grabowska; Michal Chudy; Artur Dybko; Zbigniew Brzozka (pp. 181-185).
The paper describes a flow-through microsystem with optical detection for measurement of creatinine concentration in urine and post-dialysate fluid. The microsystem is made of a transparent polymer-poly(dimethylosiloxane) (PDMS). In order to determine creatinine, classical Jaffe reaction was carried out. The influence of reaction parameters (temperature and solutions flow rate) on its sensitivity and repeatability of recorded signal was investigated. Results of creatinine determination in postdialysate fluids and urine were compared to results obtained in hospital laboratories.
Keywords: Creatinine determination; Flow-through microsystem; PDMS; Jaffe reaction; Optical detection
Polarization, steric, and focusing micro-thermal field-flow fractionation principles, theory, instrumentation, and applications in polymers and particles analysis by Josef JanÄ?a (pp. 187-196).
The benefits of the miniaturization of the separation channel for Thermal field-flow fractionation (TFFF) are analyzed theoretically and studied experimentally. It is found that the operational variables influencing the efficiency and resolution of the separation can be optimized and that the concept of a micro-TFFF is meaningful. A miniaturized TFFF channel was proposed and constructed. It has been demonstrated experimentally that micro-TFFF allows one to carry out high-performance separations under carefully chosen experimental conditions. This new technique is highly competitive in comparison with size-exclusion chromatography (SEC) of macromolecules with molar masses up to roughly one million gram per mole. However, the versatility of micro-TFFF is superior to SEC for macromolecules of ultra-high molar masses, as well as colloidal sub-micron, and micron-sized particles of synthetic, natural, or biological origin. The free choice of the carrier liquids without any modification of the separation system affords an advantage to micro-TFFF. The experimental implementation and application to polymer and particle analysis confirmed the potential of micro-TFFF.
Keywords: Miniaturization of thermal field-flow fractionation; Theoretical aspects: experimental implementation; Applications to polymers and particles characterization
Determination of precious metals in geological samples by continuous powder introduction microwave induced plasma atomic emission spectrometry after preconcentration on activated carbon by K. Jankowski; A. Jackowska; P. Å?ukasiak (pp. 197-205).
A novel method was developed for analysing geological materials for Au, Ag, Pd and Pt by continuous powder introduction microwave induced plasma atomic emission spectrometry (CPI–MIP–AES). The preconcentration of the trace metals on activated carbon (AC) was performed before conducting MIP–AES measurements in order to obtain accurate and precise analytical results. The method proposed is based on the selective sorption of precious metals that are subsequently introduced to the plasma as a dry particulate aerosol consisted of analytes collected on the sorbent. The technical design and operating conditions of the novel sample introduction system based on the fluidized-bed concept has been optimized. The microwave excitation source with integrated rectangular cavity TE101 and vertically positioned plasma torch has been used. The signal stability proved to be adequate for sequential mode of measurements due to the vertical plasma configuration as well as the MIP–AES system compatibility with the CPI technique. Calibration was done using home-made standards obtained by sorption of metals of interest from standard solutions on activated carbon. Precision is typically 1–4% relative standard deviation at the 1μgg−1 level. Under measurement conditions the detection limits for Ag, Au, Pd and Pt were 24, 43, 57 and 550ng per 1g of AC, respectively. The proposed procedure was used for Au, Ag, Pd and Pt determination in the platinum ore SARM-7 as well as Au and Ag in the Chinese soil GBW-07405 certified reference materials. The standard addition technique was used and recoveries revealed that the proposed method shows good accuracy and precision.
Keywords: Microwave induced plasma atomic emission spectrometry; Continuous powder introduction; Activated carbon, preconcentration; Precious metals; Geological materials
Characterization of iron(II)(α-diimine) chelates and their interactions with anionic, cationic and non-ionic micelles using the separation, spectrophotometric and computational methods by Sławomir Oszwałdowski; Dorota Marchut (pp. 207-219).
The Fe(II)(α-diimine) chelates as well as diimine ligands were characterized by means of liquid chromatography and capillary electrophoretic methods with the help of molecular computational methods. The diimine ligands: 2,2′-bipyridine as well as 1,10-phenathroline and its derivatives (5-chloro, 5-methyl, 5-nitro, 4,7-dimethyl, 3,4,7,8-tetramethyl, and 4,7-diphenyl) were used. The chelate parameters such as: log Pow, hydrodynamic radius, molar volume and charge were estimated. The obtained results were used for the characterization of binding of Fe(NN) (NN = α-diimine) chelates to micelles. In the second part of the work by means of spectrophotometery, it was established that the MLCT (metal-to-ligand charge transfer) bands of all Fe(NN) chelates were no solvent sensitive. The decrease in λmax (blue shift) of MLCT band of Fe(NN) chelates was observed in solutions of charged micelles. It was concluded that the hydrophobicity of Fe(II)(NN) was found to be responsible for the chelate localization into micellar structure, whereas the surface electrostatic potential of the charged micelle was affected the MLCT band of Fe(II)(NN) chelates. To rationalize the observed effect the molecular modeling method was applied. It was established the stability of λmax of MLCT band of Fe(NN) in solvents is mainly due to the D3 symmetry of the chelate. In the micellar phase, the distortion of the chelate geometry, thus the distortion of D3 symmetry from D3 to C2 leads to the observed blue shift in λmax of MLCT band. It was proposed that the blue shift in the MLCT band could be used for estimating the values of the surface potential of micelle and for establishing the relative hydrophobic character of the micellar interface.
Keywords: Iron(II)(α-diimine) chelates; LC chromatography; Capillary electrophoresis; Chelate–micelle interaction; Molecular computation
Characterization and analysis of amino acids in orange juice by HPLC–MS/MS for authenticity assessment by J.L. Gómez-Ariza; M.J. Villegas-Portero; V. Bernal-Daza (pp. 221-230).
Twenty protein α-amino acids have been used to detect adulterations in orange juices from Spanish oranges. An analytical method based on the use of normal-phase liquid chromatography coupled to mass spectrometry has been performed for detection and quantification of these compounds in this complex matrix. MS and MS/MS parameters were optimized and most abundant product ion of each amino acid were selected to be monitorized. Method performance is improved with the use of an Allure Acidix column in which mobile phase composition and flux were optimized. Good separation was achieved using water/acetonitrile (20:80) and water/methanol (10:90) at pH 3, with elution gradient. The method has been used to assess the presence of amino acids in different kinds of orange juice: packing orange juice from both frozen concentrates and recently squeezed oranges, and fresh sweet orange juice hand-squeezed in the laboratory just before the analysis. The differences in composition between the juices and the potential adulteration practices have been evaluated and discussed.
Keywords: Amino acids; Mass spectrometry; Authentification; Orange juice