A proficiency test (PT) was organized for quality control analysis of black tea. Test materials for the analyses of total
content of powder tea, moisture, total ash, acid-insoluble ash, water-soluble ash, alkalinity of water-soluble ash, water
extract, crude fiber and caffeine were sent to the participant laboratories (n:43) in 2009. The assigned value, standard deviation of the parameters and z-scores of the participant laboratories were calculated using the data reported by the participants. The percentage of the
reported results for analytes was found to be ranged from 67.5 to 100%. Acceptable z-scores were achieved by 80.5–97.5% of the participant laboratories. More than 15% of unacceptable results were obtained for
acid-insoluble ash and caffeine analyses. The quality control material for quality control analysis of black tea was developed
from the remaining material. 相似文献
Anion sensor properties of N‐alkyl‐substituted 1,4′‐diazaflavonium bromides in methanol–water were evaluated by UV–vis spectrometry. Pronounced changes were observed in the absorption spectra of all compounds for only OH?, CO32?, and CN? among F?, Cl?, Br?, I?, OH?, CO32?, NO3?, PO43?, CN?, SO42?, HSO4?, HCO3?, SCN?, NO2?, and P2O72? ions. Two new absorption bands at 385 and 685 nm accompanying the distinct color change for OH?, CO32?, and CN? ions were observed in case of all compounds. The color changes were from pink to blue for CO32? and OH? ions and from pink to purple for CN? ion. Thanks to the distinct color change, the compounds can be used as selective colorimetric anion sensors. Linear changes of absorbance of N‐heptyl‐substituted compound at 385 nm as a function of the ion concentration were used to determine CN? ion in water samples. Detection and quantification limits of the proposed method were 0.94 and 2.82 mg/L, respectively. 相似文献
N‐(2‐mercaptoethyl) acrylamide (MEAM) monomer was synthesized by acrylation of cysteamine and was cross‐linked with ethylene glycol dimethacrylate (EGDMA) via dispersion polymerization forming poly(N‐(2‐mercaptoethyl) acrylamide) (p(MEAM)) microgel. Then, the prepared microgels were tested for potential biomedical use, eg, antioxidant capacity and blood compatibility, cytotoxicity, apoptotic, and necrotic cell death; drug delivery properties were determined. Antioxidant studies of p(MEAM) microgels revealed a super antioxidant capability with total phenol content and trolox equivalent antioxidant capacity as 6.05 ± 1.15 mg/L gallic acid equivalency and 40.96 ± 2.40 mM trolox/g, respectively. Moreover, the blood compatibility of p(MEAM) microgels on fresh blood was resulted in lower than 1.0% hemolysis ratios for all the studied concentration range, and the blood clotting index was determined as 60.66% at 2.0 mg/mL at microgel concentration. The biocompatibility studies employing WST‐1 test on L929 fibroblast cells and DLD‐1 colon cancer cells have shown that p(MEAM) microgel was biocompatible up to 200 μg/mL concentration with the cell viability values of 84.54% and 86.15% on L929 fibroblast and DLD‐1 colon cancer cells, respectively. Using Captopril was used as model drug to test p(MEAM) microgel as drug delivery device for in vitro release studies at different pHs. Release profile of Captopril was found linear up to 5 hours with the released amounts of 9.81, 12.24, and 13.78 mg g‐1microgel at the pH 1.5, 7.4, and 9.0, respectively. 相似文献
In this paper Fermi-Walker derivative and Fermi-Walker parallelism and non-rotating frame concepts are given along the spherical indicatrix of a curve in E3. First, we consider a curve in Euclid space and investigate the Fermi-Walker derivative along the tangent. The concepts which Fermi-Walker derivative are analyzed along its tangent. Then, the Fermi-Walker derivative and its theorems are analyzed along the principal normal indicatrix and the binormal indicatrix of any curve in E3. 相似文献
This study illustrates the entrapment of the dye molecule fluorescein sodium salt (FSS) by hydrogel nanoparticles, which are in turn confined inside a water-in-oil-in-water double-emulsion globule, and its subsequent release by the action of the competing agent hydrochloric acid (HCl). Thus, a "double carrier" concept is being introduced in which a nanoscale delivery vehicle is being transported by a microscale delivery vehicle in order to simultaneously take advantage of both systems. This may facilitate storage and handling while protecting the active substance and improving its action upon application. 相似文献
The ground state hydrogen conformations and vibrational analysis of 3-deazauracil (3DAU) and 6-azauracil (6AU) tautomers (4-enol and 2,4-diol forms) have been calculated using ab initio Hartree-Fock (HF) and density functional theory (B3LYP) methods with 6-311++G(d,p) basis set level. The calculations have shown that the most probably preferential tautomer of 3DAU and 6AU are the 4-enol form, which gives best fit to the corresponding experimental data. The ground state conformer of the 2,4-diol form has two O-H bonds which are oriented externally and internally (to the N-H bond). The vibrational analyses of the ground state conformer of each tautomeric form of 3DAU and 6AU were done and their optimized geometry parameters (bond lengths and bond angles) were given. Furthermore, from the correlations values it was concluded that the B3LYP method is superior to the HF method for both the vibrational frequencies and the geometric parameters. 相似文献
Bis(Δ2-2-imidazolinyl)-5,5′-dioxime (H2L) and its nickel, cobalt, zinc, cadmium and mercury complexes have been prepared and tested in vitro against different microorganisms in order to assess their antimicrobial properties. We used Bacillus subtilis RSKK 244, Micrococcus flavus, Streptococcus faecalis RSKK 500, Staphylococcus aureus RSKK 490 from Gram-positive bacteria; Pseudomonas aeruginosa RSKK 356, Salmonella typhimurium RSKK 1017, Escherichia coli RSKK 550, Enterobacter aerogenes RSKK 720 from Gram-negative bacteria, Candida tropicalis RSKK 665 and Penicillium raciborskii IMI 40568.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
A novel hydrogel based on poly(sulfopropylmethacrylate) (p(SPM) with different crosslinking degrees was synthesized and characterized. The prepared hydrogels were for the first time, utilized for in situ metal nanoparticle preparation such as Ni, Co, and Cu and employed as a reaction media in catalytic reduction of 4-nitrophenol (4-NP), and 2-nitrophenol (2-NP) to 4-aminophenol and 2-aminophenol, respectively. The experimental parameters that effect reduction rates such as temperature and the amount of catalyst were investigated. The kinetics of the reduction reaction of nitro compounds under different reaction conditions were investigated to determine the activation parameter. Activation energies were found as 33.86 kJ mol? 1 and 24.96 kJ mol? 1 for 4-NP and 2-NP, respectively. It was found that hydrogel–Cu composites can provide 98% activity even at the end of the 7th repetitive usage. 相似文献
A series of sterically hindered 4-(N-R-salicylaldimine)-2,6-diphenylphenols (X), where R=H (1), 3-CH3 (2), 5-CH3 (3), 3-OCH3 (4), 4-OCH3 (5), 5-OCH3 (6), 3-tBu (7), 5-tBu (8), 3,5-tBu2(9) and 5,6-benzo(10), were synthesized and their structure as well as redox behavior studied by analytical, spectroscopic [1H, (13C) NMR, IR, UV-vis and mass spectrometry] and cyclic voltammetric (CV) techniques. Single crystal X-ray diffraction studies of 7 evidenced its existence as non-planar enol-imine tautomer structure, in which the phenol ring of the molecule is twisted around C-N single bond by 21.5(2) degrees. The packing structure of 7 is stabilized by C-H...pi(Ph) and O...O and C...O intermolecular short contact interactions. The CV of X display rate is dependent on irreversible and quasi-reversible redox waves in the anodic and cathodic regions due to oxidation and reduction of phenolic and iminic groups, respectively. As evidenced by ESR and UV-vis study, chemical oxidation of X by PbO2 and (NH4)2Ce(NO3)6 in MeCN and CHCl3 generates stable phenoxyl radicals [(g approximately 2.005 and lambda approximately 450 nm (1600-8200 M(-1) cm(-1))]. 相似文献
Nanostructured fluorescent particles derived from natural molecules were prepared by a green synthesis technique employing a microwave method. The precursors citric acid (CA) and cysteine (Cys) were used in the preparation of S- and N-doped Cys carbon dots (Cys CDs). Synthesis was completed in 3 min. The graphitic structure revealed by XRD analysis of Cys CDs dots had good water dispersity, with diameters in the range of 2–20 nm determined by TEM analysis. The isoelectric point of the S, N-doped CDs was pH value for 5.2. The prepared Cys CDs displayed excellent fluorescence intensity with a high quantum yield of 75.6?±?2.1%. Strong antimicrobial capability of Cys CDs was observed with 12.5 mg/mL minimum bactericidal concentration (MBC) against gram-positive and gram-negative bacteria with the highest antimicrobial activity obtained against Staphylococcus aureus. Furthermore, Cys CDs provided total biofilm eradication and inhibition abilities against Pseudomonas aeruginosa at 25 mg/mL concentration. Cys CDs are promising antioxidant materials with 1.3?±?0.1 μmol Trolox equivalent/g antioxidant capacity. Finally, Cys CDs were also shown to inhibit the acetylcholinesterase (AChE) enzyme, which is used in the treatment of Alzheimer’s disease, even at the low concentration of 100 μg/mL.