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Analytical and Bioanalytical Chemistry (v.369, #6)
The state-of-the-art in the analysis of estrogenic mycotoxins in cereals by R. Krska; R. Josephs (pp. 469-476).
The increasing public awareness of chemicals that mimic or otherwise interfere with the activity of natural hormones – so-called endocrine disrupters– has also led to greater study of mycotoxins with estrogenic potential. The purpose of this paper is to introduce the topic of estrogenic mycotoxins and to discuss the state-of-the-art in the analysis of these substances in cereals, with special emphasis on zearalenone (ZON) as its most relevant representative. Because the use of immunoaffinity columns (IAC) followed by high-performance liquid chromatography with fluorescence detection (HPLC–FLD) and immunoassays are currently the most frequently used methods for the determination of ZON and its metabolites, these techniques are discussed in more detail. Recent papers, which have revealed the great potential of HPLC–MS(MS) for the simultaneous detection and identification of several estrogenic mycotoxins, are discussed. The performances of the state-of-the-art methods are finally compared by study of the results obtained in recent international intercomparison studies. On the one hand, these studies revealed the good performance of both chromatographic and antibody-based methods. On the other hand, the need for better means of external quality assurance measures, especially the availability of certified reference materials and certified standards, has clearly been demonstrated.
Nanosphere-antibody conjugates with releasable fluorescent probes by R. N. Thomas; C.-Y. Guo (pp. 477-482).
Surface-functionalized, probe-containing, polymeric nanospheres with diameters between 10 nm and 40 nm (depending on the probe) were used to provide a fluorescent endpoint for nonextractive immunoassay. The probes inside the nanospheres were lanthanoid ions. Methyl methacrylate was used as the monomer to reduce random adsorption of proteins onto the nanosphere surfaces. The acid-group surface functionalization allowed the nanospheres to be conjugated to the amine groups on the antibodies (IgG). The surfaces were further functionalized with alcohol and ester groups to improve the suspension characteristics of the nanospheres. As many as four probe ions may be quantified simultaneously, although only three with a single ligand. Co-measurement of four probes required a combination of two ligands. The intensity of the fluorescence produced by these complexes allows detection with a sensitivity equivalent to enzyme-linked immunoassay.
Detection of complement C1-inhibitor with a piezoelectric immunosensor by Li Liu; Jiming Hu; Leilei Wang; Lijia Liu; Xiaodong Zhou (pp. 483-485).
A novel piezoelectric immunosensor has been developed for the detection of human complement C1-inhibitor. Anti-C1-inhibitor antibody was immobilized onto the gold electrodes of a 9 MHz AT-cut piezoelectric crystal. Coating the crystal with polyethyleneimine adhesion, followed by a glutaraldehyde cross-linking method to immobilize antibody showed better results than the physical adsorption method with respect to sensitivity and reproducibility. Under the optimized experimental conditions, the sensor showed good response to the C1-inhibitor in the range from 2.0 × 10–8 to 1.2 × 10–6 g. Other proteins in human serum did not remarkably interfere with the detection. The crystals could be regenerated 5 times, when bound materials on the crystal surface were eluted by strong acid and strong alkali solution and subsequently cleaned in an ultrasonic cleaner.
A stable glucose biosensor prepared by co-immobilizing glucose oxidase into poly(p-chlorophenol) at a platinum electrode by Jing-Juan Xu; Xiao-Qiang Zhang; Zhi-Hao Yu; Hui-Qun Fang; Hong-Yuan Chen (pp. 486-490).
An amperometric glucose biosensor was successfully developed by electrochemical polymerization of p-chlorophenol (4-CP) at a Pt electrode in the presence of glucose oxidase. The amperometric response of this biosensor to hydrogen peroxide, formed as the product of enzymatic reaction, was measured at a potential of 0.6 V (vs. SCE) in phosphate buffer solution. The performances of sensors, prepared at different monomer concentrations and polymerization potentials, were investigated in detail. The biosensor prepared under optimal conditions had a linear response to glucose ranging from 2.5 × 10–4 to 1.5 × 10–2 mol L–1 with a correlation coefficient of 0.997 and a response time of less than 2 s. Substrate selectivity of the polymer-based enzyme electrode was tested for coexisting interferents such as uric acid and ascorbic acid, and no discernible response was observed. After 90 days, the response of the biosensor remained almost unchanged, indicating very good stability.
Advantages of the iridium permanent modifier in fast programs applied to trace-element analysis of plant samples by electrothermal atomic absorption spectrometry by Emilia Vassileva; Hervé Baeten; Michel Hoenig (pp. 491-495).
The application of a fast program combined with the advantages of the iridium permanent modifier is proposed for trace element analysis of plant samples by electrothermal atomic absorption spectrometry (ETAAS). For two volatile elements (Cd, Pb) and two mid-refractory elements (Cr, Ni) it was demonstrated that coating of the platform or of the tube atomization area with Ir is an efficient means of improving the accuracy and precision of results. A detailed study of interference from individual main matrix components and from composite plant matrices has confirmed the usefulness of the whole approach. The validity of the method has been confirmed by analysis of eight reference plant materials.
Lead determination in slurries of biological materials by ETAAS using a W-Rh permanent modifier by É. C. Lima; Fernando Barbosa Jr.; Francisco J. Krug (pp. 496-501).
A tungsten-rhodium coating on the integrated platform of a transversely heated graphite atomiser (THGA) was used as a permanent chemical modifier for the determination of lead in biological materials by slurry sampling in electrothermal atomic absorption spectrometry (ETAAS). Slurries were sonicated during 20 s before being delivered to the previously W-Rh treated platform. The number of particles of biological materials introduced into the atomiser for delivering 20 μL slurry aliquot ranged from 5,100 to 39,000. The permanent W-Rh modifier remained stable during approximately 300 analytical measurements when 20 μL of slurries containing up to 1.5% m/v were delivered into the atomiser. In addition, the permanent modifier increases the tube lifetime by approximately 100% when compared to untreated integrated platforms. Also, there is less decrease of sensitivity during the atomiser lifetime when compared with the conventional modifiers, resulting in a decreased need of re-calibration during routine analysis and consequently increasing the sample throughput. The atomiser lifetime was limited to the THGA wall durability, because the W-Rh treated platform was intact after more than 650 analytical firings in a medium containing up to 1.5% m/v slurry of biological material. The detection limit based on integrated absorbance was 20 ng g–1 Pb for 1.50% m/v slurries. Results from the determination of lead in slurries of biological materials using the W-Rh permanent modifier were in agreement with those obtained with digested solutions using Pd + Mg(NO3)2.
Multiresidue determination of organophosphorus and organochlorine pesticides in human biological fluids by capillary gas chromatography by E. Pitarch; F. J. López; R. Serrano; F. Hernández (pp. 502-509).
Two multiresidue analytical methods for the simultaneous determination of organophosphorus and organochlorine pesticides in human urine and serum samples are described. The first approach is based on liquid–liquid microextraction with dichloromethane, and the second uses solid-phase extraction with C18. In both methods, the extracts are analyzed by capillary gas chromatography using nitrogen-phosphorus detection (NPD) and electron-capture detection (ECD). Limits of detection of the overall procedure of analysis are at the low ng mL–1 level. Stability experiments have been performed with spiked urine and serum samples stored at 4 °C for 1 month. Finally, the solid-phase extraction procedure was applied to real-world samples. Quantification was performed by NPD or ECD, and peak identity was confirmed by use of mass-selective detection (MSD).
Speciation of butyltin compounds in marine sediments with headspace solid phase microextraction and gas chromatography – mass spectrometry by N. Cardellicchio; S. Giandomenico; A. Decataldo; A. Di Leo (pp. 510-515).
A method for the determination of organotin compounds (monobutyl = MBT, dibutyl = DBT, and tributyltin = TBT) in marine sediments by headspace Solid Phase Microextraction (SPME) has been developed. The analytical procedure involved 1) extraction of TBT, DBT and MBT from sediments with HCl and methanol mixture, 2) in situ derivatization with sodium tetraethylborate and 3) headspace SPME extraction using a fiber coated with poly(dimethylsiloxane). The derivatized organotin compounds were desorbed into the splitless injector and simultaneously analyzed by gas chromatography – mass spectrometry.The analytical method was optimized with respect to derivatization reaction and extraction conditions. The detection limits obtained for MBT, DBT and TBT ranged from 730 to 969 pg/g as Sn dry weight. Linear calibration curves were obtained for all analytes in the range of 30–1000 ng/L as Sn. Analysis of a standard reference sediment (CRM 462) demonstrates the suitability of this method for the determination of butyltin compounds in marine sediments. The application to the determination of TBT, DBT and MBT in a coastal marine sediment is shown.
Potential of microbore HPLC within a multiresidue method for the trace analysis of plant-protective substances in water by Elizabeth Olga Hochleitner; H. Malissa Jr (pp. 516-523).
The performance of microbore HPLC as a “measurement channel” within a true multiclass/multiresidue method for monitoring plant protectants in raw and potable water is demonstrated. The method has a modular design and consists of a non-selective sampling and preparation line generating 250 μL of an “extract” from a 100-mL water sample; this extract can be introduced to up to four measurement channels, as required by the analytical task. The microbore HPLC channel can be used to quantify 34 plant protectants in the 0.1 μg L–1 concentration range by use of diode-array detection at seven different wavelengths. A solvent change is necessary to link sample preparation to microbore HPLC; this uses 50 μL of the “extract” and is accomplished directly in an autosampler vial. Performance characteristics were evaluated for tap water spiked at 0.2 μg L–1. Average recoveries were between 65 and 100% and method detection limits were 0.07 μg L–1 or better. The ability to provide comparable and accurate results was proven by participation in an interlaboratory comparison trial. The procedure for preparing microbore columns from 750 μm i.d. PEEK tubing is described in detail to enable the reader to prepare his own columns. The reproducibility of this preparation procedure was proven by an analysis-of-variance test.
Determination of gaseous toluene diisocyanate by use of solid-phase microextraction with on-fibre derivatisation by Ramón Batlle; Anders Colmsjö; Ulrika Nilsson (pp. 524-529).
An SPME method was developed for sampling gaseous 2,4-toluene diisocyanate (2,4-TDI) involving derivatisation of the isocyanate by reacting with dibutylamine (DBA). The TDI-DBA derivative thus formed was determined by LC–MS–MS utilising atmospheric pressure chemical ionisation (APCI). As a first step, DBA was loaded onto a poly(dimethylsiloxane)/divinylbenzene (PDMS–DVB) fibre coating by direct vapour-phase extraction of a highly concentrated diethyl ether solution of DBA. The DBA-loaded fibre was then exposed to an artificially generated atmosphere of gaseous 2,4-TDI. The linearity of the method ranged from 52.8 to 3100 μg m–3 (6.8 to 400 ppbv) with a sampling time of 60 min. The proposed method has been applied to 2,4-TDI determination in an artificially generated dynamic standard atmosphere, yielding an approximate method detection limit (MDL) of 2 μg m–3 (0.25 ppbv). This concentration is one twentieth of the Occupational Safety and Health Administration (OSHA) 8-hour time-weighted average (TWA) exposure limit. The sampler with the PDMS–DVB-DBA coating was found to be stable and retains the required amount of DBA for at least 10 days, an important feature for sampling systems with potential in-situ applications.
A new spectrophotometric method for the determination of total and ferric iron in rain water at the ppb level by K. S. Patel; A. Shukla; A. Goswami; S. K. Chandavanshi; P. Hoffmann (pp. 530-534).
A new, simple, selective and sensitive spectrophotometric procedure for the on-site quantification of iron at nano-gram levels in atmospheric precipitations, i.e. rain as sample source is described. It is based on the color reaction of Fe3+ with SCN– ions in the presence of a cationic surfactant, i.e. cetylpyridinium chloride (CPC), in strong HCl solution, and subsequent extraction of the complex with N-octylacetamide into toluene or chloroform. The apparent molar absorptivity of the complex is 2.60 × 105 L mol–1 cm–1 at λmax = 480 nm at an enrichment factor (EF) of 10. The detection limit (causing higher absorbance than the sum of the blank absorbance (0.009) and 3 SD) is 5 ng mL–1 Fe. Ions commonly associated with iron did not interfere in the present method. The effect of analytical variables, i.e. amount and type of the reagents, acidity, solvent, temperature, dilution, etc., in the determination of iron are discussed. The validity of the present method is checked with GF-AAS. The method has been applied to the determination of iron at the ppb level in rain water samples.
Thermal lens studies of the reaction of iron(II) with 1,10-phenanthroline at the nanogram level by Valerii V. Chernysh; Mikhail Yu. Kononets; M. A. Proskurnin; Svetlana V. Pakhomova; Vsevolod V. Komissarov; Anna I. Zatsman (pp. 535-542).
The determination of iron(II) with 1,10-phenanthroline in aqueous solutions was carried out exemplarily by thermal lens spectrometry. The peculiarities of analytical reactions at the nanogram level of reactants can be studied using this method. Under the conditions of the competing reaction of ligand protonation, the overall stability constant for iron(II) chelate with 1,10-phenanthroline was determined at a level of n × 10–7 mol L–1, logβ 3 = 21.3 ± 0.1. The rates of formation and dissociation of iron(II) tris-(1,10-phenanthrolinate) at a level of n × 10–8 mol L–1 were found to be (2.05 ± 0.05) × 10–2 min–1 and (3.0 ± 0.1) × 10–3 min–1, respectively. The conditions for the determination of iron(II) with 1,10-phenanthroline by thermal lensing were reconsidered, and ascorbic acid was shown to be the best reducing agent, which provided minimum and reproducible sample pretreatment. Changes in the conditions at the nanogram level improved both the selectivity and sensitivity of determination. The optimum measurement conditions for thermal lensing were determined not only by the absorption of the analyte and reagents, but also by the background absorption of the solvent. The limits of detection and quantification of iron(II) at 488.0 nm (excitation beam power 140 mW) are 1 × 10–9 and 6 × 10–9 mol L–1, respectively; the reproducibility RSD for the range n × 10–8–n × 10–6 mol L–1 is 2–5%.
Extraction of iridium(IV) from hydrochloric acid media with crown ether in chloroform, and its determination by ICP–AES by Kazi Zakir Hossain; Cristina T. Camagong; Takaharu Honjo (pp. 543-545).
A new method for the quantitative extraction and determination of trace amounts of iridium from hydrochloric acid media has been established based on the formation of an ion-association complex of iridium hexachloro anion IrCl6 2– with dicyclohexyl-18-crown-6 (DC18C6) oxonium cation in chloroform, then determination by inductively coupled plasma atomic emission spectrometry (ICP–AES). The effect of various factors (solvent, acid concentration, crown ether, reagent concentration, shaking time, composition of the extracted species, foreign ions, etc.) on the extraction and back-extraction of iridium has been investigated. The procedure was used to determine traces of iridium in palladium chloride and rhodium chloride.
Applicability of micellar electrokinetic chromatography to the analysis of estrogens in water by Hiroya Harino; S. Tsunoi; Toshiyuki Sato; Minoru Tanaka (pp. 546-547).
Estrone, β-estradiol and ethynylestradiol spiked in water were extracted using solid-phase extraction (SPE) and then directly determined by micellar electrokinetic chromatography (MEKC) with online concentration (sweeping). A 350 mL original sample volume (10 nM each) was concentrated to 1 mL using SPE, and ca. 240 nL of this solution was injected onto an MEKC capillary column. After sweeping, the estrogen related compounds were detected using a commercial absorbance detection system with an LOD of 0.16–0.30 nM in the original sample.