Browsing by Author "Thanakorn Pluangklang"
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Item Metadata only Determination of antioxidants in polymer by high performance liquid chromatography(Mahidol University. Mahidol University Library and Knowledge Center, 2002) Thanakorn Pluangklang; Juwadee Shiowatana; Duangjai NacaprichaPublication Metadata only Development of flow systems incorporating membraneless vaporization units and flow-through contactless conductivity detector for determination of dissolved ammonium and sulfide in canal water(2018-01-15) Waleed Alahmad; Thanakorn Pluangklang; Thitirat Mantim; Victor Cerdà; Prapin Wilairat; Nuanlaor Ratanawimarnwong; Duangjai Nacapricha; Nakhonratchasima Rajabhat University; Mahidol University; Universitat de les Illes Balears; Srinakharinwirot University; Flow Innovation-Research for Science and Technology Laboratories (Firstlabs)© 2017 Elsevier B.V. Use of membraneless vaporization (MBL-VP) unit with two cone-shaped reservoirs is presented for on-line separation and detection of non-volatile species. A flow system comprising two sets of MBL-VP units with a single in-house capacitively coupled contactless conductivity detector (C4D) was developed for dual determination of ammonium and sulfide ions. Using the continuous-flow section, two zones (280 μL) of a sample, either mixed with sodium hydroxide (for ammonium) or hydrochloric acid (for sulfide), are separately delivered into the donor reservoir of the MBL-VP units. The acceptor reservoir contains either 150 μL of 15 μM HCl solution (for ammonia) or pure water (for hydrogen sulfide), respectively. Vaporization and trapping of the ammonia or hydrogen sulfide gas from the donor reservoir into the liquid acceptor cone occur concurrently in the two separate MBL-VP units. After trapping the gas for 3 min, the two 150-μL liquid acceptors are sequentially aspirated through the C4D flow cell for recording the changes in the conductivity. Linear calibrations were obtained for ammonium from 5 to 80 µM (Volt = (0.0134 ± 0.0003) [NH4+] – (0.01 ± 0.01), r2 = 0.998) and for sulfide from 5 to 200 µM (Volt = (0.0335 ± 0.0009) [S2-] – (0.13 ± 0.09), r2 = 0.996). Analysis time for both analytes is only 320 s. Our method was applied to analyze canal water samples. The results agree well with membrane gas-diffusion flow injection techniques, using bromothymol blue for ammonium and methylene blue for sulfide. Recoveries ranged from 95% to 104%.Publication Metadata only New membraneless vaporization unit coupled with flow systems for analysis of ethanol(2013-09-24) Nuanlaor Ratanawimarnwong; Thanakorn Pluangklang; Tongchai Chysiri; Duangjai Nacapricha; Srinakharinwirot University; Mahidol University; Rajamangala University of Technology Phra NakhonThis work presents the development of a new design for a membraneless vaporization (MBL-VP) unit, called dual chamber MBL-VP for measurement of volatile compounds. With this unit, exact volumes of sample and reagent are introduced into their respective cone-shaped chambers from the base of the cones. Diffusion of volatile analyte then takes place. After an appropriate time interval, the acceptor solution is withdrawn from the chamber into the detector flow-cell, while the sample solution is withdrawn to waste. Unlike the previous MBL-VP design, problems with overflow of solutions are eliminated by precise control of the input volume to be less than the volume of the chamber. The developed flow system with the dual chamber MBL-VP unit was applied to the determination of the ethanol content of various liquid samples, using the oxidation reaction between potassium dichromate and the diffused ethanol. In addition, in order to accelerate the gas diffusion process, the donor chamber was aerated. As the result, relatively short analysis time of 144. s was achieved for ethanol content in the range of 5-50% (v/v). The proposed method was successfully validated against a gas chromatographic method for 17 alcoholic samples. Percentage recovery was in the range of 96-109%. © 2013 Elsevier B.V.Publication Metadata only A simple microfluidic electrochemical HPLC detector for quantifying Fenton reactivity from welding fumes(2014-01-01) Thanakorn Pluangklang; John B. Wydallis; David M. Cate; Duangjai Nacapricha; Charles S. Henry; Mahidol University; Colorado State University© the Partner Organisations 2014. Development and characterization of a simple microfluidic electrochemical flow cell that can be coupled with HPLC to enable dual absorbance/electrochemical detection is described. Coupling absorbance and electrochemical detection increases the information that can be gathered from a single injection, but a second (typically expensive) detection system is required. Here, an inexpensive, customizable microfluidic electrochemical detector is coupled in series with a commercial HPLC/UV system. The microfluidic device is made from poly(dimethylsiloxane) and contains carbon paste electrodes. To demonstrate the utility of this dual-detection system, the reaction products of the radical scavenging agent salicylic acid and hydroxyl radical generated by Fenton chemistry were analyzed. The dual-detection system was used to quantify 2,5-dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid, and catechol produced by the addition of H2O2to filter samples of welding fumes. Measurement recovery was high, with percent recoveries between 97-102%, 92-103%, and 95-103% for 2,5-dihydroxybenzoic acid, 2,3-dihydroxybenzoic acid, and catechol, respectively, for control samples. The methods described in this work are simple, reliable, and can inexpensively couple electrochemical detection to HPLC-UV systems.Publication Metadata only Simultaneous determination of ethanol and total sulfite in white wine using on-line cone reservoirs membraneless gas-liquid separation flow system(2019-09-01) Pitchnaree Kraikaew; Thanakorn Pluangklang; Nuanlaor Ratanawimarnwong; Kanchana Uraisin; Prapin Wilairat; Thitirat Mantim; Duangjai Nacapricha; Nakhonratchasima Rajabhat University; Mahidol University; Srinakharinwirot University; Flow Innovation-Research for Science and Technology Laboratories (Firstlabs)© 2019 Elsevier B.V. This work presents the use of a single membraneless vaporization unit (MBL-VP unit) in a flow system for the simultaneous determination of ethanol and total sulfite in white wine. The flow system comprises a MBL-VP unit with three cone-shaped reservoirs and two in-house detectors, a paired emitter-detector diodes (PEDD) and a capacitively coupled contactless conductivity detector (C4D). The sample of white wine is first acidified in the flow system. Then 200-μL of the acidified sample is delivered to the donor reservoir of the MBL-VP unit in which the two acceptor reservoirs contain 200-μL of the gas acceptor reagents, viz. acidic permanganate solution and deionized water. Vaporization of ethanol and SO2(g) (converted from sulfite) from the donor into the acceptor reservoirs is carried out for 15 s. The two acceptor solutions are then simultaneously transferred for separate detection at the PEDD and C4D detectors. Decolorization of the permanganate solution by the reduction reaction with absorbed ethanol gives an increase in the PEDD signal, whereas dissolution of the SO2(g) in the water acceptor leads to an increase in conductivity and detected by the C4D. Linear calibrations were obtained in the range of 5.0–15.0% (v/v) for ethanol (PEDD signal = ((4.0 ± 0.03) × 10−2) · (%(v/v) ethanol) – ((1.85 ± 0.35) × 10−2): r2 = 0.999) and 10–200 mg L−1 for sulfite (C4D signal = ((0.64 ± 0.015) × 10−2) · (mg L−1 sulfite) – ((3.25 ± 1.64) × 10−2): r2 = 0.999). The analysis is rapid with total analysis time of 2.5 min. Percentage of recoveries were 81–104% and 88–110% for ethanol and sulfite, respectively. The method was compared with gas chromatographic analysis and iodometric titration for ethanol and sulfite, respectively, with no statistically significant difference for the analysis of seven white wine samples.
