共查询到20条相似文献,搜索用时 31 毫秒
1.
C. Cristallini G. Enriquez De Grassi L. Guardines R. Gaussmann 《Applied biochemistry and biotechnology》1984,10(1-3):267-272
A procedure to obtain a controlled-release microencapsulated anti-inflammatory drug based on a solvent evaporation method
is described. The present method makes use of ethylcellulose as the polymer and methylene chloride as solvent. The evaporation
of solvent is controlled by means of an air stream. Variations in the preparative procedure and their effects on capsule dimensions
and permeabilities were studied. The release behavior of the drug is determined, and two different diffusion constants are
also determined: 7.0×10−10 cm2/s and 1.2×10−10 cm2/s, corresponding to low and high release time. Based on these results it is proposed that these microcapsules have a nonhomogeneous
polymeric wall, and are more porous in the outer surface. This model might be applicable to the microcapsules obtained by
means of the solvent evaporation method. 相似文献
2.
Lawuyi B Chen H Afkhami F Kulamarva A Prakash S 《Applied biochemistry and biotechnology》2007,142(1):71-80
This article demonstrates the potential of encapsulated, engineered Lactococcus lactis as a vehicle for the oral delivery of therapeutic proteins. Using alginate-poly-l-lysine-alginate membrane-encapsulated L. lactis engineered to secrete the reporter protein Staphylococcal aureus nuclease, we show comparable viability and protein secretion between free and immobilized cells. After 12 h, microcapsules
with a cell density of 4.8 × 105 colony forming unit (CFU) ml−1 grew to 2.2 × 108 CFU ml−1 and released 0.24 arbitrary unit (AU) ml−1 of nuclease, producing similar results as free cells, which grew from 3.4 × 105 to 1.9 × 108 CFU ml−1 and secreted 0.21 AU ml−1 of nuclease. Moreover, encapsulated cells at a density of 4.4 × 107 CFU ml−1 grew to 2.2 × 1010 CFU ml−1 in 12 h and secreted 15.3 AU ml−1 of nuclease although 3.1 × 107 CFU ml−1 of free cells reached only 2.3 × 109 CFU ml−1 and released 5.6 AU ml−1 of nuclease. We also show the sustained stability of the microcapsules during storage at 4°C over 8 weeks. 相似文献
3.
Zhang H Le Potier I Smadja C Zhang J Taverna M 《Analytical and bioanalytical chemistry》2006,386(5):1387-1394
An in-capillary derivatization of amino acids and peptides with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) was developed
for their subsequent capillary electrophoretic analysis with laser-induced fluorescence detection (λ
ex=488 nm). The in-capillary derivatization was achieved in zone-passing mode by introducing successive plugs of sample and
NBD-F into a fused silica capillary previously equilibrated with an alkaline borate buffer. To prevent NBD-F hydrolysis and
to achieve a reliable derivatization, NBD-F was prepared daily in absolute ethanol and a plug of absolute ethanol was introduced
between the sample and NBD-F reagent plugs. Various parameters influencing the derivatization efficiency were investigated
and the optimum conditions were as follows: background electrolyte (BGE), 20 mM borate buffer (pH 8.8); introduction time,
4 s for sample and 2 s for NBD-F; molar ratio of NBD-F/sample, above 215; temperature, 45 °C for amino acids and 35 °C for
peptides; applied voltage, +15 kV. The validation of the in-capillary derivatization method under optimal conditions showed
a good linearity between the heights of the derivative peaks and the concentrations of the amino acids. The intra-day relative
standard deviations of the migration times and the peak heights were less than 1.3% and 4.6%, respectively. The efficient
derivatization and separation of a mixture of valine, alanine, glutamic acid and aspartic acid were achieved using this technique.
Peptides such as buccaline and β-protein fragment 1–42 could also be derivatized using the developed in-capillary derivatization
procedure.
In‑capillary derivatization and separation of amino acids with different concentrations.
From the top to bottom the concentrations are 1.11×10−5 M, 5.55×10−6 M, 2.78×10−6 M, 6.95×10−7 M. for valine; 1.26×10−5 M, 6.30×10−6 M, 3.15×10−6 M, 7.88×10−7 M for alanine; 3.78×10−5 M, 1.89×10−5 M, 9.45×10−6 M, 2.36×10−6 M for glutamic acid;, 4.27×10−5 M, 2.14×10−5 M, 1.07×10−5 M, 2.68×10−6 M for aspartic acid.
Experiment conditions: injection order: 4s for sample, 1s for absolute ethanol, and then 2s for 5.24×10−2 M NBD‑F; BGE: 20 mM borate pH 8.77; Applied voltage: 15 kV. 相似文献
4.
Formations of Active Species and By-Products in Water by Pulsed High-Voltage Discharge 总被引:1,自引:0,他引:1
Formations of active species and by-products are different from bubbling different gases in a pulsed high-voltage discharge
reactor. The identification of all the products and the formation rate determination of active species are quite important
as the process is applied to wastewater disposal. Serials of measurements were conducted to do the identifications and determinations
in this paper. Amounts of · OH all increased but that of H2O2 all decreased by bubbling gas. The · OH formation rate was 3.49 × 10−7, 3.56 × 10−7, 3.21 × 10−7 and 1.94 × 10−7 mol l−1 s−1 with bubbling nitrogen, argon, air and oxygen respectively, but it was 1.61 × 10−7 mol s−1 l−1 without bubbling. Without any bubbling, the H2O2 formation rate was up to 6.53 × 10−6 mol l−1 s−1, while it was 9.97 × 10−7, 1.663 × 10−7, 1.73 × 10−6 and 3.14 × 10−6 mol l−1 s−1 with bubbling nitrogen, argon, air and oxygen, respectively. NO2− and NO3− was detected in discharged water with bubbling nitrogenous gas. Their formation made the pH decreased. 相似文献
5.
D. M. Ortega-Sotelo J. G. Gonzalez-Rodriguez M. A. Neri-Flores M. Casales L. Martinez A. Martinez-Villafañe 《Journal of Solid State Electrochemistry》2011,15(9):1997-2004
The corrosion inhibition of X-70 pipeline steel in saltwater saturated with CO2 at 50 °C with carboxyamido imidazoline has been evaluated by using electrochemical techniques. Techniques included polarization
curves, linear polarization resistance, electrochemical impedance, and electrochemical noise measurements. Inhibitor concentrations
were 0, 1.6 × 10−5, 3.32 × 10−5, 8.1 × 10−5, 1.6 × 10−4, and 3.32 × 10−4 mol l−1. All techniques showed that the best corrosion inhibition was obtained by adding 8.1 × 10−5 mol l−1 of carboxyamido imidazoline. For inhibitor concentrations higher than 8.1 × 10−5 mol l−1 a desorption process occurs, and an explanation has been given for this phenomenon. 相似文献
6.
Ali Z. Abu Zuhri Nidal A. Zatar Raqi M. Shubietah Hala H. Arafat 《Mikrochimica acta》2000,134(3-4):153-160
Two methods are described for quantitative determination of nizatidine. The first is a cathodic stripping voltammetric method
which is based on the accumulation of the compound at the hanging mercury drop electrode. The adsorptive stripping response
was evaluated with respect of accumulation time, potential, concentration, pH and other variables. A linear calibration graph
was obtained over the range 3.0×10−8–1.0×10−6 M with a detection limit 3.0×10−8 M after a 20s accumulation time at −0.2 V accumulation potential. On the other hand, it was found that the detection limit
could be lowered to 1.0×10−8 M after 180s accumulation time at −0.2 V accumulation potential. The relative standard deviation was in the range 1.2−2.0%
for six measurements. The tolerance amounts of the common excipients have also been reported.
The second is a spectrophotometric method which is based on the formation and extraction of the ion-pair complex formed between
nizatidine and either bromocresol green or bromothymol blue. The extracted colored ion-pair complexes absorb at 416 nm. The
effect of different factors such as: type of organic solvent, pH, reagent concentration, number of extraction times, shaking
time, temperature and the tolerance amount of the common excipients have been reported. The calibration graph was linear in
the range 6.0×10−7–1.8×10−5 M with a detection limit of 6.0×10−7 M and molar absorptivity of 2.1×104 lċmol−1ċcm−1 when using bromocresol green, while the calibration graph was linear in the range 3.0×10−7–1.1×10−5 M with a detection limit of 3.0×10−7 M and molar absorptivity of 3.2×104 lċmol−1ċcm−1 when using bromothymol blue. The spectrophotometric methods offer alternative methods with reasonable sensitivity, selectivity
and accuracy with relative standard deviation in the range 2.1−6.0% and 1.2−4.7% (for six measurements) when using bromothymol
blue and bromocresol green, respectively. The proposed two methods were applied for the determination of nizatidine in commercially
available dosage forms. A comparison between the voltammetric and the extraction-spectrophotometric methods was also reported.
Received April 19, 1999. Revision August 30, 1999. 相似文献
7.
Gao J Dai H Yang W Chen H Lv D Ren J Wang L 《Analytical and bioanalytical chemistry》2006,384(6):1438-1443
A rapid and convenient method for the determination of furfural is presented that is based upon sequential perturbation of
the Mn(II)-catalyzed B-Z oscillating system with different amounts of furfural using a continuous-flow stirred tank reactor
(CSTR). When the sample was injected, the change in the amplitude and/or period was linearly proportional to the logarithm
of the concentration of furfural over the range 3×10−8∼1×10−5 mol L−1. This method gave a detection limit of 3×10−9 mol L−1 under optimum conditions. Finally, the possible mechanism of furfural perturbation in the oscillating reaction is discussed.
When the furfural was injected into the Mn(II)-catalyzed B-Z oscillating system, the change in the amplitude and/or period
was linearly proportional to the logarithm of the concentration of furfural over the range 3×10−8~1×10−5 mol L−1, with a detection limit of 3×10−9 mol L−1 under optimum conditions.
相似文献
8.
A simple and new reagentless phenolic compound biosensor was constructed with tyrosinase immobilized in the gelatine matrix
cross-linked with formaldehyde. The morphologies of gelatine and gelatine/tryosinase were characterized by SEM. The tyrosinase
retains its bioactivity when being immobilized by the gelatine film. Phenolic compounds were determined by the direct reduction
of biocatalytically liberated quinone at -0.1 V vs SCE. The process parameters for the fabrication of the enzyme electrode
were studied. Optimization of the experimental parameters has been performed with regard to pH, operating potential, temperature
and storage stability. This biosensor exhibits a fast amperometric response to phenolic compounds. The linear range for catechol,
phenol, and p-Cresol determination was from 5×10−8 to 1.4×10−4 M, 5×10−8 to 7.1×10−5 M, and 1×10−7 to 3.6×10−5 M, with a detection limit of 2.1×10−8 M, 1.5×10−8 M, and 7.1×10−8 M, respectively. The enzyme electrode retained ca.77% of its activity after 7 days of storage at 4°C in a dry state. The proposed
sensor presented good repeatability, evaluated in terms of relative standard deviation (R.S.D.=8.6%) for eight different biosensors
and was applied for determination in water sample. The recovery for the sample was from 99.0% to 99.8%. 相似文献
9.
A procedure for the determination of chromium in blood has been developed with a sensitivity of 5×10−3 μg Cr. Dried blood was irradiated with a neutron flux of 1012 n·cm−2·sec−1 in the VVRS reactor for 4 weeks, then the sample was mineralized and the chromium isolated by extraction as perchromic acid.
The determination of the chromium content was accomplished by measuring the 0.32 MeV gamma energy of51Cr. In order to make correction for the interfering reaction54Fe(n,α)51Cr, the formation of chromium from high-purity iron was investigated. The chromium content of the blood samples was between
1.03×10−2 and 5.2×10−2 ppm Cr. 相似文献
10.
Simultaneous determination of silicic acid, Ca, Mg and Al in mineral water and composite tablets by Ion chromatography 总被引:1,自引:0,他引:1
Q. Xu C. Xu W. Zhang Y. P. Wang L. T. Jin H. Haraguchi A. Itoh K. Tanaka 《Chromatographia》2001,53(1-2):81-84
Summary A simple, selective and sensitive ion-chromatography method was investigated for simultaneously determining silicic acid,
Ca2+, Mg2+, Al3+ and anions (Cl− and NO
3
−
) in real samples. It involved a single-column ion-chromatograph with sodium hydroxide-methanol-water eluent and conductometric
detection. Cations were converted to complex anions by adding EDTA to the sample solution. A set of well-defined peaks of
silicic acid, Ca2+, Mg2+, Al3+, Cl− and NO
3
−
were obtained. Detection limits using 3.3σ (σ=standard deviation of blank solution) were 1.25×10−6 M for H3SiO
4
−
, 1.32×10−6 M for Ca2+, 1.28×10−6 M for Mg2+, 1.33×10−6 M for Al3+, 1.31×10−6 M for Cl− and 1.24×10−6 M for NO
3
−
. The method was successfully applied to analysis of mineral water and composite tablets. 相似文献
11.
de la Escosura-Muñiz A González-García MB Costa-García A 《Analytical and bioanalytical chemistry》2006,384(3):742-750
A new electroactive label has been used to monitor immunoassays in the determination of human serum albumin (HSA) using glassy-carbon
electrodes as supports for the immunological reactions. The label was a gold(I) complex, sodium aurothiomalate, which was
bound to rabbit IgG anti-human serum albumin (anti-HSA-Au). The HSA was adsorbed on the electrode surface and the immunological
reaction with gold-labelled anti-HSA was then performed for one hour by non-competitive or competitive procedures. The gold(I)
bound to the anti-HSA was electrodeposited in 0.1 mol L−1 HCl at −1.00 V for 5 min then oxidised in 0.1 mol L−1 H2SO4 solution at +1.40 V for 1 min. Silver electrodeposition at −0.14 V for 1 min followed by anodic stripping voltammetry were
then performed in aqueous 1.0 mol L−1 NH3–2.0×10−4 mol L−1 AgNO3. For both non-competitive and competitive formats, calibration plots in the ranges 5.0×10−10 to 1.0×10−8 mol L−1 and 1.0×10−10 to 1.0×10−9 mol L−1 HSA, respectively, with estimated detection limits of 1.5×10−10 mol L−1 (10 ng mL−1) and 1.0×10−10 mol L−1 (7 ng mL−1), respectively, were obtained. Levels of HSA in two healthy volunteer urine samples were also evaluated, using both immunoassay
formats. 相似文献
12.
A linear sweep adsorptive stripping voltammetric method for the determination of netilmicin in the presence of formaldehyde
has been proposed for the first time. In the presence of 3.0×10−3 g ml−1 formaldehyde, netilmicin exhibits a sensitive cathodic peak at −1.30 V (vs. the saturated calomel electrode, SCE) in a medium
of Britton–Robinson buffer (pH 8.7) with a scan rate of 100 mV s−1 after a preconcentration period of 120 s at −1.10 V (vs. SCE). The peak current showed a linear dependence on the netilmicin
concentration over the range 4.2×10−9–1.0×10−7 g ml−1. The achieved limits of detection and quantitation were 1.0×10−10 and 3.3×10−10 g ml−1 netilmicin, respectively. It was deduced from the experiments that the amine–aldehyde condensation product formed between
netilmicin and formaldehyde is mainly responsible for the appearance of the peak. The electrochemical behavior of netilmicin
in the presence of formaldehyde has been studied. The method was applied to the direct determination of netilmicin in injectable
formulations and spiked human urine and serum samples.
相似文献
13.
A poly(L-methionine) modified electrode, fabricated by electrochemical immobilization of the L-methionine on a glassy carbon
electrode, was used for simultaneous determination of dopamine and epinephrine through cyclic voltammetry. The electrochemical
properties of dopamine and epinephrine have been investigated. This sensor gave two separated cathodic peaks at −0.282 and
0.112 V for EP and DA, respectively. A linear response was obtained in the range of 5.0 × 10−7 to 1.0 × 10−4 mol l−1 for epinephrine, and 1.0 × 10−6 to 5.0 × 10−4 mol l−1 for dopamine. The detection limits were 3.6 × 10−7 mol l−1 and 4.2 × 10−7 mol l−1 for epinephrine and dopamine, respectively. This method was successfully applied for simultaneous determination of dopamine
and epinephrine in human urines.
The text was submitted by the authors in English. 相似文献
14.
Feng QZ Zhao LX Yan W Ji F Wei YL Lin JM 《Analytical and bioanalytical chemistry》2008,391(3):1073-1079
Highly sensitive flow-injection chemiluminescence (CL) combined with molecularly imprinted solid-phase extraction (MISPE)
has been used for determination of 2,4-dichlorophenol (2,4-DCP) in water samples. The molecularly imprinted polymer (MIP)
for 2,4-DCP was prepared by non-covalent molecular imprinting methods, using 4-vinylpyridine (4-VP) and ethylene glycol dimethacrylate
(EGDMA) as the monomer and cross-linker, respectively. 2,4-DCP could be selectively adsorbed by the MIP and the adsorbed 2,4-DCP
was determined by its enhancing effect on the weak chemiluminescence reaction between potassium permanganate and luminol.
The enhanced CL intensity was linear in the range from 1 × 10−7 to 2 × 10−5g mL−1. The LOD (S/N = 3) was 1.8 × 10−8g mL−1, and the relative standard deviation (RSD) was 3.0% (n = 11) for 1.4 × 10−6g mL−1. The proposed method had been successfully applied to the determination of 2,4-DCP in river water.
Figure Effect of 4-VP content on the ultraviolet spectrum of 2,4-DCP in chloroform 相似文献
15.
A compact miniaturized continuous flow system for the determination of urea content in milk 总被引:1,自引:0,他引:1
Willian Toito Suarez Osmundo Dantas Pessoa-Neto Vagner Bezerra dos Santos Ana Rita de Araujo Nogueira Ronaldo Censi Faria Orlando Fatibello-Filho Mar Puyol Julián Alonso 《Analytical and bioanalytical chemistry》2010,398(3):1525-1533
A multicommutation-based flow system with photometric detection was developed, employing an analytical microsystem constructed
with low temperature co-fired ceramics (LTCC) technology, a solid-phase reactor containing particles of Canavalia ensiformis DC (urease source) immobilized with glutaraldehyde, and a mini-photometer coupled directly to the microsystem which monolithically
integrates a continuous flow cell. The determination of urea in milk was based on the hydrolysis of urea in the solid-phase
reactor and the ammonium ions produced were monitored using the Berthelot reaction. The analytical curve was linear in the
urea concentration range from 1.0 × 10−4 to 5.0 × 10−3 mol L−1 with a limit of detection of 8.0 × 10−6 mol L−1. The relative standard deviation (RSD) for a 2.0 × 10−3 mol L−1 urea solution was lower than 0.4% (n = 10) and the sample throughput was 13 h−1. To check the reproducibility of the flow system, calibration curves were obtained with freshly prepared solutions on different
days and the RSD obtained was 4.7% (n = 6). Accuracy was assessed by comparing the results of the proposed method with those from the official procedure and the
data are in close agreement, at a 95% confidence level. 相似文献
16.
The creation of anoxic granulated biomass has been monitored in a laboratory USB (Upflow Sludge Blanket) reactor with the
volume of 3.6 L. The objective of this research was to verify the possibilities of post-denitrification of residual NO3-N concentrations in treated wastewater (denitrification of 10-20 mg L−1 NO3-N) and to determine the maximum hydraulic and mass loading of the granulated biomass reactor. G-phase from biodiesel production
and methanol were both tested as external organic denitrification substrates. The ratio of the organic substrate COD to NO3-N was 6. Only methanol was proven as a suitable organic substrate for this kind of reactor. However, the biomass adaptation
to the substrate took over a week. The cultivation of anoxic granulated biomass was reached at hydraulic loading of over 0.35
m h−1. The size of granules was smaller when compared with results found and described in literary reports (granules up to 1 mm);
however, settling properties were excellent and denitrification was deemed suitable for the USB reactor. Sludge volume indexes
of granules ranged from 35-50 mL g−1 and settling rates reached 11 m h−1. Maximum hydraulic and mass loadings in the USB reactor were 0.95 m3 m−2 h−1 and 6.6 kg m−3 d−1. At higher loading levels, a wash-out of the biomass occurred.
Presented at the 35th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 26–30 May
2008. 相似文献
17.
A composite film modified glassy carbon electrode (GCE) fabricated with spinning coating of multiwalled carbon nano-tube (MWNT)
/1-butyl-3-methylimidazolium tetrafluoroborate/chitosan sol was developed for the electrochemical determination of 4-nitrophenol
(4-NP). An obvious reduction peak located at about −0.688 V was observed with voltammetric measurements in the potential range
from 0.200 V to −1.00 V. Compared with the bare GCE, the reduction peak potential shifted positively and the peak current
increased significantly. All experimental parameters for the determination of 4-NP were optimized. It was found that the reduction
peak current was proportional to 4-NP concentration in the range from 3.00 × 10−7 to 2.00 × 10−5 mol l−1 with the detect limitation of 1.00 × 10−7 mol l−1 (S/N = 3) after accumulation for 90 s. The proposed method was successfully applied for the determination of trace amounts
of 4-NP in lake water. 相似文献
18.
Panpan Gai Zhiyong Guo Fei Yang Jing Duan Tingting Hao Sui Wang 《Russian Journal of Electrochemistry》2011,47(8):940-947
In this work, a highly-sensitive polymeric membrane ion selective electrode for determination of tetracycline was constructed
by using molecularly imprinted polymer (MIP) particles as quasi-ionophore. The water-compatible MIP particles targeting tetracycline
were synthesized with tetracycline as a template molecule, methacrylic acid as a functional monomer, ethylene glycol dimethacrylate
as a cross-linker, 2,2′-azobisisobutyronitrile as an initiator and lanthanum ion as a mediator. Benefited from the distinctive
performance of the quasi-ionophore and the optimized composition of the membrane and the inner filling solution, the lower
detection limit of the electrode was decreased to about 1 × 10−8 mol/l. It exhibited a good electrode slope 59.8 mV/decade near the theoretical Nernstian one, with a wide linear working
range from 2.0 × 10−8 to 1.0 × 10−3 mol/l. Due to the specific recognition of tetracycline by the MIP particles, the selectivity coefficients for routine interferences
were less than 10−4. The fabricated electrode should be used in pH 2–4, response time of which was less than 200 s when the concentration of
tetracycline was higher than 1.0 × 10−6 mol/l and no more than 30 min at the concentration of 1.0 × 10−8 mol/l. Finally, the proposed highly-sensitive ion selective electrode has been successfully applied to the determination
of tetracycline in aqueous samples. 相似文献
19.
Summary A capillary electrophoretic method for the determination of Cu(II) and Co(III) chelates with ethylenediamine in electroless
copper plating baths has been developed. The influence of carrier electrolyte parameters such as nature of counter-ion and
pH were studied and discussed. The optimised separations were carried out in a fused silica capillary (57 cm × 75 μm I.D.)
filled with an ethylenediamine sulfate electrolyte (20 mol L−1 ethylendiamine, pH7.0 with H2SO4; applied voltage, +25 kV) using direct UV detection at 214 nm. The detection limits for a signalto-noise ratio of 3 and 10s
hydrodynamic injection were 5×10−6 mol L−1 for Cu(II) and 1×10−6 mol L−1 for Co(III). The relative standard deviations of the peak areas for Cu(II) and Co(III) were found to be 1.5% and 2.4%, respectively,
with five consecutive injections of standard solution containing 5×10−5 mol L−1 of each metal ion. Application of the method to the speciation of Cu(II) and Co(III) complexes in copper plating bath samples
is also demonstrated. 相似文献
20.
A new p-tetra-butyl calix [6] arene-L-Histidine chemically modified glassy carbon electrode (BCH/GCE) has been proposed for simultaneous
investigation and determination of epinephrine (Ep) and serotonin (5-HT) by cyclic voltammetry (CV) and differential pulse
voltammetry (DPV). In potassium dihydrogen phosphate-borax (PDPB) buffer solution (pH 5.8), the anodic peaks of Ep and 5-HT
were observed at 0.27 and 0.45 V, respectively, with E up to 180 mV. The peak currents on the DP voltammogram are in a linear relationship with the concentrations of Ep in the
range of 1.0 × 10−6−1.30 × 10−4 M in the presence of 1.0 × 10−4 M 5-HT. A linear relationship was similarly found for 5-HT in the range 1.0 × 10−6− 1.40 × 10−4 M in the presence of 1.0 × 10−4 M Ep. It is found that Ep and 5-HT could be simultaneously determined with good sensitivity in the presence of 1.0 × 10−3 M ascorbic acid (AA). The developed method has been applied to the determination of Ep and 5-HT in synthetic samples with
satisfactory results.
The text was submitted by the authors in English. 相似文献