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1.
The spectral and kinetic parameters of transient species generated in the irradiation of 6-ethoxy-2,2,4-trimethyl-8-nitro-1,2-dihydroquinoline
were examined by stationary and pulse photolysis in the solvents: heptane, acetonitrile, methanol, and ethanol. Upon excitation
of the long-wavelength absorption band (λex > 450 nm), a reversible photochemical reaction was revealed, and the spectral and kinetic parameters of three transient species
observed in the photolysis were characterized (λmax = 390, 400, and 420 nm (acetonitrile), k = 97, 500, and 2000 s−1, respectively). The absorption spectra and the rate constants of the decay of transient species are almost independent of
the medium polarity and the presence of oxygen in the system. The excited state generated during irradiation to the short-wavelength
absorption band (290 < λex < 350 nm) is inactive in the photochemical reaction and deactivates without the formation of transient species. The mechanism
of the reversible photochemical reaction is suggested, which involves the opening of the heterocycle N-C bond upon photoexcitation
of the long-wavelength absorption band and the thermal back reaction. 相似文献
2.
Chen HQ Wang L Liu Y Wu WL Liang AN Zhang XL 《Analytical and bioanalytical chemistry》2006,385(8):1457-1461
A new fluorescence method for the detection of proteins with novel composite nanoparticles (CdS/PPA) has been developed. The
composite nanoparticles have been prepared through an in-situ polymerization method under ultrasonic irradiation. The surface
of the composite nanoparticles was covered with functional groups (-COOH). These groups may play a major role in the improving
the water solubility and biocompatibility of the nanoparticles. The composite particles is combined with proteins in NaAc-HCl
buffer solution (pH=1.99), which can result in strong fluorescence, and the response is linearly proportional to the concentration
of proteins. In λem/λex=650 nm/365 nm place (the stoke’ shift is 285 nm), its fluorescent strength reaches the maximum. Under
the optimum conditions, the linear range is 0.10–20.0 μg·ml−1 with the detection limit of 41 ng·ml−1 for HSA, and 0.10–15.0 μg·ml−1 with the detection limit of 35 ng·ml−1 for Human γ-IgG . The method has been applied to the determination of the total protein in human serum samples collected
from the hospital and the results are satisfactory. 相似文献
3.
Akram M. El-Didamony 《Central European Journal of Chemistry》2005,3(3):520-536
Three simple, accurate, and sensitive spectrophotometric methods (A, B and C) have been described for the indirect assay of
diltiazem hydrochloride (DIL.HCl), either in pure form or in pharmaceutical formulations. The first method (A) is based on
the oxidation of DIL.HCl by N-bromosuccinimide (NBS) and determination of unconsumed NBS by measuring the decrease in absorbance
of amaranth dye (AM) at a suitable λ
max
=521 nm. Other methods (B) and (C) involve the addition of excess cerric ammonium sulfate (CAS) and subsequent determination
of the unconsumed oxidant by a decrease in the red color of chromotrope 2R (C2R) at a suitable λ
max
=528 nm or a decrease in the orange-pink color of rhodamine 6G (Rh6G) at λ
max
=525 nm, respectively. Regression analysis of Beer-Lambert plots showed good correlation in the concentration ranges 3.0–9.0,
3.5–7.0 and 3.5–6.3 μg ml−1 for methods A, B and C, respectively. The apparent molar absorptivity, Sandell's sensitivity, detection and quantification
limits were calculated. The proposed methods have been applied successfully for the analysis of the drug in its pure form
and its dosage form. No interference was observed from a common pharmaceutical adjuvant. Statistical comparison of the results
with the reference method shows excellent agreement and indicates no significant difference in accuracy and precision. 相似文献
4.
A new method based on probe sonication extraction (USP) prior to high performance liquid chromatography (HPLC) has been developed for the determination of linear alkylbenzene sulfonates (LAS) from sewage sludge. The optimized method was designed to be cost effective compared to existing extraction methods (ultrasonic assisted extraction, Soxhlet or pressurized liquid extraction) which may require large quantities of organic solvents, or costly instrumentation or equipment.The main factors affecting the extraction efficiency (extractant volume, ultrasounds power and extraction time) were optimized using compost sludge. The detection limit of total LAS in the sludge was 10 mg kg− 1. The extraction of C10-C13 homologues is carried out using an extraction time of 7 min with 10 mL of methanol. Liquid chromatography with fluorescence (FL) detector is used for determination of LAS homologues. A mobile phase acetonitrile-water containing 0.1 M NaClO4 (65:35) and isocratic elution was used. Compounds were eluted over 6 min at a flow rate of 1 mL/min. Polar interferences are eluted between 0 and 2 min and no purification of the samples is required prior to the final determination by high performance liquid chromatography (HPLC). The recoveries of LAS in spiked sewage sludge were between 84.0% and 97.0%, which reflect the efficiency of the method for extraction of these analytes from sewage sludge. Concentration levels found were between 11,858 mg kg− 1 for digested sludge and 2379 mg kg− 1 for compost sludge. 相似文献
5.
Summary A sensitive HPLC method with marbofloxacin (MAR) as internal standard and fluorescence detection is described for the analysis
of ofloxacin (OFL) enantiomers in plasma samples. Plasma samples were prepared by adding phosphate buffer (pH 7.4, 0.1m), then extracted with trichloromethane.S-OFL,R-OFL, and the internal standard were separated on a reversed-phase column with water-methanol, 85.5∶14.5, as mobile phase.
The concentrations ofS-OFL andR-OFL eluting from the column (retention times 7.5 and 8.7 min, respectively) were monitored by fluorescence detection withλ
ex = 331 andλ
em = 488 nm. The detection and quantitation limits were 10 and 20 ng mL−1, respectively, forS-OFL and 11 and 21 ng mL−1 forR-OFL. Response was linearly related to concentration in the range 10 to 2500 ng mL−1. Recovery was close to 93% for both compounds. The method was applied to determination of the enantiomers of OFL in plasma
samples collected during pharmacokinetic studies. 相似文献
6.
López-Flores J Fernández-de Córdova ML Molina-Díaz A 《Analytical and bioanalytical chemistry》2007,388(8):1771-1777
A flow injection–solid-phase spectroscopy (FI-SPS) system implemented with photochemically induced fluorescence (PIF) is described
for the rapid and very sensitive determination of reserpine in biological fluids and pharmaceutical formulations. An intensively
fluorescent photoproduct is in-line generated, retained on C18 silica gel in the detection area and monitored at 394/489 nm (λ
ex/λ
em). After the establishment of the appropriate working variables, the system is calibrated at two different injection volumes,
100 and 800 μL, achieving detection limits of 0.33 and 0.05 ng mL−1, respectively. The RSD for reserpine at 2 ng mL−1 (800 μL) was 1.5% (n = 10). The sampling rates were 46 and 43 h−1 for each injection volume, respectively. The potential interference of some common species coexisting with reserpine in the
analysed samples was also studied. The procedure was successfully applied to commercial formulations, urine and serum without
any previous treatment of samples. Recoveries ranged from 94.9 to 100.2%. 相似文献
7.
M. A. Taher A. Mostafavi S. Z. Mohammadi Mobarakeh 《Journal of Analytical Chemistry》2007,62(11):1022-1027
This work assesses the potential of natural analcime zeolite as a sorbent for the preconcentration of palladium. Palladium
is quantitatively retained on modified analcime zeolite loaded with zincon using the column method in the pH range from 2.5
to 3.5 at a flow rate of 1 mL/min. The palladium complex was removed from the column with 5.0 mL of dimethylsulfoxide (DMSO)
and determined by third-derivative spectrophotometry. The detection limit is 0.03 μg/mL (signal-to-noise ratio = 3) in the
final solution. Since it is possible to retain 0.15 μg of palladium from 600 mL of solution passing through the column, elution
with 5.0 mL of DMSO gives a detection limit of 0.25 ng/mL for palladium in the initial aqueous solution. The calibration curve
is linear over the range 0.1 to 5.0 μg/mL of palladium(II) in the final solution with a correlation coefficient of 0.9996.
Seven replicated determinations of 5.0 μg of palladium in 5.0 mL dimethylsulfoxide gave a mean d
3
A/dλ3 (peak-to-peak signal between λ2 = 625 and λ1 = 654 nm) of 0.64 with a relative standard deviation of 1.2%. The sensitivity of the method (d
3
A/dλ3) is 0.5843 mL/μg of palladium(II) from the slope of the calibration curve. The interference of a large number of anions and
cations has been studied and the optimized conditions developed were utilized for the determination of trace palladium in
various synthetic and water samples.
The text was submitted by the authors in English. 相似文献
8.
A. P. Pivovarov 《Russian Chemical Bulletin》2008,57(2):289-291
The kinetics and mechanism of photodehydrogenation of the phosphine hydride complexes MH4L4 (M = Mo, W; L are phosphine ligands) and the formation of coordinatively unsaturated species ML4 were studied by the absorbance of long-wavelength bands with λmax at 450–460 nm appeared in the absorption spectra of the photoproducts. The rate constants of the reactions of the coordinatively
unsaturated M(DPPE)2 species (M = Mo, W; DPPE = Ph2PCH2CH2PPh2) with molecular nitrogen in benzene were determined (k
W = 200 s−1, k
Mo = 8700 s−1).
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 282–284, February, 2008. 相似文献
9.
M. V. Sultanbaev S. S. Ostakhov Sh. Kh. Gantsev F. A. Khalilullin V. P. Kazakov 《High Energy Chemistry》2010,44(5):383-386
A spectral-luminescent study of the keto-enol tautomerism of 5-fluorouracil (FU) has been performed. A discrepancy between
the absorption and fluorescence (FL) excitation spectra of aqueous FU solutions (pH 7) has been established. Photoexcitation
at the long-wavelength band (340 nm) of the FU excitation spectrum made it possible to detect the fluorescence of its dienol
tautomer (λmax = 440 nm). The quenching of tryptophan fluorescence (K = 15 × 103 l/mol) and blood fluorescence by 5-fluorouracil has been investigated. 相似文献
10.
Yuichiro Tada Kazuyasu Ibuki Noriaki Tsuchihashi Masakatsu Ueno 《Journal of solution chemistry》1997,26(6):595-607
Limiting molar conductances λo of potassium hydroxide in 2 to 25 mol%tert-butyl alcohol (TBA)-water mixtures were determined at 25°C as a function of pressure up to 196 MPa. λo’s of KOH in (2.5 to 15 mol%) 1,4-dioxane-water mixtures at 25°C and 1 atm were also determined. The excess conductance λ
o
e
of the OH- ion estimated as [λ
o
e
(OH-) = λo(KOH) - λo(KCl)] decreased with an increase in the TBA or dioxane content, as did the excess proton conductance λ
o
e
(H+) [λ
o
e
(H+) = λO(HC1) - λo(KCl)]. Although λ
o
e
(OH-) is smaller than λ
o
e
(H+) at all solvent compositions studied, the rate of decrease in λ
o
e
with organic content is larger for the OH- ion than for the H3O+ ion in both solvent mixtures except in the water-rich region of TBA-water mixtures. λ
o
e
(OH-) increases with pressure more strongly in TBA-water mixtures than in pure water, and the rate of increase in λ
o
e
(OH-) with pressure has a maximum at 5 mol% of TBA. These results are discussed in terms of the difference in stability of hydrogen
bonds between the OH- or the H3O+ ion and water molecules and the increase in repulsive forces due to the orientation [H-O O-H] of water molecules in the mixtures. 相似文献
11.
A simple and highly sensitive spectrofluorometric method was developed for the determination of some 1,4-dihydropyridine compounds
namely, nicardipine, nifedipine and isradipine in pharmaceutical preparations and biological fluids. The method is based on
the reduction of nicardipine, nifedipine and isradipine with Zn/HCl and measuring the fluorescence intensity obtained (λem/λex) at 460/364, 450/393 and 446/360 nm, respectively. The factors affecting the development of the fluorophore and its stability
were studied and optimized. The effect of some surfactants such as β-cyclodextrin (βCD), carboxymethylcelullose (CMC), sodium
dodecyl sulphate (SDS) and triton X-100, on the fluorescence intensity was studied. The fluorescence intensity-concentration
plots of nicardipine, nifedipine and isradipine were rectilinear over the ranges 0.4–6.0, 0.2–4.0 and 0.1–9.0 μg ml−1 with detection limits of 0.0028, 0.017 and 0.016 μg ml−1, respectively. The proposed method was successfully applied to commercial tablets containing the compounds; the percentage
recovery agreed well with those obtained using the official methods. The method was further extended to the in vitro determination
of the compounds in spiked human plasma and urine samples. A proposal of the reduction reaction pathway was postulated.
相似文献
12.
Jinmao You Yanyan Fu Zhiwei Sun Yourui Suo 《Analytical and bioanalytical chemistry》2010,396(7):2657-2666
2-(5-Benzoacridine)ethyl-p-toluenesulfonate (BAETS), a dual-sensitive probe, was reacted with bile acids in the presence of K2CO3 catalyst in dimethyl sulfoxide (DMSO) solvent to give BAETS–bile acid derivatives. Derivatives exhibited intense fluorescence
(FL) with an excitation maximum at λ
ex 270 nm and an emission maximum at λ
em 510 nm. MS analysis using APCI-MS indicated that derivatives had excellent APCI-MS ionizability with percentage ionization
δ values changing from 0 to 88.83% in aqueous acetonitrile and from 0 to 89.15% in aqueous methanol. The collision induced
dissociation spectra of m/z [M + H]+ contained specific fragment ions at m/z [M + H−H2O]+, [M + H−2H2O]+, [M + H−3H2O]+, 347.3, and 290.1. Repeatability was good for LC separation of BAETS–bile acid derivatives with aqueous acetonitrile as mobile
phase. The relative standard deviations (RSDs) of retention time and peak area at 6.6 nmol mL−1 levels with fluorescence detection (FL) were from 0.045 to 0.072% and from 2.16 to 2.73%, respectively. Excellent linear
responses were observed, with regression coefficients >0.9995. The FL detection limits (S/N = 3) were in the range of 18.0–36.1 fmol. The online APCI-MS detection limits are in the range of 500–790 fmol (at a signal-to-noise
ratio of 3). 相似文献
13.
Huang KJ Zhang M Xie WZ Zhang HS Feng YQ Wang H 《Analytical and bioanalytical chemistry》2007,388(4):939-946
A simple, sensitive, selective, and low-cost method is proposed for rapidly determining nitric oxide (NO) in some rat tissues.
Polymer monolith microextraction (PMME) using a poly(methacrylic acid–ethylene glycol dimethacrylate) (MAA-EGDMA) monolithic
column was combined with derivatization of NO using 1,3,5,7-tetramethyl-8-(3′,4′-diaminophenyl)-difluoroboradiaza-s-indacene (TMDABODIPY), and this was used to analyze the derivatives of NO by high-performance liquid chromatography (HPLC)
with fluorescence detection at λ
ex/λ
em = 498/507 nm. The baseline separation of TMDABODIPY and its NO derivative is performed under simple conditions in which a
C18 column is used and eluted with 50 mmol L−1 ethanolamine and methanol. The conditions for the extraction of NO derivatives were optimized. The limit of detection of
NO was 2 × 10−12 mol L−1 (S/N = 3). The linearity range of the method was 9 × 10−11−4.5 × 10−8 mol L−1. The interday and intraday relative standard deviations were less than 5%. The proposed method was successfully applied to
the determination of NO levels in some rat tissue samples including heart, kidney, and liver with recoveries varying from
87.1 to 95.2%. 相似文献
14.
A. Naeem I. M. Khan A. Ahmad 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(10):1840-1843
The convincing evidence have been given that both the interactions π-π and π-π* (between p-nitrophenol (p-NTP) and p-dimethylaminobenzaldehyde (p-DAB)) are simultaneously involved. This has been established by using IR spectrometry. Association constant K evaluated by the method of Foster under the condition [A]0 = [D]0 with apply in this equation, [A]0/A = 1/Kɛλ[D]0 + 2/ɛλ, where [A]0 is the initial concentration of acceptor equal to [D]0, A is the absorbance of the complex at λ, K is the association constant, and ɛλ is the molar absorptivity of the complex at λ. In the IR spectral studies of several related organic compounds, one comes
to the conclusion that p-NTP shows a broad band centred at 1600 cm−1 and to nitro asymmetric stretching vibrations. In the complex while the 1500 cm−1 band remains without shift, the broad band localized at 1600 cm−1 shift to 1610 cm−1. A shift of 10 cm−1 shows weak interactions. Studies on molecular complexes of organ metallic donors and acceptors are of very recent origin.
Though alkyl donors have been extensively studied, very few studies have appeared on aryl donors. 相似文献
15.
F.P. Temme 《Journal of mathematical chemistry》1998,24(1-3):133-142
The inherent (in)determinacy implicit in the SU(m≥3)×S
n↓G natural embedding aspects of (NMR) spin symmetry of clusters is investigated, as part of a multicolour modelling scheme,
where the SU2-branching level meets the initial n(S
n)=/G/ condition. We focus on correlative mappings derived from [λ]SA (self-associate) irreps for natural group embeddings and compare these with certain Yamanouchi-Gel'fand chain properties
of S
10 Mathematical decompositions of Mλ simple S
n-modules with (2≥p≥4)-branchings of λ⊵,λSA (for λ⊢N partitions of n) provide the initial insight into the monocluster spin (NP) physics of [2H]10, [11B]10 (S
10↓D
5), as aspects of (1,12)-(HC)2(11B)10 or (HC)2(2
11B10 carborane cage isotopomers. The questions raised are significant for their impact on CNP nuclear spin weighting of ro-vibrational
spectra. The methods used are those of combinatorics-via-group actions, as physical S
n-encodings applied to nuclear spin algebras.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Summary An HPLC method with fluorescence detection is presented for the analysis of enrofloxcin (ENR) and ciprofloxacin (CIP) in chicken
tissue using sarafloxacin (SAR) as internal standard. Tissue sample preparations were carried out by adding a phosphate buffer
(pH 7.4, 0.1 M), followed by extraction with trichloromethane. Fluoroquinolones were separated on a reversed-phase column
with a mobile phase of aqueous phosphate buffer-acetonitrile (80:20). The concentrations of CIP, ENR and SAR eluted off the
column, with retention times of 2.28, 3.30 and 4.40, respectively, were monitored by fluorescence detection atλ
ex 338 andλ
em 425 nm. The detection limit was 32 ng g−1 for CIP and 10 ng g−1 for ENR. The standard curves were linearly related to concentration in the range of 1 to 2000 ng g−1. Recovery was determinated as 91.3% and 78.3% for ENR and CIP, respectively. The measurement of the tissue levels of ENR
and CIP in the chicken after oral administration confirmed the utility of the proposed analytical methodology. 相似文献
17.
18.
M. A. Garcia C. Solans J. J. Aramayona S. Rueda M. A. Bregante 《Chromatographia》2000,51(7-8):487-490
Summary An HPLC method with fluorescence detection is presented for the analysis of difloxacin (DIF) and sarafloxacin (SAR) in rabbit
plasma using norfloxacin (NOR) as internal standard (Figure 1). Plasma sample preparations were carried out by adding phosphate
buffer (pH 7.4, 0.1 M), followed by extraction with trichloromethane. Fluoroquinolones were separated on a reversed-phase
column using an aqueous phosphate solution-acetonitrile (82:18) mobile phase. The concentrations of NOR, SAR and DIF eluting
off the column, with retention times of 2.16, 5.60 and 6.20, respectively, were monitored by fluorescence detection atλ
ex 338 andλ
em 425 nm. The quantitation limit was 12 ng mL−1 for SAR and DIF. Standard curves were linearly related to concentration in the range from 1 to 1500 ng mL−1. Recovery was determined as 76% and 70% for SAR and DIF, respectively. Inter-and intraassay coefficients of variation were
less than 6% for all compounds. 相似文献
19.
V. P. Tsybyshev V. A. Livshits B. B. Meshkov O. A. Fedorova S. P. Gromov M. V. Alfimov 《Russian Chemical Bulletin》1997,46(7):1239-1244
An amphiphilic crown-containing styryl dye (1) was synthesized, and the effects of irradiation, temperature, and alkali and alkali-earth metal ions on the conductivity
and optical spectra of its solutions in dioctyl phthalate were studied. Compound1 in thetrans-form almost completely exists as ion pairs (IP). Irradiation at a long-wavelength absorption maximum (λmax) results in a reversible increase in the conductivity and, hence, a degree of dissociation of IP (α); these parameters decrease
when complexes with metal ions are formed. The relaxation times for the photoinduced conductivity coincide with a decrease
in the extinction within experimental error in the 20–60°C temperature range. The photoinduced increase in α is caused bytrans—cis-isomerization and an increase in steric hindrances for the interaction of the ClO4
− anion with the N+ atom of benzothiazolium in thecis-form of1. The activation energies for the darkcis—trans-relaxation, absolute α values, and thermodynamic parameters of dissociation of IP in thetrans-form, as well as the α values in a photostationary mixture ofcis—trans-isomers, were estimated. The decrease in α after binding with metal ions is likely caused by the redistribution of the positive
charge to benzothiazolium through the conjugated system of1. Correlations between the decrease in conductivity (decrease in α) and the hypsochromic shift Δλmax after the formation of complexes between1 and metal ions were observed.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1296–1301, July, 1997. 相似文献
20.
H. N. Lee S. H. Kang S. D. Yang S. C. Sohn 《Journal of Radioanalytical and Nuclear Chemistry》2010,284(3):513-517
Phosphorous containing radioisotope waste was separated and determined by liquid–liquid extraction method through liquid scintillation
counter (LSC). In this process, ammonium phosphate was converted to phosphomolybdate (PMo) by the reaction of ammonium molybdate
(Mo) in HCl solution (0.02 M) and maximum UV/VIS absorbance (λmax) 218 nm was observed. The PMo solution was extracted with TOA (Tri-n-Octylamine)/xylene mixture and λmax 290 nm was found for this organic layer. Absorbance of aqueous and organic layer was linear through concentration. The impurities
such as Co, Cr, Gd, etc. remain in aqueous layer by treating with Mo which was determined by ICP-AES and AAS. The quenching
correction curve for 32P was calculated using LSC results. No counting change was observed as the volume of quenchers increased. The recovery was
98% and 81% for the extraction and separation process from the test using H332PO4 as standard tracer. 相似文献