Sol-gel cholinesterase biosensor for organophosphorus pesticide fluorimetric analysis

• Published in: Sensors and actuators. B, Chemical Vol. 39; no. 1; pp. 426 - 431
• Main Authors: Díaz, A. Navas, Peinado, M.C. Ramos
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Lausanne Elsevier B.V 01.03.1997; Amsterdam Elsevier; New York, NY
• Subjects: Biological and medical sciences; Biosensors; Biotechnology; Cholinesterase; Fluorimetry; Fundamental and applied biological sciences. Psychology; Methods. Procedures. Technologies; Optical fibres; Organophosphorus pesticides; Sol-gel methods; Various methods and equipments; Organophosphorus pesticides; Fluorimetry; Optical fibres; Cholinesterase; Sol-gel methods; Performance evaluation; Enzyme; Pesticides; Esterases; Carboxylic ester hydrolases; Sol gel process; Biosensor; Hydrolases; Microencapsulation; Organophosphorus compounds; Fluorometric titration; Immobilized enzyme; Quantitative analysis; Optical fiber
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/S0925-4005(97)00025-7

Sol-gel crystals derived from tetramethyl orthosilicate (TMOS) doped with cholinesterase using microencapsulation have been prepared. Organophosphorus pesticides (ORPs) are determined by fluorimetric detection based on enzymatic inhibition of immobilized cholinesterase; the percentage inhibition is correlated to pesticide concentration. The working substrate concentration (indoxyl-acetate) for ORP determination, 1.63 × 10 −4 M, is optimized by selecting a linear range in a plot of substrate concentration against signal. Precision as a relative standard deviation (RSD) is 10.2% ( n = 7) for the working substrate concentration. Fenitrothion, azinphos-ethyl, methidation, naled and mecarbam are analysed. Calibration plots have been established by measuring in a cuvette and through an optical fibre modified at its end with the immobilized cholinesterase gel. The biosensor performance is evaluated by measuring the percentage inhibition covering concentration ranges from 1.21–11.99 μg ml −1 (naled) up to 4.9–328.9 μg ml −1 (mecarbam). RSDs from 1.5 to 10.3% and detection limits from 0.12 (naled) to 57.6 μg ml −1 (methidation) have been achieved. Mass production and good storage for one month of the immobilized enzyme render the gel disposable after a single use. ORP determination is fast (inhibition time of 5 min) and the enzyme immobilization directly onto the end of the optical fibre enhances the sensitivity.