Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Analytical and Bioanalytical Chemistry (v.378, #7)
Miniaturization in analytical and bioanalytical chemistry
by Staffan Nilsson; Thomas Laurell (pp. 1676-1677).
Micro- and nanofluidics for DNA analysis by Jonas O. Tegenfeldt; Christelle Prinz; Han Cao; Richard L. Huang; Robert H. Austin; Stephen Y. Chou; Edward C. Cox; James C. Sturm (pp. 1678-1692).
Miniaturization to the micrometer and nanometer scale opens up the possibility to probe biology on a length scale where fundamental biological processes take place, such as the epigenetic and genetic control of single cells. To study single cells the necessary devices need to be integrated on a single chip; and, to access the relevant length scales, the devices need to be designed with feature sizes of a few nanometers up to several micrometers. We will give a few examples from the literature and from our own research in the field of miniaturized chip-based devices for DNA analysis, including dielectrophoresis for purification of DNA, artificial gel structures for rapid DNA separation, and nanofluidic channels for direct visualization of single DNA molecules.
Magnetophoresis and electromagnetophoresis of microparticles in liquids by Hitoshi Watarai; Masayori Suwa; Yoshinori Iiguni (pp. 1693-1699).
The magnetic field-induced migration of particles in liquids is a highly-promising technique for the micro-separation analysis of bioparticles, such as cells and large DNA. Here, new methods that make use of magnetophoresis and electromagnetophoresis to induce the migration of microparticles in liquids are briefly reviewed. Magnetic force and Lorentz force are utilized in the new methods. Some typical examples of the use of these methods are described, and the advantages of using a superconducting magnet for them are demonstrated.
Keywords: Magnetophoresis; Electromagnetophoresis; Bioparticles; Superconducting magnet
Lab-on-a-chip systems for biomedical and environmental monitoring by J. G. E. Gardeniers; A. van den Berg (pp. 1700-1703).
During the last decade, pocket-sized analytical equipment based on the “lab-on-a-chip” approach has become available. These chips, in combination with portable electronic equipment, are applicable in, for example, “point-of-care” ion analysis of body fluids, forensics, identification of explosives, tracking of pollution in environmental or waste waters, monitoring nutrients in agricultural or horticultural water, controlling quality in food production, or process control in chemical industry. This paper discusses several demonstrator systems with applications in these fields.
Keywords: Lab-on-a-chip; Ion analysis; Hydrodynamic chromatography; Micromachining
Airborne chemistry: acoustic levitation in chemical analysis by Sabina Santesson; Staffan Nilsson (pp. 1704-1709).
This review with 60 references describes a unique path to miniaturisation, that is, the use of acoustic levitation in analytical and bioanalytical chemistry applications. Levitation of small volumes of sample by means of a levitation technique can be used as a way to avoid solid walls around the sample, thus circumventing the main problem of miniaturisation, the unfavourable surface-to-volume ratio. Different techniques for sample levitation have been developed and improved. Of the levitation techniques described, acoustic or ultrasonic levitation fulfils all requirements for analytical chemistry applications. This technique has previously been used to study properties of molten materials and the equilibrium shape and stability of liquid drops. Temperature and mass transfer in levitated drops have also been described, as have crystallisation and microgravity applications.The airborne analytical system described here is equipped with different and exchangeable remote detection systems. The levitated drops are normally in the 100 nL–2 μL volume range and additions to the levitated drop can be made in the pL-volume range.The use of levitated drops in analytical and bioanalytical chemistry offers several benefits. Several remote detection systems are compatible with acoustic levitation, including fluorescence imaging detection, right angle light scattering, Raman spectroscopy, and X-ray diffraction. Applications include liquid/liquid extractions, solvent exchange, analyte enrichment, single-cell analysis, cell–cell communication studies, precipitation screening of proteins to establish nucleation conditions, and crystallisation of proteins and pharmaceuticals.
A rapid enzyme assay for β-galactosidase using optically gated sample introduction on a microfabricated chip by Hongwei Xu; Andrew G. Ewing (pp. 1710-1715).
The ability to perform enzyme assays on microchips is demonstrated using optically gated sample introduction. The hydrolysis of fluorescein mono-β-d-galactopyranoside (FMG) by β-d-galactosidase (β-Gal) is continuously monitored using a microchip for 5 to 10 min. The outcome of the reaction was analyzed by performing serial on-chip separations of fluorescent substrate, FMG, and product, fluorescein. Kinetic information about β-Gal has been successfully obtained by varying the concentration of FMG. β-Gal enzymes from two different sources including bovine liver and E. coli., have been examined and compared to each other and to results obtained using traditional assay methods. In addition, the competitive inhibition of β-Gal by phenylethyl β-d-thiogalactoside (PETG) and β-lactose has been studied using this technique. PETG is found to have higher inhibition than lactose in the hydrolysis. This separation-based enzyme assay technique avoids the possible fluorescence interference between FMG and fluorescein, which is a problem with the traditional plate assay method. Additionally, the amount of the enzyme and substrate required with this technique is at least four orders of magnitude lower than the traditional plate assay method. By using optically gated sample introduction, microchips allow continuous serial injections and separations without any potential switch, thus making this technique ideal as a sensor for enzyme assays. This technique should therefore be valuable for high-throughput screening in the drug discovery industry.
Keywords: Enzyme assay; Optically gated sample introduction; Microfabricated chip
Ultrasonic agitation in microchannels by Martin Bengtsson; Thomas Laurell (pp. 1716-1721).
This paper describes an acoustic method for inducing rotating vortex flows in microchannels. An ultrasonic crystal is used to create an acoustic standing wave field in the channel and thus induce a Rayleigh flow transverse to the laminar flow in the channel. Mixing in microchannels is strictly diffusion-limited because of the laminar flow, a transverse flow will greatly enhance mixing of the reactants. This is especially evident in chemical microsystems in which the chemical reaction is performed on a solid phase and only one reactant is actually diffusing. The method has been evaluated on two different systems, a mixing channel with two parallel flows and a porous silicon micro enzyme reactor for protein digestion. In both systems a significant increase of the mixing ratio is detected in a narrow band of frequency for the actuating ultrasound.
Keywords: Microchannels; Rotating vortex flow; Rayleigh flow; Acoustics; Ultrasonic agitation; Reagent mixing
Controlled enzyme-immobilisation on capillaries for microreactors for peptide mapping by A. Bossi; L. Guizzardi; M. R. D’Acunto; P. G. Righetti (pp. 1722-1728).
In the present paper, the covalent immobilisation of the digesting enzyme trypsin has been achieved through photo-immobilisation on a portion of a silica capillary, thus leading to the construction of a capillary electrophoretic (CE)-microreactor for peptide mapping. The CE-microreactor is characterised by being a single piece, thus ensuring no fluidic or electrical leakage. The enzyme was immobilised with a surface density of 15.8 μg/cm2, the stability was high (80% after 38 days) and the rate of conversion was 0.2 ng/s. On-line protein mapping was tested with proteins of different dimensions, showing competitiveness in terms of time (completed map within 15 min) and exhaustive maps of small proteins. The results of the CE-microreactor and the potential to immobilise biocomponents easily on a desired portion of the capillary indicate further developments towards the construction of a variety of miniaturised enzymatic screening devices for high-throughput screening analysis.
Keywords: Capillary electrophoresis; Trypsin; Photo-immobilisation; Peptide mapping
In-capillary micro solid-phase extraction and capillary electrophoresis separation of heterocyclic aromatic amines with nanospray mass spectrometric detection by Peter Viberg; Staffan Nilsson; Kerstin Skog (pp. 1729-1734).
A miniaturised technique to analyse and detect heterocyclic aromatic amines (HAs) using micro solid-phase extraction (μSPE) coupled on-line (in-capillary) to capillary electrophoresis (CE) separation with nanospray (nESI) mass spectrometry (MS) detection has been developed. HAs are mutagenic and carcinogenic compounds formed at low levels in protein-rich food during cooking. Due to the low concentrations of HAs and the high complexity of the matrix in which they exist, sensitive and selective analytical methods are required for quantification. μSPE was performed on a packed bed of C18 particles inside the CE capillary, which minimised the dead volume. The on-line coupling of SPE, CE and nESI-MS reduced the time for extraction and identification to less than half an hour, which will allow for screening of several samples per day. The new technique provides short analysis time, low sample and solvent consumption, and HAs in standard solutions were easily detected at 12–17 fmol injections, and in spiked urine samples at 750–810 fmol injections.
Keywords: On-line; Carcinogenic; Miniaturisation; Nanoelectrospray; Urine; AαC; MeAαC; PhIP; MeIQx
Mid-IR synchrotron radiation for molecular specific detection in microchip-based analysis systems by S. Kulka; N. Kaun; J. R. Baena; J. Frank; P. Svasek; D. Moss; M. J. Vellekoop; B. Lendl (pp. 1735-1740).
Microstructures constructed from SU-8 polymer and produced on CaF2 base plates have been developed for microchip-based analysis systems used to perform FTIR spectroscopic detection using mid-IR synchrotron radiation. The high brilliance of the synchrotron source enables measurements at spot sizes at the diffraction limit of mid-IR radiation. This corresponds to a spatial resolution of a few micrometers (5–20 μm). These small measurement spots are useful for lab-on-a-chip devices, since their sizes are comparable to those of the structures usually used in these devices. Two different types of microchips are introduced here. The first chip was designed for time-resolved FTIR investigations of chemical reactions in solution. The second chip was designed for chip-based electrophoresis with IR detection on-chip. The results obtained prove the operational functionality of these chips, and indicate the potential of these new devices for further applications in (bio)analytical chemistry.
Keywords: Synchrotron radiation; Time resolved IR spectroscopy; Capillary electrophoresis; Lab-on-a-chip; SU-8
Limitations of low resolution mass spectrometry in the electron capture negative ionization mode for the analysis of short- and medium-chain chlorinated paraffins by Margot Reth; Michael Oehme (pp. 1741-1747).
The analysis of complex mixtures of chlorinated paraffins (CPs) with short (SCCPs, C10–C13) and medium (MCCPs, C14–C17) chain lengths can be disturbed by mass overlap, if low resolution mass spectrometry (LRMS) in the electron capture negative ionization mode is employed. This is caused by CP congeners with the same nominal mass, but with five carbon atoms more and two chlorine atoms less; for example C11H17 37Cl35Cl6 (m/z 395.9) and C16H29 35Cl5 (m/z 396.1). This can lead to an overestimation of congener group quantity and/or of total CP concentration. The magnitude of this interference was studied by evaluating the change after mixing a SCCP standard and a MCCP standard 1+1 (S+MCCP mixture) and comparing it to the single standards. A quantification of the less abundant C16 and C17 congeners present in the MCCP standard was not possible due to interference from the major C11 and C12 congeners in the SCCPs. Also, signals for SCCPs (C10–C12) with nine and ten chlorine atoms were mimicked by MCCPs (C15–C17) with seven and eight chlorine atoms (for instance C10H12Cl10 by C15H24Cl8). A similar observation was made for signals from C15–C17 CPs with four and five chlorine atoms resulting from SCCPs (C10–C12) with six and seven chlorine atoms (such as C15H28Cl4 by C10H16Cl6) in the S+MCCP mixture. It could be shown that the quantification of the most abundant congeners (C11–C14) is not affected by any interference. The determination of C10 and C15 congeners is partly disturbed, but this can be detected by investigating isotope ratios, retention time ranges and the shapes of the CP signals. Also, lower chlorinated compounds forming [M+Cl]− as the most abundant ion instead of [M-Cl]− are especially sensitive to systematic errors caused by superposition of ions of different composition and the same nominal mass.
Keywords: Polychlorinated n-alkanes; Chlorinated paraffins; ECNI low resolution mass spectrometry; Self-interferences
Detection of transgenes in soybean via a polymerase chain reaction and a simple bioluminometric assay based on a universal aequorin-labeled oligonucleotide probe by Kyriaki Glynou; Penelope C. Ioannou; Theodore K. Christopoulos (pp. 1748-1753).
The recombinant photoprotein aequorin was used as a reporter in highly sensitive and automatable hybridization assays for the analysis of transgenic sequences in genetically modified organisms (GMO). The terminator of the nopaline synthase gene (NOS) from Agrobacterium tumefaciens and the 35S promoter sequence were detected in genetically modified soybean. The endogenous, soybean-specific, lectin gene was also detected for confirmation of the integrity of extracted DNA. A universal detection reagent was produced through conjugation of aequorin to the oligonucleotide (dA)30. Biotinylated (through PCR) products for the three target sequences were captured onto streptavidin-coated wells, and one strand was removed by NaOH treatment. The immobilized single-stranded DNAs were then hybridized with oligonucleotide probes consisting of a target-specific segment and a poly(dT) tail. This allowed the subsequent determination of all hybrids through the use of the (dA)30-aequorin conjugate as a universal reagent. The bound aequorin was measured by adding Ca2+ and integrating the light emission for 3 s. As low as 2 pM (100 amol per well) of amplified DNA was detectable for all three targets, with a signal-to-background ratio of about 2. The analytical range extended up to 2000 pM. As low as 0.05% GMO content in soybean can be detected with a signal-to-background ratio of 8.2. The overall repeatability of the proposed assay, including DNA extraction, PCR, and hybridization assay, ranged from 7.5–19.8%. The use of a (dA)30-aequorin conjugate renders the assay configuration general for any target DNA, provided that the specific probe carries a poly(dT) tail.
Keywords: Aequorin; Bioluminescence; Genetically modified organisms; Hybridization; Microtiter wells
Liquid chromatography with triple-quadrupole and quadrupole-time-of-flight mass spectrometry for the determination of micro-constituents – a comparison by Alida (Linda) A. M. Stolker; Willem Niesing; Regine Fuchs; Rob J. Vreeken; Wilfried M. A. Niessen; Udo A. Th. Brinkman (pp. 1754-1761).
The potential of liquid chromatography with triple-quadrupole mass spectrometry (LC-QqQ MS) was compared to that of quadrupole time-of-flight mass spectrometry (LC-Q-ToF MS) for the determination of microconstituents. Three applications were studied: (1) the ng/l quantification of five human drugs in surface water and waste-water effluents; (2) the quantification and confirmation of three corticosteroids in bovine urine at concentrations of 1–100 μg/l, and; (3) the confirmation of nicotine in rat plasma. In all cases, the criteria of the EU Commission Decision 2002/657/EC were followed (for confirmation analysis two MS/MS ions were monitored, and the ratio of their abundances were calculated and compared with those of standards). With both techniques fully satisfactory results were obtained in almost all instances. That is, unequivocal confirmation according to the most stringent EU criteria, those for “illegal compounds”, was possible.One main advantage of LC-Q-ToF MS is that for identification and confirmation purposes, full MS/MS spectra are available after a single injection: no second injection, as required with QqQ MS, is needed. As well as the increased efficiency, the enhanced selectivity due to the impressive mass selectivity of LC-Q-ToF MS must be emphasized, which allows accurate masses of fragment ions to be calculated. Method characteristics such as linear dynamic range and repeatability were found to be essentially the same for both techniques, but LC-QqQ MS has the advantage that its detection limits are somewhat lower.
Keywords: Pharmaceuticals; Corticosteroids; Nicotine; Confirmation; Identification
Sensitive biomonitoring of phthalate metabolites in human urine using packed capillary column switching liquid chromatography coupled to electrospray ionization ion-trap mass spectrometry by Anders Holm; Kasper Solbu; Paal Molander; Elsa Lundanes; Tyge Greibrokk (pp. 1762-1768).
A rapid and sensitive method for the determination of the phthalate monoesters monoethyl phthalate (MEP), monobutyl phthalate (MBP), monobenzyl phthalate (MBzP) and monoethylhexyl phthalate (MEHP), in human urine, using packed capillary column liquid chromatography coupled to electrospray quadrupole-ion trap mass spectrometry (ESI-QITMSn) has been developed. Sample volumes of 200 μL of deconjugated and diluted urine were loaded onto a precolumn of 30 mm×0.32 mm I.D. packed with Hypercarb 5 μm particles, using a sample carrier consisting of acetonitrile/water (15/85, v/v, adjusted to pH 2 using HCl) with a flow rate of 20 μL/min. Backflushed elution onto a 100 mm×0.32 mm I.D. analytical column packed with 5 μm Hypercarb particles was conducted using a tetrahydrofuran/water gradient where both solvents contained 10 mM ammonium acetate, at a flow rate of 4 μL/min. Determination of the monophthalates was achieved within 8 min. Ionization was performed in the negative mode and the analytes were observed as [M-H]− at m/z=193.1, 221.1, 255.1 and 277.0 for MEP, MBP, MBzP and MEHP, respectively. Quantification was performed in the multiple reaction monitoring (MRM) mode monitoring the fragments at m/z=121.1, 177.0, 183.0 and 233.0 for MEP, MBP, MBzP and MEHP, respectively. The method was validated over the concentration range 2.5–125 ng/mL in pretreated urine samples, corresponding to 25–1250 ng/mL untreated urine, yielding correlation coefficients in the range 0.996–0.999. The within-assay (n=6) and between-assay (n=6) repeatabilities were in the range 4.0–18% and 4.8–15% RSD, respectively. The mass limits of detection were in the range 32–70 pg, corresponding to concentration limits of detection of 1.6–3.5 ng/mL of untreated urine.
Keywords: Capillary liquid chromatography; Column switching; Porous graphitic carbon; Biomonitoring; Phthalates
Anionic liposomes in capillary electrophoresis: Effect of calcium on 1-palmitoyl-2-oleyl-sn-glycero-3-phosphatidylcholine / phosphatidylserine-coating in silica capillaries by Jari T. Hautala; Susanne K. Wiedmer; Marja-Liisa Riekkola (pp. 1769-1776).
The effect of calcium on phospholipid coatings in fused silica capillaries used in capillary electrophoresis was studied. The anionic liposomes used for the coating consisted of 3 mM 1-palmitoyl-2-oleyl-sn-glycero-3-phosphatidylcholine and phosphatidylserine in the ratio 80/20 mol%. Coating was performed as part of the preconditioning, and the capillaries could be used for several runs without the need for liposomes in the background electrolyte solution or for liposome rinses between runs. Phospholipids could easily be flushed away by rinsing with a chloroform-methanol (2:1 v/v) mixture, which made it possible to recoat and reuse the capillaries. A calcium:phospholipid ratio of approximately 3 gave the most stable coating. The stability of the coating and success of the coating procedure were studied by measuring the electroosmotic flow and by separating uncharged steroids, which were used as model compounds. Many parameters that affect the coating, such as preconditioning (with different acids and bases), buffer, temperature during coating, and the physical structures of liposomes, were studied, with and without calcium in the liposome solution. The separation of steroids was improved and was less dependent on coating conditions when calcium was present during the coating. Capillaries optimally coated with anionic phospholipids were applied in the separation of phenols.
Keywords: Anionic liposomes; Calcium; Phospholipid-coating; Capillary electrophoresis; HEPES
Determination of ochratoxin A in pig tissues by liquid–liquid extraction and clean-up and high-performance liquid chromatography by L. Monaci; G. Tantillo; F. Palmisano (pp. 1777-1782).
A fast, simple, and sensitive HPLC–FD method is described for determination of ochratoxin A (OTA) in pig kidney and muscle; a small mass (<2.5 g) of sample and a relatively small volume (<15 mL) of a non-halogenated extraction solvent are required. Ochratoxin B, systematically absent from all the samples investigated, was used as internal standard. Liquid–liquid partition was used for sample clean-up. Recoveries at the 1 ng g−1 level were 86±15% and 74±8% for kidney and muscle, respectively, and detection limits were 0.14 and 0.15 ng g−1. Clean-up by solid-phase extraction (SPE) is required for pig liver. A survey of the OTA content of tissues of pigs slaughtered in southern Italy revealed that 52 out of 54 analysed samples were contaminated; the OTA concentration in kidney ranged between 0.26 and 3.05 ng g−1. The effect of measurement precision on compliance with legal limits is also discussed.
Keywords: Ochratoxin A; Kidneys; Liver; Meat; HPLC
Determination of the thiol redox state of organisms: new oxidative stress indicators by Nikolaos Patsoukis; Christos D. Georgiou (pp. 1783-1792).
This study describes a new methodology by which the concentrations of non-protein (NP) thiols glutathione (GSH), cysteine (CSH), N-acetylcysteine (AcCSH), and protein (P) thiols (PSH), as well as the contribution of these components to symmetric and mixed disulfides (NPSSR, NPSSC, NPSSCAc, PSSR, PSSC, PSSCAc, PSSP) can reliably be measured. The methodology consists of a strict sequence of methods which are applied to every sample. Free thiols at any given state of the procedure are measured by Ellman’s assay, the CSH fraction is measured by its unique response in the ninhydrin assay, AcCSH is selectively measured with ninhydrin after enzymatic deacylation, proteins are separated from non-protein thiols/disulfides by precipitation with trichloroacetic or perchloric acid, disulfides are reduced into free thiols with borohydride, mixed disulfides between a protein and a non-protein component are measured by extracting the non-protein thiol from the protein pellet after borohydride treatment, and protein thiols/disulfides are measured after resolubilization of the protein pellet.When this method was applied to animal and fungal tissue, new molecular indicators of the thiol redox state of living cells were identified. The findings of the present study clearly show that the new parameters are very sensitive indicators of redox state, while at the same time the traditional parameters GSH and GSSG often remain constant even upon dramatic changes in the overall redox state of biological tissue. Therefore, unbiased assessment of the redox state also requires explicit measurement of its most sensitive thiol indicators.
Keywords: N-Acetylcysteine; Protein/non-protein thiols/disulfides; Thiol redox state
Using electrical impedance detection to evaluate the viability of biomaterials subject to freezing or thermal injury by Tian-Hua Yu; Jing Liu; Yi-Xin Zhou (pp. 1793-1800).
This paper is aimed at comprehensively investigating the dynamic low-frequency electrical impedance (DLFI) of biological materials during the processes of freezing, thawing and heating, and combinations of them. Electrical impedance detection (EID) was proposed as a means of rapidly evaluating the viability of biological materials subject to freezing or thermal injury (processes expected to be significant in the practices of cryobiology and hyperthermia). Using two experimental setups, the DLFI for selected biological materials (fresh pork and fish) under various freezing and heating conditions was systematically measured and analyzed. Preliminary results demonstrate that damage that occurs to a biological material due to freezing or heating could result in a significant deviation in its electric impedance value from that of undamaged biomaterials. Monitoring impedance change ratios under various freezing and heating conditions may offer an alternative strategy for assessing the amount of damage sustained by biomaterials subject to cryosurgery, cryo-preservation and hyperthermia. Implementation of the present method in order to develop a new micro-analysis or biochip system is also suggested.
Keywords: Viability evaluation; Freezing and thermal injury; Biochip; Electrical impedance detection; Micro-analysis system
Evaluation of free hydroxyl radical scavenging activities of some Chinese herbs by capillary zone electrophoresis with amperometric detection by Hui Li; Qingjiang Wang (pp. 1801-1805).
Due to the severe damage caused by free hydroxyl radicals (OH·) to cells and tissues, there is much interest in finding and studying effective and non-toxic OH· scavengers, including traditional Chinese herbs. In this paper, the simple and highly-sensitive technique of capillary zone electrophoresis with amperometric detection (CZE-AD) was used to study the OH· scavenging activities of aqueous extracts from some traditional Chinese herbs. Salicylic acid (SAL) was used as an OH· trap, and the content of OH· could be determined by assaying their products, 2,3-dihydroxybenzoic acid (2,3-DHBA) and 2,5-dihydroxybenzoic acid (2,5-DHBA). The optimum conditions for CZE-AD for the determination of 2,3-DHBA and 2,5-DHBA were explored. The linearity ranges of 2,3-DHBA and 2,5-DHBA were 1.0 ×10−7~1.0 ×10−4 mol L−1, and their detection limits were as low as 2×10−8 mol L−1, which were much better than the CE-UV method often used. The traditional Chinese herbs studied included Radix angelicae sinensis, Rhizoma coptidis, Ligustrum lucidum, Ligusticum wallichii, Radices glycyrrhizae and Semen plantaginis. The experiments showed that the aqueous extracts from all of the above traditional Chinese herds had free OH· scavenging activities, although to different degrees.
Keywords: Free hydroxyl radical; Scavenging activity; Chinese herbs; Capillary zone electrophoresis; Amperometric detection
Determination of polychlorobiphenyls and polycyclic aromatic hydrocarbons in the atmospheric aerosol of the Venice Lagoon by Andrea Gambaro; Laura Manodori; Ivo Moret; Gabriele Capodaglio; Paolo Cescon (pp. 1806-1814).
An analytical method for simultaneous determination of “particle”-associated and “gaseous”-phase concentrations of polychlorinated biphenyls (PCB) and polycyclic aromatic hydrocarbons (PAH) in atmospheric aerosol samples obtained by high-volume samplers using polyurethane foam adsorbent (PUF) and quartz fibber filters (QFF) has been investigated. Quality control of the analytical procedure was carried out by blank control and by evaluating limits of detection, recoveries, accuracy, and repeatability. The proposed method was subsequently used to determine PAH and PCB in the “gaseous” and “particulate” phases of the aerosols that enter the Venice Lagoon atmosphere. The highest concentrations of ∑PCB and ∑PAH were predominantly in the “gaseous” phase. In both “particulate” and “gaseous” phases the penta-CB congeners dominated total PCB concentrations whereas phenanthrene, fluoranthene, and pyrene dominated the ∑PAH concentrations. Total (“gaseous” plus “particulate”) PCB and PAH concentrations were higher at the site directly influenced by the industrial plants but the concentrations in marine aerosol samples were lower by a factor four only and must be taken into consideration when studying the chemical contamination of the Venice Lagoon.
Keywords: Polycyclic aromatic hydrocarbons; Polychlorobiphenyls; Aerosol; Venice Lagoon; Gas chromatography–mass spectrometry
An automated monitoring system for VOC ozone precursors in ambient air: development, implementation and data analysis by C. Badol; A. Borbon; N. Locoge; T. Léonardis; J.-C. Galloo (pp. 1815-1827).
An automated system for the monitoring of volatile organic compound (VOC) ozone precursors in ambient air is described. The measuring technique consists of subambient preconcentration on a cooled trap followed by thermal desorption and GC/FID analysis. First, the technical development, which permits detection limits below 0.05 ppbv to be reached, proceeded in two steps: (1) the determination of optimum sampling parameters (trap composition and conditioning, outlet split, desorption temperature); (2) the development of a reliable calibration method based on a highly accurate standard. Then, a 4-year field application of the hourly measuring chain was carried out at two urban sites. On the one hand, quality control procedures provided the best VOC identification (peak assignment) and quantification (reproducibility, blank system control). On the other hand, the success and performances of the routine experience (88% of the measurements covered more than 40 target compounds) indicated the high quality and suitability of the instrumentation which is actually applied in several French air quality monitoring networks. Finally, an example of data analysis is presented. Data handling identified important organic compound sources other than vehicle exhaust.
Keywords: NMHC analysis and sampling; Gas chromatography (GC); QC procedure; Concentrations; Sources
Analysis of dinitro- and amino-nitro-toluenesulfonic acids in groundwater by solid-phase extraction and liquid chromatography–mass spectrometry by Wai-Tang Ma; Klaus Steinbach; Zongwei Cai (pp. 1828-1835).
A reversed-phase LC–MS method with quadrupole-time of flight (QTOF) detection has been developed for the determination of four dinitro-toluenesulfonic acids and two amino-nitro-toluenesulfonic acids in groundwater. The analytes were separated by HPLC with 0.1% (v/v) formic acid as mobile phase modifier compatible with mass spectrometric detection. QTOF-MS analysis with negative ion electrospray ionization afforded good selectivity and sensitivity for analysis of the dinitro- and amino-nitro-toluenesulfonic acids. Structure elucidation and confirmation were accomplished by tandem mass spectrometry. Characteristic ions resulting from the loss of NO, NO2, and SO2 from the [M−H]− ions were detected. An intense fragment ion at m/z 80 representing the [SO3]− ion was detected for all dinitro- and amino-nitro-toluenesulfonic acids. Solid-phase extraction using a co-polymer cartridge was developed for preconcentration of the analytes from water. Good recovery (>85%) was achieved when 0.1% formic acid was added into the water samples before extraction. Method detection limits ranged from 10 to 76 ng L−1 for the targeted compounds when 10 mL water was analyzed. Groundwater samples collected from wells close to a former ammunition plant in Stadtallendorf, Germany, were analyzed for the dinitro- and amino-nitro-toluenesulfonic acids.
Keywords: Dinitro-toluenesulfonic acids; Amino-nitro-toluenesulfonic acids; Groundwater; Solid-phase extraction; LC–MS
Speciation studies by capillary electrophoresis – simultaneous determination of iodide and iodate in seawater by Zhuo Huang; Kazuaki Ito; Andrei R. Timerbaev; Takeshi Hirokawa (pp. 1836-1841).
A capillary electrophoresis (CE) method was developed for the simple and highly-sensitive determination of iodine species in seawater. The proposed method is based on the on-capillary preconcentration of iodide and iodate using the principle of transient isotachophoresis (tITP) stacking, and direct UV detection of the separated species at 226 and 210 nm, respectively. The preconcentration procedure takes advantage of the electrokinetic introduction of the terminating ion [2-(N-morpholino)ethanesulfonate (MES)] into the capillary, that enables a longer tITP state. The appropriate conditions for the tITP step were optimized by varying the MES and sample injection time and the concentration of cetyltrimethylammonium chloride (CTAC). The latter component of the separation electrolyte (SE) was shown to strongly affect the migration and therefore the enrichment of iodide due to specific ion-association. The optimized separations were performed in 12.5 mM CTAC, 0.5 M NaCl (pH 2.4). Valid calibration is demonstrated in the range 3–60 μg L−1 iodide (R=0.9992) and 40–800 μg L−1 iodate (R=0.9994). The detection limits achieved were 0.23 μg L−1 (2 nM) for iodide and 10 μg L−1 (57 nM) for iodate. Such sensitivity and linearity thresholds allowed the reported tITP-CE system to be applied to direct speciation analysis of surface and seabed seawater. The comparison of CE results with those of an ion-chromatography (IC) technique proved that the method has acceptable accuracy.
Keywords: Iodine speciation; Seawater; Capillary electrophoresis; Preconcentration; Transient isotachophoresis
Determination of trace amounts of phosphate by flow-injection photometry by Sathrugnan Karthikeyan; Seigo Hashigaya; Tasuku Kajiya; Shizuko Hirata (pp. 1842-1846).
This paper describes a simple and rapid procedure for determination of traces of phosphate by means of molybdenum blue chemistry. The use of a cost-effective home-made flow cell with a long path length in combination with a light emitting diode (LED) and a photodiode (PD) is demonstrated as a simple absorbance detector for flow-injection analysis. In this method, a sample is injected into the carrier stream through an injection valve and mixed online with mixed reagent (a mixture of molybdate, bismuth, and ascorbic acid in sulfuric acid). The color intensity of the resulting association complex, molybdenum blue, is measured photometrically (λ max 875 nm). The proposed method can be used to detect phosphate in the range 0.02–4.0 mg L−1 and the precision of the proposed procedure is less than 5% at 0.1 mg L−1 phosphorus as phosphate. The method has been successfully applied to a variety of natural water samples.
Keywords: Phosphate; Home-made flow cell; Flow-injection; Photometry; Water analysis
Air sampling of organophosphate triesters using SPME under non-equilibrium conditions by Sindra Isetun; Ulrika Nilsson; Anders Colmsjö; Rolf Johansson (pp. 1847-1853).
Solid phase micro-extraction (SPME) was used to collect air samples of semi-volatile organophosphate triesters, a group of compounds that are commonly used as flame retardants/plasticisers and have therefore become ubiquitous indoor air pollutants. SPME is a simple sampling technique with several major advantages, including time-efficiency and low solvent consumption. Analyte losses also tend to be relatively low. In quantitative SPME, measurements are normally taken after the analyte has reached partitioning equilibrium between the fibre and the sample matrix. However, equilibrium sampling of semi-volatile compounds in air with SPME often takes several hours. Clearly, time-weighted average (TWA) sampling using SPME under non-equilibrium conditions could be considerably faster. So, in this study, the possibility of sampling organophosphate triesters under non-equilibrium conditions was tested. The most important variables proved to be the fibre coating and the air velocity during sampling. The highest uptake rate was obtained with polydimethylsiloxane (PDMS, 100 μm). The rate for this fibre was 150-fold higher than obtained with PDMS/DVB and Carbowax/DVB, both 65 μm. Contrary to theoretical expectations, the uptake rate appeared to be constant for all tested air velocities over the fibre surface >7 cm/s. These findings suggest that the uptake rate for non-equilibrium SPME sampling is independent of the sampling flow above this flow rate, which would considerably enhance the robustness and flexibility of the method. Applying this method for TWA sampling, with sampling periods of 1 h, detection limits lower than 2 ng/m3 for individual organophosphate esters were obtained.
Keywords: SPME; Non-equilibrium; TWA sampling; Air sampling; Organophosphate triesters
Optimization of solid-phase extraction procedure for determination of polychlorinated dibenzo-p-dioxins, polychlorinated dibenzofurans, and coplanar polychlorinated biphenyls in humic acid containing water by Hiroaki Otaka; Hisao Shimono; Shunji Hashimoto (pp. 1854-1860).
A solid-phase extraction (SPE) method was optimized for accurate determination of polychlorinated dibenzo-p-dioxins (PCDDs), polychlorinated dibenzofurans (PCDFs), and coplanar polychlorinated biphenyls (CoPCBs) in humic acid containing surface water. Recovery experiments using humic materials revealed that humic acids permit dioxins to pass through an octadecylsilica (C18) extraction disk by associating with them under weakly alkaline conditions. Acidification of the sample before percolation improved this otherwise insufficient recovery. The analysis of surface water acidified to pH 2 gave better recovery with surrogate standards and lower quantitative values for higher-chlorinated homologues than the sample at pH 9. In all samples, the native octachlorodibenzo-p-dioxin (OCDD) peak abundance showed no difference between at pH 2 and at pH 9, indicating overestimation of the quantitative value of the homologue at pH 9. Acidification of a humic acid containing water sample can avoid overestimation of higher-chlorinated congeners caused by insufficient recovery of their corresponding surrogates.
Keywords: Polychlorinated dibenzo-p-dioxins; Polychlorinated dibenzofurans; Coplanar polychlorinated biphenyls; Surface water; Solid-phase extraction; Humic substances
Comparison of different extraction techniques for the determination of chlorinated pesticides in animal feed by Marion Gfrerer; Shuo Chen; Ernst P. Lankmayr; Xie Quan; Fenglin Yang (pp. 1861-1867).
The performances of Soxhlet extraction, dive-in Soxhlet extraction, microwave-assisted extraction (MAE), accelerated solvent extraction (ASE), fluidized-bed extraction (FBE), and ultrasonic extraction (UE) for the analysis of organochlorine pesticides in animal feed have been investigated. ASE and MAE provided significantly better extraction efficiency than Soxhlet extraction. The concentrations were 126.7 and 114.8%, respectively, of the values obtained by classical Soxhlet extraction, whereas the results from FBE and dive-in Soxhlet were comparable with those from the standard Soxhlet procedure. The reproducibility of FBE was the best, with RSDs ranging from 0.3 to 3.9%. Under the investigated operation conditions UE was not efficient, with the recoveries of target compounds being about 50% less than Soxhlet. Additionally, the performances of Soxhlet, dive-in Soxhlet, MAE, ASE and FBE were validated by determination of the certified reference material BCR-115. The results from the extraction techniques were in good agreement with the certified values.
Keywords: Microwave-assisted extraction; Fluidized-bed extraction; Accelerated solvent extraction; Animal feed; Organochlorine pesticides
Kinetic method for acetylsalicylic acid determination based on its inhibitory effect upon the catalytic decomposition of H2O2 by Claudia Mureşanu; Lucian Copolovici (pp. 1868-1872).
The catalytic reaction of catalase was investigated, by means of a Clark oxygen sensor, in the presence of various concentrations of acetylsalicylic acid. Michaelis-Menten kinetic parameters were determined from Lineweaver-Burk plots, obtained in the absence and in the presence of the inhibitor. The inhibition pattern, suggested by the Lineweave-Burk plots, corresponds to a fully mixed inhibition mechanism. A kinetic method, based on the indicator reaction: % MathType!Translator!2!1!AMS LaTeX.tdl!TeX -- AMS-LaTeX! −4 mol/L, while the detection limit was 4.12×10−4 mol/L acetylsalicylic acid with a standard deviation of 2.1×10−5 mol/L.
Keywords: Acetylsalicylic acid; Catalase; Hydrogen peroxide; Inhibition; Kinetic methods
Combined biological and chemical assessment of estrogenic activities in wastewater treatment plant effluents
by Hans-Rudolf Aerni; Bernd Kobler; Barbara V. Rutishauser; Felix E. Wettstein; René Fischer; Walter Giger; Andreas Hungerbühler; M. Dolores Marazuela; Armin Peter; René Schönenberger; A. Christiane Vögeli; Marc J.-F. Suter; Rik I. L. Eggen (pp. 1873-1873).