Juwadee Shiowatana

Mahidol University, Krung Thep, Bangkok, Thailand

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Publications (60)184.85 Total impact

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    ABSTRACT: A homemade hollow fiber flow-field fractionation (Hf-FlFFF) coupled with inductively coupled plasma mass spectrometry (ICP-MS) was set-up for silver nanoparticles (AgNPs) separation by using polysulfone hollow fiber membrane (30,000 MW cutoff) as a separation channel. Tannic acid and citrate stabilized AgNPs were synthesized and introduced into Hf-FlFFF. The effects of carrier liquid and stabilizing agent on retention behavior of AgNPs were investigated. Different elution behaviors were observed as follows: with 0.02% (w/v) FL-70, all of AgNPs were eluted from Hf-FlFFF but differences in retention behaviors were observed for AgNPs with tannic acid and citrate stabilizing agents; and with 30mM TRIS buffer, only tannic acid stabilized AgNPs were eluted from Hf-FlFFF, whereas citrate stabilized AgNPs were not eluted. In this work, tannic acid addition into carrier liquid was proposed to modify the surface of AgNPs and the surface of the membrane, and thereby adjusting the retention behaviors of AgNPs. Various concentrations of tannic acid were added into FL-70 and TRIS buffer. With the use of 0.1mM tannic acid in 30mM TRIS buffer as the carrier liquid, retention behaviors of both tannic acid stabilized- and citrate stabilized-AgNPs were similar and with similar fractionation recovery. Copyright © 2015 Elsevier B.V. All rights reserved.
    Journal of Chromatography A 08/2015; 1415. DOI:10.1016/j.chroma.2015.08.047 · 4.17 Impact Factor
  • Panida Wimuktiwan · Juwadee Shiowatana · Atitaya Siripinyanond ·
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    ABSTRACT: Flow field-flow fractionation (FlFFF) with on-line inductively coupled plasma mass spectrometer (ICP-MS) was employed for investigation of protein-silver nanoparticles (AgNPs) association. In this work, bovine serum albumin (BSA), globulin, and fibrinogen were the model proteins studied. AgNPs were prepared by reduction of silver nitrate using tannic acid as reducing and stabilizing agent. Various sizes (2.6, 10, and 26 nm) were obtained depending on the pH condition during particle preparation. The apparent association constants between BSA and AgNPs of various sizes were determined. Then, various concentrations of AgNPs of 2.6 nm were incubated with plasma proteins, i.e., albumin of 2.6 x 10-1 M; globulin of 3.1 x 10-2 M; and fibrinogen of 2.9 x 10-3 M, at 37 °C for investigation of protein-AgNPs association. Factors influencing protein-AgNPs association were investigated including effect of incubation time and effect of AgNPs concentration. Association between protein and AgNPs increased as incubation time and concentration of AgNPs increased. Further, the binding stoichiometry between BSA and AgNPs was determined to be approximately 1 : 5 x 10-7.
    Journal of Analytical Atomic Spectrometry 10/2014; 30(1). DOI:10.1039/C4JA00225C · 3.47 Impact Factor
  • Pornwilard M-M · Wilaiwan Somchue · Juwadee Shiowatana · Atitaya Siripinyanond ·
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    ABSTRACT: An on-line flow field-flow fractionation (FlFFF) with inductively coupled plasma mass spectrometry (ICP-MS) was employed for particle size characterization of selenium nanoparticles stabilized by pectin, mixed alginate/pectin, ovalbumin, and β-lactoglobulin. Under the synthesis condition used herein, the particle size increased in the following order when β-lactoglobulin, ovalbumin, mixed alginate/pectin, and pectin was used as a stabilizing agent. Upon incubation of selenium nanoparticles in gastrointestinal conditions, both in enzymatic and non-enzymatic media, particle size distributions and the surface of selenium nanoparticles changed differently. Nonetheless, more than 90 % of selenium was still presented in nanometer range after gastrointestinal digestion for the nanoparticles prepared by all types of stabilizers. In addition, the results show good agreement between the particle size observed from FlFFF and TEM technique.
    Food Research International 03/2014; 57. DOI:10.1016/j.foodres.2014.01.040 · 2.82 Impact Factor
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    ABSTRACT: Rice is a staple food for nearly half the world's population. The discrimination of geographical origin of rice in order to its authenticity is essential to prevent mislabeling and adulteration problems. The multi-element fingerprinting has a great potential for the differentiation of rice grains. A study of the capability of the high resolution inductively coupled plasma mass spectrometry (HR-ICP-MS) methodology for multi-element fingerprinting of rice has been carried out. A total of 31 Thai jasmine rice and 5 foreign (France, India, Italy, Japan and Pakistan) rice samples were analysed by high resolution ICP-MS after acid digestion. Accuracy of the whole procedure was verified by the analysis of rice flour standard reference material (NIST SRM 1568a). The concentrations of 21 elements were evaluated and used as chemical indicator to discriminate the origin of rice samples. The classification of rice samples was carried out based on elemental composition by a radar plot and multivariate data analysis, including principal component analysis (PCA) and discriminant analysis (DA). Thai jasmine rice can be differentiated from foreign rice samples by radar plots and multivariate data analysis. Furthermore, the DA can differentiate Thai jasmine rice samples according to each region of origin (northern, northeastern or central regions of Thailand). Therefore, multi-element fingerprinting combined with the use of multivariate statistical techniques can be considered as a powerful tool for rice authentication.
    Food Chemistry 12/2013; 141(4):3504-9. DOI:10.1016/j.foodchem.2013.06.060 · 3.39 Impact Factor
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    P. Cheajesadagul · J. Shiowatana · A. Siripinyanond · J. Szpunar ·
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    ABSTRACT: In recent years, research efforts have focused on the potential of analytical techniques for the determination of agricultural products according to source or geographical origin. For most of the food products, the authenticity is determined by geographical origin, botanical/cultivar origin or the absence of adulterants. Rice is one of the most important staple food crops, providing a staple diet for almost half of the world’s population, especially in Asia and America. Rice cultivar and cultivation area are crucial factors in the market prices of rice. The determination of rice authenticity is indeed essential to resolve the problems of mislabeling and misleading about origin and adulteration, which is defined as a process by adding inferior rice to premium rice, affecting the credibility of producers and traders and the right of consumers. Regarding rice, source identification is a more complex issue because it can depend on both geographical origin and cultivar type. It is recognized that the mineral and trace elemental composition of rice reflects both the cultivar and soil in which the rice grows. Thus, multielement fingerprinting has great potential for the differentiation of rice origins and can also be served as chemical descriptors of the geographical of rice. Concerning origin assignment, the use of multivariate statistical techniques, e.g. principal component analysis (PCA), discriminant analysis (DA) and cluster analysis (CA), is necessary to combine with multielemental analysis and stable isotope analysis for the discrimination of rice grains according to their geographical origins. The aim of this chapter is to provide an overview concerning the current analytical methodologies focusing on multi-element and isotope analyses such as inductively coupled plasma-mass spectrometry (ICP-MS) and isotope ratio mass spectrometry (IRMS) in combination with multivariate analysis in order to discriminate geographical origin of rice, confirming their authenticity
    Comprehensive Analytical Chemistry, Food Protected Designation of Origin — Methodologies and Applications, Edited by Miguel de la Guardia, Ana Gonzalez Illueca, 08/2013: chapter Rice: pages 623-655; Elsevier., ISBN: ISBN 13: 9780444595621 ISBN 10: 0444595627
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    ABSTRACT: A coupling of thin layer chromatography with laser ablation ICP SF MS was developed for the fractionation of Ni, V, Fe and S in crude oil and its fractions (saturate, aromatic, resin and asphaltene). The detection limits were 18 ng g(-1) and 23 ng g(-1) for nickel and vanadium, respectively, and a sample could be characterized in terms of the metal distribution as a function of species polarity within 10 min. The method was used to characterize the metal distribution in crude oils of different origins and their different fractions.
    Talanta 08/2012; 97:574-8. DOI:10.1016/j.talanta.2012.04.040 · 3.55 Impact Factor
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    ABSTRACT: This paper describes the feasibility for trace analysis of chloramphenicol using a novel immunoassay by coupling competitive measurement of chloramphenicol (CAP) to ICP-MS by the use of CAP labeled with AuNPs. Polyclonal rabbit anti-mouse immunoglobulins (anti-mouse IgG) were pre-coated on the 96-well polystyrene microplate solid support to allow the retention of mouse monoclonal to chloramphenicol (MAb-anti-CAP) antibody-CAP on the plates. Samples containing CAP as an antigen premixed with CAP–BSA protein labeled with AuNPs as an immunogenic tag were added to the MAb-anti-CAP bound solid support, physically separated from non-reacting molecules. The AuNPs were measured by ICP-MS to indirectly determine the CAP concentration in the samples. For 10 nm AuNPs, the optimal condition for CAP–BSA protein conjugation was pH 9.5 and 120 mg l−1 of CAP–BSA protein. The detection limit, linearity range, and precision (intra-assay, inter-assay) were 4.52 ng ml−1, 0–20 ng ml−1, and less than 20%, respectively.
    Journal of Analytical Atomic Spectrometry 05/2012; 27(5):884-890. DOI:10.1039/C2JA10319B · 3.47 Impact Factor
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    Purim Jarujamrus · Junfei Tian · Xu Li · Atitaya Siripinyanond · Juwadee Shiowatana · Wei Shen ·
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    ABSTRACT: Recent reports on using bio-active paper and bio-active thread to determine human blood type have shown a tremendous potential of using these low-cost materials to build bio-sensors for blood diagnosis. In this work we focus on understanding the mechanisms of red blood cell agglutination in the antibody-loaded paper. We semi-quantitatively evaluate the percentage of antibody molecules that are adsorbed on cellulose fibres and can potentially immobilize red blood cells on the fibre surface, and the percentage of the molecules that can desorb from the cellulose fibre surface into the blood sample and cause haemagglutination reaction in the bulk of a blood sample. Our results show that 34 to 42% of antibody molecules in the papers treated with commercial blood grouping antibodies can desorb from the fibre surface. When specific antibody molecules are released into the blood sample via desorption, haemagglutination reaction occurs in the blood sample. The reaction bridges the red cells in the blood sample bulk to the layer of red cells immobilized on the fibre surface by the adsorbed antibody molecules. The desorbed antibody also causes agglutinated lumps of red blood cells to form. These lumps cannot pass through the pores of the filter paper. The immobilization and filtration of agglutinated red cells give reproducible identification of positive haemagglutination reaction. Results from this study provide information for designing new bio-active paper-based devices for human blood typing with improved sensitivity and specificity.
    The Analyst 03/2012; 137(9):2205-10. DOI:10.1039/c2an15798e · 4.11 Impact Factor
  • Chayayos Arkasuwan · Atitaya Siripinyanond · Juwadee Shiowatana ·
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    ABSTRACT: A hyphenated method of continuous-flow dialysis and on-line inductively coupled plasma mass spectrometry (ICP-MS), with and without the use of hydride generation sample introduction, was developed for the study of arsenic bioaccessibility in shrimp. The method was based on a simulated gastric digestion in a batch system followed by a continuous-flow intestinal digestion. The simulated intestinal digestion was performed in a dialysis bag placed inside a channel in a flowing stream of dialyzing solution (NaHCO3). The pH of the dialysate was monitored on-line to ensure pH changes similar to the situation in the gastrointestinal tract. The concentrations of total arsenic and inorganic arsenic in the dialysate were determined by ICP-MS without and with hydride generation, respectively. With the parameters used in the hydride generation as follows: 8% (v/v) of HCl; 1% (m/v) of NaBH4; and a pre-reduction solution (10% (w/v) KI in 5% (w/v) ascorbic acid), only inorganic arsenic can form arsine, implying that hydride generation-ICP-MS can be used to detect inorganic arsenic only. The method was applied for the estimation of arsenic bioaccessibility in shrimp samples, by which the bioaccessibility from shrimp was found to be approximately 55%, contributed from inorganic arsenic only 1% or 2%, and mostly from organic arsenic. Further, the effect of ascorbic acid and fruit juices on arsenic bioaccessibility was investigated which was found not to cause any significant changes in bioaccessibility.
    International Journal of Mass Spectrometry 10/2011; 307(1):61-65. DOI:10.1016/j.ijms.2010.09.029 · 1.97 Impact Factor
  • Pornwilard M.-M · Rak Hansawek · Juwadee Shiowatana · Atitaya Siripinyanond ·
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    ABSTRACT: Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) was applied to study source identification by using elemental fingerprint analysis combined with the use of multivariate statistical analysis of gem corundum samples with different colors (red, blue, purple, yellow) from six countries (Kenya, Madagascar, Nigeria, Tanzania, Cambodia and Thailand). With LA-ICP-MS, the element concentrations in the samples were calculated using NIST 612 standard glass reference material as the external standard, with Al being used as the internal standard. The optimum conditions of laser ablation, i.e., 9 mJ laser power, 100% laser energy, a spot size of 200 μm and a repetition rate of 20 Hz, were selected to improve the signal intensities. The multivariate data analysis, including principal component analysis (PCA) and linear discriminant analysis (LDA) was used for classification study of samples. Two categories of gem corundum were analyzed including the gem corundum of the same color and the gem corundum of different colors. In the case of gem corundum of the same color classification, the LDA provided good scatter plot that could differentiate rubies between South East Asia and African countries and blue sapphires from Madagascar and Nigeria. For the classification of gem corundum with different colors, the LDA with the use of normalization factor was effective for the identification of the origin of corundum samples with 80% accuracy.
    International Journal of Mass Spectrometry 09/2011; 306(1):57–62. DOI:10.1016/j.ijms.2011.06.010 · 1.97 Impact Factor
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    ABSTRACT: An on-line coupling between a continuous-flow sequential extraction (CFSE) unit and flow field-flow fractionation with cross flow matrix removal (FlFFF/CFM) with ICP-OES detection was developed for determination of metal leachability from soil. The use of high concentration of Mg(NO3)2 in exchangeable phase can cause undesirable matrix effects by shifting ionization equilibrium in the plasma, etc., resulting in a clear need for matrix removal. Therefore, the capability of FlFFF/CFM to remove Mg matrix ion from soil extract was evaluated. Poly(ethylene imine) (PEI) having molecular weight of 25,000 Da was added to form complexes with analyte elements (Cu, Mn, Pb, and Zn) but not the matrix element (Mg). The free Mg matrix ions were then removed by filtering off through the ultrafiltration membrane, having a 1000-Da molecular weight cut-off, inside the FlFFF channel. With the use of FlFFF/CFM, matrix removal efficiency was approximately 83.5%, which was equivalent to approximately 6-fold dilution of the matrix ion. The proposed hyphenated system of CFSE and FlFFF/CFM with ICP-OES detection was examined for its reliability by checking with SRM 2710 (a highly contaminated soil from Montana). The metal contents determined by the proposed method were not significantly different (at 95% confidence) from the certified values.
    Spectrochimica Acta Part B Atomic Spectroscopy 06/2011; 66(6):476-482. DOI:10.1016/j.sab.2011.04.012 · 3.18 Impact Factor
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    ABSTRACT: Lead doped keratin film standard was introduced as a new calibration standard for LA-ICP-MS determination of Pb along hair strands. The Pb doped keratin film standard was prepared by precipitation of hair protein solution casting in Pb standard solutions in the presence of trichloroacetic acid as a denaturant solution. Sulfur, which is a major matrix element in hair, was used as an internal standard element to normalize Pb intensity and to correct for variations in ablation efficiency and plasma condition. The method was applied to quantitatively determine Pb distribution along a single human hair strand obtained from workers in a battery manufacturing factory in Thailand who faced risk of Pb exposure. Single hair strands were analyzed along their length by LA-ICP-MS with a fixed spot size of 50 μm. The position of an analyzed hair sample on a strand was converted into time (hair closer to the scalp is newer) on the basis of an average hair growth rate of 0.33 mm per day. The patterns of Pb distribution of each worker in the same battery factory were different suggesting that these workers might either not be involved in the same activities or not work in the same room. This study demonstrated the applicability of LA-ICP-MS for rapid acquisition and tracking Pb concentrations along a single hair strand.
    Journal of Analytical Atomic Spectrometry 03/2011; 26(3):493-498. DOI:10.1039/C0JA00082E · 3.47 Impact Factor
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    ABSTRACT: A method was developed for the direct analysis of petroleum samples. A silica gel plate, commonly used in thin layer chromatography, was impregnated for 30 min with a sample solution and analyzed by laser ablation-ICP MS. The use of a doubly focusing sector field mass analyzer allowed the demonstration of the absence of carbon-related polyatomic interferences. Matrix suppression effects, common in nebulization-based sample introduction, were absent which enabled quantitation by external calibration. The detection limits were in the low ng g−1 range. The method was validated by the analysis of NIST 1084a and 1085b certified reference materials (wear metals in lubricating oils) and applied to the analysis of crude oil and asphaltene samples.
    Journal of Analytical Atomic Spectrometry 03/2011; 26(3):618-622. DOI:10.1039/C0JA00118J · 3.47 Impact Factor
  • Kanchana Songsilawat · Juwadee Shiowatana · Atitaya Siripinyanond ·
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    ABSTRACT: Flow field-flow fractionation (Fl-FFF) with off-line electrothermal atomic absorption spectrometry (ETAAS) detection was developed and employed for particle size characterization of Ag NPs stabilized by citrate, pectin, and alginate. Citrate stabilized-Ag NPs were prepared from sodium borohydride reduction of silver nitrate. Sodium citrate was used as the capping agent to stabilize Ag NPs and prevent the aggregation process. Pectin stabilized- and alginate stabilized-Ag NPs were prepared from ascorbic acid reduction of silver nitrate. Pectin and alginate were used as the capping agent for pectin stabilized- and alginate stabilized-Ag NPs, respectively. Three types of Ag NPs were characterized by using FlFFF, zeta potentiometer, and TEM technique. The mean particle sizes of Ag NPs as characterized by FlFFF were 9 nm, 19 nm, and 45 nm for citrate stabilized-, pectin stabilized-, and alginate stabilized-Ag NPs, respectively, in deionized water. Further, FlFFF with ETAAS detection was employed to observe the aggregation of Ag NPs of various types in environmental water in the absence and presence of humic acid. Citrate stabilized-Ag NPs underwent aggregation more rapid than the pectin stabilized- and alginate stabilized-Ag NPs as the latter two types were sterically stabilized. Further, humic acid could prolong the stability of Ag NPs in the environment.
    Journal of Chromatography A 12/2010; 1218(27):4213-8. DOI:10.1016/j.chroma.2010.12.040 · 4.17 Impact Factor
  • Manita Untang · Juwadee Shiowatana · Atitaya Siripinyanond ·
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    ABSTRACT: A sensitive, selective, rapid, and user-friendly field test kit was developed for the determination of cyanide. The method was based on a reaction to generate hydrogen cyanide from the solution containing cyanide by reaction with sulfuric acid in a specially designed reaction bottle. The gaseous hydrogen cyanide diffused and was collected on a paper strip impregnated with p-nitrobenzaldehyde and o-dinitrobenzene in sodium hydroxide. Hydrogen cyanide reacted with p-nitrobenzaldehyde to form an intermediate p-cyanobenzadehyde cyanohydrin, which reacted with o-dinitrobenzene to give a purple compound, the dianion of o-nitrophenyl hydroxylamine. The intensity of the purple color depended on the concentration of cyanide in the test solution. The developed field test kit could be used for the detection ofcyanide as low as 0.01 mg l−1 within 10 min. The cyanide field test kit was applied to determine cyanide concentrations in natural water and commercial fruit juices with good accuracy as validated by using the APHA/AWWA/WEF standard method 4500-CN−.
    Analytical methods 11/2010; 2(11):1698-1701. DOI:10.1039/C0AY00458H · 1.82 Impact Factor
  • Atitaya Samontha · Juwadee Shiowatana · Atitaya Siripinyanond ·
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    ABSTRACT: Sedimentation field-flow fractionation-inductively coupled plasma-mass spectrometry (SdFFF-ICP-MS) was successfully applied to investigate particle size distribution of titanium dioxide (TiO(2)) in sunscreen samples after hexane extraction to remove organic components from the samples. Three brands of sunscreen products of various sun protection factor (SPF) value were used as samples. Different particle size distribution profiles were observed for sunscreen samples of various brands and SPF values; however, the particle size distributions of titanium dioxide in most sunscreen samples investigated in this work were larger than 100 nm. The titanium dioxide concentrations were higher for the products of higher SPF values. By comparing the results obtained from online SdFFF-ICP-MS and those from the off-line ICP-MS determination of titanium after acid digestion, ICP-MS was found to effectively atomize and ionize the titanium dioxide particle without the need for acid digestion of the samples. Therefore, the online coupling between SdFFF and ICP-MS could be effectively used to provide quantitative information of titanium dioxide concentrations across particle size distribution profiles.
    Analytical and Bioanalytical Chemistry 10/2010; 399(2):973-8. DOI:10.1007/s00216-010-4298-z · 3.44 Impact Factor
  • Wimut Sermsri · Purim Jarujamrus · Juwadee Shiowatana · Atitaya Siripinyanond ·
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    ABSTRACT: Flow field-flow fractionation (FlFFF) was used for size characterization of gold nanoparticles. The measured particle sizes obtained from FlFFF for the commercial 10 nm gold nanoparticle standard and the gold nanoparticles synthesized in the laboratory were in good agreement with those measured by transmission electron microscopy (TEM). Further, the capability of alpha-tocopherol to induce enlargement of gold nanoparticles by catalysis of the reduction of AuCl(4)(-) by citrate was observed by monitoring the changes in particle size of gold nanoparticles using FlFFF. The effects of alpha-tocopherol and incubation time on enlargement of the gold nanoparticles were examined. Higher concentrations of alpha-tocopherol resulted in larger nanoparticles. At fixed alpha-tocopherol concentration, larger nanoparticles were formed at longer incubation times.
    Analytical and Bioanalytical Chemistry 02/2010; 396(8):3079-85. DOI:10.1007/s00216-010-3511-4 · 3.44 Impact Factor
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    ABSTRACT: Sequential extraction (water, Driselase, protease XIV) and extraction with simulated gastric and intestinal fluids were proposed to characterize the binding and the bioaccessibility of chromium in two commercial food supplements obtained by incorporation of this element into yeast. Chromium in Cr-enriched yeast was found to be hardly extractable with water, Driselase, or simulated gastric fluid (recoveries of approximately 10-20%), but proteolysis or gastrointestinal fluid digestion released more than half of the chromium present. Fractionation with size-exclusion chromatography with Cr-specific detection by inductively coupled plasma mass spectrometry (ICP MS) allowed the distinction of two fractions: one below approximately 1 kDa and one 1-5 kDa; they contained the entirety of the released Cr with proportions varying as a function of the extracting solution and the origin of sample. When collected and investigated by reversed-phase high-performance liquid chromatography-ICP MS, the low molecular mass fraction was found to release Cr(III), whereas the heavier one showed most of Cr bound in fairly stable hydrophobic complexes. However, an attempt of their identification by electrospray ionization MS/MS and matrix-assisted laser desorption ionization MS was not successful.
    Analytical and Bioanalytical Chemistry 11/2009; 396(3):1355-64. DOI:10.1007/s00216-009-3285-8 · 3.44 Impact Factor
  • W. Somchue · W. Sermsri · J. Shiowatana · A. Siripinyanond ·
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    ABSTRACT: Two types of proteins, including β-lactoglobulin (BLG) and hen egg white protein (HEW), were examined for their ability to encapsulate α-tocopherol (α-TOC) after salt-induced gelation of the proteins. Parameters affecting encapsulation efficiency were investigated including the type of salt, as well as concentrations of salt, protein, and α-TOC. Concentrations of protein and α-TOC revealed to have an influence on encapsulation efficiency. The optimum preparation condition of BLG-encapsulated α-TOC was as follows: BLG of 0.5% (w/v); α-TOC of 100mM; and CaCl2 of 25mM. The optimum preparation condition of HEW-encapsulated α-TOC was as follows: HEW of 4.0% (w/v); α-TOC of 50mM; and ZnCl2 of 25mM. With the selected preparation conditions, encapsulation efficiency by BLG aggregates was approx. 20% and that by HEW was approx. 32%. From the in vitro estimation, the release of α-TOC was nearly 100% in simulated gastric condition. Alginate was therefore used for coating of these encapsulated particles to prolong the release of α-TOC till simulated intestinal condition. The α-TOC of approx. 55% and 38% were retained and released in the simulated intestinal condition from BLG- and HEW-encapsulated particles, respectively.
    Food Research International 10/2009; 42(8):909-914. DOI:10.1016/j.foodres.2009.04.021 · 2.82 Impact Factor
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    ABSTRACT: Reference materials play an important role for evaluating the accuracy of analytical results, and are essential parts of good laboratory practice. They represent a key tool for quality control of chemical analyses. In Thailand, the demand of food and environmental reference materials is constantly increasing, and the National Institute of Metrology (NIMT, Thailand) is responding to the urgent needs for affordable materials, which require collaborative efforts at the national level. This paper describes the preparation of a new glutinous rice reference material, along with homogeneity and stability studies and the analytical work carried out for the certification of the contents of inorganic elements. The incurred material was collected from an actual rice paddy field. Material preparation along with homogeneity and stability testing were carried out at the Environmental Research Training Centre (ERTC). The homogeneity study was designed to have three experimental conditions; (A) 10 bottles of candidate materials being analyzed each with 2 replicates, (B) 20 bottles with 2 replicates, (C) 10 bottles with 7 replicates, in order to study the suitable treatments for homogeneity testing in the reference material production. It was shown that a minimum number of 10 bottles with duplicate analyses are enough to demonstrate the homogeneity of candidate reference material. Certification of a candidate reference material in a single laboratory using reference method was confirmed with an interlaboratory comparison participated by a certain number of well recognized testing laboratories in Thailand. Further elaborative results will be discussed. KeywordsInorganic analysis-Elements-Rice-Reference material
    Accreditation and Quality Assurance 04/2009; 15(4):223-231. DOI:10.1007/s00769-009-0621-9 · 0.97 Impact Factor