共查询到20条相似文献,搜索用时 15 毫秒
1.
Nabila M. Guindy Zeinab M. Abou-Gamra Michel F. Abdel-Messih 《Monatshefte für Chemie / Chemical Monthly》2000,131(8):857-866
Summary. The kinetics of the formation of the 1:3 complex of chromium(III) with L-glutamic acid and DL-lysine were studied spectrophotometrically at and 550 nm. The reaction was found to be first order in both reactants. Increasing the hydrogen ion concentration from 3.2×10−5 to 1.0×10−3 molċdm−3 retarded the reaction rate which is of the form . Values of 28.8 and 63.6 kJċmol−1 were obtained for the energy of activation and −184 and −116 Jċ K−1ċmol−1 for the entropy of activation for L-glutamic acid and DL-lysine. The logarithms of the formation constants of the two complexes were found to be 5.9 and 5.1.
Received January 7, 2000. Accepted (revised) March 8, 2000 相似文献
2.
Vesna Kunti? Dusěan Malesěev Zorica Radovi? Vladana Vukojevi? 《Monatshefte für Chemie / Chemical Monthly》2000,18(5):769-777
In the present work, rutin (3,3′ ,4′ ,5,7-pentahydrohyflavone-3-rhamnoglucoside) was determinated via a complexing reaction with a titanyloxalate anion. K2[TiO(C2O4)2] and rutin react in 50% ethanol forming a 1:2 complex in a pH range from 4.00 to 11.50, in which the TiO(C2O4)2 2− ion is linked to rutin through the 4-carbonyl and 5-hydroxyl group. The thermodynamic stability constant log β2 0 of the complex is determined to 10.80 at pH = 6.50. The change of the standard Gibbs free energy Δ G0 amounts to −61 kJċ mol−1, indicating that the process of complex formation is spontaneous. The optimal conditions for the spectrophotometric determination of microconcentrations of rutin are at pH=6.40 and λ= 430 nm, where the complex shows an absorption maximum with a molar absorption coefficient a 430=(60±2)ċ103 dm3ċ mol−1ċ cm−1. The method is applied rutin determination from tablets. 相似文献
3.
Vesna Kuntić Dusěan Malesěev Zorica Radović Vladana Vukojević 《Monatshefte für Chemie / Chemical Monthly》2000,131(7):769-777
Summary. In the present work, rutin (3,3′ ,4′ ,5,7-pentahydrohyflavone-3-rhamnoglucoside) was determinated via a complexing reaction with a titanyloxalate anion. K2[TiO(C2O4)2] and rutin react in 50% ethanol forming a 1:2 complex in a pH range from 4.00 to 11.50, in which the TiO(C2O4)2
2− ion is linked to rutin through the 4-carbonyl and 5-hydroxyl group. The thermodynamic stability constant log β2
0 of the complex is determined to 10.80 at pH = 6.50. The change of the standard Gibbs free energy Δ G0 amounts to −61 kJċ mol−1, indicating that the process of complex formation is spontaneous. The optimal conditions for the spectrophotometric determination
of microconcentrations of rutin are at pH=6.40 and λ= 430 nm, where the complex shows an absorption maximum with a molar absorption coefficient a
430=(60±2)ċ103 dm3ċ mol−1ċ cm−1. The method is applied rutin determination from tablets.
Received January 4, 2000. Accepted (revised) February 17, 2000 相似文献
4.
[PdCl(terpy)]Clċ3H2O has been synthesized both by interaction of [PdCl4]2− and cis-[Pd(DMSO)2Cl2] with terpy (2,2′:6′,2′′-terpyridine). Complex formation of [PdCl(terpy)]+ with L-cysteine, S-methyl-L-cysteine, and L-methionine was studied as a function of temperature (298–308 K) using of stopped-flow spectrophotometry in methanol-water
(95:5 (v/v)). The ionic strength and acidity of the solutions were adjusted to 0.10 molċdm−3 with CH3SO3H. The second-order rate constant for the reaction of [PdCl (terpy)]+ with L-cysteine amounts to 9.60±0.5 M
−1s−1. L-Methionine and S-methyl-L-cysteine are unreactive under the same experimental conditions. The entropy of activation is strongly negative, which is
compatible with an associative mechanism. 相似文献
5.
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
6.
Nicolas C. Imlinger Manfred Krell Michael R. Buchmeiser 《Monatshefte für Chemie / Chemical Monthly》2007,138(4):285-291
Summary. Platinum(II) chloride was used in the hydrosilylation of 1,1,3,3-tetramethyldisiloxane and divinylbenzene. The reaction was
monitored online by FTIR spectroscopy and reaction kinetics were determined by Self Modeling Curve Resolution (SMCR). The
hydrosilylation polymerization follows a second order polyaddition kinetics with k = 2.03 × 10−4 dm3 mol−1 s−1. 相似文献
7.
Jun Yue Bai Liang Wang Hong Jing Wang Peng Fei Huang Yu Qing Zhao Sheng Di Fan 《Mikrochimica acta》2006,156(3-4):321-326
The electrochemical behavior of epinephrine (EP) at a mercaptoacetic acid (MAA) self-assembled monolayer modified gold electrode
was studied. The MAA/Au electrode is demonstrated to promote the electrochemical response of epinephrine by cyclic voltammetry.
The possible reaction mechanism is also discussed. The diffusion coefficient D of EP is 6.85 × 10−6 cm2 s−1. In 0.1 mol L−1 phosphate buffer (pH 7.20), a sensitive oxidation peak was observed at 0.177 V, and the peak current is proportional to the
concentration of EP in the range of 1.0 × 10−5–2.0 × 10−4 mol L−1 and 1.0 × 10−7–1.0 × 10−6 mol L−1. The detection limit is 5 × 10−8 mol L−1. The modified electrode is highly stable and can be applied to the determination of EP in practical injection samples. The
method is simple, quick, sensitive and accurate. 相似文献
8.
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
9.
Xiaoying Liu Yonghong Li Xinsheng Liu Xiandong Zeng Bo Kong Shenglian Luo Wanzhi Wei 《Journal of Solid State Electrochemistry》2012,16(3):883-889
A simple sensor based on bare carbon ionic liquid electrode was fabricated for simultaneous determination of dihydroxybenzene
isomers in 0.1 mol L−1 phosphate buffer solution (pH 6.0). The oxidation peak potential of hydroquinone was about 0.136 V, catechol was about 0.240 V,
and resorcinol 0.632 V by differential pulse voltammetric measurements, which indicated that the dihydroxybenzene isomers
could be separated absolutely. The sensor showed wide linear behaviors in the range of 5.0 × 10−7–2.0 × 10−4 mol L−1 for hydroquinone and catechol, 3.5 × 10−6–1.535 × 10−4 mol L−1 for resorcinol, respectively. And the detection limits of the three dihydroxybenzene isomers were 5.0 × 10−8, 2.0 × 10−7, 5.0 × 10−7 mol L−1, respectively (S/N = 3). The proposed method could be applied to the determination of dihydroxybenzene isomers in artificial wastewater and
the recovery was from 93.9% to 104.6%. 相似文献
10.
In the presence of carbonate and uranine, the chemiluminescent intensity from the reaction of luminol with hydrogen peroxide
was dramatically enhanced in a basic medium. Based on this fact and coupled with the technique of flow-injection analysis,
a highly sensitive method was developed for the determination of carbonate with a wide linear range. The method provided the
determination of carbonate with a wide linear range of 1.0 × 10−10–5.0 × 10−6 mol L−1 and a low detection limit (S/N = 3) of carbonate of 1.2 × 10−11 mol L−1. The average relative standard deviation for 1.0 × 10−9–9.0 × 10−7 mol L−1 of carbonate was 3.7% (n = 11). Combined with the wet oxidation of potassium persulfate, the method was applied to the simultaneous determination
of total inorganic carbon (TIC) and total organic carbon (TOC) in water. The linear ranges for TIC and TOC were 1.2 × 10−6–6.0 × 10−2 mg L−1 and 0.08–30 mg L−1 carbon, respectively. Recoveries of 97.4–106.4% for TIC and 96.0–98.5% for TOC were obtained by adding 5 or 50 mg L−1 of carbon to the water samples. The relative standard deviations (RSDs) were 2.6–4.8% for TIC and 4.6–6.6% for TOC (n = 5). The mechanism of the chemiluminescent reaction was also explored and a reasonable explanation about chemical energy
transfer from luminol to uranine was proposed.
Figure Chemiluminescence profiles in batch system. 1, Injection of 100 μL of K2CO3 into 1.0 mL luminol-1.0 mL H2O2 solution; 2-3 and 4-5, Injection in sequence of 100 μL of K2CO3 and 100 μL of uranine into 1.0 ml luminol-1.0 mL H2O2 solution; Cluminol = 1.0 × 10−7 mol/L, CH2O2 = 1.0 × 10−5 mol/L, Curanine = 1.0 × 10−5 mol/L, CK2CO3 = 1.0 × 10−7 mol/L except for 4-5 where CK2CO3 = 1.0 × 10−4 mol/L 相似文献
11.
The antitumor mechanism of etoposide (VP-16) is investigated using pulse radiolysis technology. The oxidizing mechanism of VP-16 is studied by sodium persulfate, and the reaction rate constant is 4.04× 109 L· mol-1 · s-1. The electron-transfer between VP-16 and tyrosine is observed and the reaction rate constant is 1.1 - 108 L · mol-1· s-1. 相似文献
12.
The electrochemical behavior of the ofloxacin–copper complex, Cu(II)L2, at a mercury electrode, and the interaction of DNA with the complex have been investigated. The experiments indicate that
the electrode reaction of Cu(II)L2 is an irreversible surface electrochemical reaction and that the reactant is of adsorbed character. In the presence of DNA,
the formation of the electrochemically non-active complexes Cu(II)L2-DNA, results in the decrease of the peak current of Cu(II)L2. Based on the electrochemical behavior of the Cu(II)L2 with DNA, binding by electrostatic interaction is suggested and a new method for determining nucleic acid is proposed. Under
the optimum conditions, the decrease of the peak current is in proportional to the concentration of nucleic acids in the range
from 3 × 10−8 to 3 × 10−6 g · mL−1 for calf thymus DNA, from 1.6 × 10−8 to 9.0 × 10−7 g · mL−1 for fish sperm DNA, and from 3.3 × 10−8 to 5.5 × 10−7 g · mL−1 for yeast RNA. The detection limits are 3.3 × 10−9, 6.7 × 10−9 and 8.0 × 10−9 g · mL−1, respectively. The method exhibits good recovery and high sensitivity in synthetic samples and in real samples. 相似文献
13.
Francisco Ros Pilar Jiménez María Victoria Roux 《Monatshefte für Chemie / Chemical Monthly》2007,138(10):941-949
Summary. The cohesion potential energy of the crystal of one enantiomer of ethyl 3-cyano-3-(3,4-dimethyloxyphenyl)-2,2,4-trimethylpentanoate,
−47.7 ± 0.1 kJ mol−1 (0–90°C), was found out from the heat of sublimation (123.2 ± 5.1 kJ mol−1, 78.6°C) and the kinetic energies for the gas phase and the crystal. It was found that the entropy function of Debye’s theory of solids mathematically agreed with the vibrational entropy of the gas (variationally obtained), allowing to disclose
the vibrational energy using the Debye energy function (E
vib 835.0 kJ mol−1 (78.6°C), E
0 included). E
kin for the crystal (771.1 kJ mol−1 (78.6°C)) was obtained by Debye’s theory with the experimental heat capacity. The cohesion energy represented a moderate part of the sublimation energy.
The cohesion energy of the racemic crystal, −44.2 kJ mol−1, was obtained by the heat of formation of the crystal in the solid state (3.0 kJ mol−1, 83.3°C) and E
kin for the crystal (by Debye’s theory). The decrease in cohesion on formation of the crystal accounted for the energy of formation. The change in potential
energy on liquefaction of the racemate from the gas state was disclosed obtaining added-up E
vib + rot for the liquid in the way as to E
vib for the gas, the Debye entropy function being increasedly suited for the liquid (E
vib + rot 763.4 kJ mol−1 (115.4°C)). Positive ΔE
pot, 13.0 kJ mol−1, arised from the increase in electronic energy (Δ
l
νmean − 154.3 cm−1, by the dielectric nature of the liquid), added to the cohesion energy. 相似文献
14.
Francisco Ros Pilar Jiménez María Victoria Roux 《Monatshefte für Chemie / Chemical Monthly》2007,28(4):941-949
The cohesion potential energy of the crystal of one enantiomer of ethyl 3-cyano-3-(3,4-dimethyloxyphenyl)-2,2,4-trimethylpentanoate,
−47.7 ± 0.1 kJ mol−1 (0–90°C), was found out from the heat of sublimation (123.2 ± 5.1 kJ mol−1, 78.6°C) and the kinetic energies for the gas phase and the crystal. It was found that the entropy function of Debye’s theory of solids mathematically agreed with the vibrational entropy of the gas (variationally obtained), allowing to disclose
the vibrational energy using the Debye energy function (E
vib 835.0 kJ mol−1 (78.6°C), E
0 included). E
kin for the crystal (771.1 kJ mol−1 (78.6°C)) was obtained by Debye’s theory with the experimental heat capacity. The cohesion energy represented a moderate part of the sublimation energy.
The cohesion energy of the racemic crystal, −44.2 kJ mol−1, was obtained by the heat of formation of the crystal in the solid state (3.0 kJ mol−1, 83.3°C) and E
kin for the crystal (by Debye’s theory). The decrease in cohesion on formation of the crystal accounted for the energy of formation. The change in potential
energy on liquefaction of the racemate from the gas state was disclosed obtaining added-up E
vib + rot for the liquid in the way as to E
vib for the gas, the Debye entropy function being increasedly suited for the liquid (E
vib + rot 763.4 kJ mol−1 (115.4°C)). Positive ΔE
pot, 13.0 kJ mol−1, arised from the increase in electronic energy (Δ
l
νmean − 154.3 cm−1, by the dielectric nature of the liquid), added to the cohesion energy. 相似文献
15.
Ashraf A. Mohamed 《Monatshefte für Chemie / Chemical Monthly》2001,56(2):919-928
A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of iodide. The method is based on the catalytic effect of iodide on the reaction of triflupromazine (TFP) with H2O2. The reaction is followed spectrophotometrically by tracing the oxidation product at 498 nm within 1 min after addition of H2O2. The optimum reaction conditions are TFP (0.4 × 10−3 M), H2SO4 (1.0M), H3PO4 (2.0M), and H2O2 (1.6M) at 30°C. Following this procedure, iodide can be determined with a linear calibration graph up to 4.5 ng ċ cm−3 and a detection limit of 0.04 ng ċ cm−3, based on the 3 Sb criterion. The method can also be applied to the determination of iodate and periodate ions. Determination of as little as 0.2, 1.0, 2.0, and 4.0 ng ċ cm−3 of I−, IO3 -, or IO4 - in aqueous solutions gave an average recovery of 98% with relative standard deviations below 1.6% (n = 5). The method was applied to the determination of iodide in Nile river water and ground waters as well as in various food samples after alkaline ashing treatment. The method is compared with other catalytic spectrophotometric procedures for iodide determination. 相似文献
16.
Ashraf A. Mohamed 《Monatshefte für Chemie / Chemical Monthly》2001,132(8):919-928
Summary. A new selective, sensitive, and simple kinetic method is developed for the determination of trace amounts of iodide. The
method is based on the catalytic effect of iodide on the reaction of triflupromazine (TFP) with H2O2. The reaction is followed spectrophotometrically by tracing the oxidation product at 498 nm within 1 min after addition of
H2O2. The optimum reaction conditions are TFP (0.4 × 10−3
M), H2SO4 (1.0M), H3PO4 (2.0M), and H2O2 (1.6M) at 30°C. Following this procedure, iodide can be determined with a linear calibration graph up to 4.5 ng ċ cm−3 and a detection limit of 0.04 ng ċ cm−3, based on the 3 Sb criterion. The method can also be applied to the determination of iodate and periodate ions. Determination of as little as
0.2, 1.0, 2.0, and 4.0 ng ċ cm−3 of I−, IO3
-, or IO4
- in aqueous solutions gave an average recovery of 98% with relative standard deviations below 1.6% (n = 5). The method was applied to the determination of iodide in Nile river water and ground waters as well as in various food
samples after alkaline ashing treatment. The method is compared with other catalytic spectrophotometric procedures for iodide
determination.
Received January 19, 2001. Accepted (revised) March 12, 2001 相似文献
17.
A sensitive adsorptive anodic stripping procedure for the determination of trace zirconium at a carbon paste electrode (CPE)
has been developed. The method is based on adsorptive accumulation of the Zr(IV)-alizarin red S(ARS) complex onto the surface
of the CPE, followed by oxidation of adsorbed species. The optimal experimental conditions include the use of 0.10 mol · L−1 ammonium acetate buffer (pH 4.3), ARS, an accumulation potential of 0.20 V (versus SCE), an accumulation time of 2 min, a
scan rate of 200 mV · s−1 and a second-order derivative linear scan mode. The oxidation peak for the complex appears at 0.69 V. The peak current is
proportional to the concentration of Zr(IV) over the range of 1.0 × 10−9–2.0 × 10−7 mol · L−1, and the detection limit is 3 × 10−10 mol · L−1 for a 2 min adsorption time. The relative standard deviations (n = 8) for 5.0 × 10−8 and 5.0 × 10−9 mol · L−1 Zr(IV) are 3.3 and 4.8%, respectively. The proposed method was applied to the determination of zirconium in ore samples with
satisfactory results. 相似文献
18.
Determination of the effective components in traditional Chinese medicine is one of the key steps for its identification.
In this paper a novel and sensitive chemiluminescence (CL) method for the determination of rhein coupled with flow-injection
analysis (FIA) is developed. It is based on the strong sensitizing effect on the weak CL reaction between luminol and ferricyanide
in alkaline solution. Under optimal experimental conditions, the relative CL intensity is proportional to the concentration
of rhein in the range of 7.0 × 10−12–7.0 × 10−10 mol L−1 and 1.0 × 10−9–4.0 × 10−5 mol L−1, the detection limit is 1.478 × 10−13 mol L−1, and the relative standard deviation (RSD) for 9 parallel measurements of 1.408 × 10−7 mol L−1 rhein is 3.4%. The method was successfully applied to the determination of rhein in pharmaceutical preparations. The possible
mechanism of CL is also briefly discussed. 相似文献
19.
Zirconium (IV) was determined spectrophotometrically by reaction with quercetin as primary ligand and oxalate as secondary
ligand. Polyvinylpyrrolidone (PVP) was used as protective colloid to solubilize the formed zirconium quercetin oxalate ternary
complex. The molar absorptivity of the 1:3:1 (zirconium–quercetin–oxalate) complex is 7.31 × 104 L·mol−1 cm−1 at 430 nm with a stability constant of 8.2 × 1020 and its detection limit is 0.16 mg/L. Beer’s law is rectilinear up to 1.46 mg/L of zirconium (IV). The sensitivity index
is 1.25 ng cm−2.
The reaction of aluminium (III) with quercetin in presence of PVP as a surfactant has been studied spectrophotometrically.
The molar absorptivity of the 1:3 (aluminium–quercetin) complex is 8.09 × 104 × L·mol−1·cm−1 at 433 nm, its stability constant is 2.6 × 1013 with sensitivity index of 0.33 ng·cm−2 and its detection limit is 0.08 mg/L. The optimal conditions for the quantitative determination of zirconium and aluminium
were studied. The proposed methods are examined by statistical analysis of the experimental data. The methods are free from
interference of most cations and anions. The proposed methods have been used to determine zirconium and aluminium in industrial
waste water.
Received May 30, 2001; accepted November 2, 2001; published online July 15, 2002 相似文献
20.
Radoi A Compagnone D Batic M Klincar J Gorton L Palleschi G 《Analytical and bioanalytical chemistry》2007,387(3):1049-1058
Bulk screen-printed electrodes (bSPEs) modified with zirconium phosphate (ZrP) and Meldola blue (MB) and by electrochemical deposition of a Reineckate film
(bMBZrPRs-SPEs) have been constructed and used as NADH sensors. Cyclic voltammetric investigation of these bulk electrochemically
modified screen-printed electrodes revealed stable catalytic activity in oxidation of the reduced form of the coenzyme nicotinamide
adenine dinucleotide (NADH). Flow-injection analysis (FIA) coupled with amperometric detection confirmed the improved stability
of the bMBZrPRs-SPEs (10−4 mol L−1 NADH, %RSD = 4.2, n = 90, pH 7.0). Other conditions, for example applied working potential (+50 mV relative to Ag|AgCl), flow rate (0.30 mL min−1) and pH-dependence (range 4.0–10.0) were evaluated and optimized. A glycerol biosensor, prepared by immobilizing glycerol
dehydrogenase (GDH) on the working electrode area of a bMBZrPRs-SPE, was also assembled. The biosensor was most stable at pH 8.5 (%RSD = 5.6, n = 70, 0.25 mmol L−1 glycerol). The detection and quantification limits were 2.8 × 10−6 and 9.4 × 10−6 mol L−1, respectively, and the linear working range was between 1.0 × 10−5 and 1.0 × 10−4 mol L−1. To assess the effect of interferences, and recovery by the probe we analyzed samples taken during fermentation of chemically
defined grape juice medium and compared the results with those obtained by HPLC. 相似文献