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 "dual-acceptor channel" membraneless gas-diffusion unit for simultaneous determination of ethanol and acetaldehyde in liquors using reverse flow injection
(2018-01-01)
Choengchan, Nathawut
;
Poontong, Bangerdsuk
;
Mathaweesansurn, Arjnarong
;
Maneerat, Noppadol
;
Motomizu, Shoji
A new design of membraneless gas-diffusion unit with dual acceptor channels for separation, collection and simultaneous determination of two volatile analytes in liquid sample is presented. The unit is comprised of three parallel channels in a closed module. A sample is aspirated into the central channel and two kinds of reagents are introduced into the other two channels. Two analytes are isolated from the sample matrix by diffusion into head-space and absorbed into the specific reagents. Non-absorbed vapor is released by opening the programmable controlled lid. The unit was applied to liquors for measurement of ethanol and acetaldehyde using reverse flow injection. Dichromate and nitroprusside were exploited as reagents for colorimetric detection of ethanol and acetaldehyde, respectively. Good linearity ranges (r2 > 0.99) with high precision (RSD < 2%) and high accuracy (recovery: 90 - 105%) were achieved. The results were compared to the results by GC-FID and no significant difference was observed by paired t-test (95% confidence).
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A low-cost method for determination of calcium carbonate in cement by membraneless vaporization with capacitively coupled contactless conductivity detection
(2010-05-15)
Sereenonchai, Kamonthip
;
Teerasong, Saowapak
;
Chan-Eam, Sumonmarn
;
Saetear, Phoonthawee
;
Choengchan, Nathawut
This work presents a flow analysis method for direct quantitation of calcium carbonate in cement without pretreatment of the sample. The method is based on online vaporization of CO<inf>2</inf> gas following acidification of the sample inside a small chamber that has a flow of acceptor solution passing around it. Solubilization of the CO<inf>2</inf> gas into the acceptor stream changes the conductivity of the acceptor solution causing an increase of signal at the capacitively coupled contactless conductivity detection (C4D) placed at the outlet of the vaporization chamber. This chamber is an adaption from previous work reported on 'membraneless vaporization' (MBL-VP). The method can be used in the quality control of production of mixed cement. These cement materials usually have calcium carbonate contents at high concentration range (e.g., 33-99% (w/w) CaCO<inf>3</inf>). Analysis of samples by this method is direct and convenient as it requires no sample pretreatment. The method is low-cost with satisfactory accuracy and acceptable precision. © 2010 Elsevier B.V.
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Microfluidic analysis with front-face fluorometric detection for the determination of total inorganic iodine in drinking water
(2018-01-01)
Inpota, Prawpan
;
Strzelak, Kamil
;
Koncki, Robert
;
Sripumkhai, Wisaroot
;
Jeamsaksiri, Wutthinan
A microfluidic method with front-face fluorometric detection was developed for the determination of total inorganic iodine in drinking water. A polydimethylsiloxane (PDMS) microfluidic device was employed in conjunction with the Sandell-Kolthoff reaction, in which iodide catalyzed the redox reaction between Ce(IV) and As(III). Direct alignment of an optical fiber attached to a spectrofluorometer was used as a convenient detector for remote front-face fluorometric detection. Trace inorganic iodine (IO <inf>3</inf> - and I - ) present naturally in drinking water was measured by on-line conversion of iodate to iodide for determination of total inorganic iodine. On-line conversion efficiency of iodate to iodide using the microfluidic device was investigated. Excellent conversion efficiency of 93 - 103% (%RSD = 1.6 - 11%) was obtained. Inorganic iodine concentrations in drinking water samples were measured, and the results obtained were in good agreement with those obtained by an ICP-MS method. Spiked sample recoveries were in the range of 86%(±5) - 128%(±8) (n = 12). Interference of various anions and cations were investigated with tolerance limit concentrations ranging from 10-6 to 2.5 M depending on the type of ions. The developed method is simple and convenient, and it is a green method for iodine analysis, as it greatly reduces the amount of toxic reagent consumed with reagent volumes in the microfluidic scale.
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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
;
Sonsa-Ard, Thitaporn
;
Vimolkanjana, Chavin
;
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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Simple flow system with in-line gas-diffusion unit for determination of ethanol employing hypsochromic shift of visible absorbance band of methyl orange
(2020-01-01)
Ratanawimarnwong, Nuanlaor
;
Sinpun, Montatip
;
Chankaw, Panuwat
;
Choengchan, Nathawut
;
Nacapricha, Duangjai
The effect of solvent composition on the uv–visible spectrum of methyl orange was investigated for application to the quantitative determination of ethanol. At fixed pH, there was a hypsochromic shift of the absorbance band of methyl orange with increasing ethanol concentration. Using acetate buffer at pH 3.40 the change of absorbance at 530 nm of a solution of methyl orange containing known concentrations of standard ethanol was measured to provide a calibration curve. In order to apply this method to the analysis of alcoholic samples, such as distilled spirits, blended spirits and liquid herbal medicines, a simple gas-diffusion unit coupled with flow system was employed to separate the ethanol from sample matrices. Using the gas diffusion-flow system and employing an evaporation time of 2 min, a linear calibration range of 5–45% (v/v) ethanol was achieved ((ΔA = (0.0078 ± 0.0002)x(ethanol, %(v/v)) + (0.040 ± 0.005)), r2 = 0.998). The limit of detection (3σ blank/slope) was 2.23% (v/v). The developed gas diffusion-flow system was applied to the analysis of colorless distilled spirits, yellow blended spirits and dark brown herbal medicines that are available in the local markets of Bangkok, Thailand. Validation of the method was carried out by comparing the results with analysis using gas chromatography. There was no statistically significant difference at the 95% confidence level for all alcoholic samples analyzed.
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Quality control of gasohol using a micro-unit for membraneless gas diffusion
(2009-01-01)
Muncharoen, Sasithorn
;
Sitanurak, Jirayu
;
Tiyapongpattana, Warawut
;
Choengchan, Nathawut
;
Ratanawimarnwong, Nuanlaor
This work describes the development of a new spectrophotometric flow technique suitable for monitoring of ethanol content in gasohol fuel. Membraneless gas-diffusion (MBL-GD) was applied with one-step aqueous extraction of gasohol (1:2 gasohol/water). Segments of aqueous extract and color developing reagent were allowed to flow into two separate channels in the MBL-GD device. Inside the device, ethanol vapor can diffuse across a small headspace between the two channels (donor and acceptor). Introduction of an air-segment behind the zone of acceptor reagent to stop dispersion of the colored zone greatly improves the rapidity of analysis using this MBL-GD technique. Two methods were developed for quality control of gasohol by measuring ethanol content. Method I is suitable for direct calibration of E5 and E10. Method II is recommended for E20. These methods have high accuracy with good precision (% RSD: 1 to 4.9, n=45) and have a sample throughput of 26 samples per hour. E10 samples were compared with analysis using a standard GC method. © 2008 Springer-Verlag.
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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
;
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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Chemometrics-assisted cross injection analysis for simultaneous determination of phosphate and silicate
(2016-07-14)
Uraisin, Kanchana
;
Janya, Supavita
;
Phechkrajang, Chutima
;
Choengchan, Nathawut
;
Tiyapongpattana, Warawut
This work presents a novel method for simultaneous spectrophotometric determination of phosphate and silicate by using a cross injection analysis (CIA) coupled with the use of partial least squares (PLS) for data evaluation. The detection principle is based on the well-known ‘molybdenum blue’ method. The molybdate ions in the presence of stannous chloride in acidic medium give phosphomolybdenum blue and silicomolybdenum blue as products. In this work, all the liquids, including sample and reagents were simultaneously introduced into a CIA platform by using two peristaltic pumps for controlling the x-channel and y-channel flow which was automatically manipulated by using in-house control board. Crossflow provides sufficient mixing inside the platform prior detection of the absorption spectra of blue complexes in the wavelength of 400–900 nm. Since spectra of the blue colour product of phosphate and silicate are resemblant, these two analytes therefore reciprocally interfere with one another. This results in difficulty in simultaneous analysis of phosphate and silicate. In this work, PLS was utilised as assistor of CIA system for simultaneous analysis of phosphate and silicate using molybdenum blue reaction without using any modification of reagents and addition of selective masking agent. The calibration ranges are 0.1–6 mgP L−1 and 5–100 mgSi L−1 for phosphate and silicate, respectively. By using CIA coupled with PLS for data evaluation, the analysis of two analytes was achieved within 1.5 min with only single injection. The developed system was applied to natural water samples and the system was validated with the conventional methods. By statistical paired t-test, there was no evidence of significant difference at 95% confidence level (t<inf>stat</inf> = 2.28, t<inf>critical</inf> = 2.31 and t<inf>stat</inf> = 0.62, t<inf>critical</inf> = 2.31 for phosphate and silicate, respectively). This implied that the chemometrics-assisted CIA system was successfully developed for simultaneous spectrophotometric determination of phosphate and silicate.
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Transparent Cross-Flow Platform as Chemiluminescence Detection Cell in Cross Injection Analysis
(2023-02-01)
Somboonsuk, Thachkorn
;
Saetear, Phoonthawee
;
Mantim, Thitirat
;
Ratanawimarnwong, Nuanlaor
;
Wilairat, Prapin
This work presents the use of a transparent ‘Cross Injection Analysis’ (CIA) platform as a flow system for chemiluminescence (CL) measurements. The CL-CIA flow device incorporates introduction channels for samples and reagents, and the reaction and detection channels are in one acrylic unit. A photomultiplier tube placed above the reaction channel detects the emitted luminescence. The system was applied to the analysis of (i) Co(II) via the Co(II)-catalyzed H<inf>2</inf>O<inf>2</inf>-luminol reaction and (ii) paracetamol via its inhibitory effect on the catalytic activity of Fe(CN)<inf>6</inf>3− on the H<inf>2</inf>O<inf>2</inf>-luminol reaction. A linear calibration was obtained for Co(II) in the range of 0.002 to 0.025 mg L−1 Co(II) (r2 = 0.9977) for the determination of Co(II) in water samples. The linear calibration obtained for the paracetamol was 10 to 200 mg L−1 (r2 = 0.9906) for the determination of pharmaceutical products. The sample throughput was 60 samples h−1. The precision was ≤4.2% RSD. The consumption of the samples and reagents was ca. 170 µL per analysis cycle.
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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
;
Chompoosor, Apiwat
;
Maneeprakorn, Weerakanya
;
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%.

Choengchan, Nathawut

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