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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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γ-Irradiated Chitosan Stabilized Silver Nanoparticles as Novel Colorimetric Sensors for Mercury(II) and Iron(II) Detections in Real Samples
(2023-06-01)
Thepchuay, Yanisa
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Jommala, Nareerat
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Wonglakhon, Tanakorn
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Nuengmatcha, Prawit
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Ninwong, Benjawan
This contribution presents a novel method for simple and rapid colorimetric detection of Hg(II) and Fe(II) ions in real samples using silver nanoparticles (AgNPs). The AgNPs were green-synthesized in aqueous solution using γ-irradiated chitosan as a reducing and stabilizing agent. The γ-chitosan stabilized AgNPs were found to be spherical with a diameter of 11.39 ± 2.23 nm. The AgNPs are highly selective for Hg(II) and Fe(II) ions, and when Hg(II) is present in solution, the yellowish AgNPs solution is turned to light yellow, while in the presence of Fe(II) the color of the AgNPs solution is changed to dark brown. The change of solution color is proposed via (i) The reoxidation of Ag(0) in AgNPs to Ag(I) for the Hg(II) detection and (ii) The aggregation of AgNPs in solution for the Fe(II) detection. Under optimal conditions, the method exhibits good linearity from 0.5 to 5.0 ppm (r 2 = 0.9965) for Hg(II) and from 0.05 to 10.0 ppm (r 2 = 0.9994) for Fe(II). The limit of detections (LODs) for Hg(II) and Fe(II) analyses are 0.22 and 0.18 ppm, respectively. Tap waters spiked with both ions show excellent percentage recoveries (93.48–99.53%) with good precision (%RSD < 5%). The developed method was for the first time successfully applied to the assessment of Fe(II) contents in pharmaceutical products, and has potential to be developed as an effective detection kit for assessing Hg(II) and Fe(II) ions in real samples.
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Upregulation of Hox-hydrogenase gene expression by nutrient adjustment in the filamentous non-heterocystous cyanobacterium Arthrospira sp. PCC 8005
(2020-12-01)
Raksajit, Wuttinun
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Maneeruttanarungroj, Cherdsak
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Mäenpää, Pirkko
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Lehto, Kirsi
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Incharoensakdi, Aran
Arthrospira sp. PCC 8005 is potentially able to produce hydrogen catalysed by hox gene–encoded bidirectional hydrogenase with the aid of hyp gene–encoded accessory proteins. In the present study, we investigated the physiological factors affecting the hoxE, hoxY, hoxH, and hypF transcription in Arthrospira sp. PCC 8005. About a 4-fold increase of biomass and chlorophyll-a content was observed in cells grown for 7 days in Zarrouk’s medium supplemented with Fe2+. Cells grown in N-deprived medium with added Ni2+ had increased H<inf>2</inf> production and hydrogenase activity with a maximal value of 7.24 ± 0.25 μmol H<inf>2</inf> mg−1 Chla h−1 and 0.61 ± 0.03 μmol H<inf>2</inf> mg−1 Chla h−1, respectively. RT-PCR analysis revealed that cells grown in the N-deprived medium supplemented with Fe2+ or Ni2+ increased hoxE, hoxY, and hoxH transcripts. However, the highest increase of the hoxE, hoxY, hoxH, and hypF transcripts was observed in cells grown in the S-deprived medium supplemented with a combination of Fe2+ and β-mercaptoethanol. These results indicated that the increased expression of hox genes in Arthrospira sp. PCC 8005 can be achieved by proper adjustment of the nutrients in the growth medium. Phylogenetic analysis revealed that the small hydrogenase subunit, HoxY sequence, from Arthrospira sp. PCC 8005 was clustered together along with other cyanobacterial HoxY which is highly related to Arthrospira platensis NIES46.
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Development of non-enzymatic N-doped graphene supported cobalt/iron amperometric based sensor for glucose detection in urine
(2019-01-24)
Janyasupab, Metini
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Promptmas, Chamras
We presented a cost-effective design of electrochemical based biosensor for non-enzymatic glucose detection in urine. By incorporating low-cost, non-precious cobalt (Co)/iron (Fe) metals, the sensor was employed onto the three-electrode system for quantifying glucose level from 0 to 3.25 mM in artificial urine medium and clinical simulated urine solution, namely, Surine. In particular, the fabricated CoFe nanoparticles on N-doped graphene (NG) biosensor was assessed electrochemical performances by cyclic voltammetry and amperometry at applied potential of +0.90 V versus Ag/AgCl, in comparison with that of CoFe on carbon supported. Based on the results, it was found that two processes of catalytic oxidation and oxide depletion are involved in glucose detection. More importantly, the as-prepared biosensor exhibited an outstanding sensitivity of 476.67 µA.cm-2.mM-1 with R2 of 0.9974 in Surine. Furthermore, the low limit of detection was estimated to be 37.7 µM (signal-to-noise ratio of 3) with an excellent anti-interference property toward ascorbic acid, uric acid, and chlorine ions, providing a promising advancement for future glucose measurement in urine, applicable for sustainable diabetic prognosis and management.
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Impact of substrate feed patterns on solids reduction by the cannibal process
(2015-03-01)
Khanthongthip, Passkorn
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Novak, John T.
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Doyle, Michael L.
A biological solids reduction process that uses a sidestream anaerobic reactor (Cannibal process) was investigated to better understand why variations in solids reduction occur in field installations. Field observations indicated that single stage, high sludge age processes would frequently not provide a low solids yield. To study this, laboratory sequencing batch reactors were operated, one as a conventional activated sludge system and the other two with a side-stream anaerobic reactors. The controland oneanaerobic side-stream system were operated with a 5-minute feed cycle to mimic a plug flow system. The other anaerobic side-stream system operated with a 4-hour feed cycle to simulate complete mix. The 5 minutes feed Cannibal system generated up to 80% less biological solids than the control. The 4 hours feed Cannibal system produced less biological solids than the conventional activated sludge system but remained higher than for system with a 5-minute feed time.
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Tandem measurements of iron and creatinine by cross injection analysis with application to urine from thalassemic patients
(2015-01-01)
Choengchan, N.
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Mantim, T.
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Inpota, P.
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Nacapricha, D.
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Wilairat, P.
This work presents development of a method for the dual determination of Fe(III) and creatinine using cross injection analysis (CIA). Two CIA platforms connected in series accommodated sample and reagents plugs aspirated via y-direction channels while water was pumped through the x-direction channel toward a flow-through cell of a diode array UV-vis. detector. Iron was detected from the colorimetric reaction between Fe(II) and 2-(5-bromo-2-pyridylazo)-5-(N-propyl-N-(3-sulfopropyl)amino) aniline (5-Br-PSAA), with prior reduction of Fe(III) to Fe(II) by ascorbic acid. The Jaffes reaction was employed for the detection of creatinine. Under the optimal conditions, good linearity ranges were achieved for iron in the range 0.5 to 7 mg L-1 and creatinine in the range 50 to 800 mg L-1. The CIA system was applied to spot urine samples from thalassemic patients undergoing iron chelation therapy, and was successfully validated with ICP-OES and batchwise Jaffes method. Normalization of urinary iron excretion with creatinine is useful for correcting the iron concentration between urine samples due to variation of the collected urine volume.

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