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Analytical and Bioanalytical Chemistry (v.367, #2)
Calixarenes in analytical and separation chemistry by R. Ludwig (pp. 103-128).
Discovered in the 1940’s, [1n]metacyclophanes with the common name calix[n]arenes which is derived from for the molecule’s shape enjoyed a remarkable interest in almost all fields of chemistry since the 1980’s, which is highlighted by several books [1–8]. Over 50 reviews concerning their synthesis, properties and applicabilities were published, many of those with emphasis on organic synthesis and structural properties are cited in ¶[P. 5–6 in 2]. Of interest for analytical chemists are reviews on calixarenes and the structurally related resorcin[n]arenes (or calix[n]resorcarenes) and calixpyrroles concerning potentiometric sensors [9–12], chromo- and fluorophores [13, 14], molecular switches [15], metal ion binding in solution [16–19], redox properties [20] and anion binding [21–24]. Other recent reviews deal with thermodynamic aspects [25], organometallic compounds [26], P-containing calixarenes [27–29], as well as molecular dynamics modeling [30–33]. It is a vital field with over 200 publications per year. Therefore, this article presents only selected results on complexation, solvent extraction and membrane transport with the emphasis on ion and molecular recognition which can be used for analytical purposes, without attempting to cover all available references.
Pre-column (hν-HPLC) photochemical reaction for the on-line characterization of photoproducts using p-aminobenzoic acid as a model substance by S. N. Parlar; J. P. Surmann (pp. 129-131).
A special photochemical reactor on the basis of high-pressure resistant reaction coils has been constructed, which can be coupled to an HPLC-system before the separation column. By means of the so-called “on-line pre-column (hν-HPLC)”-method, the starting compounds can be irradiated on-line, the conversion products formed can be separated and detected subsequently. The efficiency of the proposed method was proved by using p-aminobenzoic acid (PABA) as a model substance.
Influence of process parameters on the composition of gaseous standard mixtures of n-propanethiol obtained by thermal decomposition of surface compounds by P. Konieczka (pp. 132-140).
A method for preparation of gaseous standard mixtures of n-propanethiol based on thermal decomposition of surface immobilized compounds bonded to silica gel is described. On the basis of the experimentally established relationships between n-propanethiol concentration and generation time, the influence of the mixture composition on diluting gas flow rate, decomposition temperature, and surface compound bed mass was determined.
Separation of trace amounts of palladium (II) with crown ether from hydrochloric acid and potassium thiocyanate media by K. Zakir Hossain; T. Honjo (pp. 141-145).
A new method for the separation of trace amounts of palladium from hydrochloric acid and potassium thiocyanate media has been established based on the formation of an ion-pair complex of palladium thiocyanate anion Pd(SCN)4 2– and the cationic potassium complex of dicyclohexyl-18-crown-6 (DC18C6) in chloroform. The effect of various factors (solvent, crown ether, potassium thiocyanate, hydrochloric acid, reagent concentration, shaking time, phase volume ratio, composition of the extracted species, foreign ions, etc.) on the extraction and back-extraction of palladium has been investigated. The method can be combined with subsequent FAAS determination of palladium. The procedure was applied to determine palladium traces in chloroplatinic acid and rhodium chloride.
Determination of trace metals in high purity gold by I. Karadjova; S. Arpadjan; L. Jordanova (pp. 146-150).
The possibility of using ETAAS or ICP-AES for the determination of trace amounts of Ag, Bi, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Pd, Pt and Sb in pure gold is investigated. The influence of the matrix element on the atomization of the trace analytes is studied and optimal instrumental parameters are defined. An analytical method based on matrix element reductive separation followed by spectrometric determination of trace analytes is proposed as an alternative for the analysis of high purity gold. Advantages and disadvantages of proposed analytical procedures from the viewpoint of achieved repeatability, reproducibility and detection limits and of the duration of analysis are discussed.
Determination of uranium in tap water by ICP-MS by M. El Himri; A. Pastor; M. de la Guardia (pp. 151-156).
A fast and accurate procedure has been developed for the determination of uranium at μg L–1 level in tap and mineral water. The method is based on the direct introduction of samples, without any chemical pre-treatment, into an inductively coupled plasma mass spectrometer (ICP-MS). Uranium was determined at the mass number 238 using Rh as internal standard. The method provides a limit of detection of 2 ng L–1 and a good repeatability with relative standard deviation values (RSD) about 3% for five independent analyses of samples containing 73 μg L–1 of uranium. Recovery percentage values found for the determination of uranium in spiked natural samples varied between 91% and 106%. Results obtained are comparable with those found by radiochemical methods for natural samples and of the same order for the certified content of a reference material, thus indicating the accuracy of the ICP-MS procedure without the need of using isotope dilution. A series of mineral and tap waters from different parts of Spain and Morocco were analysed.
Analysis of poly-β-hydroxybutyrate in environmental samples by GC-MS/MS by D. Elhottová; J. Tříska; S. O. Petersen; H. Šantrůčková (pp. 157-164).
Application of gas chromatography-mass spectrometry (GC-MS) can significantly improve trace analyses of compounds in complex matrices from natural environments compared to gas chromatography only. A GC-MS/MS technique for determination of poly-β-hydroxybutyrate (PHB), a bacterial storage compound, has been developed and used for analysis of two soils stored for up to 319 d, fresh samples of sewage sludge, as well as a pure culture of Bacillus megaterium. Specific derivatization ¶of β-hydroxybutyrate (3-OH C4 : 0) PHB monomer units by N-tert-butyl-dimethylsilyl-N-methyltrifluoracetamide (MTBSTFA) improved chromatographic and mass spectrometric properties of the analyte. The diagnostic fragmentation scheme of the derivates tert-butyldimethylsilyl ester and ether of β-hydroxybutyric acid (MTBSTFA-HB) essential for the PHB identification was shown. The ion trap MS was used, therefore the scan gave the best sensitivity and with MS/MS the noise decreased, so the S/N was better and also with second fragmentation the amount of ions increased compared to SIM. The detection limit for MTBSTFA-HB by GC-MS/MS was about 10–13 g μL–1 of injected volume, while by GC (FID) and GC-MS (scan) it was around 10–10 g μL–1 of injected volume. Sensitivity of GC-MS/MS measurements of PHB in arable soil and activated sludge samples was down to 10 pg of PHB g–1 dry matter. Comparison of MTBSTFA-HB detection in natural soil sample by GC (FID), GC-MS (scan) and by GC-MS/MS demonstrated potentials and limitations of the individual measurement techniques.
Combined protocol for the analysis of polycyclic aromatic hydrocarbons (PAHs) and polychlorobiphenyls (PCBs) from sediments using focussed microwave assisted (FMW) extraction at atmospheric pressure by H. Budzinski; M. Letellier; S. Thompson; K. LeMenach; P. Garrigues (pp. 165-171).
A microwave-assisted protocol has been developed using focussed microwaves at atmospheric pressure for the extraction of PAHs and PCBs from sediments. It combines extraction and purification assisted by microwaves. This protocol has been applied to the quantification of 12 individual PAHs, 8 individual PCBs and 8 PCB coeluted mixtures from two Standard Reference Materials and one natural sediment. The results for both classes of compounds (PAHs and PCBs) are good in terms of recoveries, which are always greater than 70% and in most cases around 100%. The reproducibility is also good with coefficients of variation below 10% in most cases. This protocol has the great advantage of saving time, the time dedicated to the preparation / extraction assisted by microwaves being reduced to less than half an hour.
Spectroelectrochemical investigation of direct electron transfer between resting horseradish peroxidase and its oxidation states promoted by DNA by X. Chen; C. Ruan; J. Kong; J. Deng (pp. 172-177).
Direct electron transfer between resting horseradish peroxidase (HRP) and its oxidation states was observed at a gold mesh electrode in a spectroelectrochemical cell in the presence of DNA. The conversion between HRP and the oxidized species induced electrochemically was found to be reversible and parallel to that initiated chemically. DNA played an important role as electron carrier and promoted the electron transfer between HRP and the electrodes. Voltammetric results and CD spectra indicated an interaction between HRP and DNA. Moreover, the secondary structure of HRP was slightly disturbed upon mixing with DNA. The direct spectroelectrochemistry of HRP at a gold mesh electrode presented new information on its bioelectrochemical characteristics.
Amperometric biosensor based on D-aminoacid oxidase for the R-perindopril assay by J. F. van Staden; R. -I. Stefan; H. Y. Aboul-Enein (pp. 178-180).
A new amperometric biosensor based on D-aminoacid oxidase is described for the assay of R-perindopril. R-perindopril can be determined in the 400–¶20 nmol/L concentration range; the detection limit is ¶10 nmol/L. The selectivity was checked with S-perindopril, D- and L-proline, and polyvinylpyrrolidone. The main interfering species was D-proline. An automated system for the assay of R-perindopril based on the concept of flow injection with an amperometric biosensor (based on D-aminoacid oxidase) as detector is also described. The system is suitable for the on-line monitoring of R-perindopril at a sampling rate of 72 samples/h, in the linear range: 100 nmol/L –20 nmol/L with an RSD better than 0.09% (n = 10).
Determination of ‘arsenosugars’ in algae with anion-exchange chromatography and an inductively coupled plasma mass spectrometer as element-specific detector by G. Raber; K.A. Francesconi; K.J. Irgolic; W. Goessler (pp. 181-188).
The retention behavior of four naturally occurring dimethylarsinoylribosides with –CH2-CHOH-CH2X (X = OH, HO3POCH2CHOHCH2OH, SO3H, OSO3H) as aglycones, of arsenous acid, arsenic acid, methylarsonic acid, and dimethylarsinic acid was investigated on a Hamilton PRP-X100 anion-exchange column with aqueous solutions of ammonium dihydrogen phosphate (20 mmol/L) in the pH range of 3.8–9.0 as mobile phase. A HP 4500 inductively coupled plasma mass spectrometer (ICP-MS) served as arsenic-specific detector. The influence of pH, temperature, and the concentration of methanol in the mobile phase on the retention times of these arsenic compounds was explored. An aqueous 20 mM ammonium dihydrogen phosphate solution at pH 5.6 at a column temperature of 40 °C was considered optimal as it allowed ¶the separation of seven of the arsenic compounds within 16 min. Only arsenous acid and the ribose with the glycerol aglycone have overlapping signals with both migrating almost with the solvent front. At a concentration of 0.50 ng As mL–1 the relative standard deviations (n = 3) of the signal areas of the eight arsenic compounds was in the range from 3.5 to 8.1%. The linear calibration curves (peak areas) from 0.5 to 10 ng/mL had correlation coefficients ¶> 0.997. Extracts obtained from the brown algae Fucus spiralis and Halidrys siliquosa were chromatographed under the optimized conditions. Both species contained the sulfate riboside as the major arsenic compound (∼55% of total extractable arsenic) together with the sulfonate- and phosphate riboside. Arsenic acid was a significant constituent of Halidrys siliquosa (∼6.5%), but was not detected in Fucus spiralis.
Phase-selective a.c. adsorptive stripping voltammetry of lumazine on a hanging mercury drop electrode by M.S. Ibrahim (pp. 189-194).
The electrochemical behavior of lumazine (LMZ), an important antibacterial agent, has been studied at the hanging mercury drop electrode (HMDE). The nature of the process taking place at the HMDE was clarified. Its adsorption behavior at HMDE has been studied by using a.c and cyclic voltammetry (CV). Both the molecule and its reduced product appeared to be adsorbed at the surface of the electrode. Controlled adsorptive accumulation of LMZ on the HMDE provides the basis for the direct stripping measurement of that compound in the subnanomolar concentration level. Experimental and instrumental parameters for the quantitative determination were optimized. Phase-selective a.c voltammetry provided the best signal and gave a detection limit of 0.15 μg L–1 (9.0 × 10–10 mol/L) LMZ in aqueous solution. Molecules or ions which may interfere were studied.
Automation of the GC/MS analysis of mineral oil contaminations in water by O. Lerch; P. Zinn; H. -J. Götze (pp. 195-200).
An automation of the sample preparation and analysis of mineral oil contaminations in water was developed. The automated sample preparation was carried out according to ISO/DIS 9377–4 [1]. The standard is applicable to the determination of hydrocarbons in the boiling range of n-decane (n-C10) up to n-tetracontane (n-C40) by GC. Extraction of the sample and clean-up of the extract were performed by an autosampler with a movable head which is capable of carrying different syringes for gas and liquid handling. A GC/MS-system with a programmed temperature vaporizing (PTV) injector including the possibility of large volume injections (LVI) was employed for the analysis. The recovery of analytes was 101.8%, the repeatability 2.9% relative standard deviation (RSD). The linear range covered 0.3 to 40 mg/L oil but may be larger since no higher concentrations were measured. With an FID, being the detector of choice mentioned in the standard, it should be possible to achieve at least four orders of magnitude in the linear range. The limit of determination was found to be 0.3–0.4 mg/L, the limit of detection 0.1–0.2 mg/L [2]. Measurements of spiked deionized, bidistilled water and spiked water from a lake confirmed the accuracy of the analysis. Due to automation and miniaturization of the analysis it is possible to economize time and chemicals without loss of precision and accuracy.
A factorial design for optimizing a flow injection analysis system by J. R. Luna; J. F. Ovalles; A. León; M. Buchheister (pp. 201-203).
The use of a factorial design for the response exploration of a flow injection (FI) system is described and illustrated by FI spectrophotometric determination of paraquat. Variable response (absorbance) is explored as a function of the factors flow rate and length of the reaction coil. The present study was found to be useful to detect and estimate any interaction among the factors that may affect the optimal conditions for the maximal response in the optimization of the FI system, which is not possible with a univariate design. In addition, this study showed that factorial experiments enable economy of experimentation and yield results of high precision due to the use of the whole data for calculating the effects.
Studies on the potentiometric thallium(III)-selective carbon paste electrode and its possible applications by K. Vytřas; E. Khaled; J. Ježková; H. N. A. Hassan; B. N. Barsoum (pp. 203-207).
Construction, performance characteristics and applications of a carbon paste thallium(III) ion-selective electrode are described. The electrode, which is based on ion-associate compounds formed between cetylpyridinium and chlorothallate(III) complexes dissolved in tricresyl phosphate as pasting liquid, showed near-Nernstian response over the concentration range of 5.8 × 10–6– 2.9 × 10–3 mol/L. Potentiometric titrations of thallium(III) with cetylpyridinium chloride were affected by higher concentrations of excess halides, probably due to the formation of higher halogenothallates.
Electrothermal atomic absorption spectrometric determination of trace elements in high-purity silver after total and partial reductive separation of the matrix by S. Arpadjan; I. Karadjova; L. Jordanova (pp. 207-209).
A sensitive and reliable ETAAS determination of metal traces in high purity silver after total (Bi, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb) and partial (As, Hg, Sb, Se) separation of the matrix with ascorbic acid is described. The temperature program is optimized for analyte determination in ascorbic acid media and in 1% silver solution.
Improvement of direct determination of trace nickel in environmental samples by diffuse reflection spectroscopy using chromaticity characteristics by N. I. Ershova; V. M. Ivanov (pp. 210-211).
Cellulose and chromaton-N-super as solid supports for direct determination of the immobilized nickel complexes with dimethylglyoxime and benzyldioxime by diffuse reflection spectroscopy were compared. The advantage of chromaton-N-super with use of benzyldioxime is shown. Detection limit is 0.02 μg/mL. The proposed method was applied for the analysis of soil.
Capillary electrophoretic determination of dithiocarbamates and ethyl xanthate by A. K. Malik; W. Faubel (pp. 211-214).
A simple and sensitive capillary electrophoretic method was developed for the separation and determination of sodium methyldithiocarbamate (metham), manganese ethylenebisdithiocarbamate (maneb) and ethyl xanthate in boric acid buffer by direct UV absorbance detection at λ = 254 nm. The separation is dependent on pH and nature of the buffer. The detection limits (S/N = 3) are 1.7 × 10–6 mol/L for ethyl xanthate, 1.3 × 10–6 mol/L for metham and 2.1 × 10–6 mol/L for maneb. The method has been successfully applied to the analysis of wheat samples spiked with maneb and in a commercial sample.