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Analytical and Bioanalytical Chemistry (v.368, #7)
Fiber-in-tube solid-phase microextraction: a fibrous rigid-rod heterocyclic polymer as the extraction medium by Y. Saito; Y. Nakao; M. Imaizumi; T. Takeichi; Y. Kiso; K. Jinno (pp. 641-643).
A novel “fiber-in-tube” configuration has been applied to the extraction tube of solid phase microextraction (SPME), and the direct coupling of the extraction process to liquid chromatography (LC) has been accomplished for the analysis of n-butylphthalate in wastewater. By using this fiber-in-tube SPME/LC system the preconcentration factor for the phthalate was about 160 with 20 min extraction and no interference peak was observed in the chromatogram. The results also showed the potential applications of this fiber-in-tube SPME/LC for the analysis of sub-ppb level (i.e., lower than 1 ng/mL) of various organic analytes in aqueous sample matrix without a large solvent consumption during the preconcentration process.
Comparison of different excitation methods for X-ray spectral analysis: the case of synchrotron radiation by G. E. Gigante; B. Gonsior (pp. 644-648).
Different excitation means, protons, photons and electrons (PIXE, XRFA, and EPMA, respectively) have previously been compared with regard to the figures of merit, i.e. detection power, precision and accuracy. The aim in this article is to compare synchrotron radiation SR as another excitation method with the methods mentioned above. From this point of view the evaluation of (SR) was missing as an again independently optimized excitation method and was based as previously on practical problems of trace analysis, in this case on the determinations of traces in lead. The experiment has been performed with thick homogeneous samples of lead, the same samples already used in the former work, so that a direct comparison is possible. The calculation of the figures of merit is based on the measurements of the blank values and their relative standard deviation for the detection limit and on the random errors for the precision. Regarding the thick homogeneous target of lead XRFA still turns out to be the best method, whereas Synchrotron X-Ray Fluorescence SY-XRF compares favorably, at least for larger atomic numbers Z. Even PIXE is inferior to (SY-XRF) in the case of larger Z; when information on the lateral distribution of the elements is of interest, PIXE is indispensable.
Determination of Cd and Pb at μg/L levels by HHPN-beam injection flame furnace-AAS by J. Neira; H. Berndt (pp. 649-655).
Flame-heated tubes are widespread in flame-AAS, mainly for the determination of hydride-forming elements. Instead of the introduction of gaseous compounds liquids can also be introduced continuously in such an absorption cell. With the aid of an HPLC pump the liquid is forced through a very fine nozzle, generating an aerosol beam less than 0.5 mm in diameter. This beam travels a distance of 10 cm as a “free-flying aerosol jet” into the sample introduction hole of a metal tube furnace placed in the flame. Both introduction of the entire sample and the long residence time lead to a considerable improvement in power of detection. The detection limit for 100 μL samples amounts to 7 μg/L (Pb) and to 0. 2 μg/L (Cd), which means an increase in power of detection of between one and two orders of magnitude compared to conventional flame-AAS. The relative standard deviation (100 μL sample volume, N = 10) was found to be 1.3% (signal area) for 600 μg/L Pb and to be 1.5% (signal-area) for 15 μg/L Cd. RSD values from measurements in peak-height amounted to 2.2% (Pb) and to 1.7% (Cd).
Measurements for certification of chlortetracycline reference materials within the European Union Standards, Measurements and Testing programme by M. Juhel-Gaugain; J. D. G. McEvoy; L. A. VanGinkel (pp. 656-663).
The experimental design of a material certification programme is described. The matrix reference materials (RMs) comprised chlortetracycline (CTC)-containing and CTC-free lyophilised porcine liver, kidney and muscle produced under the European Commission’s Standards Measurements and Testing (SMT) programme. The aim of the certification programme was to determine accurately and precisely the concentration of CTC and 4-epi-chlortetracycline (epi-CTC) contained in the RMs. A multi-laboratory approach was used to certify analyte concentrations. Participants (n = 19) were instructed to strictly adhere to previously established guidelines. Following the examination of analytical performance criteria, statistical manipulation of results submitted by 13 laboratories, (6 withdrew) allowed an estimate to be made of the true value of the analyte content. The Nalimov test was used for detection of outlying results. The Cochran and Bartlett tests were employed for testing the homogeneity of variances. The normality of results distribution was tested according to the Kolmogorov-Smirnov-Lilliefors test. One-way analysis of variance (ANOVA) was employed to calculate the within and between-laboratory standard deviations, the overall mean and confidence interval for the CTC and epi-CTC content of each of the RMs. Certified values were within or very close to the target concentration ranges specified in the SMT contract. These studies have demonstrated the successful production and certification of CTC-containing and CTC-free porcine RMs.
Investigations on the water content of candidate reference material CRM 679 cabbage powder by S. Korhammer; H.-D. Isengard; N. Langer; E. Denzel; B. Markert; H. Muntau; R. Herzig; Ph. Quevauviller (pp. 664-668).
The determination of the residual water content by thermal methods and especially by Karl Fischer titration in a candidate reference material of the European Commission (candidate CRM 679 cabbage powder) is described and discussed.
Rapid simultaneous determination of four anthracene derivatives using a single non-linear variable-angle synchronous fluorescence spectrum by Wei Sui; Chun Wu; Yao Qun Li (pp. 669-675).
A rapid, simple and inexpensive spectrofluorimetric method has been developed for the simultaneous identification and quantification of anthracene (ANT), 9,10-dimethylanthracene (DIM), 2-aminoanthracene (AMI) and dibenz[ah]anthracene (DIB). A well-resolved spectrum for the mixture of these four compounds is obtained based on a single non-linear variable-angle synchronous scanning. The linear concentration ranges are 10–1000, 5–500, 50–1000 and 10–200 ng mL–1 for ANT, DIM, AMI and DIB, respectively, at λex/λem = 358/380, 399/408, 414/465 and 298/394 nm, respectively. The analyses are performed in cyclohexane. Recoveries of 90.0–111.0% in synthetic mixtures are obtained. The detection limits are 2.0 ng mL–1 for DIM, 2.7 ng mL–1 for ANT, 15.8 ng mL–1 for AMI and 4.2 ng mL–1 for DIB. The method has also been applied to several real water samples with satisfactory results.
The stability of non-ionic surfactants and linear alkylbenzene sulfonates in a water matrix and on solid-phase extraction cartridges by M. Petrović; D. Barceló (pp. 676-683).
The stability of nonylphenol ethoxylates (NPEO), alcohol ethoxylates (AEO), coconut diethanol amides (CDEA) and linear alkylbenzene sulfonates (LAS) in a water matrix and preconcentrated on SPE cartridges was studied. A stability study was carried out in a water matrix (spiked ground water and real-world waste water) comparing different pretreatment procedures (addition of sulfuric acid to pH = 3, preservation with 1% and 3% of formaldehyde). When stored in a water matrix serious qualitative and quantitative changes occurred in waste water during the period of time studied (30 days). The losses of C12–C14 alcohol ethoxylates ranged from 72% to 88% when the sample was preserved with acid and from 17% to 86% when the sample was preserved with formaldehyde (3%). Simultaneously, an enrichment of the shorter alkyl chain homologues (C7EO and C10EO) was observed. The losses of NPEO were from 45% (sample preserved by acidification or by addition of 3% of formaldehyde) to 85% (sample preserved with 1% of formaldehyde). Additionally, an increase in concentration of polyethylene glycols (PEGs) and formation of different acidic forms, such as monocarboxylated (MCPEGs) and dicarboxylated polyethylene glycols (DCPEGs) were observed. The stability of surfactants preconcentrated on SPE cartridges was studied as a function of storage time and storage conditions (room temperature, 4 °C and –20 °C). The results indicate that disposable SPE cartridges can be recommended for the stabilization of non-ionic surfactants and LAS. Storage at –20 °C is feasible for long periods (up to ¶3 months for ground water and up to 2 months for waste water), while storage at 4 °C can be recommended for a maximum of 1 month. When cartridges were kept at –20 °C the losses of AEOs (n = 12, 13 and 14), preconcentrated from waste water, ranged from 17 to 29% (after 60 days) and other compounds suffered small losses (maximum of 14% for C13LAS). At room temperature, after 7 days, the losses were less than 11%, indicating that shipping of samples by mail can be done without any special requirements.
Microwave assisted methodology for the determination of organic pollutants in organic municipal wastes and soils: extraction of polychlorinated biphenyls using heat transformer disks by R.-A. Düring; St. Gäth (pp. 684-688).
Known benefits of microwave assisted extraction (MAE) of polychlorinated biphenyls (PCB) from solid matrices could be proven by the described approach using n-heptane as solely applied extraction solvent. Heat transfer within the extraction vessels was achieved by heat transformer disks which absorb microwave energy and transform it into heat rapidly and independently of the temperature present in the sample-solvent system. Disadvantageous co-extraction of polar substances could be ruled out and thus clean-up of the samples was simplified and sufficient for subsequent GC-MS analysis. Comparison with other extraction techniques confirmed the efficiency of this method also for aged samples.
Characterization of aquatic humic substances and their metal complexes by immobilized metal-chelate affinity chromatography on iron(III)-loaded ion exchangers by P. Burba; B. Jakubowski; R. Kuckuk; K. Küllmer; K. G. Heumann (pp. 689-696).
The analytical fractionation of aquatic humic substances (HS) by means of immobilized metal-chelate affinity chromatography (IMAC) on metal-loaded chelating ion exchangers is described. The cellulose HYPHAN, loaded with different trivalent ions, and the chelate exchanger Chelex 100, loaded to 90% of its capacity with Fe(III), were used. The cellulose HYPHAN, loaded with 2% Fe(III), resulted in HS distribution coefficients Kd of up to 103.7 mL/g at pH 4.0 continuously decreasing down to 101.5 at pH 12, which were appropriate for HS fractionation by a pH-depending chromatographic procedure. Similar distribution coefficients Kd were obtained for HS sorption onto Fe(III)-loaded Chelex 100. On the basis of Fe-loaded HYPHAN both, a low-pressure and high-pressure IMAC technique, were developed for the fractionation of dissolved HS applying a buffer-based pH gradient for their gradual elution between pH 4.0 and 12.0. By coupling the Chelex 100 column under high-pressure conditions with an inductively coupled plasma mass spectrometer an on-line characterization of HS metal species could be achieved. Using these fractionation procedures a number of reference HS were characterized. Accordingly, the HA (humic acids) and FA (fulvic acids) studied could be discriminated into up to 6 fractions by applying cellulose HYPHAN, significantly differing in their Cu(II) complexation capacity but hardly in their substructures assessed by conventional FTIR. In the case of using Chelex 100 exchanger resin two major UV active HS fractions were obtained, which significantly differ in their complexation properties for Cu(II) and Pb(II), respectively.
Rapid determination of PAHs in soil samples by HPLC with fluorimetric detection following sonication extraction by M. N. Kayali-Sayadi; S. Rubio-Barroso; C. A. Díaz-Díaz; L. M. Polo-Díez (pp. 697-701).
A rapid method for the determination of PAHs in soil samples based on their extraction with methylene chloride by sonication and subsequent separation by HPLC with fluorimetric detection is proposed. A Hypersil Green PAH column was used with a gradient of acetonitrile/water as the mobile phase, together with a program of nine excitation and emission wavelength pairs. Recoveries were in the range 70–98%, except for acenaphthene and naphthalene, at concentration levels 1.08–442 μg/kg with relative standard deviations in the range 2–15% (n = 4). Total PAHs found in soil samples were in the range 15–282 μg/kg. The results were compared with those obtained by applying the 3540 EPA method for two samples.
Extraction of antimony and arsenic from fresh and freeze-dried plant samples as determined by HG-AAS by M. Krachler; H. Emons (pp. 702-707).
Six extraction media (acetic acid, EDTA, tetrabutylammonium hydroxide, NaOH, MeOH/H2O, acetonitrile/H2O) were tested for their ability to extract antimony (Sb) and arsenic (As) from freeze-dried poplar leaves, pine shoots and spruce shoots, as well as from a peat matrix. Additionally, the extraction efficiency of Sb and As in fresh and freeze-dried elder leaves and poplar leaves was compared. Total concentrations of Sb and As of aliquots (∼220 mg) of the freeze-dried samples were analysed by flow injection hydride generation atomic absorption spectrometry (FI-HG-AAS) after open vessel digestion with adequate mixtures of nitric, sulfuric, hydrochloric, and perchloric acid. Three reference materials GBW 07602 Bush Branches and Leaves, GBW 07604 Poplar Leaves, and SRM 1575 Pine Needles were analysed with every batch of samples to ensure the accuracy and precision of the applied analytical procedures. The use of hydrofluoric acid in the digestion mixture leads to distinctly lower As values (down to 40%) than actual concentrations in the investigated plant materials. Extraction efficiencies were generally low and lower for Sb than for As. Solutions of 0.66 mol L–1 NaOH liberated highest amounts of Sb with ∼10% for poplar leaves, and ∼19% each for pine shoots and spruce shoots. Distinctly higher concentrations of As in NaOH extracts of poplar leaves (22%), pine shoots (32%), and spruce shoots (36%) were quantified. Extraction experiments resulted in yields of 7–9% from fresh elder and poplar leaves, respectively, and 8–13% for freeze-dried samples for Sb. The corresponding values for As were 10–35% for the fresh material and 7–37% for the freeze-dried samples.
High resolution inductively coupled plasma mass spectrometry (HR-ICPMS) determination and multivariate evaluation of 10 trace elements in mussels from 7 sites in Limfjorden, Denmark by I. E. Bechmann; S. Stürup; L. V. Kristensen (pp. 708-714).
The contents of V, Cr, Co, Ni, Cu, Ga, Rb, Cd, Ba, and Pb in the soft tissue of blue mussel (Mytilus edulis) were determined by a high resolution inductively coupled plasma mass spectrometry (HR-ICPMS) method. Sample digestions were performed in closed microwave vessels using nitric acid and hydrogen peroxide. Using HR-ICPMS it is possible to resolve the analytical peaks from otherwise interfering polyatomic ions with a mass resolution setting of 4000 (Cr, Ni, Cu). The proposed method was validated using a mussel tissue reference material (NIST SRM 2974). The proposed method was applied to real samples of blue mussel from seven sites in the inlet “Limfjorden”, Denmark, and the levels of trace elements found were compared with the levels found in an earlier study. For the mussel samples large inter-regional differences in trace element concentrations in the tissues were recorded. The mussels from the different sites could be separated using principal component analysis (PCA). Comparison with the levels of trace elements in mussels found in 1982 showed that the trace elemental contamination has increased during the last 15 years. From the data obtained, mussel tissue appears to be good bio-indicator for identification of coastal areas exposed to metallic contaminants.
Microdetermination of proteins using m-carboxychlorophosphonazo as detection probe by enhanced resonance light scattering spectroscopy by Qianfeng Li; Xingguo Chen; Hongyi Zhang; Chunxia Xue; Yuquan Fan; Zhide Hu (pp. 715-719).
Proteins can be determined using a common spectrofluorometer to detect the intensity of resonance light scattering (RLS). Under acidic conditions, the reaction between m-carboxychlorophosphonazo (CPA-mK) and proteins enhances the weak light scattering of CPA-mK drastically. This enhanced intensity is proportional to the concentration of proteins. The linear ranges for human serum albumin are 0.5–35.0 μg/mL, with detection limits of 0.104 μg/mL. The method yields results comparable to those of the calorimetric method using Coomassie Brilliant Blue G-250 (CBB) with relative standard deviations of 0.72–2.10% (n = 10). There is almost no interference by amino acids and most of the metal ions.
Voltammetric trace analysis of DNA and RNA by S. Reher; Y. Lepka; G. Schwedt (pp. 720-726).
A voltammetric determination of DNA/RNA is described. The new aspect is the use of the extracellular endonuclease Serratia marcescens in the sample preparation. Using this enzyme it is possible to determine DNA/RNA with a detection limit of 2–5 pg/mL. This satisfies the requirements of the WHO and the FDA.
Calibrated nanoinjections of mercury vapor by M. Vasjari; V. M. Mirsky (pp. 727-729).
A simple technique for the calibration of mercury vapor chemosensors is described. It is based on a reductive deposition of a well-defined quantity of mercury (0) onto gold wire followed by thermal evaporation of the mercury into the sensor cell. The quantity of mercury on the gold wire was measured electrochemically by oxidation before and after heating, as well as after storage under different conditions. It is shown that the technique can be used for calibrated injections of nanogram quantities of mercury. The approach was applied to test the performance of ultrasensitive mercury chemoresistors.
A new application of humic substances: activation of supports for invertase immobilization by A. H. Rosa; A. A. Vicente; J. C. Rocha; H. C. Trevisan (pp. 730-733).
Invertase was immobilized on aminopropyl silica (APTS-SiO2) activated with humic substances (APTS-SiO2-HS) and on aminopropyl silica activated with glutaraldehyde (APTS-SiO2-GA). The resulting activity of both systems was compared. Humic substances (HS) used for the activation of the silica were extracted from soil of Cananéia, São Paulo State, Brazil, according to the procedure recommended by the International Humic Substances Society. Activity was determined by measuring the rate of formation of reduced sugars using the reaction with dinitrosalicylic acid (DNS). The amount of HS bound on the APTS-SiO2 was equal to 50 mg. The maximum amount of invertase immobilized on APTS-SiO2-HS was 15200 U/g while in the system APTS-SiO2-GA it was 13400 U/g. The experimental enzymatic activity was 3700 and 3300 U/g, for the systems APTS-SiO2-HS and APTS-SiO2-GA, respectively. Considering the increased amount and activity of immobilized enzyme compared with the glutaraldehyde method, it was concluded that this technique opens a new perspective in the preparation of supports for enzyme immobilization employing humic substances.
Lead in micro-samples of whole blood by Rhenium-cup in-torch vaporization-inductively coupled plasma-atomic emission spectrometry (ITV-ICP-AES) by W. Vander Wilp; V. Karanassios (pp. 734-736).
A method is described for screening of lead in diluted micro-samples of whole blood by a Re-cup, in-torch vaporization (ITV) sample introduction system for inductively coupled plasma-atomic emission spectrometry (ICP-AES). The method required minimum sample preparation. For example, blood was diluted with water and Triton X-100 in 0.5% HNO3 and, 5 μL were deposited on the Re-cup of the ITV sample introduction system. Samples were dried and charred in-situ prior to vaporization. Levels 1, 2, 3 and 4 (Pb concentration: 4.04, 10.3, 20.59 and 39.36 μg/dL) of NIST Standard Reference Material 955b ‘lead in bovine blood’ were used to test accuracy and precision. Accuracy was acceptable and precision was below 10% for levels 2–4 and 15% for level 1.