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1.
Francesco Crea Concetta De Stefano Demetrio Milea Silvio Sammartano 《Journal of solution chemistry》2009,38(1):115-134
Results of an investigation on phytate interactions with zinc(II) cation in NaNO3aq at different ionic strengths (0.1≤I/mol⋅L−1≤1.0) are reported. Stability constants of various Zn
i
H
j
Phy(12−2i−j)− species were determined by potentiometry (ISE-H+ glass electrode) and the corresponding formation enthalpies by direct calorimetric titrations. Data obtained were used to
provide an exhaustive speciation scheme of zinc(II) in the presence of phytate, as well as a comprehensive representation
of the binding ability of phytate toward zinc(II) in different conditions. Different pL50 values [an empirical parameter already proposed, expressed as the −log 10
C
Phy, where C
Phy is the total phytate concentration necessary to bind 50% zinc(II)] were calculated in several conditions, and equations were
formulated to model its dependence on different variables, such as ionic strength, temperature and pH. Other empirical predictive
relationships are also proposed.
Previous contributions to this series reviewed in ref. [1]. 相似文献
2.
De Stefano C Milea D Porcino N Sammartano S 《Analytical and bioanalytical chemistry》2006,386(2):346-356
Interactions between myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate) (phytic acid) and cadmium(II) were studied by using potentiometry (at
25 °C with the ISE-H+ glass electrode) in different metal to ligand (Phy) ratios (1:1≤Cd2+:Phy≤4:1) in NaClaq at different ionic strengths (0.1≤I/mol L−1≤1). Nine CdiHjPhy(12−2i−j)− species are formed with i=1 and 2 and 4≤j≤7; and trinuclear Cd3H4Phy2−. Dependence of complex formation constants on ionic strength was modeled by using Specific ion Interaction Theory (SIT) equations.
Phytate and cadmium speciation are also dependent on the metal to ligand ratio. Stability of CdiHjPhy(12−2i−j)− species was modeled as a function of both the ligand protonation step (j) and the number of metal cations bound to phytate
(i), and relationships found were used for the prediction of species other than those experimentally determined (mainly di-
and tri-protonated complexes), allowing the possibility of modeling Phy and Cd(II) behavior in natural waters and biological
fluids. A critical evaluation of phytate sequestering ability toward cadmium(II) has been made under several experimental
conditions, and the determination of an empirical parameter has been proposed for an objective “quantification” of this ability.
A thorough analysis of literature data on phytate–cadmium(II) complexes has been performed.
Previous contributions to this series: [1–8] 相似文献
3.
Francesco Crea Concetta De Stefano Demetrio Milea Silvio Sammartano 《Monatshefte für Chemie / Chemical Monthly》2010,39(2):511-520
Abstract
The results of an investigation on the interactions between phytate ion (myo-inositol hexaphosphate, Phy) and some lanthanoid cations (La3+, Nd3+, Sm3+, Dy3+, and Yb3+) are reported. The stability constants of various LnH j Phy species (Ln = generic lanthanoid) were determined by potentiometry (ISE-H+ glass electrode) in NaClaq at I = 0.15 mol dm−3 and t = 25 °C, and the corresponding formation enthalpies by calorimetric titration. The thermodynamic data obtained were used to provide a speciation scheme for the lanthanoid(III)–phytate systems at different temperatures. The sequestering ability of this ligand toward Ln3+ was also evaluated by calculation of pL50 values (the total concentration of ligand necessary to bind 50% of a cation present in trace amounts) under different conditions, and equations were formulated to model their dependence on temperature and pH. 相似文献4.
Biosorption of copper (II) and cadmium (II) by live Phanerochaete chrysosporium immobilized by growing onto polyurethane foam material in individual packed bed columns over two successive cycles of sorption–desorption
were investigated in this study. Initial pH and concentrations of the metals in their respective solutions were set optimum
to each of those: 4.6 and 35 mg·l−1 in case of copper and 5.3 and 11 mg·l−1 for cadmium. The breakthrough curves obtained for the two metals during sorption in both the cycles exhibited a constant
pattern at various bed depths in the columns. The maximum yield of the columns in removing these metals were found to be,
respectively, 57% and 43% for copper and cadmium indicating that copper biosorption by the immobilized fungus in its column
was better than for cadmium. Recovery values of the sorbed copper and cadmium metals from the respective loaded columns by
using 0.1 N HCl as eluant was observed to be quite high at more than 65% and 75%, respectively, at the end of desorption in
both the cycles. Breakthrough models of bed-depth service time, Adams–Bohart, Wolborska, and Clark were fitted to the experimental
data on sorption of copper and cadmium in the columns, and only the Clark model could fit the sorption performance of the
columns well over the entire range of ratios of concentrations of effluent to influent, i.e., C/C
0 for both copper and cadmium biosorption. The kinetic coefficients of mass transfer and other suitable parameters in the system
were determined by applying the experimental data at C/C
0 ratios lower than 0.5 to the other three models. 相似文献
5.
Xin Jin Zhen Wang San-Ping Chen Zhu-Jun Wang Sheng-Li Gao 《Journal of Thermal Analysis and Calorimetry》2012,107(2):813-822
Two crystal samples, sodium 5-methylisophthalic acid monohydrate (C9H6O4Na2·H2O, s) and sodium isophthalic acid hemihydrate (C8H4O4Na2·1/2H2O, s), were prepared from water solution. Low-temperature heat capacities of the solid samples for sodium 5-methylisophthalic
acid monohydrate (C9H6O4Na2·H2O, s) and sodium isophthalic acid hemihydrate (C8H4O4Na2·1/2H2O, s) were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 379 K. The experimental
values of the molar heat capacities in the measured temperature region were fitted to a polynomial equation on molar heat
capacities (C
p,m) with the reduced temperatures (X), [X = f(T)], by a least-squares method. Thermodynamic functions of the compounds (C9H6O4Na2·H2O, s) and (C8H4O4Na2·1/2H2O, s) were calculated based on the fitted polynomial equation. The constant-volume energies of combustion of the compounds
at T = 298.15 K were measured by a precise rotating-bomb combustion calorimeter to be Δc
U(C9H6O4Na2·H2O, s) = −15428.49 ± 4.86 J g−1 and Δc
U(C8H4O4Na2·1/2H2O, s) = −13484.25 ± 5.56 J g−1. The standard molar enthalpies of formation of the compounds were calculated to be Δ
f
H
m
θ
(C9H6O4Na2·H2O, s) = −1458.740 ± 1.668 kJ mol−1 and Δ
f
H
m
θ
(C8H4O4Na2·1/2H2O, s) = −2078.392 ± 1.605 kJ mol−1 in accordance with Hess’ law. The standard molar enthalpies of solution of the compounds, Δ
sol
H
m
θ
(C9H6O4Na2·H2O, s) and Δ
sol
H
m
θ
(C8H4O4Na2·1/2H2O, s), have been determined as being −11.917 ± 0.055 and −29.078 ± 0.069 kJ mol−1 by an RD496-2000 type microcalorimeter. In addition, the standard molar enthalpies of hydrated anion of the compounds were
determined as being Δ
f
H
m
θ
(C9H6O4
2−, aq) = −704.227 ± 1.674 kJ mol−1 and Δ
f
H
m
θ
(C8H4O4Na2
2−, aq) = −1483.955 ± 1.612 kJ mol−1, from the standard molar enthalpies of solution and other auxiliary thermodynamic data through a thermochemical cycle. 相似文献
6.
Z. H. Zhang T. Cui J. L. Zhang H. Xiong G. P. Li L. X. Sun F. Xu Z. Cao F. Li J. J. Zhao 《Journal of Thermal Analysis and Calorimetry》2010,101(3):1143-1148
The molar heat capacities of the room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluoroborate (BMIPF6) were measured by an adiabatic calorimeter in temperature range from 80 to 390 K. The dependence of the molar heat capacity
on temperature is given as a function of the reduced temperature (X) by polynomial equations, C
P,m (J K−1 mol−1) = 204.75 + 81.421X − 23.828 X
2 + 12.044X
3 + 2.5442X
4 [X = (T − 132.5)/52.5] for the solid phase (80–185 K), C
P,m (J K−1 mol−1) = 368.99 + 2.4199X + 1.0027X
2 + 0.43395X
3 [X = (T − 230)/35] for the glass state (195 − 265 K), and C
P,m (J K−1 mol−1) = 415.01 + 21.992X − 0.24656X
2 + 0.57770X
3 [X = (T − 337.5)/52.5] for the liquid phase (285–390 K), respectively. According to the polynomial equations and thermodynamic relationship,
the values of thermodynamic function of the BMIPF6 relative to 298.15 K were calculated in temperature range from 80 to 390 K with an interval of 5 K. The glass transition
of BMIPF6 was measured to be 190.41 K, the enthalpy and entropy of the glass transition were determined to be ΔH
g = 2.853 kJ mol−1 and ΔS
g = 14.98 J K−1 mol−1, respectively. The results showed that the milting point of the BMIPF6 is 281.83 K, the enthalpy and entropy of phase transition were calculated to be ΔH
m = 20.67 kJ mol−1 and ΔS
m = 73.34 J K−1 mol−1. 相似文献
7.
Lebedev B. V. Bykova T. A. Lobach A. S. 《Journal of Thermal Analysis and Calorimetry》2000,62(1):257-265
The temperature dependence of the molar heat capacity (C0
p) of hydrofullerene C60H36 between 5 and 340 K was determined by adiabatic vacuum calorimetry with an error of about 0.2%. The experimental data were
used for the calculation of the thermodynamic functions of the compound in the range 0 to340 K. It was found that at T=298.15 K and p=101.325 kPa C0
p (298.15)=690.0 J K−1 mol−1,Ho(298.15)−Ho(0)= 84.94 kJ mol−1,So(298.15)=506.8 J K−1 mol−1, Go(298.15)−Ho(0)= −66.17 kJ mol−1. The standard entropy of formation of hydrofullerene C60H36 and the entropy of reaction of its formation by hydrogenation of fullerene C60 with hydrogen were estimated and at T=298.15 K they were ΔfSo= −2188.4 J K−1 mol−1 and ΔrSo= −2270.5 J K−1mol−1, respectively.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
I. E. Paukov Yulia A. Kovalevskaya Irina A. Kiseleva Tatiana N. Shuriga 《Journal of Thermal Analysis and Calorimetry》2010,99(2):709-712
Low-temperature heat capacity of natural zinnwaldite was measured at temperatures from 6 to 303 K in a vacuum adiabatic calorimeter.
An anomalous behavior of heat capacity function C
p(T) has been revealed at very low temperatures, where this function does not tend to zero. Thermodynamic functions of zinnwaldite
have been calculated from the experimental data. At 298.15 K, heat capacity C
p(T) = 339.8 J K−1mol−1, calorimetric entropy S
o(Т) – S
o(6.08) = 329.1 J K−1 mol−1, and enthalpy Н
o(Т) − Н
o(6.08) = 54,000 J mol−1. Heat capacity and thermodynamic functions at 298.15 K for zinnwaldite having theoretical composition were estimated using
additive method of calculation. 相似文献
9.
De Stefano C Milea D Pettignano A Sammartano S 《Analytical and bioanalytical chemistry》2003,376(7):1030-1040
The acid–base properties of phytic acid [myo-inositol 1,2,3,4,5,6-hexakis(dihydrogen phosphate)] (H12Phy; Phy12–=phytate anion) were studied in aqueous solution by potentiometric measurements ([H+]-glass electrode) in lithium and potassium chloride aqueous media at different ionic strengths (0<I mol L–13) and at t=25 °C. The protonation of phytate proved strongly dependent on both ionic medium and ionic strength. The protonation constants obtained in alkali metal chlorides are considerably lower than the corresponding ones obtained in a previous paper in tetraethylammonium iodide (Et4NI; e.g., at I=0.5 mol L–1, logK3H=11.7, 8.0, 9.1, and 9.1 in Et4NI, LiCl, NaCl and KCl, respectively; the protonation constants in Et4NI and NaCl were already reported), owing to the strong interactions occurring between the phytate and alkaline cations present in the background salt. We explained this in terms of complex formation between phytate and alkali metal ions. Experimental evidence allows us to consider the formation of 13 mixed proton–metal–ligand complexes, MjHiPhy(12–i–j)–, (M+=Li+, Na+, K+), with j7 and i6, in the range 2.5pH10 (some measurements, at low ionic strength, were extended to pH=11). In particular, all the species formed are negatively charged: i+j–12=–5, –6. Very high formation percentages of M+–phytate species are observed in all the pH ranges investigated. The stability of alkali metal complexes follows the trend Li+Na+K+. Some measurements were also performed at constant ionic strength (I=0.5 mol L–1), using different mixtures of Et4NI and alkali metal chlorides, in order to confirm the formation of hypothesized and calculated metal–proton–ligand complex species and to obtain conditional protonation constants in these multi-component ionic media.Presented at SIMEC–02, Santiago de Compostela, 2–6 June 2002 相似文献
10.
Sulata K. Sahu Manjulata Sahu Raman S. Srinivasa Thiagarajan Gnanasekaran 《Monatshefte für Chemie / Chemical Monthly》2012,97(3):1207-1214
Abstract
Heat capacities of PbCrO4(s), Pb2CrO5(s), and Pb5CrO8(s) were measured by differential scanning calorimetry. The measured heat capacities as a function of temperature are expressed as C p <PbCrO4> J K−1 mol−1 = 150.37 + 27.74 × 10−3 T − 2.80 × 106 T −2 (T = 300–750 K), C p <Pb2CrO5> J K−1 mol−1 = 194.55 + 76.09 × 10−3 T − 4.64 × 106 T −2 (T = 300–700 K), and C p <Pb5CrO8> J K−1 mol−1 = 323.35 + 184.80 × 10−3 T − 5.48 × 106 T −2 (T = 300–600 K). From the measured heat capacity data, thermodynamic functions such as enthalpy increments, entropies, and Gibbs energy functions were derived. 相似文献11.
Joanna Kobyłecka Bogdan Ptaszyński Anna Zwolinńska 《Monatshefte für Chemie / Chemical Monthly》2000,131(1):1-11
Summary. Sparingly water soluble complexes of lead(II), cadmium(II), and zinc(II) with N-phosphonomethylglycine (glyphosate, NPMG) of the general formulae C3H6O5NPPb, C3H6O5NPCdċ2H2O, and C3H6O5NPZn were synthesized. The complexes were also precipited from a dilute Roundup solution, and their solubility in water was
determined. Thermal, diffractometric, and IR spectrophotometric analyses were carried out. It was found that the metal is
bonded to glyphosate through the oxygen atoms of the carboxylic and phosphonate groups; metal-nitrogen binding is absent in
the above compounds. Studying the complexing behaviour in solution by UV spectrophotometry pointed out that a complex of the
composition Pb(II) : NPMG=1:1 with an absorption band at 232 nm is formed. Its stability constant as determined by Job’s method is logK=5.9±0.1. Using potentiometric techniques, the dissociation constant of N-phosphonomethylglycine and the stability constants
of its complexes with cadmium (II) and zinc (II) were determined.
Received June 30, 1999/Accepted July 21, 1999. 相似文献
12.
Ming-Lai Fu Norma L. Rangel Richard D. Adams Jorge M. Seminario 《Journal of Cluster Science》2010,21(4):867-878
Abstract
Thiacalix[4]arenes are a unique family of polydentate ligands that offer a combination of four soft sulfur atoms together with four hard phenol oxygen atoms for binding to metal ions. In this study, the tetranuclear cadmium (II) complex Cd4II(tca)2·1.5CH2Cl2 (tca4− = tetra-anionic p-tert-butylthiacalix[4]arene) (1) was synthesized by reaction of a deprotonated p-tert-butylthiacalix[4]arene and various CdII salts. The structure of 1 was established by single crystal X-ray diffraction analysis. The neutral complex 1 contains a square arrangement of four cadmium (II) ions sandwiched between two tca4− ligands that have a ‘cone’ conformation similar to that of the free ligand. The absorption and emission properties of the free ligand H4tca and complex 1 have been recorded and explained by DFT calculations of the molecular orbitals and electronic transitions between them. 相似文献13.
Nahid Shahabadi Soheila Kashanian Marzieh Khosravi Maryam Mahdavi 《Transition Metal Chemistry》2010,35(6):699-705
The water-soluble Ni(II) complex, [Ni(bipy)2(phen-dione)](OAc)2·2H2O (bipy = 2,2′-bipyridine and phen-dione = 1,10-phenanthroline-5,6-dione) has been synthesized and characterized by physico-chemical
and spectroscopic methods. The binding interactions of this complex with calf thymus DNA (CT-DNA) were investigated using
fluorimetry, spectrophotometry, circular dichroism and viscosimetry. In fluorimetric studies, the enthalpy and entropy of
the reaction between the complex and CT-DNA showed that the reaction is exothermic (ΔH = −123.9 kJ mol−1; ΔS = −323.5 J mol−1 K−1). The competitive binding studies showed that the complex could not release methylene blue completely. The complex showed
absorption hyperchromism in its UV–Vis spectrum with DNA. The calculated binding constant, K
b obtained from UV–Vis absorption studies was 2 × 105 M−1. Moreover, the complex induced detectable changes in the CD spectrum of CT-DNA, as well as changes in its viscosity. The
results suggest that this nickel(II) complex interact with CT-DNA via a groove-binding mode. 相似文献
14.
Marcelo H. Gehlen 《Cellulose (London, England)》2009,16(6):1069-1073
Depolymerization of cellulose in homogeneous acidic medium is analyzed on the basis of autocatalytic model of hydrolysis with
a positive feedback of acid production from the degraded biopolymer. The normalized number of scissions per cellulose chain,
S(t)/n° = 1 − C(t)/C0, follows a sigmoid behavior with reaction time t, and the cellulose concentration C(t) decreases exponentially with a linear and cubic time dependence, C(t) = C0exp[−at − bt
3], where a and b are model parameters easier determined from data analysis. 相似文献
15.
H. X. Ma B. Yan Y. H. Ren Y. Hu Y. L. Guan F. Q. Zhao J. R. Song R. Z. Hu 《Journal of Thermal Analysis and Calorimetry》2011,103(2):569-575
3,3-Dinitroazetidinium (DNAZ) salt of perchloric acid (DNAZ·HClO4) was prepared, it was characterized by the elemental analysis, IR, NMR, and a X-ray diffractometer. The thermal behavior
and decomposition reaction kinetics of DNAZ·HClO4 were investigated under a non-isothermal condition by DSC and TG/DTG techniques. The results show that the thermal decomposition
process of DNAZ·HClO4 has two mass loss stages. The kinetic model function in differential form, the value of apparent activation energy (E
a) and pre-exponential factor (A) of the exothermic decomposition reaction of DNAZ·HClO4 are f(α) = (1 − α)−1/2, 156.47 kJ mol−1, and 1015.12 s−1, respectively. The critical temperature of thermal explosion is 188.5 °C. The values of ΔS
≠, ΔH
≠, and ΔG
≠of this reaction are 42.26 J mol−1 K−1, 154.44 kJ mol−1, and 135.42 kJ mol−1, respectively. The specific heat capacity of DNAZ·HClO4 was determined with a continuous C
p mode of microcalorimeter. Using the relationship between C
p and T and the thermal decomposition parameters, the time of the thermal decomposition from initiation to thermal explosion (adiabatic
time-to-explosion) was evaluated as 14.2 s. 相似文献
16.
Peroxydisulfate (PDS) oxidizes N,N′-ethylenebis(isonitrosoacetyleacetoneimine)copper(II) complex, CuIIL, to the corresponding copper(III) complex, [CuIIIL]+. The kinetic runs were performed in the presence of EDTA to scavenge any trace metal impurities. The kinetics of the reaction
at constant pH, ionic strength, and temperature obeys the rate law d[CuIIIL]/dt = 2k
2[CuIIL][S2O8
2−] with k
2 having a value of (8.85 ± 0.32) × 10−2 M−1 s−1 at μ = 0.30 M and T = 25.0 °C. The rate constant k
2 is not affected by variation of pH over the range 3.60–5.20. The second order rate constant is also unaffected by changing
ionic strength. The values of k
obs were determined over the temperature 25.0–40.0 °C range. The enthalpy of activation, ∆H*, and entropy of activation, ∆S*, have been calculated as 34.9 ± 0.5 kJ mol−1 and −173.3 ± 11.4 J K−1 mol−1, respectively. The kinetics of this reaction, as far as we know, is the first evidence that copper(III) is the likely reactive
species in copper catalyzed PDS oxidation reactions. 相似文献
17.
The reaction products of Cu(II) 2-chlorobenzoate and the imidazole (1), and of Cu(II) 2,6-dichlorobenzoate and the imidazole
(2) formulated as CuL’2⋅2imd⋅2H2O and CuL”2⋅2imd⋅2H2O (L’=C7H4ClO2
−, L”=C7H3Cl2O2
−, imd=imidazole), were prepared and characterized by means of spectroscopic measurements and thermochemical properties. The blue
(1) and green (2) complexes were obtained as solids with a 1:2:2 molar ratio of metal to carboxylate ligand to imidazole.
When heated at a heating rate of 10 K min−1 the hydrated complexes, (1) and (2), lose some of the crystallization water molecules and then decompose to gaseous products.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
Igor E. Paukov Yulia A. Kovalevskaya Alexei E. Arzamastcev Natalia A. Pankrushina Elena V. Boldyreva 《Journal of Thermal Analysis and Calorimetry》2012,108(1):243-247
Heat capacity of methacetin (N-(4-methoxyphenyl)-acetamide) has been measured in the temperature range 5.8–300 K. No anomalies in the C
p(T) dependence were observed. Thermodynamic functions were calculated. At 298.15 K, the values of entropy and enthalpy are equal
to 243.1 J K−1 mol−1 and 36360 J mol−1, respectively. The heat capacity of methacetin in the temperature range 6–10 K is well fitted by Debye equation C
p = AT
3. The thermodynamic data obtained for methacetin are compared with those for the monoclinic and orthorhombic polymorphs of
paracetamol. 相似文献
19.
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
20.
Dagmara Jacewicz Dariusz Wyrzykowski Krzysztof ?amoj? Diana Czerwińska Paulina Czaja Lech Chmurzyński 《Structural chemistry》2012,23(2):333-340
The thermal decomposition of trans-K[Cr(C2O4)2(OH2)2]·3H2O and cis-K[Cr(C2O4)2(OH2)2] has been studied using the TG–MS technique. The measurements were carried out in an argon atmosphere over the temperature
range of 293–873 K. The influence of the complex structures and configurational geometry on the stability of the transition
products and the pathways of thermal transformations has been discussed. Furthermore, the kinetics of the isomerization reactions
of the [Cr(C2O4)2(OH2)2]− complex ion catalyzed by five different metal ions: Be2+, Mg2+, Ca2+, Sr2+ and Ba2+ have been studied. The isomerization reactions were studied in aqueous solution at five various temperatures (283–303 K),
at constant concentration of metal ions (C = 0.1 M) and the constant ionic strength of solution (Na+, NO3
−) I = 2.4 M. The rates of the isomerization reaction were determined spectrophotometrically by monitoring of absorbance changes
at 410 nm. 相似文献