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A new mechanism for resonance Rayleigh scattering detection of minoxidil based on catalytic oxidation of silver nanoparticles
(2022-07-05)
Teerasong, Saowapak
;
Praditweangkum, Wiboon
;
Chompoosor, Apiwat
This work presents a new method for minoxidil detection based on silver nanoparticle (AgNP) oxidation. Minoxidil, which is a pyrimidine N-oxide, can be reduced to its corresponding pyrimidine via a redox reaction. In this system, acetate buffer serves as a proton source. AgNPs act as electron donors that contribute electrons to the reaction, producing Ag+. Consequently, the sizes and numbers of AgNPs in the system decrease, which results in a decline in their resonance Rayleigh scattering (RRS). By monitoring the RRS intensity at 409 nm, a change in intensity was linearly related to the minoxidil concentration over a concentration range of 0.5 – 5.0 mM. The detection limit was 0.35 mM. This approach is simple and rapid. It is done by directly mixing the drug and AgNPs in an acidic buffer. The reaction was completed within 2 min. This proposed method was successfully utilized for quantification of minoxidil in topical hair-growth formulations.
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Poly(vinyl alcohol) capped silver nanoparticles for antioxidant assay based on seed-mediated nanoparticle growth
(2017-08-01)
Teerasong, Saowapak
;
Jinnarak, Amornrassamee
;
Chaneam, Sumonmarn
;
Wilairat, Prapin
;
Nacapricha, Duangjai
A simple and rapid method for measurement of total antioxidant capacity (TAC) was developed. In this work, gallic acid was used as the antioxidant standard. Poly(vinyl alcohol) embedded silver nanoparticles (PVA-AgNPs) were employed as a colorimetric sensor. The detection principle was based on the seed-mediated nanoparticle growth technique. The PVA-AgNPs act as a catalyst in the reduction of Ag+ by gallic acid by providing nucleation seeds. Ag+ was reduced to Ag° and accumulated on the PVA-AgNP surface, leading to an increase in the size of particles. The absorbance of the colloidal solution was drastically enhanced with a small red shift. Under optimal conditions, a linear response was established between the change in absorbance and the TAC value expressed in terms of gallic acid equivalents. The linear range was from 25 to 200 μM with a detection limit of 22.1 μM. Satisfactory precision was obtained with % relative standard deviation (RSD) of 2.17. The developed sensor was successfully applied for TAC assessment of commercial ginger products. The PVA-AgNP sensor offers rapid analysis (within 5 min) compared to other nanoparticle-based antioxidant assays. Synthesis of the particles and assay involved less-toxic chemicals, and is therefore a “greener” method.
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Sequential injection for determination of gamma-aminobutyric acid based on its effect on second order light scattering of silver nanoparticles
(2016-08-01)
Jinnarak, Amornrassamee
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Anantavichian, Pattarapon
;
Intanin, Apichai
;
Fungladda, Suchada
;
Choengchan, Nathawut
An automated sequential injection (SI) with second order light scattering (SOS) detection for determination of gamma-aminobutyric acid (GABA) was developed. Quantitation is based on electrostatic interaction between GABA and citrate-capped silver nanoparticles (AgNPs). In acetate buffer at pH 3.8, the positively charged GABA induces the nanoparticles to aggregate. This results in a change of light scattering monitored using a spectrofluorometer. In this work, working standard solutions of GABA were prepared in-line by the SI system pumping appropriate volumes of a stock solution of GABA and acetate buffer into a holding coil. Solution of AgNPs was subsequently drawn into the coil. The reaction zone was then transferred to the spectrofluorometer, set with excitation and detection wavelengths at 300 and 600 nm, respectively. Under optimised condition, the SOS intensity was proportional to the concentration of GABA. As a result, a linear curve was obtained in the range of 100–400 mg L−1 GABA, with a lower limit of detection of 39.6 mg L‐1. Good precision of analysis was achieved, with 0.6 and 3.3% relative standard deviation (RSD) for external calibration (n = 5) and standard addition (n = 3), respectively. The developed method was successfully applied for quantification of GABA in dietary supplements (2 samples) and samples of instant green tea (2 samples).
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A novel colorimetric method for detection of gamma-aminobutyric acid based on silver nanoparticles
(2016-06-28)
Jinnarak, Amornrassamee
;
Teerasong, Saowapak
A novel, simple and rapid colorimetric method for determination of gamma-aminobutyric acid (GABA) was developed using a negatively charged citrate-capped silver nanoparticle (AgNP) probe. At an acidic pH of 3.8, GABA had a positive charge due to a protonation of amine groups. Therefore GABA could induce an aggregation of AgNPs due to electrostatic interaction. This caused a decrease in the surface plasmon resonance spectra of the colloidal solution at wavelength of 390 nm with a slight red shift. At the same time, the color of the suspension turned from yellow to green upon aggregation. Quantification of GABA was done spectrophotometrically. Under optimum conditions, the method showed a linear calibration in range of 100-500 mg L-1 GABA, with a detection limit of 57.7 mg L-1. The method was successfully applied to measure GABA quantities in dietary supplements.
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A simple and rapid method based on anti-aggregation of silver nanoparticles for detection of poly(diallyldimethylammonium chloride) in tap water
(2016-01-01)
Trisaranakul, Wichaya
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Chompoosor, Apiwat
;
Maneeprakorn, Weerakanya
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Nacapricha, Duangjai
;
Choengchan, Nathawut
A simple and rapid method was developed for the detection of poly(diallyldimethylammonium chloride) (PDADMAC) using citrate-capped silver nanoparticles (AgNPs). Detection was based on anti-aggregation of AgNPs in phosphate buffer caused by PDADMAC. Due to its positive charges, PDADMAC was adsorbed onto AgNPs via electrostatic interaction with citrate, which resulted in the charges at the particle surfaces to become positive and caused repulsion among particles. Furthermore, long-chain PDADMAC provided steric hindrance. These two effects promoted the dispersion of AgNPs in the phosphate buffer. A change in the state of dispersion influenced the surface plasmon resonance (SPR) of AgNPs. Therefore, in this work, the concentration of PDADMAC was determined by monitoring changes in absorbance (at 396 nm) caused by SPR of AgNPs. Under optimal conditions, the calibration was linear over the range of 1 to 100 mg L-1 with a detection limit of 0.7 mg L-1. Satisfactory precision was obtained (RSD = 2.8%). This method was successfully applied to the determination of PDADMAC in tap water samples. The recoveries ranged from 86.0 - 107.5%.
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Colorimetric sensor using silver nanoparticles for determination of hydrogen peroxide based on a flow injection system
(2013-09-01)
Teerasong, Saowapak
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Sonsa-Ard, Thitaporn
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Vimolkanjana, Chavin
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Choengchan, Nathawut
;
Chompoosor, Apiwat
In this work, a colorimetric probe using a flow injection (FI) system and silver nanoparticles (AgNPs) was developed for determination of hydrogen peroxide (H2O2) concentration. AgNPs have catalytic ability for decomposition of H2O2, producing silver ions and superoxide. The reaction mechanism of H2O2 and AgNPs at various concentrations is described. H2O2 concentration was quantified by monitoring decrease in AgNPs surface plasmon resonance during the decomposition reaction. Under the optimum condition, the detection limit for H2O2 was 0.6 mg/l. The flow system developed in this study provided good precision of analysis (relative standard deviation = 2.97%) with high throughput (18 samples/h). This method was successfully applied to analysis of H2O2 in pharmaceutical and household products. Therefore, the method is feasible for on-line monitoring H2O2 in manufacturing process quality control. © Copyright 2013 American Scientific Publishers All rights reserved.

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