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1.
An automated on-line sample-preparation method using a computer-controlled pretreatment system (Auto-Pret AES system) coupled with ICP-AES was developed. In this work, an iminodiacetate chelating resin, packed in a mini-column and installed in the system was employed for the collection/concentration of 13 trace metals, including such toxic metals as Be, Cd, Cr, Cu and Pb. The limits of detection of the proposed method for trace metals were in the range of 0.001 (Be) -0.18 (Pb) ng mL-1. The enrichment factors for metal ions were about 19 times, when 5 mL of samples were used. The sample throughput was 11 h-1. The accuracy and the precision of the method were evaluated using river-water reference materials, SLRS-4 from NRCC, JSAC 0301-1 and JSAC 0302 from the Japan Society for Analytical Chemistry. The proposed method can be favorably applied to the collection/concentration of trace metals in natural water samples. 相似文献
2.
Wannarat Chueangchayaphan Piyawadee Luangchuang Narong Chueangchayaphan Muhammad Azwadi Sulaiman Yeampon Nakaramontri 《高分子科学》2021,39(6):725-735
Acrylonitrile rubber(NBR) composites filled with barium titanate(BT) were prepared using an internal mixer and a two-roll mill. Also, a secondary filler, namely carbon nanotubes(CNT), was added in order to find a potential synergistic blend ratio of BT and CNT. The cure characteristics, tensile and dielectric properties(dielectric constant and dielectric loss) of the composites were determined. It was found that NBR/BT composites with CNT secondary filler, at a proper BT:CNT ratio, exhibited shorter scorch time(t_(s1)) and cure time(t_(c90)) together with superior tensile properties and reinforcement efficiency, relative to the one with only the primary filler. In addition, the NBR/BT-CNT composite with 80 phr BT and 1-2 phr CNT had dielectric constant of 100-500, dielectric loss of 12-100 and electrical conductivity below 10~(-4) S/m together with high thermal stability. Thus, with a proper BT:CNT mix and filler loading, we can produce mechanically superior rubber composites that are easy to process and low-cost, for flexible dielectric materials application. 相似文献
3.
Kidyu K Thaisuchat H Meepowpan P Sukdee S Nuntasaen N Punyanitya S Pompimon W 《Natural product communications》2011,6(8):1069-1072
A new clerodane diterpenoid has been isolated from the acetone extract of bulbils of Dioscorea bulbifera. The structure of compound 1 was established as 15,16-epoxy-6alpha-O-acety1-8beta-hydroxy- 9-nor-clero-13(16),14-diene-17,12;18,2-diolide on the basis of comprehensive spectroscopic techniques. 相似文献
4.
Jutapol Jumpatam Bundit Putasaeng Narong Chanlek Prasit Thongbai 《Molecules (Basel, Switzerland)》2021,26(7)
The microstructure, dielectric response, and nonlinear current-voltage properties of Sr2+-doped CaCu3Ti4O12/CaTiO3 (CCTO/CTO) ceramic composites, which were prepared by a solid-state reaction method using a single step from the starting nominal composition of CCTO/CTO/xSrO, were investigated. The CCTO and CTO phases were detected in the X-ray diffraction patterns. The lattice parameter increased with increasing Sr2+ doping concentration. The phase compositions of CCTO and CTO were confirmed by energy-dispersive X-ray spectroscopy with elemental mapping in the sintered ceramics. It can be confirmed that most of the Sr2+ ions substituted into the CTO phase, while some minor portion substituted into the CCTO phase. Furthermore, small segregation of Cu-rich was observed along the grain boundaries. The dielectric permittivity of the CCTO/CTO composite slightly decreased by doping with Sr2+, while the loss tangent was greatly reduced. Furthermore, the dielectric properties in a high-temperature range of the Sr2+-doped CCTO/CTO ceramic composites can be improved. Interestingly, the nonlinear electrical properties of the Sr2+-doped CCTO/CTO ceramic composites were significantly enhanced. The improved dielectric and nonlinear electrical properties of the Sr2+-doped CCTO/CTO ceramic composites were explained by the enhancement of the electrical properties of the internal interfaces. 相似文献
5.
The problem of a two-dimensional fully mixed region collapsing in continuously density-stratified medium is considered. This
article deals with the numerical treatment of the advective terms in the Navier-Stokes equations in the Oberbeck-Boussinesq
approximation. Comparisons are performed between the upwind scheme, flux-limiter schemes, namely, Minmod, Superbee, Van Leer,
and Monotonized Centred (MC), the monotone adaptive stencil schemes, namely, ENO3 and SMIF, and weighted stencil scheme WENO5.
We used laboratory experimental data of Wu as a benchmark test to compare performance of different numerical approaches. It
is found that the flux-limiter schemes have the smallest numerical diffusion. The WENO5 scheme describes more accurately the
width of collapse region variation with time. All considered schemes give a realistic pattern of internal gravity waves generated
by collapse region. 相似文献
6.
Narong Punnim 《Graphs and Combinatorics》2002,18(3):597-603
We prove that if G runs over the set of graphs with a fixed degree sequence d, then the values χ(G) of the function chromatic number completely cover a line segment [a,b] of positive integers. Thus for an arbitrary graphical sequence d, two invariants minχ(d):=a and maxχ(d):=b naturally arise. For a regular graphical sequence d=r
n
:=(r,r,…,r) where r is the degree and n is the number of vertices, the exact values of a and b are found in all situations, except the case where n and r are both even and n<2r.
Received: September 16, 2000 Final version received: December 13, 2001
Acknowledgments. We would like to thank Professor Tommy R. Jensen for his useful comment and editing thorough the paper. 相似文献
7.
Lenghor N Grudpan K Jakmunee J Staggemeier BA Quigley WW Prazen BJ Christian GD Ruzicka J Synovec RE 《Talanta》2003,59(6):1153-1163
A sequential injection analysis (SIA) system is coupled with dynamic surface tension detection (DSTD) for the purpose of studying the interfacial properties of surface-active samples. DSTD is a novel analyzer based upon a growing drop method, utilizing a pressure sensor measurement of drop pressure. The pressure signal depends on the surface tension properties of sample solution drops that grow and detach at the end of a capillary tip. In this work, SIA was used for creating a reagent concentration gradient, and for blending the reagent gradient with a steady-state sample. The sample, consisting of either sodium dodecyl sulfate (SDS) or poly(ethylene glycol) at 1470 g mol−1 (PEG 1470), elutes with a steady-state concentration at the center of the sample plug. Reagents such as Brij®35, tetrabutylammonium (TBA) hydroxide and β-cyclodextrin were introduced as a concentration gradient that begins after the sample plug has reached the steady-state concentration. By blending the reagent concentration gradient with the sample plug using SIA/DSTD, the kinetic surface pressure signal of samples mixed with various reagent concentrations is observed and evaluated in a high throughput fashion. It was found that the SIA/DSTD method consumes lesser reagent and required significantly less analysis time than traditional FIA/DSTD. Four unique chemical systems were studied with regard to how surface activity is influenced, as observed through the surface tension signal: surface activity addition, surface activity reduction due to competition, surface activity enhancement due to ion-pair formation, and surface activity reduction due to bulk phase binding chemistry. 相似文献
8.
Treetepvijit S Preechaworapun A Praphairaksit N Chuanuwatanakul S Einaga Y Chailapakul O 《Talanta》2006,68(4):1329-1335
The electrochemical analysis of tetracyclines was investigated using nickel-implanted boron-doped diamond thin film electrode (Ni-DIA) by cyclic voltammetry and high performance liquid chromatographic with amperometry. Cyclic voltammetry was used to study the electrochemical oxidation of tetracyclines. Comparison experiments were carried out utilizing as-deposited BDD and glassy carbon electrodes. Ni-DIA electrode provided well-resolved oxidative irreversible cyclic voltammograms and the highest current signals among the electrode studied. High performance liquid chromatography (HPLC) with amperometric detection was also studied. The chromatography was performed using a commercially available Inertsil C18 column, with the mobile phase being: 80% phosphate buffer (pH 2.5)-20% acetonitrile and detected at 1.55 V. The methods were validated over the concentration range 0.05-100 ppm with the overall average recoveries from 83.3 to 102.5% and R.S.D. of less than 10%. The proposed method was further applied to analyse shrimp samples. 相似文献
9.
10.
Lenghor N Staggemeier BA Hamad ML Udnan Y Tanikkul S Jakmunee J Grudpan K Prazen BJ Synovec RE 《Talanta》2005,65(3):722-729
Design and development of a dynamic interfacial pressure detector (DIPD) is reported. The DIPD measures the differential pressure as a function of time across the liquid-liquid interface of organic liquid drops (i.e., n-hexane) that repeatedly grow in water at the end of a capillary tip. Using a calibration technique based on the Young-Laplace equation, the differential pressure signal is converted, in real-time, to a relative interfacial pressure. This allows the DIPD to monitor the interfacial tension of surface active species at liquid-liquid interfaces in flow-based analytical techniques, such as flow injection analysis (FIA), sequential injection analysis (SIA) and high performance liquid chromatography (HPLC). The DIPD is similar in principle to the dynamic surface tension detector (DSTD), which monitors the surface tension at the air-liquid interface. In this report, the interfacial pressure at the hexane-water interface was monitored as analytes in the hexane phase diffused to and arranged at the hexane-water interface. The DIPD was combined with FIA to analytically measure the interfacial properties of cholesterol and Brij®30 at the hexane-water interface. Results show that both cholesterol and Brij®30 exhibit a dynamic interfacial pressure signal during hexane drop growth. A calibration curve demonstrates that the relative interfacial pressure of cholesterol in hexane increases as the cholesterol concentration increases from 100 to 10,000 μg ml−1. An example of the utility of the DIPD as a selective detector for a chromatographic separation of interface-active species is also presented in the analysis of cholesterol in egg yolk by normal-phase HPLC-DIPD. 相似文献