Enhancement of selectivity and sensitivity for a novel colorimentric determination of glyphosate usin Mn-ZnS quantum dots embedded molecularly imprinted polymers

การเพิ่มสภาพไวและความจำเพาะเจาะจงในการตรวจวัดปริมาณไกลโฟเซตด้วยวิธีตรวจวัดทางสีแบบใหม่โดยใช้แมงกานีส-ซิงค์ซัลไฟด์ควอนตัมดอทที่เคลือบด้วยพอลิเมอร์ที่มีรอยพิมพ์ประทับโมเลกุล

Name: Pornchanok Sawetwong

LCSH: Colorimetry

Classification :.LCCS: QD

LCSH: Colorimetric analysis

LCSH: Glyphosate

LCSH: Molecular imprinting

LCSH: Polymers

Abstract: This thesis presents the development of a highly sensitive and selective colorimetric assay for glyphosate herbicide in whole grain samples. The colorimetric detection is based on the catalytic activity of Mn-ZnS quantum dot embedded MIP nanoparticles (Mn-ZnS QD-MTP) on the reaction of ABTS oxidized by an H202. Glyphosate imprinted polymer successfully synthesized on an Mn-ZnS QD surface using a poly (Nisopropylacrylamide) (NIPAM) and N, N'-Methylenebisacrylamide (MBA) as the functional monomers, 2,2'-azobis(2-methyl propionitrile) or AIBN as an initiator, and glyphosate as a template molecule. Its catalytic activity depends on binding or nonbinding of glyphosate molecules on the synthetic recognition sites of the Mn-ZnS QDsMIP. Glyphosate analyze selectively binding on the cavities embedded in the MnZnS QD surface, and subsequently tum-off or inhibit the ABTS oxidation and obvious color change to light green. The change of reaction color fi·om dark green to light green depends on the concentration of glyphosate. Development of a colorimetric assay for glyphosate determination was carried out based on two approaches; (i) UV-Visible spectrophotometry for glyphosate detection in the solution, and (ii) a three-dimensional microfluidic paper-based analytical device (3D-!1PAD) detected by images captured via digital camera and sent to the lmageJ program. UV-Visible spectrophotometry was used to monitor changes in absorbance during the reac tion. Glyphosate inhibits the oxidation of ABTS by binding to the recognition sites ofMn-ZnS QD-MIP. This inhibition suppresses the generation of "OH from H20 2, thereby blocking the oxidation of the ABTS colorimetric probe. The distinctive color change of ABTS, from dark green to light green, and the appearance of a maximum absorption wavelength at 420 nm was monitored. Optimal conditions were as the following: using an Mn-ZnS QD-MIP concentration of 50 )lg mL-1, an ABTS concentration of30 mM, an H20 2 concentration of90 mM, along with an acetate buffer solution (0.2 M, pH 2.0), for a 20 minute incubation period at 35 °C. The developed colorimetric in the solution assay exhibits a linear cal ibration over the range of 0.01-30)lg mL- 1, with linear correlation coefficient(~) of0.9920. The three-dimensional microfluidic paper-based analytical device (3D-)lPAD) is a portable, disposable, and cost-efficient alternative technology. The 3D-)lPAD was fabricated by screen-printing using the relatively new material of pen guard enamel color to create hydrophobic barrier. The foldable 3D-)lPAD is comprised of three layers (top/middle/bottom) designed as detection zone, an immobilized Mn-ZnS QD-MIP disc and sample loading. The assay on 3D-)lPAD can determine glyphosate by ImageJ detection, over a working ranged of0.005 to 50 )lg mL-1, with a detection limit of0.002)lg mL- 1. The 3D-)lPAD that was developed gives acceptable recoveries ranging from80.6% to 119.9% and a high level ofprecision with %RSD values from 0.1% to 6.3%. Our 3D-)lPAD is highly accurate with a small percent of relative different from a certified value of CRM, e.g. 0.4% for intraday and 0.7% for inter-day. Finally, the fabricated 3D-)lPAD provides solid reproducibility (1.7 % RSD for 10 devices of0.05)lg mL-1 glyphosate determination). The developed 3D-)lP AD was successfully applied to determine glyphosate concentrations in whole grain samples. The final development can be applied as an alternative technique due to its highly selective and sensitive colorimetric method and well suited to food-quality control and on-site environmentalmonitoring applications, without sophisticated instrumentation.

Ubon Ratchathani University. The Office of Academic Resources

Address: UBON RATCHATHANI

Email: library@ubu.ac.th

Name: Maliwan Amatatongchai

Role: Advisor

Created: 2020

Modified: 2567-10-17

Issued: 2024-10-17

วิทยานิพนธ์/Thesis

application/pdf

CallNumber: QD P836 2020

eng

DegreeName: Master of Science

Level: Master's Degree

Descipline: Major in Chemistry

Grantor: Ubon Ratchathani University

©copyrights Ubon Ratchathani University

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