Teerasong, Saowapak

Preferred name

Teerasong, Saowapak

Alternative Name

Teerasong, S.

Main Affiliation

School of Science

saowapak.te@kmitl.ac.th

Now showing 1 - 10 of 34

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Poly(vinyl alcohol) capped silver nanoparticles for antioxidant assay based on seed-mediated nanoparticle growth
(2017-08-01)
Teerasong, Saowapak
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Jinnarak, Amornrassamee
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Chaneam, Sumonmarn
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Wilairat, Prapin
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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 analysis with electrochemical detection as a tool for economic and rapid evaluation of total antioxidant capacity
(2011-06-15)
Chan-Eam, S.
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Teerasong, S.
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Damwan, K.
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Nacapricha, D.
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Chaisuksant, R.
This work presents a new flow-based coupled electrochemical technique for evaluation of "total antioxidant capacity (TAC)". A sequential injection (SI) with amperometric detection was applied to the TAC analysis of commercial instant ginger infusion beverages using 2,2′-azino-bis(3- ethylbenzothiazoline-6-sulfonic acid) (ABTS) assay. Besides having chromogenic properties, the ABTS reagent behaves as an electroactive species at the glassy carbon electrode in phosphate buffer pH 7.0, the decrease of the cathodic current signal of the ABTS+ radical after reaction with antioxidants can be monitored. The SI system, furnished with an in-house electrochemical detection cell (ECD), was optimized with respect to the applied potential, sample and reagent volume, and flow rate to the detector. Gallic acid was used as the standard antioxidant and the capacity was reported as gallic acid equivalent (GAE) unit. TAC measurements of ginger infusions at the optimum condition were performed using the proposed technique and also with the classical batch spectrophotometric ABTS assay. TAC values obtained from our method and the standard method are in good agreement (r2 = 0.956). The SI-amperometric technique provided satisfactory precision (4.11% RSD) with rapid sample throughput (40 samples h-1). Also using this method, the consumption of the expensive ABTS reagent was greatly reduced. © 2011 Elsevier B.V. All rights reserved.
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Enhanced Stability of Gold Nanoparticles with Thioalkylated Carboxyl-Terminated Ligands for Applications in Biosensing
(2024-06-14)
Ngernpimai, Sawinee
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Puangmali, Theerapong
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Kopwitthaya, Atcha
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Tippayawat, Patcharaporn
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Chompoosor, Apiwat
Gold nanoparticles (AuNPs) are widely recognized for their remarkable optical and chemical properties, making them versatile materials with diverse applications in sensing, catalysis, and biomedical fields. However, their susceptibility to aggregation and poor dispersion under different environmental stresses limits their utility in practical applications. In this study, we investigate the efficacy of utilizing carboxylate-terminated ligands to stabilize AuNPs and enhance their stability and functionality. Through a series of experiments, including assessments of pH buffer effects, ionic strength variations, freeze-drying stress, and protein adsorption, we demonstrate the effectiveness of these ligands in maintaining the stability of AuNPs within a pH range of 5-10. This enables them to resist aggregation in the presence of high concentrations of electrolytes and facilitates rapid redispersion after freeze-drying, enabling long-term storage of AuNPs in a dry powder form without compromising their stability or functionality. Moreover, the ligands efficiently prevent nonspecific protein binding. We explore application of these stabilized AuNPs conjugated with specific monoclonal antibodies for detection of Listeria monocytogenes, highlighting their potential for use in biosensing applications. This research underscores the significance of carboxylate-terminated ligands in stabilizing AuNPs, offering insights into the development of reliable and functional nanomaterials for various biomedical and biosensing applications.
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Microfluidic paper-based analytical device for convenient use in measurement of iodate in table salt and irrigation water
(2020-01-01)
Duangdeewong, Chomphunud
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Sitanurak, Jirayu
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Wilairat, Prapin
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Nacapricha, Duangjai
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Teerasong, Saowapak
We report a convenient microfluidic paper-based analytical device (µPAD) for the determination of iodate. The µPAD was fabricated using an ink-stamp with a simple circle design. Colorimetric detection of iodate employs the oxidation of hydroxylamine by the iodate to generate nitrite which reacts with the Griess reagent producing an intense magenta color. The images were recorded by a digital camera, and converted to a green scale color intensity by ImageJ. Calibration of iodate was linear in the range of 50–400 mg L−1 with a detection limit of 38.1 mg L−1. With such a wide linear range, the method can be applied to various kinds of samples with the entire process completed in 50 s. Good precision of measurement was obtained (<2 %RSD). Iodate levels were determined using the µPADs in table salt and irrigation water samples. The measured concentrations of the samples correlated well with the values as found by the standard iodometric titration (no statistical difference at a 95% confidence level). The developed device is simple with easy fabrication and rapid operation. It is portable and cost-effective and therefore suitable for quality control of iodate levels in the manufacturing and agricultural industries.
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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
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Intanin, Apichai
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Fungladda, Suchada
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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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Influence of a Non-ionic Surfactant on the Release of Rhodamine B from Poly(vinyl) Alcohol/Polyoxalate/Span-80 Composite Nanofibers Prepared by Emulsion Electrospinning
(2024-10-26)
Phromviyo, Nutthakritta
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Chompoosor, Apiwat
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Teerasong, Saowapak
Controlling drug release using a nanocomposite method is crucial; however, burst release must be avoided in order to obtain effective controllable drug release. In this study, poly(vinyl) alcohol/polyoxalate/Span-80 (PVA/ POX/ Span-80) composite nanofibers loaded with Rhodamine B were produced using emulsion electrospinning. The objective of this work was to evaluate the cooperative roles of POX and Span-80 on nanofibrous scaffold stability and drug release regulation by monitoring Rhodamine B release performance from electrospun composite nanofibers. The microstructure and hydrophilic properties of the emulsion electrospun nanofibers were studied using scanning electron microscopy (SEM), water contact angle, and swelling tests. According to the results, increasing the POX content had a significant effect on the size of nanofibers. The water contact angles increased as the POX content increased. The release of Rhodamine B was governed by a two-stage diffusion mechanism that was greatly influenced by PVA/POX ratios and Span-80. To compare release behavior, non-emulsion electrospun nanofibers without Span-80 were prepared as control samples. Emulsion nanofibers were found to release at a slower rate than non-emulsion nanofibers. The in vitro release profiles revealed that Rhodamine B was released from emulsion electrospun fibers in a sustainable manner and that no initial burst release was observed. These findings imply that emulsion electrospun nanofibers can potentially be used to deliver drugs, nutraceuticals, and fragrances in a prolonged manner.
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Zone fluidics for measurement of octanol-water partition coefficient of drugs
(2015-02-20)
Wattanasin, Panwadee
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Saetear, Phoonthawee
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Wilairat, Prapin
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Nacapricha, Duangjai
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Teerasong, Saowapak
A novel zone fluidics (ZF) system for the determination of the octanol-water partition coefficient (P<inf>ow</inf>) of drugs was developed. The ZF system consisted of a syringe pump with a selection valve, a holding column, a silica capillary flow-cell and an in-line spectrophotometer. Exact microliter volumes of solvents (octanol and phosphate buffer saline) and a solution of the drug, sandwiched between air segments, were sequentially loaded into the vertically aligned holding column. Distribution of the drug between the aqueous and octanol phases occurred by the oscillation movement of the syringe pump piston. Phase separation occurred due to the difference in densities. The liquid zones were then pushed into the detection flow cell. In this method, absorbance measurements in only one of the phase (octanol or aqueous) were employed, which together with the volumes of the solvents and pure drug sample, allowed the calculation of the P<inf>ow</inf>. The developed system was applied to the determination of the P<inf>ow</inf> of some common drugs. The log (P<inf>ow</inf>) values agreed well with a batch method (R2=0.999) and literature (R2=0.997). Standard deviations for intra- and inter-day analyses were both less than 0.1log unit. This ZF system provides a robust and automated method for screening of P<inf>ow</inf> values in the drug discovery process.
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A Screen Printed Graphene Based Electrochemical Sensor for Single Drop Analysis of Hydroquinone in Cosmetic Products
(2019-08-01)
Duekhuntod, Wannida
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Karuwan, Chanpen
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Tuantranont, Adisorn
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Nacapricha, Duangjai
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Teerasong, Saowapak
A graphene modified carbon paste sensor (or so-called graphene based sensor) was developed for electrochemical detection of hydroquinone. The sensor was fast fabricated using screen-printing technique. By integrating three fundamental electrodes on a single device, the sensor is small and portable. A determination is based on a one drop analysis. A 60 μ.L-drop of sample was placed onto the sensor prior to cyclic voltammetric measurement. The method relies on green analysis since it lowers the consumption of sample and waste generation. Under the optimal conditions, a linear calibration was achieved in range of 1.0 x 10-4 to 5.0 x 10-3 M hydroquinone. The detection limit was 7 x 10-5 M, a sensitive adequate for measuring hydroquinone in cosmetic products. The sensor provided good precision (%RSD = 2.78) and accuracy (recoveries = 87-114%), with analysis times of less than a minute. The sensor was applied to determine the presence of hydroquinone in whitening creams. The results obtained from the developed sensor satisfactorily agreed with the HPLC method, indicating the reliability of the method. Due to its advantages in terms of rapidity, low-cost and portability, the device is a viable choice for on-site screening for hydroquinone contamination in whitening products.
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A scanner-based microplate platform for high-throughput oxytetracycline detection using diazotization-coupling chemistry with greenness evaluation
(2026-06-01)
Puttasa, Papawarin
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Ngernpimai, Sawinee
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Tippayawat, Patcharaporn
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Park, Myoung‑Hwan
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Teerasong, Saowapak
Routine oxytetracycline (OTC) monitoring of aquaculture effluents, water sources, and pharmaceutical products is essential for environmental management and regulatory compliance. However, existing analytical methods remain largely instrumental and low-throughput. Herein, a microvolume, high-throughput, scanner-based colorimetric microplate platform is developed for OTC determination using a sensitive and selective diazotization-coupling chemistry with RGB digital image analysis. Sulfanilamide is diazotized with nitrite to generate reactive diazonium species, which subsequently couple with OTC to form a strongly colored yellow-orange azo dye. Only microliter-scale volumes of reagents and samples are required in each well, and the reaction is completed within a few minutes, enabling simultaneous analysis of up to 96 samples. The microplate is imaged with a flatbed scanner, and color responses are quantified using ImageJ software. A linear calibration range of 1 − 40 μM was obtained with a detection limit of 0.33 μM. The platform was successfully applied to OTC determination in aquaculture effluents, tap water, drinking water, and pharmaceutical samples. It exhibited high selectivity against other antibiotics with no observable cross-reactivity. The green analytical procedure index (GAPI) confirmed the method’s environmental friendliness. Overall, the scanner-based microplate platform offers a simple, low-cost, portable, and high-throughput alternative to conventional OTC assays.
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Miniaturized chromate-free chloride assay in fish sauce based on linear height calibration of AgCl precipitate in inverted microtubes
(2026-06-01)
Chantiwas, Rattikan
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Wilairat, Prapin
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Putthasa, Papawarin
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Cheotchinda, Benjamapohn
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Teerasong, Saowapak
A miniaturized, chromate-free methodology for chloride determination in high-salt food matrices is presented in accordance with the principles of Green Analytical Chemistry. Classical argentometric precipitation is adapted to a microvolume, instrument-light assay by confining silver chloride formation within inverted microcentrifuge tubes and directly measuring the height of the compact precipitate layer using a simple ruler. Because the cylindrical tube region has a constant cross-sectional area, precipitate height is directly proportional to chloride concentration, enabling straightforward linear calibration without optical detection, signal transduction, or complex data processing. Controlled tube inversion and low-speed centrifugation ensure that precipitation occurs exclusively within this cylindrical zone, producing a sharp, reproducible solid–liquid interface. Under optimized conditions (150 µL sample volume and 180 µL of AgNO₃ in nitric acid; centrifugation at 600 rpm for 3 min followed by 5 min settling), the method provides a linear working range of 50–500 mM chloride (r² = 0.9988), a detection limit of 14 mM, and relative standard deviations of 3–4 % at 200–300 mM. Validation of 12 commercial Thai fish sauce samples showed no statistically significant differences compared to AOAC potentiometric titration at the 95% confidence level, with recoveries of 100–103 % and %RSD values of 1–4.2 %. The primary advantage of this method is its strictly linear height–concentration relationship, enabled by geometry-controlled confinement of the precipitate. Unlike other miniaturized or paper-based assays, it eliminates the need for image analysis or device fabrication. From a green chemistry perspective, the assay eliminates the use of potassium chromate indicators and disposable paper-based devices, operates at the microliter scale using reusable plastic microtubes, and requires only low-speed centrifugation. Analytical Greenness (AGREE), Analytical Eco-scale, Green Analytical Procedure Index (GAPI), and White Analytical Chemistry (WAC) evaluations (AGREE score: 0.76; Eco-scale: 83; WAC score: 88.9) classify the method as an excellent example of green analysis. The proposed approach offers a robust and sustainable screening tool for chloride determination in high-salt foods.
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Teerasong, Saowapak

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