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Analytica Chimica Acta (v.622, #1-2)
Preparation and characterization of superporous agarose–reticulated vitreous carbon electrodes as platforms for electrochemical bioassays by Ashwin K. Rao; Stephen E. Creager (pp. 1-10).
Three-dimensional flow-through electrodes were fabricated using superporous agarose (SPA) and reticulated vitreous carbon (RVC) composite materials that were suitable as a platform for sandwich assays. These SPA–RVC composite electrodes were fabricated by fitting a SPA–RVC composite cylinder inside a graphite tube and subsequently fixing the graphite tube onto a polypropylene micropipette tip. The electrode design allows for ease in reagent/washing steps involved in sandwich assay protocols and could easily be made portable. The electrode materials were characterized with respect to pore-size distribution, total free volume, ligament and bulk densities of the RVC, and physical structural characteristics. Coulometric detection of redox molecules such as K3Fe(CN)6 and 4-aminophenol was possible using SPA–RVC electrodes by the trapping of these redox molecules inside the SPA–RVC electrodes. Avidin affinity molecules were covalently immobilized onto the SPA matrix inside the RVC electrodes by periodate-activation followed by reductive amination. The amount of avidin immobilized inside the SPA–RVC electrodes was (5±0.06)×10−11mol, which was determined by saturating the avidin sites with biotinylated fluorescein (b-fluo) and subsequently determining the amount of immobilized b-fluo via a standard addition method using fluorescence spectroscopy. Non-specific binding of labeled enzymes such as biotinylated alkaline phosphatase (b-ALP) onto the SPA–RVC electrodes without avidin capture sites was determined to be less than 1% compared to the specific binding of b-ALP on avidinylated SPA–RVC electrodes.
Keywords: Reticulated vitreous carbon; Superporous agarose; Flow-through electrodes; Sandwich assays
Role of carbon nanotubes in electroanalytical chemistry by Lourdes Agüí; Paloma Yáñez-Sedeño; José M. Pingarrón (pp. 11-47).
This review covers recent advances in the development of new designs of electrochemical sensors and biosensors that make use of electrode surfaces modification with carbon nanotubes. Applications based on carbon nanotubes-driven electrocatalytic effects, and the construction and analytical usefulness of new hybrid materials with polymers or other nanomaterials will be treated. Moreover, electrochemical detection using carbon nanotubes-modified electrodes as detecting systems in separation techniques such as high performance liquid chromatography (HPLC) or capillary electrophoresis (CE) will be also considered. Finally, the preparation of electrochemical biosensors, including enzyme electrodes, immunosensors and DNA biosensors, in which carbon nanotubes play a significant role in their sensing performance will be separately considered.
Keywords: Electroanalytical chemistry; Carbon nanotubes; Modified electrodes; Electrochemical sensors; Electrochemical biosensors
Role of molecularly imprinted polymers for selective determination of environmental pollutants—A review by Valérie Pichon; Florence Chapuis-Hugon (pp. 48-61).
The molecularly imprinted polymers (MIPs) are synthetic polymers possessing specific cavities designed for a target molecule. By a mechanism of molecular recognition, the MIPs are used as selective tools for the development of various analytical techniques such as liquid chromatography, capillary electrochromatography, solid-phase extraction (SPE), binding assays and biosensors. This review describes the application of MIPs to the determination of environmental pollutants in these different analytical approaches with a special emphasis on their potential as selective SPE sorbent for the selective extraction of target analytes from complex matrices.
Keywords: Molecularly imprinted polymer; Solid-phase extraction; Separation; Pseudo-immunoassay; Sensors; Environmental analysis
Speciation analysis of mercury in seawater from the lagoon of Venice by on-line pre-concentration HPLC–ICP-MS by W.R.L. Cairns; M. Ranaldo; R. Hennebelle; C. Turetta; G. Capodaglio; C.F. Ferrari; Aurélien Dommergue; P. Cescon; C. Barbante (pp. 62-69).
A method based on the coupling of HPLC with ICP-MS with an on-line pre-concentration micro-column has been developed for the analysis of inorganic and methyl mercury in the dissolved phase of natural waters. This method allows the rapid pre-concentration and matrix removal of interferences in complex matrices such as seawater with minimal sampling handling. Detection limits of 0.07ngL−1 for inorganic mercury and 0.02ngL−1 for methyl mercury have been achieved allowing the determination of inorganic mercury and methyl mercury in filtered seawater from the Venice lagoon. Good accuracy and reproducibility was demonstrated by the repeat analysis of the certified reference material BCR-579 coastal seawater. The developed HPLC separation was shown to be also suitable for the determination of methyl mercury in extracts of the particulate phase.
Keywords: Mercury; Speciation; Analysis; High Performance Liquid Chromatography; Inductively coupled plasma-mass spectrometry
Investigation of DGT as a metal speciation technique for municipal wastes and aqueous mine effluents by Tahir Yapici; Ismail I. Fasfous; John Murimboh; Chuni L. Chakrabarti (pp. 70-76).
This paper reports the results of an investigation on the performance of the Diffusive Gradient in Thin Films (DGT) Technique in speciation of metals in aqueous samples of municipal wastes and mine effluents. The DGT was assessed regarding its suitability for in situ determination of metal speciation in municipal wastes and aqueous mine effluents. As the thickness of the diffusive gel layer of the DGT was increased to 0.40, 0.80, and 1.60mm, a decrease in the amount of accumulated metal mass was observed for most of the metals studied in all the effluent samples. However, the results were different from one field-study site to another. Effect of kinetics also was observed in the amount of accumulated metal mass by the DGT. The computer speciation code, Windermere Humic Aqueous Model (WHAM VI), was used to predict the metal speciation of Cd, Cu, Ni, Pb, Co, and Zn, and WHAM predictions were compared with those of the experimentally determined metal speciation by the DGT technique (free and labile metal ions). This comparison showed good similarities between the theoretically predicted WHAM VI values and the experimentally measured values by DGT. The DGT technique was found to be simple and useful for investigating chemical speciation of trace metals in aqueous samples of municipal wastes and aqueous mine effluents.
Keywords: Diffusive Gradient in Thin Film Technique; Municipal wastes; Aqueous mine effluents; Trace metals; Diffusive gel layer thicknesses
Multielemental determination in breast cancerous and non-cancerous biopsies by inductively coupled plasma-mass spectrometry following small volume microwave-assisted digestion by J. Millos; M. Costas-Rodríguez; I. Lavilla; C. Bendicho (pp. 77-84).
A microwave-assisted digestion method amenable to analysis of small size biological samples (<30mg dry mass) has been optimized for determining twelve elements (Ag, As, Cd, Co, Cu, Cr, Mn, Mo, Ni, Pb, Se and Zn) by inductively coupled plasma-mass spectrometry (ICP-MS) in breast cancerous and non-cancerous biopsies. The use of three small volume PTFE closed vials (6-mL capacity) placed inside a conventional microwave vessel allows to drastically diminishing the volume of acid needed for digestion. A Plackett–Burman experimental design was used to evaluate the robustness of the digestion procedure. Effects of nitric acid volume, need for predigestion step, microwave power and digestion time were assessed. No significant effects were found, the digestion method being robust enough to be recommended for a routine practice. The method was successfully validated against CRM BCR 185 (bovine liver), CRM NRCC TORT-2 (lobster hepatopancreas), CRM NRCC DORM-2 (dogfish muscle) and CRM NRCC DOLT-2 (dogfish liver). Procedural detection limits ranged from 0.54 to 40ngg−1. Within-batch precision values were less than 3%, whereas between-batch precision values were in the range 2–11%. Forty-seven biopsies from thirty-nine women were analyzed: 20 samples corresponding to mammoplasties from healthy women and 27 samples from patients suffering from cancer pathology, 19 of which corresponded to tumour and 8 to adjacent normal tissue. After applying parametric and non-parametric statistical tests, a significant accumulation of Cu, Mn, Zn and Se in cancerous tissues was demonstrated.
Keywords: Breast biopsies; Trace elements; Inductively coupled plasma-mass spectrometry; Small volume microwave digestions
Multivariate range modeling, a new technique for multivariate class modeling by M. Forina; P. Oliveri; M. Casale; S. Lanteri (pp. 85-93).
MRM, multivariate range modeling, is based on models built as parallelepipeds in the space of the original variables and/or of discriminant variables as those of linear discriminant analysis. The ranges of these variables define the boundary of the model. The ranges are increased by a “tolerance” factor to take into account the uncertainty of their estimate.MRM is compared with UNEQ (the modeling technique based on the hypothesis of multivariate normal distribution) and with SIMCA (based on principal components) by means of the sensitivities and specificities of the models, the estimates of type I (sensitivity) and II error rates (specificity) evaluated both with the final model built with all the available objects and by means of cross validation. UNEQ and SIMCA models were obtained with the usual critical significance value of 5% and with the model forced to accept all the objects of the modeled category.The performance parameters of the class models are critically discussed focusing on their uncertainty.
Keywords: Chemometrics; UNEQ; SIMCA
On line photochemically induced excitation–emission-kinetic four-way data by A. Jiménez Girón; I. Durán-Merás; A. Espinosa-Mansilla; A. Muñoz de la Peña; F. Cañada Cañada; A.C. Olivieri (pp. 94-103).
The determination of folic acid and its two main serum metabolites, 5-methyltetrahydrofolic acid and tetrahydrofolic acid, has been accomplished using four-way data modelled by the third-order multivariate calibration methods unfolded and N-dimensional partial least-squares (U-PLS and N-PLS), in combination with the separate procedure known as residual trilinearization (RTL). The four-way data were acquired by following the photochemical reaction of these compounds by on line irradiation with a UV lamp. The excitation–emission matrices (EEMs) were recorded as a function of the irradiation time, using a fast scanning spectrofluorimeter. The method achieves selectivity from the different rates at which the corresponding photoproducts of the folic acid derivatives are formed and degraded. Several N-dimensional chemometric algorithms were used and the method was applied to the determination of these compounds in serum samples. The best algorithms to perform the multivariate calibration were U-PLS and N-PLS in combination with the separate residual trilinearization procedure, achieving the second-order advantage. The approach allows minimizing or eliminating traditionally time-consuming sample pre-treatments and can facilitate quantifying an analyte in its native environment.
Keywords: Folic acid; Tetrahydrofolic acid; 5-Methyltetrahydrofolic acid; Photochemically induced fluorescence; Four-way data; Unfolded partial least-squares/residual trilinearization; N; -Dimensional partial least-squares/residual trilinearization
Label-free detection of DNA hybridization based on poly(indole-5-carboxylic acid) conducting polymer by Xuemei Li; Jianping Xia; Shusheng Zhang (pp. 104-110).
An electrochemical method to directly detect DNA hybridization was developed on the basis of a new conductive polymer, which was polymerized on the glassy carbon electrode with an indole monomer having a carboxyl group, indole-5-carboxylic acid (ICA). Hybridization with complementary, non-complementary and one-base mismatched DNA targets was studied by cyclic voltammetry (CV). Results showed a significant decrease in the current upon addition of complementary target. The change in peak current that was used as an index of sensor response was found to be linear with target concentration in the range of 3.34×10−9 to 1.06×10−8M. The detection limit was 1.0nM.
Keywords: Electrochemical DNA sensor; Label-free detection; Poly(indole-5-carboxylic acid); Hybridization
Disposable mercury-free cell-on-a-chip devices with integrated microfabricated electrodes for the determination of trace nickel(II) by adsorptive stripping voltammetry by Christos Kokkinos; Anastasios Economou; Ioannis Raptis; Thanassis Speliotis (pp. 111-118).
This work reports the fabrication of disposable three-electrode cells with integrated sputtered metal-film electrodes. The working electrode was a bismuth-film electrode (BiFE) while the reference and counter electrodes were made of Ag and Pt, respectively. The deposition of the metal layers was carried out by sputtering of the respective metals on a silicon substrate while the exact geometry of the electrodes was defined via a metal mask placed on the substrate during the deposition process. Initially, the electrodes were characterised by cyclic voltammetry. The utility of these devices was tested for the trace determination of Ni(II) by square wave adsorptive stripping voltammetry (SWAdSV) after complexation with dimethylglyoxime (DMG). The experimental variables (the presence of oxygen, the DMG concentration, the preconcentration potential, the accumulation time and the SW parameters), as well as potential interferences, were investigated. Using the selected conditions, the 3 σ limit of detection was 100ngL−1 for Ni(II) (for 90s of preconcentration) and the relative standard deviation for Ni(II) was 2.3% at the 10μgL−1 level ( n=8). Finally, the method was applied to the determination of Ni(II) in a certified river water sample.
Keywords: Nickel(II); Square-wave adsorptive stripping voltammetry; Bismuth-film electrode; Disposable sensors; Sputtered electrodes; Microfabrication
Electrogenerated chemiluminescence reaction of tris(2,2′-bipyridine)ruthenium(II) with 2,5-dimethylthiophene as co-reactant in aqueous solution by Hitoshi Kodamatani; Yu Komatsu; Shigeo Yamazaki; Keiitsu Saito (pp. 119-125).
A novel effective co-reactant for electrogenerated chemiluminescence (ECL) of Ru(bpy)32+ has been found. α-Position-dialkylated thiophene derivatives such as 2,5-dimethylthiophene (DMT) could be used as a co-reactant for Ru(bpy)32+ ECL. The reaction mechanism of the Ru(bpy)32+/DMT system was proposed on the basis of the identification of the reaction product, the relationship between the molecular structure and the chemiluminescent intensity, and the electrochemical study. The obtained reaction mechanism was similar to that of the Ru(bpy)32+/aliphatic tertiary amine system. Based on these results, the preliminary studies of the Ru(bpy)32+ ECL detection system using DMT as a co-reactant were performed. Under the optimal ECL conditions, the plot of ECL intensity versus the concentration of Ru(bpy)32+ was linear over the concentration range 1.0×10−8 to 1.5×10−7M (determination coefficient=0.9996).
Keywords: Electrogenerated chemiluminescence; Tris(2,2′-bipyridine)ruthenium(II); 2,5-Dimethylthiophene; Tri-; n; -propylamine
Evaluation of the physiologically based extraction test as an indicator of metal toxicity in mussel tissue by P. Navarro; G. Arana; N. Etxebarria; J.R. Dean (pp. 126-132).
In order to estimate the bioaccessibility of metals from mussel tissues, an in vitro physiologically based extraction test was applied to simulate the human gastrointestinal conditions. The samples were subjected to human body temperature, and Ag, Co, Cr, Cu, Mn, Ni, Pb and Sn were sequentially extracted with simulated gastric solution, followed by extraction with a simulated intestinal solution. Both gastric and intestinal extracted solutions and microwave-digested residue were analysed by ICP-MS. The procedure was applied to a certified reference material NIST 2977 (mussel tissue) to prove the accuracy of the method. Some mussel tissue samples from Northern Spain were subjected to this procedure to determine their metal content and their metal oral bioaccessibility.
Keywords: Mussel; Physiologically based extraction test; Metal toxicity; Inductively coupled plasma-mass spectrometer
Development and application of the diffusive gradients in thin films technique for the measurement of total dissolved inorganic arsenic in waters by Jared G. Panther; Kathryn P. Stillwell; Kipton J. Powell; Alison J. Downard (pp. 133-142).
The diffusive gradients in thin films (DGT) technique, utilizing an iron-hydroxide adsorbent, has been investigated for the in situ accumulation of total dissolved inorganic As in natural waters. Diffusion coefficients of the inorganic AsV and AsIII species in the polyacrylamide gel were measured using a diffusion cell and DGT devices and a variety of factors that may affect the adsorption of the As species to the iron-hydroxide adsorbent, or the diffusion of the individual As species, were investigated. Under conditions commonly encountered in environmental samples, solution pH and the presence of anions, cations, fulvic acid, FeIII–fulvic acid complexes and colloidal iron-hydroxide were demonstrated not to affect uptake of dissolved As. To evaluate DGT as a method for accumulation and pre-concentration of total dissolved inorganic As in natural waters, DGT was applied to two well waters and a river water that was spiked with As. For each sample, the concentration obtained with use of DGT followed by measurement by hydride generation atomic absorption spectrometry with a Pd modifier (HG-AAS) was compared with the concentration of As measured directly by HG-AAS. The results confirmed that DGT is a reliable method for pre-concentration of total dissolved As.
Keywords: Iron-hydroxide adsorbent; Arsenate; Arsenite; Diffusion coefficients; Natural water
A simple microfluidic chlorine gas sensor based on gas–liquid chemiluminescence of luminol-chlorine system by Zhao-Xin Gao; Hai-Fang Li; Jiangjiang Liu; Jin-Ming Lin (pp. 143-149).
In this work, a microfluidic chlorine gas sensor based on gas–liquid interface absorption and chemiluminescence detection was described. The liquid chemiluminescence reagent-alkaline luminol solution can be stably sandwiched between two convex halves of a microchannel by surface tension. When chlorine gas was introduced into the micro device, it was dissolved into the interfacial luminol solution and transferred to ClO−, and simultaneously luminol was excited and chemiluminescence emitted. The emitted chemiluminescence light was perpendicularly detected by a photomultiplier tube on a certain detection region. The remarkable advantage of the detection system is that both adsorption and detection were carried out at the gas–liquid interface, which avoids the appearance of bubbles. The whole analytical cycle including filling CL reagent, sample injection, CL detection and emptying the device was as short as 30s. The linear concentration range of chlorine gas detection with direct introduction of sample method is from 0.5 to 478ppm. The detection limit of this method is 0.2ppm for standard chlorine gas and the relative standard deviation of five determinations of 3.19ppm spiked chlorine sample was 5.2%.
Keywords: Microfluidic device; Gas sensor; Chlorine; Gas–liquid chemiluminescence
Automated on-line column-switching HPLC-MS/MS method with peak focusing for measuring parabens, triclosan, and other environmental phenols in human milk by Xiaoyun Ye; Amber M. Bishop; Larry L. Needham; Antonia M. Calafat (pp. 150-156).
Parabens (esters of p-hydroxybenzoic acid) and triclosan are widely used as preservatives and antimicrobial agents, respectively, in personal care products, pharmaceuticals, and food processing. Because of their widespread use and potential risk to human health, assessing human exposure to these compounds in breastfed infants is of interest. We developed a sensitive method, using a unique on-line solid-phase extraction-high performance liquid chromatography-tandem mass spectrometry system with peak focusing feature, to measure in human milk the concentrations of five parabens (methyl-, ethyl-, propyl-, butyl-, and benzyl parabens), triclosan, and six other environmental phenols: bisphenol A (BPA); ortho-phenylphenol (OPP); 2,4-dichlorophenol; 2,5-dichlorophenol; 2,4,5-trichlorophenol; and 2-hydroxy-4-methoxybenzophenone (BP-3). The method, validated by use of breast milk pooled samples, shows good reproducibility (inter-day coefficient of variations ranging from 3.5% to 16.3%) and accuracy (spiked recoveries ranging from 84% to 119% at four spiking levels). The detection limits for most of the analytes are below 1ngmL−1 in 100μL of milk. We tested the usefulness of the method by measuring the concentrations of these twelve compounds in four human milk samples. We detected methyl paraben, propyl paraben, triclosan, BPA, OPP, and BP-3 in some of the samples tested. The free species of these compounds appear to be the most prevalent in milk. Nevertheless, to demonstrate the utility of these measures for exposure and risk assessment purposes, additional data about sampling and storage of the milk, and on the stability of the analytes in milk, are needed.
Keywords: Parabens; Triclosan; Milk; HPLC-MS/MS; Phenols
Enantiomeric discrimination of 1,1′-binaphthol by room temperature phosphorimetry using γ-cyclodextrin as chiral selector by Xiao Hua Zhang; Yu Wang; Wei Jun Jin (pp. 157-162).
In the presence of a small amount of 1,2-dibromopropane (1,2-DBP), 1,1′-binaphthol (BINOL) displays strong room temperature phosphorescence in γ-cyclodextrin (γ-CD) solution without deoxygenation. The phosphorescence intensity as well as the phosphorescence lifetime of ( S)-BINOL is greater than that of ( R)-BINOL, indicating a distinct chiral discrimination of γ-CD toward this pair of enantiomers. Both ( R)-BINOL and ( S)-BINOL exhibit a double exponential phosphorescence decay with lifetimes of 5.89ms and 17.3ms for ( R)-BINOL and 7.58ms and 23.6ms for ( S)-BINOL, respectively. The association constant obtained for ( S)-BINOL/γ-CD/1,2-DBP ternary complex is larger than that for ( R)-BINOL/γ-CD/1,2-DBP complex. Thus, the observation of RTP lifetime differences between ( R)-BINOL and ( S)-BINOL can be attributed to their different ability to form complexes with chiral γ-CD, which is further supported by an analysis of the proton NMR chemical shift differences between ( R)-BINOL and ( S)-BINOL.
Keywords: Chiral discrimination; Room temperature phosphorescence; 1,1′-Binaphthol; Phosphorescence lifetime; Heavy atom perturber
Insights into the potentiometric response behaviour vs. Li+ of LiFePO4 thin films in aqueous medium by F. Sauvage; J.-M. Tarascon; E. Baudrin (pp. 163-168).
The potentiometric response of PLD-made LiFePO4 thin films versus Li+ ions in aqueous solutions has been investigated, and a sensitivity of 54mVdec−1 has been observed in a Li+ concentration range of 1–10−4M. Physical and electrochemical measurements of electrodes aged in aqueous medium show a slight surface oxidation with formation of heterosite-FePO4 that we show to be responsible for the stable potential response measured. Cyclic voltamperometry measurements operated in different Li+ concentration clearly highlight the key relation between the material lithium ion insertion/de-insertion capability and its potentiometric sensing response implying a faradaic-governed sensing mechanism. Based on such a finding, selection criteria (enlisting among others the potential of the redox couple, the nature of the insertion process) are herein underlined in the search for new sensitive materials.
Keywords: LiFePO; 4; Aqueous medium; Ion sensors; Pulsed Laser Deposition; Thin films
Home-made capillary array electrophoresis for high-throughput amino acid analysis by Kaiying Liu; Hui Wang; Jiling Bai; Li Wang (pp. 169-174).
A capillary array electrophoresis (CAE) with confocal rotary scanner for high-throughput carboxytetramethylrhodamine succinimidyl ester (TAMRA)-labeled amino acid (AA) analysis is presented. Performance of the CAE setup was evaluated with AA samples. Up to 128 capillaries could be detected in parallel. For the first time, the device was applied to separate the enantiomers of isoleucine, cysteine, and glutamic acid with cyclodextrin-modified electrolytes by capillary zone electrophoresis. Baseline separation of seven AAs is also demonstrated using micellar electrokinetic chromatography method.
Keywords: Capillary array electrophoresis; Confocal fluorescence scanner; Chiral separation; 532; nm laser
Computer simulation and theory of the diffusion- and flow-induced concentration dispersion in microfluidic devices and HPLC systems based on rectangular microchannels by Werner E. Morf; Peter D. van der Wal; Nicolaas F. de Rooij (pp. 175-181).
The dynamics of formation of solute peaks in microfluidic systems are investigated by computer simulation. A finite-element numerical procedure is applied to analyze the diffusion- and flow-controlled concentration dispersion in a 40μm-high rectangular flow-through channel. Two-dimensional concentration profiles are shown for channels with cross sections of large aspect ratio. The final shapes of the peaks are formed during a very short time period, ranging from a few milliseconds to about 1s for low and high flow velocities, respectively. The observed standard half-width σ of the peaks is found to strictly follow a linear function of t1/2 over the whole time range. The extrapolated long-term peak characteristics are in perfect agreement with theoretical predictions. For comparison, theoretical results on the concentration dispersion for solute peaks in open-channel liquid-chromatography (HPLC) are re-examined and applied.
Keywords: Microfluidic system; Chromatography; Rectangular channel; Concentration dispersion; Peak profile; Computer simulation; Finite-difference method; Theory
Development of an enzyme-linked immunosorbent assay for toosendanin by Jing Zhang; Gang Feng; Li Luo; Xiang Yang Yu; Zhi Qing Ma; Jun Tao Feng; Xian Jin Liu; Xing Zhang (pp. 182-188).
Enzyme-linked immunosorbent assays (ELISAs) were developed by using polyclonal antibody for toosendanin (TSN), a biopesticide from Melai toosendan Sieb. et Zucc. Their application in the determination of this analyte in spiked cabbage, tomato and apple samples was studied. The haptens, 28-hemisuccinyl-TSN (TSN-S) and 28-hemiglutaryl-TSN (TSN-G) were synthesized by using esterification. Immunogen and coating antigen were synthesized by using the mixed anhydride reaction and active ester protocol, respectively. Rabbits were immunized with TSN-G-BSA and TSN-S-BSA. Using the selected antibody and coating antigen, an indirect competitive ELISA for TSN was developed, which showed an IC50 value of 1.023μgmL−1, with a detection limit of 0.009μgmL−1. A direct competitive ELISA using an enzyme tracer was also developed. The assay showed an IC50 value of 0.840μgmL−1 with a detection limit of 0.014μgmL−1. Both assays displayed high cross-reactivity to a closely structurally related compound. Recoveries of TSN from both immunoassays of fortified samples ranged from 76.4% to 113.2% and 75.1% to 132.3%, respectively. Linear regression analysis showed good correlation between the TSN concentrations derived from ELISA and HPLC analyses, which suggested that the ELISA is a convenient supplementary analytical tool for monitoring TSN.
Keywords: Toosendanin; Hapten; Polyclonal antibody; Enzyme-linked immunosorbent assay
Potential of near infrared spectroscopy for the analysis of mycotoxins applied to naturally contaminated red paprika found in the Spanish market by J.M. Hernández-Hierro; R.J. García-Villanova; I. González-Martín (pp. 189-194).
The potential of the near infrared spectroscopy (NIRS) technique for the analysis of red paprika for aflatoxin B1, ochratoxin A and total aflatoxins is explored. As a reference, the results from a chromatographic method with fluorescence detection (HPLC-FD) following an immunoaffinity cleanup (IAC) were employed. For the NIRS measurement, a remote reflectance fibre-optic probe was applied directly onto the samples of paprika. There was no need for pre-treatment or manipulation of the sample. The modified partial least squares (MPLS) algorithm was employed as a regression method. The multiple correlation coefficients (RSQ) and the prediction corrected standard errors (SEP(C)) were respectively 0.955 and 0.2μgkg−1, 0.853 and 2.3μgkg−1, 0.938 and 0.3μgkg−1 for aflatoxin B1, ochratoxin A and total aflatoxins, respectively. The capacity for prediction of the developed model measured as ratio performance deviation (RPD) for aflatoxin B1 (5.2), ochratoxin A (2.8) and total aflatoxins (4.4) indicate that NIRS technique using a fibre-optic probe offers an alternative for the determination of these three parameters in paprika, with an advantageously lower cost and higher speed as compared with the chemical method. Content of aflatoxin B1 and total aflatoxins are the parameters currently employed by the food regulations to limit the levels of the four aflatoxins in many foodstuffs. In addition, aflatoxin B1 itself is an excellent indicator for aflatoxins’ contamination since it is always the most abundant and toxic.
Keywords: Aflatoxins; Ochratoxin A; Spanish paprika; Near infrared spectroscopy; Fibre-optic probe
Quantitation of ultraviolet-induced single-strand breaks using oligonucleotide chip by Sukdeb Pal; Min Jung Kim; Jaebum Choo; Seong Ho Kang; Kyeong-Hee Lee; Joon Myong Song (pp. 195-200).
A simple, accurate and robust methodology was established for the direct quantification of ultraviolet (UV)-induced single-strand break (SSB) using oligonucleotide chip. Oligonucleotide chips were fabricated by covalently anchoring the fluorescent-labeled ssDNAs onto silicon dioxide chip surfaces. Assuming that the possibility of more than one UV-induced SSB to be generated in a small oligonucleotide is extremely low, SSB formation was investigated quantifying the endpoint probe density by fluorescence measurement upon UV irradiation. The SSB yields obtained based on the highly sensitive laser-induced fluorometric determination of fluorophore-labeled oligonucleotides were found to coincide well with that predicted from a theoretical extrapolation of the results obtained for plasmid DNAs using conventional agarose gel electrophoresis. The developed method has the potential to serve as a high throughput, sample-thrifty, and time saving tool to realize more realistic, and direct quantification of radiation and chemical-induced strand breaks. It will be especially useful for determining the frequency of SSBs or lesions convertible to SSBs by specific cleaving reagents or enzymes.
Keywords: Surface coverage; Alkaline phosphatase-digestion; Single-strand breaks; Oligonucleotide chip; Laser-induced fluorescence