Papers by Siripat Suteerapataranon
Journal of flow injection analysis, Jun 1, 2008
A simple flow injection analysis-spectrophotometric system for the rapid determination of total p... more A simple flow injection analysis-spectrophotometric system for the rapid determination of total polyphenols (TP) in tea extracts was developed. The method is based on Folin-Ciocalteu (FC) reaction, which involves the oxidation/reduction of polyphenolic compounds by FC reagent in alkaline medium, producing a blue molybdenum-tungsten complex. The linear range of the calibration graph was 10-500 mg gallic acid equivalent (GAE)/l. The relative standard deviation (RSD) (n=5) of the calibration graph was 2.93%. The precisions (%RSD, n=10) of the determination at low and high concentrations were 2.74% for the 10 mg GAE/l and 3.02% for the 500 mg GAE/l, respectively. The detection limit was 7 mg/l. The sample throughput was 30 per hour. The TP contents in tea extracts determined by the developed system were compared with those determined by the standard batch method and no significant difference was found (t test, at 95% confidence level).
Talanta, Dec 6, 2002
Flow injection (FI) and sequential injection (SI) systems with anodic stripping voltammetric dete... more Flow injection (FI) and sequential injection (SI) systems with anodic stripping voltammetric detection have been exploited for simultaneous determination of some metals. A pre-plated mercury film on a glassy carbon disc electrode was used as a working electrode in both systems. The same film can be repeatedly applied for at least 50 analysis cycles, thus reducing the mercury consumption and waste. A single line FI voltammetric system using an acetate buffer as a carrier and an electrolyte solution was employed. An injected standard/sample zone was mixed with the buffer in a mixing coil before entering a flow cell. Metal ions were deposited on the working electrode by applying a potential of -1.1 V vs Ag/AgCl reference electrode. The stripping was performed by anodically scanning potential of working electrode to +0.25 V, resulting a voltammogram. Effects of acetate buffer concentration, flow rate and sample volume were investigated. Under the selected condition, detection limits of 1 mug l(-1) for Cd(II), 18 mug l(-1) for Cu(II), 2 mug l(-1) for Pb(II) and 17 mug l(-1) for Zn(II) with precisions of 2-5% (n=11) were obtained. The SI voltammetric system was similar to the FI system and using an acetate buffer as a carrier solution. The SI system was operated by a PC via in-house written software and employing an autotitrator as a syringe pump. Standard/sample was aspirated and the zone was then sent to a flow cell for measurement. Detection limits for Cd(II), Cu(II), Pb(II) and Zn(II) were 6, 3, 10 and 470 mug l(-1), respectively. Applications to water samples were demonstrated. A homemade UV-digester was used for removing organic matters in the wastewater samples prior to analysis by the proposed voltammetric systems.
Sustainability, 2022
The COVID-19 pandemic has forced analytical chemistry educators in Thailand to change methods of ... more The COVID-19 pandemic has forced analytical chemistry educators in Thailand to change methods of teaching and learning to new normal ones. Higher education has faced additional challenges because of a lack of hands-on experiments and an increasing number of students in foundation chemistry courses being hindered from practicing skills. This work aimed to develop a Lab-at-Home (LAH) for new normal, analytical chemistry experimentation. The LAH implemented a hands-on green chemistry experiment, i.e., colorimetric determination of iron using non-hazardous reagents (supporting Sustainable Development Goal (SDG) 12-responsible consumption and production). The LAH was sent to students at their location before the synchronous class, where the instructors were prompt to supervise. Thus, this supports SDG4-quality education and SDG10-reduced inequalities. The learning outcome achievements, i.e., the analytical characteristics and colorimetry principles comprehension, as well as the ability t...
Trace heavy metals are very important in the environment due to their serious toxicity although p... more Trace heavy metals are very important in the environment due to their serious toxicity although presenting at very low concentrations. They may accumulate in food chain. The development of new methods for quantifying trace metals is required and challenged. Most of the sensitive and selective methods recently available such as ICP-MS, ICP-AES and GF-AAS are too expensive and are not practically applied in a developing country, i.e. Thailand. Alternative cost-effective methods based on combination of flow techniques for sample pretreatment e.g. preconcentration/separation with some spectrometric detection systems have been proposed. Voltammetry, especially anodic stripping voltammetry is a promising technique for the determination of trace elements. It is relatively low-cost but provides high sensitivity and can be simultaneous determination of multi-elements. However, batch voltammetry consists of a time consuming and a tedious analysis procedure. Flow techniques have been applied t...
Chemistry of Natural Compounds, 2016
Plants are the largest reservoir of secondary metabolites that contribute to combating different ... more Plants are the largest reservoir of secondary metabolites that contribute to combating different diseases from ancient times [1]. Oroxylum indicum (L.) Benth. ex Kurz, a plant belonging to the Bignoniaceae family, is known as an Asian medical plant and is used in folk medicine for the treatment of rheumatism, diarrhea, and dysentery [2, 3]. Considering its wide traditional uses, we have carried out phytochemical studies of O. indicum and evaluated the antibacterial and antioxidative activities of its crude extracts and isolated compounds. Studies of the chemical constituents of the leaves, roots, stems, and twigs of O. indicum show that it possesses flavonoids, xanthones, coumarin, quinine, one cyclohexylethanoid, benzaldehyde, and one phenylpropanoid. Their structures were elucidated by spectroscopic analysis including UV, IR, and NMR. To the best of our knowledge, the 11 compounds (6-16) in O. indicum are reported for the first time. The antibacterial and antioxidative activities of the extracts and isolated compounds were also evaluated using 2-fold serial dilutions and flow injection analysis (FIA) methods, respectively. Isolation and purification of O.
Total polyphenols (TP) in some Chiang Rai leaf tea products were analysed by spectrophotometric m... more Total polyphenols (TP) in some Chiang Rai leaf tea products were analysed by spectrophotometric method based on Folin-Ciocalteau's reaction. The TP contents in green, oolong and black tea products, produced at different degree of fermentation, were compared. The leaf tea samples included 12 samples of green tea, 11 samples of oolong tea, and 4 samples of black tea. Polyphenols react with W and Mo compounds in Folin- Ciocalteau reagent resulting in a blue complex. The absorption wavelength used was 739 nm. Calibration graphs were constructed using gallic acid as a standard solution. It was found that in average green tea samples contained higher TP content (8.75±2.04%wt) than oolong tea (7.47±2.24%wt) and black tea (3.98±2.11%wt) samples, respectively. It indicated that the degree of fermentation in tea manufacturing process could possibly affect the TP content in tea products. Green tea, less fermented tea, contained the highest amount of TP, whereas oolong and black teas, under...
Water Research, 2006
The release of metal ions from a coal mining tailing area, Lamphun, Northern Thailand, is studied... more The release of metal ions from a coal mining tailing area, Lamphun, Northern Thailand, is studied by leaching tests. Considerable amounts of Mn, Fe, Al, Ni and Co are dissolved in both simulated rain water (pH 4) and 10 mg L À1 humic acid (HA) solution (Aldrich humic acid, pH 7). Due to the presence of oxidizing pyrite and sulfide minerals, the pH in both leachates decreases down to $3 combined with high sulfate concentrations typical to acid mine drainage (AMD) water composition. Interaction of the acidic leachates upon mixing with ground-and surface water containing natural organic matter is simulated by
Talanta, 2002
Flow injection (FI) and sequential injection (SI) systems with anodic stripping voltammetric dete... more Flow injection (FI) and sequential injection (SI) systems with anodic stripping voltammetric detection have been exploited for simultaneous determination of some metals. A pre-plated mercury film on a glassy carbon disc electrode was used as a working electrode in both systems. The same film can be repeatedly applied for at least 50 analysis cycles, thus reducing the mercury consumption and waste. A single line FI voltammetric system using an acetate buffer as a carrier and an electrolyte solution was employed. An injected standard/sample zone was mixed with the buffer in a mixing coil before entering a flow cell. Metal ions were deposited on the working electrode by applying a potential of -1.1 V vs Ag/AgCl reference electrode. The stripping was performed by anodically scanning potential of working electrode to +0.25 V, resulting a voltammogram. Effects of acetate buffer concentration, flow rate and sample volume were investigated. Under the selected condition, detection limits of 1 mug l(-1) for Cd(II), 18 mug l(-1) for Cu(II), 2 mug l(-1) for Pb(II) and 17 mug l(-1) for Zn(II) with precisions of 2-5% (n=11) were obtained. The SI voltammetric system was similar to the FI system and using an acetate buffer as a carrier solution. The SI system was operated by a PC via in-house written software and employing an autotitrator as a syringe pump. Standard/sample was aspirated and the zone was then sent to a flow cell for measurement. Detection limits for Cd(II), Cu(II), Pb(II) and Zn(II) were 6, 3, 10 and 470 mug l(-1), respectively. Applications to water samples were demonstrated. A homemade UV-digester was used for removing organic matters in the wastewater samples prior to analysis by the proposed voltammetric systems.
Talanta, 2005
Sequential injection with "Lab-at-Valve (LAV)" approach is demonstrated for potentiometric determ... more Sequential injection with "Lab-at-Valve (LAV)" approach is demonstrated for potentiometric determination of chloride. The LAV flowthrough electrode system consists of two Ag/AgCl electrodes: one as a reference electrode, silver chloride activated surface-silver wire soaked in a constant-concentration chloride ion solution in a small tube covered with a polymer-membrane, another as a working electrode (a similar silver chloride activated surface-silver wire) placed in a flow channel. The electrode system is attached at one port of a 10 port multiposition valve. A modified autoburette was used as a propelling device. Using SI operation via a program written in-house, based on LabVIEW ® , a standard/sample is inserted, via the selection valve, in potassium nitrate as an electrolyte and water is used as a carrier. The zones are transported from the holding coil to the flow cell to monitor the difference in potential due to concentration cell behavior. The potential difference is then recorded as a peak. Peak height is proportional to logarithm of chloride concentration. The SI-LAV for chloride determination is very simple, fast, precise, accurate, automatic and economical. Applications to mineral drinking water and surface water have been made. The results agree with those of IC and titrimetric methods.
Food Chemistry, 2012
A simple flow injection (FI)-spectrophotometric system for the screening of antioxidant capacity ... more A simple flow injection (FI)-spectrophotometric system for the screening of antioxidant capacity in herbal extracts was developed. The analysis was based on the color disappearance due to the scavenging of 2,2diphenyl-1-picrylhydrazyl (DPPH) radical by antioxidant compounds. DPPH Å and ascorbic acid were used as reagent and antioxidant standard, respectively. Effects of the DPPH Å concentration, DPPH Å flow rate, and reaction coil length on sensitivity were studied. The optimized condition provided the linear range of 0.010-0.300 mM ascorbic acid with less than 5%RSD (n = 10). Detection limit and quantitation limit were 0.004 and 0.013 mM, respectively. Comparison of antioxidant capacity in some herbal extracts determined by the FI system and a standard method was carried out and no significant difference was obtained.
Food Chemistry, 2009
Caffeine in Chiang Rai tea infusions was found to be dependent on infusion conditions (water temp... more Caffeine in Chiang Rai tea infusions was found to be dependent on infusion conditions (water temperature and infusion time), and leaf form (non-ground or ground) but independent of tea variety and type. For non-ground leaf samples, the higher the water temperature and the longer the infusion time, the higher the caffeine concentrations in tea infusions. After infusing for longer than 15 min, the dissolution rate of caffeine became slower and the concentration was essentially constant. For ground leaves, the caffeine content was not influenced by infusion time. Caffeine concentrations in tea infusions from Camellia sinensis var. sinensis (26.8 ± 0.81 and 22.3 ± 5.55 mg/100 ml for ground and non-ground samples, respectively) were not significantly different from that of Camellia sinensis var. assamica (24.4 ± 0.66 and 20.3 ± 5.07 mg/100 ml for ground and non-ground samples, respectively). The difference in caffeine concentration between green tea (28.1 ± 8.19 mg/100 ml) and oolong tea (20.3 ± 1.52 mg/100 ml) was not statistically significant.
Sustainability, 2021
To minimize chemical waste and protect the environment, our team has used green analysis with nat... more To minimize chemical waste and protect the environment, our team has used green analysis with natural reagents. In this work, we designed a natural-reagent assay kit for iron determination and implemented it in chemistry education in Thailand. The iron assay method was adapted from Thai local wisdom of testing water quality using guava leaves. The guava leaf powder served as a natural reagent in the assay. The kit included equipment, standard and buffer solutions and a manual. A smart device with a built-in camera was used as a detector. Educators in six universities in Thailand implemented the kit in laboratories with modifications depending on their learning outcomes. The kit implementation was evaluated using a survey with questions in four aspects: usability, learning achievement, green chemistry and portability. The high average scores for all questions (> 4.00 of 5.00 points), with the average overall score of 4.53 ± 0.60, indicated satisfaction regarding in all aspects. Us...
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Papers by Siripat Suteerapataranon