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Development of a Tannic Acid-Gelatin Modified Filter Paper Membrane for Trace Lead Detection in Water
(2026-06-16)
Rattanadechawan, Arinrada
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Choengchan, Nathawut
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Mantim, Thitirat
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Donpudsa, Suchao
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Karuwan, Chanpen
A novel membrane-based solid-phase extraction (SPE) device was developed using cellulose filter paper modified with a tannic acid–gelatin (TA/GE) composite for the preconcentration of lead (Pb(II)) ions from aqueous samples. The TA/GE sorbent layer was fabricated via cross-linking gelatin with tannic acid at pH 9, forming a stable, partially insoluble network that enhances the membrane’s mechanical strength and ion-binding capability. Characterization by SEM confirmed the successful modification, while micro-XRF analysis demonstrated the membrane’s effective adsorption and elution of Pb(II). After preconcentration, square wave anodic stripping voltammetry (SWASV) was used for quantitative determination. The method exhibited linear range of 10–100 μg·L–1, with a limit of detection (LOD) of 2.7 μg·L–1. Method validation using a certified reference material for trace metals in water produced a combined measurement uncertainty (U) of 9 μg·L–1 at the 95% confidence level for a sample containing 61 μg·L–1 Pb(II), showing no significant deviation from the certified value. The developed method was further applied to drinking water and river water samples, achieving recoveries of 82–110% for spiked samples. These results confirm that the TA/GE-modified membrane provides a simple, low-cost, and environmentally friendly platform for trace Pb(II) analysis, with performance meeting both WHO (10 μg·L–1) and Thailand Pollution Control Department (50 μg·L–1) regulatory standards for drinking and surface water.
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Valorization of eggshell waste to metal-doped CaO catalysts for producing dimethyl carbonate by transesterification of propylene carbonate with methanol
(2026-05-01)
Seeharaj, Panpailin
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Werupho, Sakila
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Puyamsai, Araya
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Choengchan, Nathawut
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Kim-Lohsoontorn, Pattaraporn
To align with a circular economy, this study aimed to extend the lifecycle of eggshell waste by valorizing it into a catalyst for producing the green chemical dimethyl carbonate (DMC) through the transesterification of propylene carbonate (PC) with methanol. CaO derived from eggshells was modified by doping with 10 mol% of aliovalent metal cations, including Na+, Mg2+, and Ce3+, via a calcination-hydration-dehydration process. The catalyst activity was tested under atmospheric air at 40–70 °C for 1–3 h. Metal-doped CaO possessed better activity than pure CaO, and the performance was ranked in order as CaO < Na–CaO < Ce–CaO < Mg–CaO. At the optimized reaction conditions of 50 °C for 2 h, the Mg–CaO catalyst exhibited the best performance, with 77% PC conversion, 62% DMC selectivity, and 37% DMC yield. This improvement correlated with the high surface-active area and optimum basicity induced by incorporating Mg2+ into the CaO structure and forming MgO–CaO mixed oxide phases. This study demonstrated a greener process for producing DMC under mild conditions using metal-doped CaO catalysts derived from eggshell waste.
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A Novel Cross Injection Analysis for Simultaneous Multi-Determination of Diabetic Nephropathy Biomarkers in Urine
(2026-05-01)
Inpota, Prawpan
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Choengchan, Nathawut
This work presents, for the first time, a novel cross injection analysis (CIA) system for the simultaneous multi-determination of key biomarkers associated with diabetic nephropathy—namely, albumin, creatinine, and glucose—within a single analytical run. Unlike conventional flow-based techniques that rely on sequential measurements, the proposed CIA platform integrates multiple analytical pathways into a unified design, enabling one-shot multi-analyte analysis without the need for complex separation units or injection valves. The system employs peristaltic pumps and a rectangular platform with orthogonal flow channels, allowing concurrent aspiration and efficient transport of reaction products to compact detectors. Albumin determination was based on ion-association with tetrabromophenolphthalein ethyl ester. Creatinine was measured using the Jaffé reaction. Glucose was colorimetrically detected via its reaction with 3,5-dinitrosalicylic acid. The developed CIA provides enhanced sensitivity through its pre-mixing effect, enabling reliable quantification of trace analytes. Excellent analytical performance was achieved, including wide linear ranges (r2 > 0.99), good precision (RSD < 7%), and rapid analysis (5 min). The method was validated against established reference methods, showing no significant differences, and successfully applied to urine with satisfactory recoveries (84.8–107.3%). Importantly, the proposed system adheres to green chemistry by minimizing reagent consumption and waste generation, offering a sustainable approach for multi-parameter clinical analysis.
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A double-layered paper-based analytical device for speciation and simultaneous determination of iron in waters within single-shot analysis
(2025-08-01)
Thongchan, Surachet
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Sookpotarom, Punyapat
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Praditweangkum, Wiboon
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Thongyoo, Panumart
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Sojic, Neso
This work demonstrates the use of a paper-based analytical device (PAD) for the speciation and the simultaneous determination of iron (Fe) in waters within a single-shot analysis. The PAD is designed as having stacked, double layers viz., the topside and underside layers. Each layer (25 × 25 mm2) consists of a defined circular hydrophilic reservoir (10 mm Ø), situated in the adhesive glue-fabricated hydrophobic zone. Both layers are assembled by a two-sided mounting tape (3.0 mm thickness). The sample is introduced onto the topside reservoir and only Fe (II) reacts specifically with bathophenanthroline (Bphen) to form the stable, red-colored product. Consecutively, the sample flows vertically and exposes the underside reservoir. Then, the PAD is flipped, and the new class of the fluorescein derivative is transferred to the underside reservoir. Fe (III) selectively forms the complex with the fluorophore, and this results in quenching of the green, fluorescent light under UV irradiation. The optical image of each reservoir is captured via a smart phone camera under a light control studio and their color intensities are evaluated by ImageJ™ software. Under the optimal conditions, the calibrations, ranging from 0–0.5 mg L-1 Fe (II) and 0–10 mg L-1 Fe (III) are observed with good linearity (r2 > 0.99). Detection limits (3SD) of 0.02 mg Fe (II) L-1 and 0.21 mg Fe (III) L-1 are achieved. The developed PAD offers good recoveries (94.8–107 %) and high precision (RSD < 4 %). It is also successfully validated against the UV–visible spectrophotometric and the ICP-OES methods. The Fe contents are not significant differences at 95 % confidence under the statistical paired t-test (Fe(II): t<inf>cal</inf> = -0.28, t<inf>cri</inf> = 2.45 and Fe (III): t<inf>cal</inf> = 1.77, t<inf>cri</inf> = 2.45). Remarkedly, The PAD enables the simultaneous determination of Fe(II) and Fe(III) without cross- reactivity effect.
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A new coumarin-based “OFF–ON” fluorescent sensor for H2S detection in HeLa cells
(2025-02-05)
Sontisiri, Pakornsiri
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Promrug, Dusit
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Arthan, Dumrongkiet
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Choengchan, Nathawut
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Thongyoo, Panumart
A new “OFF–ON” coumarin-based fluorescent probe for H<inf>2</inf>S detection was designed and successfully developed through O-sulfonylation between a dabsyl quencher and 7-hydroxy-4-methylcoumarin as a fluorescent reporter, based on a FRET approach. This H<inf>2</inf>S responsive probe, utilizing H<inf>2</inf>S assisted thiolysis of a sulfonate ester as the sensing strategy, demonstrated excellent performance towards H<inf>2</inf>S with a limit of detection (LoD) of 1.64 µM, along with superb selectivity, good stability and high specificity towards H<inf>2</inf>S without interference from other biomarkers and analytes. Moreover, dabsyl-7-hydroxy-4-methylcoumarin (dabsylcoumarin) is capable of permeating the cell membrane and effectively visualizing the level of H<inf>2</inf>S in the living HeLa cells without cytotoxicity.
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Superhydrophobic eggshell for fabrication of hydrophobic barrier of paper-based analytical device for colorimetric determination of ammonium ion in water
(2024-05-01)
Thangjitsirisin, Kanyapak
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Seeharaj, Panpailin
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Choengchan, Nathawut
This work demonstrates the first application of the superhydrophobic eggshell as an environmental-friendly material for fabricating the hydrophobic barrier of a paper-based analytical device (PAD). The eggshell surface was modified by mixing the pulverized chicken eggshell biowaste with stearic acid and a polystyrene binder to accomplish superhydrophobicity. The PAD (10 × 10 mm2) is comprised of the circular-shaped hydrophilic reservoir (Ø 5 mm). The liquid barrier was fabricated by painting both the topside and the underside of the filter paper with the dispersed superhydrophobic eggshell solution. The SEM images revealed that the microsized superhydrophobic eggshell particles absorbed onto the porous surface of the cellulose fibril. A coated surface with a water contact angle of 155.39° ± 1.02° (n = 10) on the paper substrate was achieved, and this indicated superhydrophobicity. The eggshell barrier enabled excellent water and chemical resistance. The fabricated PAD was applied for the colorimetric determination of ammonium cations (NH<inf>4</inf>+), based on the modified Berthelot reaction. Samples and chromogenic solutions were aliquoted onto the hydrophilic reservoir, with subsequent capture of the optical image of the stable, green-colored product by a smart phone under a light-controlled studio. The green color intensities were evaluated by ImageJ™ and plotted against the standard NH<inf>4</inf>+ concentrations. A wide linear calibration range 5.0 to 100 mg N/L was achieved with good linearity (r2 > 0.99). The PAD confirmed satisfied analytical recovery (Mean ± SD: 100.6 % ± 0.97, n = 11 samples) and high precision (RSD = 0.85 %: 10-PAD replicate measurements of 1.0 mg N/L). The limit of detection (3 SD of blank/slope) of 1.05 mg N/L was found sensitive enough to monitor the NH<inf>4</inf>+ contents in freshwater. The results, determined by the developed PAD and ion chromatography, showed no significant difference under the statistical paired t-test at 95 % confidence (t<inf>stat</inf> = -1.80, t<inf>cri</inf> = 2.57, n = 6 samples).
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A Microfluidic Paper-based Analytical Device for Simultaneous Measurement of Albumin, Creatinine and Uric Acid in Urine based on Standard Addition Method
(2024-01-03)
Wisaichon, Wannakan
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Choengchan, Nathawut
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Praditweangkum, Wiboon
This work describes a simple method for the simultaneous measurement of urinary albumin, creatinine and uric acid using a standard addition approach on a microfluidic paper-based analytical device (µPAD). Hydrophobic barrier of the µPAD was created by stamping indelible ink onto a filter paper. The µPAD was designed with a flower-liked configuration. After aliquoting urine to a central sample zone, the sample flowed to ten surrounding channels, namely “the inner channels”, where the blank (water) or standard solutions had been added. The inner channels were connected to circular reagent zones where reagents had been immobilized. Tetrabromophenolphthalein ethyl ester, alkaline picrate, and a mixed solution of ferric chloride and ferric cyanide were used as the chromogenic reagents for the colorimetric detections of albumin, creatinine, and uric acid, respectively. Each reagent zone was linked with a circular detection zone through a second channel, namely “the outer channels”. The blue-, orange-and greenish-blue colored products were observed in the detection zones for the measurement of albumin, creatinine, and uric acid, correspondingly. A digital image of the µPAD was captured with a mobile phone. The color intensities were evaluated by ImageJ™ and were employed for the quantitative analyses. The standard addition calibrations were found to be linear (r2 > 0.99) for the spiked analyte concentrations up to 100 mg L-1 albumin, 1000 mg L-1 creatinine, and 50 mg dL-1 uric acid. The paper platform provided high precision (RSD < 5 %) and good analytical recovery (91.8-109.7 %). Under paired t-test, the results obtained by the developed µPAD and the validating methods were not significantly different at 95 % confidence (albumin: t<inf>stat</inf> =-0.130, t<inf>cri</inf> = 3.182, creatinine: t<inf>stat</inf> =-0.133, t<inf>cri</inf> = 3.182, and uric acid: t<inf>stat</inf> = 1.119, t<inf>cri</inf> = 3.182).
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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
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Sookpotarom, Punyapat
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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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Transparent Cross-Flow Platform as Chemiluminescence Detection Cell in Cross Injection Analysis
(2023-02-01)
Somboonsuk, Thachkorn
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Saetear, Phoonthawee
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Mantim, Thitirat
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Ratanawimarnwong, Nuanlaor
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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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Multi-well plate as headspaces for paper-based colorimetric detection of sulfur dioxide gas: An alternative method of sulfite titration for determination of formaldehyde
(2023-01-25)
Yodpach, Nattapon
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Chantiwas, Rattikan
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Wilairat, Prapin
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Choengchan, Nathawut
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Praditweangkum, Wiboon
This work describes the analysis of formaldehyde using a 96-well microplate as multiple headspaces for the separation of sulfur dioxide gas generated from the sulfite remaining after its reaction with the formaldehyde in the sample. The quantitation of the gas is by colorimetric detection of an indicator paper placed over the microplate. The samples are aqueous extracts of various foods that are possibly adulterated with formaldehyde. A known excess amount of sulfite is added to the extract solution aliquoted in the well. The remaining sulfite is acidified with hydrochloric acid to generate sulfur dioxide gas which diffuses through the headspace above the solution to be absorbed at the moist strip of the indicator paper placed over the mouth of the wells. Anthocyanins extracted from the butterfly pea flower is used as the pH indicator giving a color change from the increase of hydrogen ions by hydrolysis of the absorbed sulfur dioxide gas. The exposed paper strip is scanned, and the digital images of the colored region analyzed using ImageJ software. The optimized method has a linear range of 200–1000 mg L−1 formaldehyde with limit of detection ((2.57*SD of intercept)/(slope of calibration line)) of the aqueous extract of 40 mg L−1 and coefficient of determination (r2) > 0.9979. Samples of fresh produce, such as seafood, meat, and vegetables, and various processed food were analyzed for their possible formaldehyde content. The results obtained from the headspace paper-based colorimetric detection are not statistically different from the values obtained from the titration method by paired t-tests.

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