| 1. |
- Bjarnason, Bjarni, et al.
(författare)
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Enzyme flow immunoassay using a Protein G column for the screening of triazine herbicides in surface and waste water
- 2001
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 426:2, s. 197-207
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Tidskriftsartikel (refereegranskat)abstract
- A method for screening of triazine herbicides in surface and waste water is presented. The method is based on an enzyme flow immunoassay (EFIA) for the detection of the free fraction of a horse radish peroxidase (HRP)-labelled antigen (tracer). This was accomplished by trapping the bound tracer fraction in a Protein G column, allowing the residual free tracer fraction to pass and be detected spectrophotometrically after incubation with an enzyme substrate. As compared with detecting the bound tracer fraction this reduces the regeneration requirements of the Protein G column used for capturing the bound fraction and, therefore, reduces assay time. A polyclonal antibody directed against simazine showed no reactivity towards tracers that were thiopropionic acid derivatives of atrazine, simazine and terbutylazine. It had good sensitivity towards tracers using derivatives of 2-chloro-4,6-(alkylamino)-s-triazines such as atrazine and simazine. The highest sensitivity was obtained with an Et/Cl/N-C5-HRP tracer because this tracer could be used in combination with the lowest concentration of antibody. The detection limit was 0.1 μgl-1 with a linear range between 0.1 and 10 μgl-1 and an assay throughput of 12 h-1. Natural water samples from various locations in Russia were analysed for triazines and the results were compared with a previously developed fluorescein flow immunoassay for triazines. The results were further verified by supported liquid membrane (SLM) extraction combined with HPLC. The results show that the two immunoassays behave differently and that the sample matrix influences their performance, however, no false negative results were obtained. The possible reasons for the different results between the two immunoassays are discussed. (C) 2001 Elsevier Science B.V.
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| 2. |
- Dzgoev, A., et al.
(författare)
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Optimization of a charge coupled device imaging enzyme linked immuno sorbent assay and supports for the simultaneous determination of multiple 2,4-D samples
- 1997
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 347:1-2, s. 87-93
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Tidskriftsartikel (refereegranskat)abstract
- A chemiluminescent microformat enzyme linked immune sorbent assay (ELISA) has been optimized for the simultaneous determination of multiple 2,4-dichlorophenoxyacetic acid (2,4-D) samples. The competitive immunoassay employed a 2,4-D-BSA conjugate, anti-2,4-D monoclonal antibodies and alkaline phosphatase (AP) labelled anti-mouse IgG. The bound AP conjugate was determined by quantitating the chemiluminescence emission from the enzymatic decomposition of the luminogenic substrate, CSPD, by AP using a cooled charge coupled device (CCD) camera. The detection limit for the simultaneous determination of multiple samples was 4.3x10-10 M corresponding to 96 pg ml-1 or 192 fg well with a coefficient of variation (CV, %) of 12.5%. The linear range of the assay was 4.5 x 10-7-4.5 x 10-10 M. The ability of gold coated silicon wafers and glass capillaries to serve as solid phase supports in the imaging ELISA was investigated. The highly reflective gold surfaces improved both the linear range and the sensitivity of the assay, as compared to thick-film patterned surfaces. The capillary supports, on the other hand, lead to a reduction in the linear range and the sensitivity of the assay, as compared to the thick-film patterned surfaces. Initial studies indicate that the capillaries guide the light and may provide a built-in mechanism for collecting the emitted light. Strategies for further development of support materials for imaging-based detectors will be discussed.
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| 3. |
- Gascón, Jordi, et al.
(författare)
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Performance of two immunoassays for the determination of atrazine in sea water samples as compared with on-line solid phase extraction-liquid chromatography-diode array detection
- 1996
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 330:1, s. 41-51
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Tidskriftsartikel (refereegranskat)abstract
- Two immunoassay formats, magnetic particles-based assay (Atrazine RaPID assay and Atrazine High-Sensitivity RaPID assay) and microtiter plate based assay (Department of Entomology and Environmental Toxicology, University of California in Davis) were evaluated for the determination of atrazine in sea water samples. The results obtained were compared and validated with those obtained by using on-line solid phase extraction followed by liquid chromatography-diode array detection (on-line SPE-LC-DAD). The correlation between both techniques was good when analyzing levels of atrazine ranging from 0.01 to 5 μg/l in samples showing salt concentration values varying from 0 to 35 g/l and pH values from 2 to 10. One of these immunoassays (Atrazine High-Sensitivity RaPID assay) was employed to directly analyze atrazine in real estuarine and coastal water samples. The same samples were analyzed after filtration and C18 Empore disks extraction.
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| 4. |
- Hedenfalk, M., et al.
(författare)
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Modulation of the measuring range of a radioimmunoassay using an organic water two phase system
- 1997
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 341:2-3, s. 269-274
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Tidskriftsartikel (refereegranskat)abstract
- A commercially available radioimmunoassay (RIA) kit was used to study the effects of organic solvents on antigen-antibody interactions. The RIA analysis was carried out in aqueous-organic two phase systems. After exposure to hydrophobic organic solvents the antibodies retained full binding capacity, while less hydrophobic solvents caused partial inactivation of the antibodies. A practical analysis for digoxigenin in organic solvents was developed using the RIA kit with polyclonal antibodies against digoxin. The sensitivity was modulated four orders of magnitude by the choice of organic solvent. The main factor influencing the sensitivity was the partitioning of digoxigenin between the aqueous and the organic phases. The technique developed is promising for the analysis of a variety of antigens dissolved in organic solvents.
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| 5. |
- Mecklenburg, M., et al.
(författare)
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Differentiation of human serum samples by surface plasmon resonance monitoring of the integral glycoprotein interaction with a lectin panel
- 2002
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Ingår i: Analytica Chimica Acta. - 0003-2670 .- 1873-4324. ; 459:1, s. 25-31
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Tidskriftsartikel (refereegranskat)abstract
- Bacterial infection and inflammation result in massive changes in serum glycoproteins. These changes were investigated by the interaction of the saccharide glycoprotein moiety with lectins. A panel of eight lectins (Canavalia ensiformis, Bandeiraea simplicifolia BS-I, Arachis hypogaea, Phytolacca americana, Phaseolus vulgaris, Artocarpus integrifolia, Triticum vulgaris and Pisum sativum) was used to differentiate human serum glycoproteins obtained from patients with various bacterial infections. Lectin functionalised sensing layers were created on gold-coated wafers and lectin-glycoprotein interactions were monitored by surface plasmon resonance. The interaction of the lectin panel with serum glycoproteins produces unique patterns. Principal component analysis (PCA) was used to analyse the patterns. The actual panel of eight lectins enabled discrimination between sera obtained from patients sick with bacterial infection and healthy patients. Extended lectin panels have the potential to distinguish between types of bacterial infection and identify specific disease state. © 2002 Elsevier Science B.V. All rights reserved.
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| 6. |
- Miyabayashi, Akiyoshi, et al.
(författare)
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A potentiometric enzyme electrode for monitoring in organic solvents
- 1989
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 219:C, s. 27-36
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Tidskriftsartikel (refereegranskat)abstract
- A potentiometric enzyme electrode is described for monitoring reactions in organic solvents. By use of an enzyme deposited on magnetic particles which are attracted to the tip of the electrode by means of a magnetic field, it is possible to produce an electrode in which the enzyme can easily be exchanged. As an example, studies of the chymotrypsin-catalyzed ester synthesis in diisopropyl ether and in toluene at varying water contents are reported. The results are consistent with those obtained from batch experiments. Operational behaviour and signal stability of the system makes this kind of potentiometric enzyme electrode attractive for monitoring bioorganic processes.
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| 7. |
- Momeni, Naghi, et al.
(författare)
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CCD-camera based capillary chemiluminescent detection of retinol binding protein
- 1999
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 387:1, s. 21-27
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Tidskriftsartikel (refereegranskat)abstract
- A chemiluminescence (CL) assay for retinol-binding protein (RBP) was designed and optimized using a charge coupled device (CCD)-camera based detection system. A sandwich ELISA was designed based on the anti-RBP antibodies immobilized in glass capillaries pre-treated with silica sol. The immobilization was predominantly by physisorption of the protein on the silica surface. The RBP bound to the anti-RBP antibodies was detected by using an anti-RBP-horseradish peroxidase (HRP) conjugate. The reaction of the HRP with hydrogen peroxide and luminol and 4-iodophenol generated the CL. The CL emitted from the glass capillaries was detected by a cooled slow scan CCD camera at an optimized exposure time. The approximately linear range of RBP determination was between 11 pg ml−1 and 11 ng ml−1 with a coefficient of variation of 5–11% (n=6) over this range.
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| 8. |
- Tang, Xiao-Jing, et al.
(författare)
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Polyethyleneimine-coated reticulated vitreous carbon electrode with immobilized enzymes as a substrate detector
- 1998
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 374:2-3, s. 185-190
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Tidskriftsartikel (refereegranskat)abstract
- Polyethyleneimine (PEI) was covalently coupled to carbodiimide-activated reticulated vitreous carbon (RVC). The PEI-coated RVC was activated with glutaraldehyde, and glycerol dehydrogenase and diaphorase were then immobilized. The PEI-coated RVC with immobilized enzymes functioned both as an enzyme reactor and a working electrode in an amperometric detection system where NAD+/NADH was recycled by the immobilized enzymes. The coated RVC electrode showed good properties compared to uncoated RVC, such as a long lifetime and a constant response to a series of injections in a flow-injection system, resulting in a relative standard deviation of 1.4%. The calibration graph was linear from the detection limit 0.1μM to 2mM NADH in the absence of recycling.
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| 9. |
- Xie, Bin, et al.
(författare)
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Microbiosensor based on an integrated thermopile
- 1994
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Ingår i: Analytica Chimica Acta. - : Elsevier BV. - 0003-2670. ; 299:2, s. 165-170
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Tidskriftsartikel (refereegranskat)abstract
- A microbiosensor based on an integrated thermopile was designed and fabricated on a quartz chip. The thermopile, which was manufactured by doping boron in polysilicon together with aluminium, provided a potential output of ca. 2 mV K. A silicone rubber membrane was used to form and seal the microchannel. The total column volume was 20 μl. Glucose oxidase and catalase were co-immobilized on spherical CPG beads (controlled pore glass) and in turn charged into the microchannel. Using 1 μl sample volumes, a linear range of 2 to 25 mM glucose was obtained using a flow rate of 105 μl min. The relative standard deviation for 100 glucose samples (10 mM) was 5%.
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| 10. |
- Ye, Lei, et al.
(författare)
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Molecular imprinting on microgel spheres
- 2001
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Ingår i: Analytica Chimica Acta. - 0003-2670. ; 435:1, s. 187-196
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Tidskriftsartikel (refereegranskat)abstract
- Molecularly imprinted polymers have been prepared in various configurations including, for example, polymer beads, monoliths and membranes for different applications. The most common form of imprinted polymer is, however, still the irregularly shaped particle obtained by grinding the traditional, macroporous polymer monolith. We herein present a novel and efficient approach leading to imprinted microspheres, i.e. microgels bearing binding sites specific to target molecules. Imprinted microgels are proposed to be the basic components in previously reported, molecularly imprinted, cross-linked polymers, although the polymers themselves may exist in different forms depending on the preparation method utilised. Chemical modification of the molecularly imprinted microspheres introduces additional functionalities that may be used to couple sensing elements in various assay formats, or for the immobilisation of the imprinted microspheres on various transducers towards the development of biomimetic sensors.
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