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Analytical and Bioanalytical Chemistry (v.380, #1)
Solution to Spectroscopy Challenge 6 by Silvia Paasch; Reiner Salzer (pp. 5-6).
The winner of the sixth spectroscopy challenge (published in issue 379/1) is: Xiancui Li, Hong Kong University of Science and Technology, ChinaThe award entitles the winner to select a Springer book from our catalogue up to a value of €75,-. Our Congratulations!
A polypyrrole-based solid-contact Pb2+-selective PVC-membrane electrode with a nanomolar detection limit by Jolanda Sutter; Ernö Lindner; Robert E. Gyurcsányi; Ernö Pretsch (pp. 7-14).
Ion-selective electrodes (ISE) based on conventional plasticized PVC membranes with solid inner contact (SC) have so far had unsatisfactory lower detection limits. Here it is shown that electropolymerization of pyrrole in the presence of potassium hexacyanoferrate(II)/(III) on Pt results in adequate inner contact for SC-ISE. The nanomolar lower detection limit achieved with the Pb2+-selective PVC membranes investigated is comparable with values obtained with optimized internal solutions of liquid-contact ISE.
Keywords: Ion-selective electrode; Solid contact; Polypyrrole; Lower detection limit
A rapid biosensor for viable B. anthracis spores by Antje J. Baeumner; Barbara Leonard; John McElwee; Richard A. Montagna (pp. 15-23).
A simple membrane-strip-based biosensor assay has been combined with a nucleic acid sequence-based amplification (NASBA) reaction for rapid (4 h) detection of a small number (ten) of viable B. anthracis spores. The biosensor is based on identification of a unique mRNA sequence from one of the anthrax toxin genes, the protective antigen (pag), encoded on the toxin plasmid, pXO1, and thus provides high specificity toward B. anthracis. Previously, the anthrax toxins activator (atxA) mRNA had been used in our laboratory for the development of a biosensor for the detection of a single B. anthracis spore within 12 h. Changing the target sequence to the pag mRNA provided the ability to shorten the overall assay time significantly. The vaccine strain of B. anthracis (Sterne strain) was used in all experiments. A 500-μL sample containing as few as ten spores was mixed with 500 μL growth medium and incubated for 30 min for spore germination and mRNA production. Thus, only spores that are viable were detected. Subsequently, RNA was extracted from lysed cells, selectively amplified using NASBA, and rapidly identified by the biosensor. While the biosensor assay requires only 15 min assay time, the overall process takes 4 h for detection of ten viable B. anthracis spores, and is shortened significantly if more spores are present. The biosensor is based on an oligonucleotide sandwich-hybridization assay format. It uses a membrane flow-through system with an immobilized DNA probe that hybridizes with the target sequence. Signal amplification is provided when the target sequence hybridizes to a second DNA probe that has been coupled to liposomes encapsulating the dye sulforhodamine B. The amount of liposomes captured in the detection zone can be read visually or quantified with a hand-held reflectometer. The biosensor can detect as little as 1 fmol target mRNA (1 nmol L−1). Specificity analysis revealed no cross-reactivity with 11 organisms tested, among them closely related species such as B. cereus, B. megaterium, B. subtilis, B. thuringiensis, Lactococcus lactis, Lactobacillus plantarum, and Chlostridium butyricum. Also, no false positive signals were obtained from nonviable spores. We suggest that this inexpensive biosensor is a viable option for rapid, on-site analysis providing highly specific data on the presence of viable B. anthracis spores.
Keywords: BiosensorB. anthracisRNA; Detection; Spore; Viable; Biosecurity; Protective antigen
Detection strategies for bioassays based on luminescent lanthanide complexes and signal amplification by Tanja Steinkamp; Uwe Karst (pp. 24-30).
Two attractive detection strategies for bioassays are reviewed in this article. Both approaches use the highly sensitive time-resolved luminescence detection of lanthanide complexes in combination with a signal amplification scheme. While enzyme-amplified lanthanide luminescence (EALL) has been an established technique for more than a decade, nanoparticles doped with luminescent lanthanide complexes have been introduced very recently. In this paper, the basic properties and major applications of both techniques are presented, and their future perspectives are discussed critically.
Keywords: Lanthanides; Luminescence; Bioassays; Amplification
Determination of 5-fluorouracil in hospital effluents by Susanne N. Mahnik; Blanka Rizovski; Maria Fuerhacker; Robert M. Mader (pp. 31-35).
Cytostatic anticancer drugs are an increasingly important issue in the environmental debate, mainly due to the lack of knowledge about the fate of these toxic substances. Over the last decades, 5-fluorouracil (5-FU) has been one of the most frequently used antineoplastic agents and may, therefore, be regarded as one of the pilot substances for environmental contamination. As a prerequisite for these investigations, a method for the determination of 5-FU in hospital effluents has been developed. Waste water samples were enriched by solid-phase extraction on ENV+ columns (concentration factor 500) and analysed by capillary electrophoresis using a buffer containing 80% 160 mM sodium borate buffer (pH 9.5) and 20% acetonitrile (v/v). This method is applicable within the range 5–500 μg 5-FU L−1. The standard curve (correlation coefficient >0.99) was linear with recovery rates from 80 to 96% and an accuracy from 9.0 to 20% (intra-assay standard deviation 0.7–8.9%; inter-assay standard deviation 2.2–9.5%). Based on the consumption of 5-FU in oncologic departments and the detection limit of 1.7 μg L−1, this method covers the range necessary to evaluate 5-FU in hospital effluents. The applicability of the method was proven by chemical analysis of real hospital waste water samples. Obtained over a time period of 1 month (range 20–122 μg 5-FU L−1), the results were similar to those calculated by an input–output model. The presented method provides an analytical tool necessary to face the monitoring of environmental contamination problems.
Keywords: 5-Fluorouracil; Capillary electrophoresis; Hospital effluents
Electronic tongue for pharmaceutical analytics: quantification of tastes and masking effects by Andrey Legin; Alisa Rudnitskaya; David Clapham; Boris Seleznev; Kevin Lord; Yuri Vlasov (pp. 36-45).
The organoleptic aspects of pharmaceutical formulations affect their acceptability to the patient and hence can have an important effect on concordance with treatment. Objective evaluation of these aspects, particularly the taste of the formulation and the drug substance it contains, is difficult. Whilst volunteer taste panels can be used to good effect their utility is limited, particularly during very early stage development when the toxicological profile of the active pharmaceutical ingredient (API) is yet to be established in detail. A potentiometric “electronic tongue” has been applied to analyse a variety of 41 individual substances and mixtures of particular interest for pharmaceutical research and development. The electronic tongue (ET) was capable of discriminating between substances with different taste modalities and could also distinguish different substances eliciting the same basic taste; the ET is promising in terms of quantifying the content of each substance and has an ability to detect nuances of the basic taste (e.g. lingering or short-lived). After calibration the electronic tongue was successfully applied to predicting bitterness strength of binary mixtures with a sweetener in terms of “apparent” or “perceived” quinine content. In order to render a formulation palatable it is often necessary to mask the (usually bitter) taste of the API by the addition of masking agents such as sweeteners and flavours. The ET proved capable of distinguishing between formulations with different levels of sweetener and/or flavour in a manner that was consistent with their masking efficiency as perceived by a small human taste panel. A suitably calibrated ET could have the benefit of providing the pharmaceutical formulator with reliable data concerning the taste of the product quickly and with a reduced need to ask volunteers to taste active pharmaceutical samples. Early development activities could be facilitated when human tasting is usually not possible in the absence of the required toxicological data.
Keywords: Electronic tongue; Pharmaceutical analytics; Quantification of taste
Multi-analyte single-membrane biosensor for the serotype-specific detection of Dengue virus by Natalya V. Zaytseva; Richard A. Montagna; Eun Mi Lee; Antje J. Baeumner (pp. 46-53).
A multi-analyte biosensor based on nucleic acid hybridization and liposome signal amplification was developed for the rapid serotype-specific detection of Dengue virus. After RNA amplification, detection of Dengue virus specific serotypes can be accomplished using a single analysis within 25 min. The multi-analyte biosensor is based on single-analyte assays (see Baeumner et al (2002) Anal Chem 74:1442–1448) developed earlier in which four analyses were required for specific serotype identification of Dengue virus samples. The multi-analyte biosensor employs generic and serotype-specific DNA probes, which hybridize with Dengue RNA that is amplified by the isothermal nucleic acid sequence based amplification (NASBA) reaction. The generic probe (reporter probe) is coupled to dye-entrapping liposomes and can hybridize to all four Dengue serotypes, while the serotype-specific probes (capture probes) are immobilized through biotin–streptavidin interaction on the surface of a polyethersulfone membrane strip in separate locations. A mixture of amplified Dengue virus RNA sequences and liposomes is applied to the membrane and allowed to migrate up along the test strip. After the liposome-target sequence complexes hybridize to the specific probes immobilized in the capture zones of the membrane strip, the Dengue serotype present in the sample can be determined. The amount of liposomes immobilized in the various capture zones directly correlates to the amount of viral RNA in the sample and can be quantified by a portable reflectometer. The specific arrangement of the capture zones and the use of unlabeled oligonucleotides (cold probes) enabled us to dramatically reduce the cross-reactivity of Dengue virus serotypes. Therefore, a single biosensor can be used to detect the exact Dengue serotype present in the sample. In addition, the biosensor can simultaneously detect two serotypes and so it is useful for the identification of possible concurrent infections found in clinical samples. The various biosensor components have been optimized with respect to specificity and sensitivity, and the system has been ultimately tested using blind coded samples. The biosensor demonstrated 92% reliability in Dengue serotype determination. Following isothermal amplification of the target sequences, the biosensor had a detection limit of 50 RNA molecules for serotype 2, 500 RNA molecules for serotypes 3 and 4, and 50,000 molecules for serotype 1. The multi-analyte biosensor is portable, inexpensive, and very easy to use and represents an alternative to current detection methods coupled with nucleic acid amplification reactions such as electrochemiluminescence, or those based on more expensive and time consuming methods such as ELISA or tissue culture.
Keywords: Dengue virus; Biosensor; Multi-analyte; Liposome; Serotype-specific; Rapid
Ultratrace voltammetric determination of DNA-bound platinum in patients after administration of oxaliplatin by G. Weber; J. Messerschmidt; A. C. Pieck; A. M. Junker; A. Wehmeier; U. Jaehde (pp. 54-58).
Oxaliplatin, a novel diaminocyclohexane-platinum complex, is used for the treatment of metastatic colorectal cancer. The amount of DNA-adduct formation of this drug in white blood cells of patients is determined after isolation of the DNA by density gradient centrifugation and a four-step solid phase extraction procedure. DNA is quantified by UV spectrometry, and platinum is determined after mineralization of the DNA sample by adsorptive stripping voltammetry (formazone method). It is possible to determine Pt-nucleotide ratios in clinical samples down to five Pt atoms in 108 nucleotides, and the dynamic range of the method covers three orders of magnitude. An absolute amount of 25 μg of DNA is sufficient for such measurements. With the method described, the time-dependent formation of oxaliplatin DNA adducts can be monitored in clinical studies, which may help us to understand inter-individual differences in the responses of patients to oxaliplatin-based therapy.
Keywords: Oxaliplatin; Adsorptive stripping voltammetry; DNA
Interlaboratory comparison to evaluate a standardized calibration procedure for the headspace analysis of aromatic solvents in blood by R. Heinrich-Ramm; M. Blaszkewicz; M. Bader (pp. 59-67).
The determination of volatile organic compounds in blood by headspace gas chromatography is one of the central and long-established analytical techniques in occupational medical biomonitoring. Nevertheless, the relatively low success rate in intercomparison programs shows that the headspace technique is insufficiently standardized. A critical stage of the analytical procedure seems to be the preparation of calibration standards in biological matrices. As part of an extensive interlaboratory comparison by the Analyses of Hazardous Substances in Biological Materials working group of the DFG Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area, three typical procedures were compared with one another using typical aromatic solvents as an example. The best correlations between the participating laboratories and the best results for the analyses of samples from interlaboratory comparisons were obtained when highly concentrated stock solutions of the aromatic compounds in ethanol were first diluted with physiological saline and then used for spiking horse blood in headspace vials. This procedure can be easily standardized and is therefore recommended by the Analyses of Hazardous Substances in Biological Materials working group for the preparation of headspace calibration standards for aromatic compounds.
Keywords: Headspace analysis; Biomonitoring; Organic solvents
Trace analysis of rapamycin in human blood by micellar electrokinetic chromatography by Wolfgang Buchberger; Matthias Ferdig; Rudolf Sommer; Thuy Diep Thanh Vo (pp. 68-71).
A capillary electrophoretic method with UV detection at 278 nm has been developed for analysis of the immunosuppressant rapamycin (sirolimus) in human blood at low microgram per liter levels. Separation has been achieved in an acidic carrier electrolyte containing sodium dodecylsulfate and 30% (v/v) acetonitrile. For sample clean-up and preconcentration, an off-line solid-phase extraction step using a silica-based reversed-phase material and an on-capillary focussing technique were employed. The latter allows the injection of increased sample volumes without excessive band broadening. Although this new method is less sensitive than existing liquid chromatographic procedures combined with mass spectrometry, it is fully suited to routine analysis of rapamycin in blood from patients treated with this drug. Last but not least the low costs make it an attractive alternative to established methods.
Keywords: Rapamycin; Micellar electrokinetic chromatography; Blood analysis
Characterization of UVC-induced DNA damage in bloodstains: forensic implications by Ashley Hall; Jack Ballantyne (pp. 72-83).
The ability to detect DNA polymorphisms using molecular genetic techniques has revolutionized the forensic analysis of biological evidence. DNA typing now plays a critical role within the criminal justice system, but one of the limiting factors with the technology is that DNA isolated from biological stains recovered from the crime scene is sometimes so damaged as to be intractable to analysis. Potential remedies for damaged DNA are likely to be dependent upon the precise nature of the DNA damage present in any particular sample but, unfortunately, current knowledge of the biochemical nature, and the extent, of such DNA damage in dried biological stains is rudimentary. As a model for DNA damage assessment in biological stains recovered from crime scenes, we have subjected human bloodstains and naked DNA in the hydrated and dehydrated states to varying doses of UVC radiation. It was possible to damage the DNA sufficiently in a bloodstain to cause a standard autosomal short tandem repeat (STR) profile to be lost. However, a detailed analysis of the process, based upon assays developed to detect bipyrimidine photoproducts (BPPPs), single- and double-strand breaks, and DNA–DNA crosslinks, produced some unexpected findings. Contrary to the situation with living tissues or cells in culture, the predominant UVC-induced damage to DNA in bloodstains appears not to be pyrimidine dimers. Although some evidence for the presence of BPPPs and DNA crosslinks was obtained, the major form of UVC damage causing genetic profile loss appeared to be single-strand breaks. It was not possible, however, to preclude the possibility that a combination of damage types was responsible for the profile loss observed. We demonstrate here that a significant measure of protection against UVC-mediated genetic profile loss in dried biological stain material is afforded by the dehydrated state of the DNA and, to a lesser extent, the DNA cellular milieu.
Keywords: Bloodstains; UV-induced DNA damage; Forensic DNA typing; UVDE; Single-stranded breaks; T4 endonuclease V; CV-PDG
Platinum concentration in silicone breast implant material and capsular tissue by ICP-MS by S. V. M. Maharaj (pp. 84-89).
Inductively coupled plasma-mass spectrometry (ICP-MS) was used to determine the concentration of platinum (Pt) in silicone breast implant gel (range, 0.26–48.90 μg g−1 Pt; n=15), elastomer (range, 3.05–28.78 μg g−1 Pt; n=7), double lumen (range, 5.79–125.27 μg g−1 Pt; n=7), foam (range, 5.79–8.36 μg g−1 Pt; n=2), and capsular tissue (range, 0.003–0.272 μg g−1 Pt; n=15). The results show that very high levels of Pt are present in the encasing elastomer, double lumen, and foam envelope materials. Silicone breast implants can be a source of significant Pt exposure for individuals with these implants.
Keywords: Platinum; Breast implants; Silicone; Polydimethylsiloxane; PDMS; ICP-MS
High-throughput chemiluminometric determination of prostate-specific membrane antigen mRNA in peripheral blood by RT-PCR using a synthetic RNA internal standard by Evaggelia Emmanouilidou; Penelope C. Ioannou; Theodore K. Christopoulos (pp. 90-97).
A quantitative reverse transcriptase polymerase chain reaction (RT-PCR) method, employing internal standard (IS) RNA and a simplified chemiluminometric hybridization assay, is described for the determination of prostate-specific membrane antigen (PSMA) mRNA. The recombinant RNA IS has the same binding sites and size as the amplified PSMA mRNA. Biotinylated PCR products (263 bp) from PSMA mRNA and RNA IS are captured in microtiter wells coated with streptavidin, and hybridized with alkaline phosphatase-conjugated probes. The bound alkaline phosphatase (AP) is measured by using a chemiluminogenic substrate. The ratio of the luminescence values obtained for PSMA mRNA and the RNA IS is a linear function of the initial amount of PSMA mRNA present in the sample before RT-PCR. The linear range extends from 500 to 5,000,000 PSMA mRNA copies and the overall reproducibility of the assay, including RT-PCR and hybridization, ranges from 7.4 to 16.6%. Samples containing total RNA from PSMA-expressing LNCaP cells give luminescence ratios linearly related to the number of cells in the range 0.5–5,000 cells.
Keywords: Quantitative RT-PCR; PSMA mRNA; Peripheral blood; Chemiluminescence; Hybridization
Ferrocene-containing polyelectrolyte multilayer film-covered electrodes: electrocatalytic determination of ascorbic acid and use of inner blocking layers to improve the upper detection limit of the electrodes by Aihua Liu; Jun-ichi Anzai (pp. 98-103).
A multilayer film composed of ferrocene(Fc)-appended poly(allylamine hydrochloride) (Fc-PAH) and poly(potassium vinylsulfate) (PVS) has been prepared on the surface of a gold(Au) electrode by using a layer-by-layer self-assembly technique. Fc-containing polyelectrolyte multilayer (PEM) film-modified electrodes can electrochemically catalyze the oxidation of ascorbic acid successfully. For a 2 (Fc-PAH/PVS) bilayer-covered electrode the catalytic current increased linearly with increasing concentration of ascorbic acid over the concentration range 6 μmol L–1–3 mmol L–1. To extend the dynamic range for ascorbic acid, the surface of the Au electrode was first covered with a (PAH/PVS)2 film on which an additional (Fc-PAH/PVS)5 film was coated. This strategy successfully extended the dynamic range of the electrode up to 25 mmol L–1 ascorbic acid, because the (PAH/PVS)2 layer blocked access of ascorbic acid to the electrode surface. The upper detection limit of the (PAH/PVS)2 (Fc-PAH/PVS)5 film-modified electrode is much higher than those of Fc-based ascorbic acid sensors reported so far. Electron transfer is diffusion-controlled within the (PAH/PVS)2(Fc-PAH/PVS)5 film.
Keywords: Ferrocene; Polyelectrolyte multilayer film; Ascorbic acid; Inner blocking layer; Dynamic detection range
The fluorescence enhancement effect of the Tb-Gd-guanosine-5′-triphosphate-phen system and its analytical application by Zongshan Zhao; Jinghe Yang; Xia Wu; Benyu Su; Changxia Sun; Shufang Liu (pp. 104-107).
It has been found that Tb3+ can react with guanosine-5′-triphosphate (GTP) and o-phenanthroline (phen), resulting in the intrinsic fluorescence of Tb3+. This fluorescence can be enhanced by adding La3+, Gd3+, Lu3+, Sc3+, Y3+, and so on, among which Gd3+ produces the greatest enhancement. These are new co-luminescence systems. The experiments indicate under optimum conditions, the fluorescence intensity of the Tb-Gd-GTP-phen system is proportional to the concentration of GTP over the range 1×10−9 to 3×10−5 mol/l. The detection limit is 3.1×10−10 mol/l. The proposed method provides the most sensitive fluorimetry of GTP so far. The mechanism of the Tb-Gd-GTP-phen system has also been studied. The data indicates that there is a large congeries of Tb-Gd-GTP-phen, and the fluorescence enhancement of the Tb-Gd-GTP-phen system is considered to originate from intramolecular and intermocular energy transfers, and the energy-insulating sheath of the Gd complex.
Keywords: Energy transfers; Fluorescence enhancement; Guanosine-5′-triphosphate; Determination; Rare earth ion
Direct determination of copper in urine using a sol–gel optical sensor coupled to a multicommutated flow system by Paula C. A. Jerónimo; Alberto N. Araújo; M. Conceição B. S. M. Montenegro; Celio Pasquini; Ivo M. Raimundo Jr (pp. 108-114).
In this work, a multicommutated flow system incorporating a sol–gel optical sensor is proposed for direct spectrophotometric determination of Cu(II) in urine. The optical sensor was developed by physical entrapment of 4-(2-pyridylazo)resorcinol (PAR) in sol–gel thin films by means of a base-catalysed process. The immobilised PAR formed a red 2:1 complex with Cu(II) with maximum absorbance at 500 nm. Optical transduction was based on a dual-colour light-emitting diode (LED) (green/red) light source and a photodiode detector. The sensor had optimum response and good selectivity towards Cu(II) at pH 7.0 and its regeneration was accomplished with picolinic acid. Linear response was obtained for Cu(II) concentrations between 5.0 and 80.0 μg L−1, with a detection limit of 3.0 μg L−1 and sampling frequency of 14 samples h−1. Interference from foreign ions was studied at a 10:1 (w/w) ion:Cu(II) ratio. Results obtained from analysis of urine samples were in very good agreement with those obtained by inductively coupled plasma mass spectrometry (ICP–MS); there was no significant differences at a confidence level of 95%.
Keywords: Cu(II) optical sensor; Sol–gel; 4-(2-Pyridylazo)resorcinol; Multicommutation; Urinary copper
Continuous solid-phase extraction and preconcentration of bisphenol A in aqueous samples using molecularly imprinted columns by Blanca San Vicente; Fernando Navarro Villoslada; María C. Moreno-Bondi (pp. 115-122).
A bisphenol A (BPA) molecularly imprinted polymer, the composition of which was optimised using a chemometric approach, has been applied to the selective preconcentration of the template from aqueous samples. The selectivity of the polymer toward BPA and related compounds was evaluated chromatographically. The BPA-imprinted polymer was packed in a column and used for continuous on-column solid-phase extraction (MISPE) of aqueous samples followed by subsequent analysis by HPLC with fluorescence detection of the eluted fractions. The composition of the washing solvent applied in the MISPE procedure was optimised to favour the specific interactions of the MIP with BPA and to remove the non-selectively bound matrix components. The MISPE method has proven to be effective for selective preconcentration of BPA in aqueous samples (recoveries >84% obtained in the eluate for 10–100 mL sample volumes) enabling detection and quantification limits of 1.0 and 3.3 ng mL−1, respectively (based on 25 mL sample size). Analytical recoveries were between 92 and 101% for river water samples spiked with known amounts of BPA (30, 60, and 80 ng mL−1); relative standard deviations (RSD) were lower than 5.0%.
Keywords: Bisphenol A; Molecularly imprinted polymer; MISPE; Water analysis; Endocrine disruptors
Stability of fluoroquinolone antibiotics in river water samples and in octadecyl silica solid-phase extraction cartridges by Esther Turiel; Antonio Martín-Esteban; Guy Bordin; Adela R. Rodríguez (pp. 123-128).
Intensive use of antibiotics in human and veterinarian medicine and in industrial farming (food additives) has resulted in the transport of important quantities of the active ingredients to environmental waters. Environmental analysis usually requires sample storage for certain periods of time and, consequently, it is of great importance to know the stability of antibiotics in these kinds of sample. Thus, in this work the stability in river water of oxolinic acid (Oxo) and ciprofloxacin (Cip), taken as representatives of fluoroquinolone and quinolone antibiotics respectively, has been evaluated. The stability of these compounds in river water has been studied both in containers and on C18 solid-phase extraction cartridges (SPE) under different storage conditions (time, light, and temperature). Data analysis revealed that Cip and Oxo have different degradation profiles with different degradation kinetics in river water. It was also concluded that these antibiotics are stable both in the containers and on SPE cartridges for at least 2 weeks at ambient temperature, and stability can be increased substantially if samples are stored at low temperatures (4 and −18°C).
Keywords: Stability study; Fluoroquinolone antibiotics; River water samples; Solid-phase extraction
Rapid determination of inorganic elements in airborne particulate matter by using acidified subcritical-water extraction and inductively-coupled plasma–optical-emission spectrometry by Juan J Morales-Riffo; Pablo Richter (pp. 129-134).
A rapid and simple method has been developed for determination of inorganic elements in airborne particulate matter (PM10) by using acidified subcritical water and ICP–OES. Elements such as Al, As, B, Ba, Cd, Cu, Fe, Mn, Pb, Se, and Zn were rapidly and efficiently extracted from PM10 samples with a solution of 0.1 mol L−1 HNO3 under subcritical conditions. The method requires approximately 5% of the amount of acid used in the standard microwave extraction procedure. The material selected for the subcritical extraction manifold was poly ether ether ketone (PEEK), to avoid sample contamination with elements present in previously reported stainless-steel manifolds. The extraction temperature, time of static and dynamic extraction, and flow rate of acidified water were studied keeping the pressure controlled at about 1,500 psig. The efficiency of extraction of most of the analytes increased with temperature, tending to quantitative extraction at temperatures near 150°C. After the extraction process the analytes were determined directly in the extract by ICP–OES. When the method was compared with the USEPA counterpart, the results indicate that under optimized conditions (static extraction time: 15 min, dynamic extraction time: 30 min, flow rate: 2 mL min−1) the analytes were extracted with recoveries between 73 and 158%. Alternatively, by using an extraction time of 15 min, the method could be used to screen for all the elements, with recoveries over 50%. The developed method was applied to the determination of inorganic elements in airborne particulate matter in the atmosphere of Santiago, Chile.
Keywords: Inorganic elements; PM10 samples; Acidified subcritical-water extraction; ICP–OES
Simultaneous determination of zinc, copper, lead, and cadmium in fuel ethanol by anodic stripping voltammetry using a glassy carbon–mercury-film electrode by Marcelo Firmino de Oliveira; Adelir Aparecida Saczk; Leonardo Luiz Okumura; Andréa Pires Fernandes; Mercedes de Moraes; Nelson Ramos Stradiotto (pp. 135-140).
A new, versatile, and simple method for quantitative analysis of zinc, copper, lead, and cadmium in fuel ethanol by anodic stripping voltammetry is described. These metals can be quantified by direct dissolution of fuel ethanol in water and subsequent voltammetric measurement after the accumulation step. A maximum limit of 20% (v/v) ethanol in water solution was obtained for voltammetric measurements without loss of sensitivity for metal species. Chemical and operational optimum conditions were analyzed in this study; the values obtained were pH 2.9, a 4.7-μm thickness mercury film, a 1,000-rpm rotation frequency of the working electrode, and a 600-s pre-concentration time. Voltammetric measurements were obtained using linear scan (LSV), differential pulse (DPV), and square wave (SWV) modes and detection limits were in the range 10−9–10−8 mol L−1 for these metal species. The proposed method was compared with a traditional analytical technique, flame atomic absorption spectrometry (FAAS), for quantification of these metal species in commercial fuel ethanol samples.
Keywords: Alternative fuel; Ethanol; Heavy metals; Mercury film electrode; Anodic stripping voltammetry
Adsorptive stripping voltammetric determination of cobalt in the presence of dimethylglyoxime and cetyltrimethylammonium bromide by Mieczyslaw Korolczuk; Aleksandra Moroziewicz; Malgorzata Grabarczyk; Romualda Kutyła (pp. 141-145).
A sensitive procedure for determination of micro-traces of Co(II) by adsorptive stripping voltammetry is proposed. The procedure exploits the enhancement of the cobalt peak obtained by use of the system Co(II)–dimethylglyoxime–piperazine-1,4-bis(2-ethanesulfonic acid)–cetyltrimethylammonium bromide. Using the optimized conditions, a detection limit (based on the 3σ criterion) for Co(II) of 1.2×10−11 mol L−1 (0.7 ng L−1) was achieved. The calibration plot for an accumulation time of 30 s was linear from 5×10−11 to 4×10−9 mol L−1. The procedure was validated by analysis of certified reference materials and natural water samples.
Keywords: Cobalt; Determination; Adsorptive stripping voltammetry
Standard addition method applied to solid-state stripping voltammetry: determination of zirconium in minerals and ceramic materials by A. Doménech-Carbó; M. Moya-Moreno; M. T. Doménech-Carbó (pp. 146-156).
An application of the standard addition method to stripping voltammetry of solid materials immobilized in inert electrodes is described. The method allows the determination of the mass fraction of a depositable metal M in a material on addition of known amounts of a standard material containing M to a mixture of that material and a reference compound of a second depositable metal, R. After a reductive deposition step, voltammograms recorded for those modified electrodes immersed in a suitable electrolyte produce stripping peaks for the oxidation of the deposits of M and R. If no intermetallic effects appear the quotients between the peak areas and the peak currents for the stripping oxidation of M and R vary linearly with the mass ratio of the added standard and the reference compound, thus providing an electrochemical method for determining the amount of M in the sample. The method has been applied to the determination of Zr in minerals, ceramic frits, and pigments, using ZnO as reference material and ZrO2 as the standard.
Keywords: Standard addition; Stripping voltammetry; Zirconium; Ceramics
Raman microscopic investigations of BaTiO3 precursors with core–shell structure by M. Rössel; H.-R. Höche; H. S. Leipner; D. Völtzke; H.-P. Abicht; O. Hollricher; J. Müller; S. Gablenz (pp. 157-162).
Due to their outstanding dielectric and ferroelectric properties, barium titanate (BaTiO3)-based ceramics have found many applications in electronic devices. To optimise the final quality of such ceramics, a detailed knowledge of the complex processes involved in the formation of BaTiO3 is required. The phase formation process in ordered structures of the BaCO3/TiO2 system was analysed by X-ray diffraction and by Raman spectral imaging (RSI) as a function of the annealing temperature. RSI was used for the first time as a locally resolving method for phase analysis, and proved to be a useful tool in examining the formation process of BaTiO3 starting from spherical, core–shell structured precursors of the type TiO2 core/BaCO3 shell. The Raman spectra of different BaO–TiO2 phases appearing as intermediate phases during the formation of BaTiO3 were recorded for separately-prepared pure substances. Using these spectra as fingerprints, and choosing phase filters by setting wave number windows, “phase landscape pictures” of the samples at different temperatures during the genesis of BaTiO3 could be created with a lateral resolution of up to 200 nm. These pictures confirm shell-like formation of the different barium titanate phases according to the diffusion of barium and oxygen ions from the Ba-rich shell into the TiO2 core. At an intermediate state of the phase formation process, the phase sequence Ba2TiO4, BaTiO3, BaTi2O5, BaTi4O9 and BaTi5O11 to TiO2 was detected from the outer to the inner parts of the core–shell structures.
Keywords: Barium titanate; Core–shell structure; Phase diagram; Formation mechanism; Raman microscopy; Spectral imaging
Identification and quantification of cotton-bound, cyclic polycarboxylic acids by means of isocratic HPLC by Christian Schramm; Beate Rinderer (pp. 163-167).
Cotton fabrics are modified by means of polycarboxylic acids (PCA) in combination with an inorganic catalyst in order to impart durable press properties. To evaluate the effectiveness of cyclic PCA, 100% cotton fabrics were treated with 1,2,3,4,5,6-cyclohexanehexacarboxylic acid (CH-HCA), 1,3,5-cyclohexanetricarboxylic acid (CH-TCA), 1,2,3,4-cyclopentanetetracarboxylic acid (CP-TCA), and 1,2,3,4-tetrahydrofurantetracarboxylic acid (THF-TCA) in combination with sodium hypophosphite (SHP) as catalyst. The amount of PCA that reacted with the cellulosic material was determined by means of isocratic HPLC (Aminex HPX-87-H). The results clearly indicate that the cyclic PCA are less effective in respect of durable press performance. CH-TCA does not react with the cellulosic material thus confirming the assumption that the crosslinking reaction between PCA and the cellulose proceeds via a five-membered cyclic anhydride.
Keywords: HPLC; Cyclic polycarboxylic acid; Cotton; Durable press finishing
Use of the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate in countercurrent chromatography by A. Berthod; S. Carda-Broch (pp. 168-177).
Room temperature ionic liquids (RTIL) are molten salts that are liquids at room temperature. Their liquid state makes them possible candidates as solvents in countercurrent chromatography (CCC), which uses solvents as both the mobile and stationary phases. The study focuses on 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM PF6), an easy to synthesize and purify RTIL whose melting point is −8°C. It is shown that BMIM PF6 behaves like a solvent of significant polarity (comparable with that of ethanol). The ternary phase diagram water–acetonitrile–BMIM PF6 is given, because it was necessary to add acetonitrile to reduce the ionic liquid viscosity. The 40:20:40% w/w water–acetonitrile–BMIM PF6 biphasic liquid system was found to be appropriate as a biphasic liquid system for CCC. Different aromatic solutes, including bases, acids, and neutral compounds, were injected into the CCC column to estimate their distribution constants between the ionic liquid-rich phase and the aqueous phase. The resulting Kil/w constants were compared with the corresponding literature octanol–water partition coefficients, Ko/w. The important drawbacks in the use of RTIL in CCC are clearly pointed out: high viscosity producing pressure build-up, UV absorbance limiting the use of the convenient UV detector, and non-volatility precluding the use of the evaporative light-scattering detector for continuous detection.
Keywords: Countercurrent chromatography; 1-Butyl-3-methylimidazolium hexafluorophosphate; Ionic liquid; Distribution constant; Hydrophobicity
Indirect determination of chloride and sulfate ions in alcohol fuel by capillary electrophoresis by Elisabete A. Pereira; Alessandra Stevanato; Arnaldo A. Cardoso; Marina F. M. Tavares (pp. 178-182).
A capillary zone electrophoresis method using indirect UV detection for the analysis of chloride and sulfate in alcohol fuel samples was developed. The anions were analyzed in less than 3 min using an electrolyte containing 10 mmol l−1 chromate and 0.75 mmol l−1 hexamethonium bromide (HMB) as electroosmotic flow modifier. Coefficients of variation were better than 0.6% for migration time (n=10) and between 2.05 and 2.82% for peak area repeatabilities. Analytical curves of peak area versus concentration in the range of 0.065–0.65 mg kg−1 for chloride and 0.25–4.0 mg kg−1 for sulfate were linear with coefficients of correlation higher than 0.9996. The limits of detection for sulfate and chloride were 0.033 and 0.041 mg kg−1, respectively. Recovery values ranged from 85 to 103%. The method was successfully applied for the quantification of sulfate and chloride in five alcohol fuel samples. The concentration of sulfate varied from 0.45 to 3.12 mg kg−1. Chloride concentrations were below the method’s LOD.
Keywords: Capillary electrophoresis; Inorganic anions; Alcohol fuel