Choengchan, Nathawut

Preferred name

Alternative Name

Choengchan, N.

Choengchan, Nuthawut

Main Affiliation

School of Science

nathawut.ch@kmitl.ac.th

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A Double-layered Paper-based Analytical Device for Determination of Iron in Water Samples based on Standard Addition Method
(2024-01-03)
Srikritsadawong, Pongpichet
;
Sookpotarom, Punyapat
;
Thongchan, Surachet
;
Choengchan, Nathawut
A simple method for the determination of iron involved a novel paper-based analytical device (PAD) was developed. The PAD was composed of two layers. Each layer contained a circular hydrophilic reservoir (10 mm Ø) that was situated in a rectangular filter paper (25 Î 25 mm2). The hydrophobic area was created by painting the paper with a “waterproof” glue. The top and the bottom layers were assigned as “the filtration” and “the detection” platforms, respectively. The procedure was started by pipetting an aliquot of bathophenanthroline (Bphen) onto the hydrophilic zone of the bottom layer followed by spiking of standard solutions (0.1-0.5 mgL-1 Fe2+). The red complex was developed. Then, the top and the bottom layers were assembled by two-sided mounting tape. Later, a water sample was dropped onto the top layer, which removed (filtered) any suspended particles in the water sample. When the filtrate was exposed to the bottom layer, a further colored product formed. The bottom layer was removed and placed in a light-controlled box, and the optical image of the product was captured using a smartphone. Its intensity was evaluated through ImageJ™. Linear standard addition plots were obtained (r2 > 0.99). The PAD provided high precision (RSD < 6%) with good recovery (92.6-102%). It was applied to the analysis of drinking, tap, canal and river water samples without any prior filtration. The iron amounts were compared to the results obtained by the spectrophotometric method, and there was not significantly difference at 95% confidence (Paired-t test, n = 5 samples, t<inf>stat</inf> = 2.68, t<inf>cri</inf> = 2.78).
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Foldable paper-based analytical device for membraneless gas-separation and determination of iodate based on fluorescence quenching of gold nanoclusters
(2021-01-01)
Lert-itthiporn, Aurachat
;
Srikritsadawong, Pongpichet
;
Choengchan, Nathawut
A new design of a paper-based analytical device (PAD) for membraneless gas-separation with subsequent determination of iodate is presented. The rectangular PAD was invented as the folded pattern, where two circular reservoirs: the donor reservoir and the acceptor reservoir were situated in “a single paper” for convenient use. The hydrophobic barrier of each reservoir was easily fabricated by painting with a permanent marker. The PAD was demonstrated for the quantitative analysis of iodate, based on the fluorescence quenching of the bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs). The BSA-AuNCs were fast prepared by a microwave-assisted approach. The nanoclusters solution was applied into the acceptor reservoir, while the sample, iodide and sulfuric acid were sequentially aliquoted into the donor reservoir. After folding the PAD, the donor and the acceptor were mounted together via a two-sided mounting tape. The headspace between the two reservoirs allows membraneless gas-separation of free iodine from the donor to diffuse into the acceptor. Etching of gold core of the nanoclusters in the acceptor resulted in quenching of the red emission, was monitored by two methods, i.e. “fluorometric detection” (λ<inf>ex</inf>: 490 nm, λ<inf>em</inf>: 630 nm) and “image capture” of the acceptor under the UV irradiation by a smart phone's camera. Two calibrations were plotted accordingly to their detections and good linearities (r2 ˃ 0.98) were observed from 0.005 to 0.1 mmol L−1 iodate. High accuracy (mean recovery: 95.1 (±4.6) %) and high precision (RSD < 3%) were obtained. The lower limits of detection were 0.005 mmol L−1 (with fluorometric detection) and 0.01 mmol L−1 (with image capture). The method was effectively applied for the measurement of iodate in iodized salts and fish sauces without prior sample pre-treatment.
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Preparation of gold nanoparticles-bacterial cellulose nanopaper and its application as 2D-microcuvette for spectrophotometric determination of hydrogen peroxide
(2021-01-01)
Lert-Itthiporn, Aurachat
;
Phunpruch, Saranya
;
Prommajun, Munlika
;
Srikritsadawong, Pongpichet
;
Choengchan, Nathawut
This work presents a new method development using the gold nanoparticles (AuNPs)-bacterial cellulose (BC) nanopaper for the spectrophotometric determination of hydrogen peroxide (H<inf>2</inf>O<inf>2</inf>). The AuNPs were embedded in the BC nanopaper, where the nanopaper played two roles as both the reducing agent and the template for the as-prepared AuNPs. The preparation process was started by putting the wet bare BC nanopaper (Ø 30 mm and 3 mm thickness) into 0.75 mmol L-1 HAuCl<inf>4</inf> (25.0 mL). This solution was vigorously and continuously stirred for 60 min at 90ºC. After the embedding process, color of the nanopaper was changed from milky-white to wine-red. The AuNPs-BC nanopaper was characterized by UV-visible spectrophotometer, FE-SEM and EDS. Absorption spectrum of the nanopaper showed the characteristic peak of Au0 at 525 nm. The amount of 97.3 weight % of Au0 was found. The spectrophotometric assay was carried out by dropping the aliquots of 100 µL of sample and 400 µL of 20 mmol L-1 citrate buffer (pH 6.0) onto the AuNPs-BC nanopaper. The nanopaper was then kept in a plastic back for 10 min. In the presence of H<inf>2</inf>O<inf>2</inf>, the wine-red color of the AuNPs-BC nanopaper was turned to pale red accordingly to reduction of Auo to Au(III) by H<inf>2</inf>O<inf>2</inf>. Decreasing in the absorbance of the nanopaper at 525 nm was monitored using UV-visible spectrophotometer. Detection limit (y<inf>B</inf> + 3S<inf>B</inf>) of 0.79 % (v/v) was observed and this value was enough sensitive for the determination of H<inf>2</inf>O<inf>2</inf> in wound cleaner and hair dye samples. The H<inf>2</inf>O<inf>2</inf> contents in all samples were agreed well with the label values. Good analytical recovery (88.8 to 97.2 %) with high precision (RSD: 3.3 %) were obtained. These results confirmed that the as-prepared nanopaper was successfully synthesized and was effectively applied as the two dimensional (2D)-microcuvette for the spectrophotometric determination of H<inf>2</inf>O<inf>2</inf> in real samples.

Choengchan, Nathawut

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