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1.
Ilona Šperlingová Ludmila Dabrowská Vladimír Stránský Šárka Dušková Jan Kučera Monika Tvrdíková Milon Tichy 《Analytical and bioanalytical chemistry》2010,397(2):433-438
Ethylene glycol monobutyl ether (EGBE), an industrial solvent, is absorbed by the body not only by inhalation but also by
dermal absorption (liquid or vapour). EGBE is metabolized to butoxyacetic acid (BAA). Pooled freeze-dried urine candidate
reference material (RM) was prepared from urine obtained from persons occupationally exposed to EGBE. This material has the
advantage of containing butoxyacetic acid in both the free and conjugated (glutamine and glycine) forms, as found in native
urine. In all GC method modifications used, acid hydrolysis was used to release BAA from its conjugated form. The amount of
butoxyacetic acid in homogeneity and stability testing was measured by GC after derivatisation with N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide. Detection was by MS in EI mode, in the authors’ laboratory. For interlaboratory comparison of the
reference material GC methods with MS, FID, and ECD were used. Different extraction solvents (dichloromethane–isopropanol
2:1, ethyl acetate, or dichloromethane) and derivatisation reagents (trimethylsilyldiazomethane, N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide) were used. Using ANOVA (at the statistical level α = 0.05) no changes were found in the concentration of butoxyacetic acid during fifteen month isochronous stability testing,
or in homogeneity testing. The uncertainty contributions were u
h = 8.8 mg L−1 and u
s = 6.5 mg L−1. The concentration of butoxyacetic acid in freeze-dried urine RM was evaluated from the results of eight laboratory data
sets within an interlaboratory comparison by use of the interactive statistical software IPECA. The contribution to total
uncertainty derived from interlaboratory comparison was u
i = 12.7 mg L−1. The reference value (c = 273 ± 33 mg L−1) is an unweighted arithmetic average of accepted results. The value is traceable to the pure butoxyacetic acid (98% w/w; Acros Organic #257760010) used as calibrant. The uncertainty given is combined expanded uncertainty derived from the results
from interlaboratory comparison, and from homogeneity and stability tests (k = 2). The reference material will be used to verify method performance in the biological monitoring of occupational exposure
to EGBE. 相似文献
2.
Summary The biologically active amines agmatine, cadaverine, histamine, phenethylamine, putrescine, spermidine, and tyramine have
been determined in different varieties of grape, aszu grape, wine and aszu wine from the Tokaj region of Hungary. Ion pairs
formed between the amines and octanesulphonic acid were separated by liquid chromatography on a μBondapak C18 reversed-phase column, and spectrofluorimetric detection was performed after post-column derivatization witho-phthalaldehyde and 2-mercaptoethanol. The method was linear for the amines between 0.1 and 10 mg L−1, and for spermidine between 1 and 30 mg L−1.
Comparison of the results revealed that the qualitative and quantitative content of biologically active amines was mostly
determined by the vintage of the wine and the technology used for wine-making. The biogenic amine content of Tokaj wines is
well below suggested limits for any of the amines, showing that the wine-making technology of the Tokaj region is of high
quality. The levels of biologically active amines (identified and quantified by HPLC) in grapes, wines and aszu wines can
provide useful information about the weather, growth ofBotrytis cinerea in Tokaj, and aspects of the methods used for wine-making.
Presented at Balaton Symposium on High Performance Separation Methods, Siófok, Hungary, September 1–3, 1999 相似文献
3.
Cruz MP Valente IM Gonçalves LM Rodrigues JA Barros AA 《Analytical and bioanalytical chemistry》2012,403(4):1031-1037
In wines, the presence of high levels of acetaldehyde (AA) not only is responsible for undesirable characteristic odours but
can also cause health adverse effects. Such sensorial activity of AA can be overcome by adding sulphites during winemaking,
due to the formation of adducts between AA and sulphites, which lower the sensorial impact of AA. Nevertheless, bound AA can
be released during wine storage; therefore, the knowledge of its total amount can be important to estimate the long-term wine
quality. The proposed methodology is based on the extraction of AA from wines using gas-diffusion microextraction and determination
by liquid chromatography. Free and bound forms of AA could be differentiated and determined using an alkaline hydrolysis step
to dissociate the sulphites–AA adducts. This methodology was successfully applied to different wine types, with free AA values
ranging between 5 and 26 mg L−1 and total form between 154 and 906 mg L−1. Bound AA was above 90% of the total content determined for all samples analysed, and higher amounts were obtained for white
wines (around 98%). Other carbonyl compounds were also identified in the extracts using mass spectrometry. 相似文献
4.
The oxidation of N,N-dimethylhydroxylamine (DMHAN) by nitrous acid is investigated in perchloric acid and nitric acid medium, respectively. The
effects of H+, DMHAN, ionic strength and temperature on the reaction are studied. The rate equation in perchloric acid medium has been
determined to be −d[HNO2]/dt = k[DMHAN][HNO2], where k = 12.8 ± 1.0 (mol/L)−1 min−1 when the temperature is 18.5 °C and the ionic strength is 0.73 mol/L with an activation energy about 41.5 kJ mol−1. The reaction becomes complicated when it is performed in nitric acid medium. When the molarity of HNO3 is higher than 1.0 mol/L, nitrous acid will be produced via the reaction between nitric acid and DMHAN. The reaction products
are analyzed and the reaction mechanism is discussed in this paper. 相似文献
5.
Mark A. W. Lawrence Sonia E. Thomas Paul T. Maragh Tara P. Dasgupta 《Transition Metal Chemistry》2011,36(5):553-563
The kinetics of the intra-molecular electron transfer of an adduct of l-ascorbic acid and the [Fe3IIIO(CH3COO)6(H2O)3]+ cation in aqueous acetate buffer was studied spectrophotometrically, over the ranges 2.55 ≤ pH ≤ 3.74, 20.0 ≤ θ ≤ 35.0 °C,
at an ionic strength of 0.50 and 1.0 mol dm−3 (NaClO4). The reaction of l-ascorbic acid and the complex cation involves the rapid formation of an adduct species followed by a slower reduction in
the iron centres through consecutive one-electron transfer processes. The final product of the reaction is aqueous iron(II)
in acetate buffer. The proposed mechanism involves the triaqua and diaqua-hydroxo species of the complex cation, both of which
form adducts with l-ascorbic acid. At 25 °C, the equilibrium constant for the adduct formation was found to be 86 ± 15 and 5.8 ± 0.2 dm3 mol−1 for the triaqua and diaqua-hydroxo species, respectively. The kinetic parameters derived from the rate expression have been
found to be: k
0 = (1.12 ± 0.02) × 10−2 s−1 for the combined spontaneous decomposition and k
1 = (4.47 ± 0.06) × 10−2 s−1 (ΔH
1‡ = 51.0 ± 2.3 kJ mol−1, ΔS
1‡ = −100 ± 8 J K−1 mol−1), k
2 = (4.79 ± 0.38) × 10−1 s−1 (ΔH
2‡ = 76.5 ± 0.8 kJ mol−1, ΔS
2‡ = 6 ± 3 J K−1 mol−1) for the triaqua and diaqua-hydoxo species, respectively. 相似文献
6.
Yan-Jun Zheng Yun-Tao Duan Yan-Fang Zhang Qiu-Hong Pan Jing-Ming Li Wei-Dong Huang 《Chromatographia》2009,217(6)
A new method for simultaneous determination of organic acids in red wine and must by liquid chromatography was studied. The
determination of organic acids in wines can be achieved in less than 13 min, preceded only by a simple sample dilution and
filtration step. With this method, the chromatographic separation of eight organic acids and interfering peaks present in
red wine, required only one reversed phase column (Waters Atlantis dC18 column, 4.6 × 150 mm ID, 5 μm). As mobile phase, isocratic
acetonitrile–0.01 mol L−1 KH2PO4 at pH 2.7 5:95 (v/v) at a flow rate of 0.8 mL min−1 was used. Detection wavelength was set at 210 nm except for ascorbic acid which was detected at 243 nm. Application to red
wine and must confirmed good repeatability and showed a wide variation range for concentrations of organic acids. 相似文献
7.
Hassan A. Ewais 《Transition Metal Chemistry》2009,34(5):539-547
The oxidation of [CoII(nta)(ox)(H2O)2]3− and [CoII(nta)(ph)(H2O)2]3− (nta = nitrilotriacetate, ox = oxalic acid and ph = phthalic acid) by periodate have been studied kinetically in aqueous
solution over 20–40 °C and a variety of pH ranges. The rate of oxidation of [CoII(nta)(ox)(H2O)2]3− by periodate, obeys the following equation: d[CoIII]/dt = [CoII(nta)(ox)(H2O)23−][H5IO6] {k
4
K
5 + (k
5
K
6
K
2/[H+]} while the reaction of [CoII(nta)(ph)(H2O)2]3− with periodate in aqueous acidic medium obeys the following rate law: d[CoIII]/dt = k
6
K
8[CoII]T [IVII]T/{1 + [H+]/K
7 + K
8[IVII]
T
}. Initial cobalt(III) products were formed and slowly converted to final products, fitting an inner-sphere mechanism. Thermodynamic
activation parameters have been calculated. A common mechanism for the oxidation of ternary nitrilotriacetatocobalt(II) complexes
by periodate is proposed and supported by an excellent isokinetic relationship between ΔH* and ΔS* values for these reactions. 相似文献
8.
Bojana Beljkaš Jovana Matić Ivan Milovanović Pavle Jovanov Aleksandra Mišan Ljubiša Šarić 《Accreditation and quality assurance》2010,15(10):555-561
The objective of this research was to test suitability of the Dumas combustion method to completely substitute the Kjeldahl
method in routine laboratory determination of crude protein content in cereals and oilseeds. The validation of the method
demonstrated that it is able to determine crude protein content in cereals and oilseeds in an efficient and accurate manner,
with a detection limit w(N) = 0.006%, quantification limit w(N) = 0.019%, repeatability precision RSD
r = 0.41%, intra-laboratory reproducibility precision RSD
R = 0.74%, trueness, expressed in terms of bias b = 0.43%, and linear response between (2.36–19.2) mg N. Measurement uncertainty, expressed as relative expanded uncertainty
(coverage factor k = 2, confidence level 95%), was calculated from validation data (U
rel = 2.24%). In order to examine the relationship between two methods, 15 cereal grain and oilseed samples were analyzed using
Dumas and Kjeldahl procedure. The Kjeldahl procedure gave slightly lower w(N) values than the Dumas procedure: w
K(N) = 0.9905 w
D(N) = 0.0376 (R
2
= 0.9996). Relative standard deviations and results of homogeneity test obtained during analysis of complex cereal products
(cereal breakfast and muesli bars) show that the Dumas combustion method may be less suitable for analysis of such samples
compared to Kjeldahl method. 相似文献
9.
Three chromium(III) complexes of general formula [Cr(ox)2(pdaH)]2− (where ox = C2O4
2− and pdaH− is N,O-bonded 2,3-, 2,4- or 2,5-pyridinedicarboxylic acid anion) were obtained and characterized in solution. Acid-catalysed
aquation of [Cr(ox)2(pdaH)]2− gave two products: [Cr(ox)(pdaH)(H2O)2]0 (P1) and cis-[Cr(ox)2(H2O)2]2− (P2). The kinetics of these reactions were studied spectrophotometrically, within the 0.1–1.0 M HClO4 range, and the pseudo-first-order rate constants for the oxalato (k
obs1) and pdaH− (k
obs2) ligands dissociation were calculated based on the determined pseudo-first-order rate constants (k
obs) and P1:P2 molar ratio. The dependencies of the pseudo-first-order rate constants on [H+] are as follows: k
obs1 = b
1[H+] and k
obs2 = b
2[H+], where b
1 and b
2 are the second-order rate constants for the oxalato and pdaH− ligands dissociation, respectively. Kinetic parameters were determined and the mechanism of the pdaH− ligand dissociation is proposed. 相似文献
10.
A study of the electrochemistry of uranium in LiF–BeF2 system important for molten salt reactor concept was conducted at W and Ni electrodes. Cyclic voltammetry and chronopotentiometry
methods were used. Two-step reduction mechanism for U4+ ions involving one electron exchange in soluble/soluble U4+/U3+ system and three electron exchange in the second step were found on W electrode. Both processes were identified as reversible
and diffusion-controlled. Based on voltammetric and chronopotentiometric measurements, the diffusion coefficient of U4+ ions at 813 K was calculated: D(U4+) = 1.26 × 10−6 cm2 s−1 and D(U4+) = 1.28 × 10−6 cm2 s−1, respectively. Formation of U–Ni alloys was observed on Ni electrode. 相似文献
11.
Silvia Berto Francesco Crea Pier Giuseppe Daniele Concetta De Stefano Enrico Prenesti Silvio Sammartano 《Journal of solution chemistry》2009,38(10):1343-1356
The formation constants of dioxouranium(VI)-2,2′-oxydiacetic acid (diglycolic acid, ODA) and 3,6,9-trioxaundecanedioic acid
(diethylenetrioxydiacetic acid, TODA) complexes were determined in NaCl (0.1≤I≤1.0 mol⋅L−1) and KNO3 (I=0.1 mol⋅L−1) aqueous solutions at T=298.15 K by ISE-[H+] glass electrode potentiometry and visible spectrophotometry. Quite different speciation models were obtained for the systems
investigated, namely: ML0, MLOH−, ML22−, M2L2(OH)−, and M2L2(OH)22−, for the dioxouranium(VI)–ODA system, and ML0, MLH+, and MLOH− for the dioxouranium(VI)–TODA system (M=UO22+ and L = ODA or TODA), respectively. The dependence on ionic strength of the protonation constants of ODA and TODA and of
both metal-ligand complexes was investigated using the SIT (Specific Ion Interaction Theory) approach. Formation constants
at infinite dilution are [for the generic equilibrium pUO22++q(L2−)+rH+
⇌(UO22+)
p
(L)
q
H
r
(2p−2q+r);β
pqr
]: log 10
β
110=6.146, log 10
β
11−1=0.196, log 10
β
120=8.360, log 10
β
22−1=8.966, log 10
β
22−2=3.529, for the dioxouranium(VI)–ODA system and log β
110=3.636, log 10
β
111=6.650, log 10
β
11−1=−1.242 for dioxouranium(VI)–TODA system. The influence of etheric oxygen(s) on the interaction towards the metal ion was
discussed, and this effect was quantified by means of a sigmoid Boltzman type equation that allows definition of a quantitative
parameter (pL
50) that expresses the sequestering capacity of ODA and TODA towards UO22+; a comparison with other dicarboxylates was made. A visible absorption spectrum for each complex reaching a significant percentage
of formation in solution (KNO3 medium) has been calculated to better characterize the compounds found by pH-metric refinement. 相似文献
12.
Michele Antoniuk Presta Ben Bruyneel Renato Zanella Jeroen Kool Johannes G. Krabbe Henk Lingeman 《Chromatographia》2009,69(Z2):167-173
Turbulent-flow chromatography (TFC) on-line coupled to liquid chromatography mass spectrometry (LC-MS) is used to determine
flavonoids and resveratrol in different types of wines. A fully automated system was developed in which 10 mL of sample (diluted
wine) was passed over a TFC column, after which the retained analytes were separated by reversed-phase LC and detected by
negative ion mode atmospheric-pressure chemical ionization (APCI) MS. The method proved to be fast, non-laborious, robust
and sensitive. The feasibility of the method was tested on several red, white and rose wines. Quantitation of resveratrol
was possible using the standard addition procedure. Red wine showed the highest amount of resveratrol (4 mg L−1), while rose and white wine contained concentrations which were about ten fold lower. 相似文献
13.
Irina Karadjova Julijana Cvetković Trajče Stafilov Sonja Arpadjan 《Central European Journal of Chemistry》2007,5(3):739-747
The parameters of analytical procedures developed for direct ETAAS determination of Pb in wine are discussed. Atomic absorption
spectrometers based on transversal and longitudinal Zeeman effect, wall and integrated platform atomization with two main
approaches: (i) measurements in the presence of modifier and (ii) measurements without using any modifier are compared. The
optimal temperature programs are defined according to the pre-treatment and atomization curves constructed in the presence
of different types of wines. For all investigated instrumental systems, 1:1 dilution of wine sample with 0.2 mol L−1 HNO3 is recommended. Matrix interferences observed, call for standard addition calibration method for Pb quantification in wines.
The detection limit (3σ) achieved for wine diluted in the ratio of 1:1 varied from 0.8 to 1.9 μg L−1 depending on the instrument used. The relative standard deviation for the concentration range of 10 to 80 μg L−1 Pb in wine is typically between 4–8%. The accuracy of the analytical procedures recommended was confirmed by comparing the
results obtained with those found for wine samples previously digested with HNO3-H2O2 mixture, by added/found method and by parallel analysis using different instruments. A total of 66 wine samples from different
regions of Macedonia were analyzed.
相似文献
14.
Karadjova IB Lampugnani L D'Ulivo A Onor M Tsalev DL 《Analytical and bioanalytical chemistry》2007,388(4):801-807
A rapid, accurate, and precise method is described for the determination of Pb in wine using continuous-flow hydride generation
atomic fluorescence spectrometry (CF-HGAFS). Sample pretreatment consists of ten-fold dilution of wine followed by direct
plumbane generation in the presence of 0.1 mol L−1 HCl and 1% m/v K3[Fe(CN)6] with 1% m/v NaBH4 as reducing agent. An aqueous standard calibration curve is recommended for Pb quantification in wine sample. The method
provides a limit of detection and a limit of quantification of 0.3 μg L−1 and 1 μg L−1, respectively. The relative standard deviation varies between 2–6% (within-run) and 4–11% (between-run) at 3–30 μg L−1 Pb levels in wine. Good agreement has been demonstrated between results obtained by CF-HGAFS and direct electrothermal atomic
absorption spectrometry in analyses of red and white wines within the concentration range of 9.2–25.8 μg L−1 Pb. 相似文献
15.
This study was conducted to investigate the effect of a photocatalysis/oxidant system for the treatment of humic acid and
hazardous heavy metals in aqueous solutions. Hydrogen peroxide, ozone, and potassium peroxodisulfate were tested as oxidants.
The effect of oxidant concentration was conducted with a pH of 7, a UV intensity of 64 W, and a TiO2 dosage of 0.3 g L−1. The oxidant addition in the UV/TiO2 system enhanced the degradation efficiency of humic acid and hazardous heavy metals compared to no addition of an oxidant.
The addition of oxidants over the amounts of H2O2 50 mg L−1, O3 20 g m−3, and K2S2O8 50 mg L−1 inhibits the system efficiency. The negative effect of higher oxidant concentrations likely results from OH radical quenching
caused by the excess oxidant. Therefore, the optimal dosages of oxidants such as a hydrogen peroxide, ozone, and potassium
peroxodisulfate were found to be 50 mg L−1, 20 g m−3, and 50 mg L−1, respectively. The degradation efficiency of UV/TiO2/oxidant systems for the removal of humic acid and hazardous heavy metals was much greater in the UV/TiO2/H2O2 system using H2O2 as an oxidant. 相似文献
16.
Pyreu Dmitrii Kozlovskii Eugenii Gruzdev Matvei Kumeev Roman 《Journal of Thermal Analysis and Calorimetry》2011,103(3):1073-1077
The mixed-ligand complex formation in the systems Cd2 + Edta4–(CH2)
n
(NH2)2, n = 2 (En), 6 (L) has been NMR and calorimetrically studied in aqueous solution at 298.15 K and the ionic strength of I = 0.5 (KNO3). The thermodynamic parameters of formation of the CdEdtaL2−, CdEdtaHL−, (CdEdta)2L4−, and (CdEdta)2En4− complexes have been determined. The most probable coordination mode for the complexone and the diamine ligand in the mixed-ligand
complexes was discussed. 相似文献
17.
Chromium(III)-lutidinato complexes of general formula [Cr(lutH)
n
(H2O)6−2n
]3−n (where lutH− is N,O-bonded lutidinic acid anion) were obtained and characterized in solution. Acid-catalysed aquation of [Cr(lutH)3]0 leads to only one ligand dissociation, whereas base hydrolysis produces chromates(III) as a result of subsequent ligand liberation
steps. The kinetics of the first ligand dissociation were studied spectrophotometrically, within the 0.1–1.0 M HClO4 and 0.4–1.0 M NaOH range. In acidic media, two reaction stages, the chelate-ring opening and the ligand dissociation, were
characterized. The dependencies of pseudo-first-order rate constants on [H+] are as follows: k
obs1 = k
1 + k
−1/K
1[H+] and k
obs2 = k
2
K
2[H+]/(1 + K
2[H+]), where k
1 and k
2 are the rate constants for the chelate-ring opening and the ligand dissociation, respectively, k
−1 is the rate constant for the chelate-ring closure, and K
1 and K
2 are the protonation constants of the pyridine nitrogen atom and coordinated 2-carboxylate group in the one-end bonded intermediate,
respectively. In alkaline media, the rate constant for the first ligand dissociation depends on [OH−]: k
obs1 = k
OH(1) + k
O[OH−], where k
OH(1) and k
O are rate constants of the first ligand liberation from the hydroxo- and oxo-forms of the intermediate, respectively, and
K
2 is an equilibrium constant between these two protolytic forms. Kinetic parameters were determined and a mechanism for the
first ligand dissociation is proposed. The kinetics of the ligand liberation from [Cr(lut)(OH)4]3− were also studied and the values of the pseudo-first-order rate constants are [OH−] independent. 相似文献
18.
Grace O. Ogunlusi Jide Ige Olayinka A. Oyetunji Jonathan F. Ojo 《Transition Metal Chemistry》2009,34(5):483-491
The kinetics of the reactions between azido-pentacyanocobaltate(III), Co(CN)5N3
3−, and iron(II) polypyridyl complexes, Fe(LL)3
2+ (LL = bipy, phen), have been studied in both neutral and acidic aqueous solutions at I = 0.1 mol dm−3 NaCl. The reactions were carried out under pseudo-first-order conditions in which the concentration of Fe(LL)3
2+ was kept constant, and the second-order rate constants obtained for the reactions at 35 °C were within the range of 0.156–0.219
dm3 mol−1 s−1 for LL = bipy and 0.090–0.118 dm3 mol−1 s−1 for LL = phen. Activation parameters were measured for these systems. The dependence of reaction rates on acid was studied
in the range [H+] = 0.001–0.008 mol dm−3. The reaction in acid medium shows interesting kinetics. Two reactive species were identified in acid medium, namely, the
protonated cobalt complex and the azido-bridged binuclear complex. The electron-transfer process is proposed to go by mixed
outer- and inner-sphere mechanisms in acid medium, in which electron transfer through the bridged inner-sphere complex (k
5) is slower than through the outer-sphere path (k
4).
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
19.
Zhicheng Zhang Paul Gibson Sue B. Clark Guoxin Tian Pier Luigi Zanonato Linfeng Rao 《Journal of solution chemistry》2007,36(10):1187-1200
In acidic aqueous solutions, the protonation of gluconate is coupled with the lactonization of gluconic acid. With a decrease
of pC
H, two lactones (δ- and γ-) are sequentially formed. The δ-lactone forms more readily than the γ-lactone. In 0.1 mol⋅L−1 gluconate solutions, if pC
H>2.5 then only the δ-lactone is generated. When the pC
H is decreased below 2.0, formation of the γ-lactone is observed although the δ-lactone still predominates. In solutions with I=0.1 mol⋅L−1 NaClO4 and room temperature, the deprotonation constant of the carboxylic group was determined to be log 10
K
a=3.30±0.02 using the NMR technique, and the δ-lactonization constant obtained by batch potentiometric titrations was log 10
K
L=−(0.54±0.04). Using ESI-MS, the rate constants for the δ-lactonization and the reverse hydrolysis reaction at pC
H≈5.0 were estimated to be k
1=3.2×10−5 s−1 and k
−1=1.1×10−4 s−1, respectively. 相似文献
20.
Hasan Marai Ewa Kita Joanna Wojciechowska Paula Wróbel 《Transition Metal Chemistry》2012,37(2):215-223
The following chromium(III) complexes with serine (Ser) and aspartic acid (Asp) were obtained and characterized in solution:
[Cr(ox)2(Aa)]2− (where Aa = Ser or Asp), [Cr(AspH−1)2]− and [Cr(ox)(Ser)2]−. In acidic solutions, [Cr(ox)2(Aa)]2− undergoes acid-catalysed aquation to cis-[Cr(ox)2(H2O)2]− and the appropriate amino acid. [Cr(ox)(Ser)2]− undergoes consecutive acid-catalysed Ser liberation to give [Cr(ox)(H2O)4]+, and the [Cr(Asp)2]− ion is converted into [Cr(Asp)(H2O)4]2+. Kinetics of these reactions were studied under isolation conditions. The determined rate expressions for all the reactions
are of the form: k
obs = a + b[H+]. Reaction mechanisms are proposed, and the meaning of the determined parameters has been established. Evidence for the formation
of an intermediate with O-monodentate amino acid is given. The effect of the R-substituent at the α-carbon atom of the amino
acid on the complex reactivity is discussed. 相似文献