| 11. |
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| 12. |
- Palchetti, I, et al.
(författare)
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Determination of anticholinesterase pesticides in real samples using a disposable biosensor
- 1997
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Ingår i: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 337:3, s. 315-321
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Tidskriftsartikel (refereegranskat)abstract
- A choline amperometric biosensor based on screen-printed electrodes was assembled and used to assess the inhibitory effect of organophosphorus and carbamic pesticides on acetylcholinesterase activity both in standard solutions and real samples, Acetylcholinesterase catalyses the cleavage of acetylcholine to choline and acetate, therefore the amount of choline measured using the biosensor is directly related to the enzyme activity. The extent of enzyme inhibition can be used as an index of the amount of anticholinesterase pesticides present. The hydrophobicity of organophosphorus and carbamic pesticides led to the evaluation of organic, water miscible solvents for use in the proposed method. Berate buffer containing 1% v/v acetonitrile was selected since it exhibited the least influence on enzyme activity from the tested solvents (acetonitrile, acetone, tetrahydrofuran and ethylacetate). Other solvents (dimethylsulfoxide and methanol) were avoided as they exhibited electrochemical interferences. An inhibition calibration curve was obtained using carbofuran, a strong inhibitor of acetylcholinesterase. The lowest detectable standard solution (mean +/-3 standard deviation of the blank) was 2 mu gl(-1) following an incubation time of 10 min. The method was then applied to real samples (fruits and vegetables) showing its suitability as a rapid screening assay (12 min per test) for the assessment of anticholinesterase pesticides, The biosensor results were compared with a standard analytical technique (gas chromatography with nitrogen phosphorus detector, GC-NPD).
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| 13. |
- White, SF, et al.
(författare)
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Development of a mass-producible glucose biosensor and flow-injection analysis system suitable for on-line monitoring during fermentations
- 1996
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Ingår i: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 321:03-feb, s. 165-172
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Tidskriftsartikel (refereegranskat)abstract
- Screen printed amperometric glucose biosensors were constructed and optimised for use in a flow injection analysis (FIA) system. The sensors were fabricated using a catalytic metallised carbon based ink, allowing a working potential of +350 mV (Ag/AgCl). Overall the sensors displayed a high degree of reliability and robustness. A linear response was obtained over the range 0.1 to 25 mM glucose with a slope of 1.35 +/- 0.20 mu A/mM. The within electrode coefficient of variation at each concentration tested (n = 10) was less than 2% (or 0.1 mM for concentrations below 5 mM). In addition, it was demonstrated that a single sensor can be used in the FIA system over a seven day period indicating a high level of operational stability. These sensors fulfil the criteria necessary for a mass produced device, which would be suitable for the on-line monitoring of glucose consumption during microbial fermentation.
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| 14. |
- 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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| 15. |
- 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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| 16. |
- 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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| 17. |
- 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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| 18. |
- 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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| 19. |
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| 20. |
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