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1.
V. A. Davankov 《Chromatographia》1997,44(5-6):279-282
Summary Through a straightforward mathematical derivation it is shown that the compressibility correction factor equals the ratio
of gas pressure at the column outlet to the average pressure in the column,
. Therefore, by multiplying by this factor, the experimentally measured retention volumes can be recalculated to the average
pressure in the column. Corrected retention volumes thus represent the volume of the mobile phase under real conditions of
chromatography in the column.
Appropriate definitions for corrected retention volumes and factorj are formulated. 相似文献
2.
This work is a theoretical and experimental investigation of the binary retention time (t
step) when the disturbance is made to a chromatographic system by adding a small flow of one of the pure components. The established
theory is for addition of a pulse: in this case, the retention time (t
pulse) depends on the two binary isotherm gradients, and should be independent of the choice of pulse gas. From the column material
balance, the value of t
step also depends on the column pressure drop and perturbation gas—the value of t
step should always be greater for the more-adsorbed component. The theory has been validated from results on the nitrogen–argon–5A
zeolite system at 25, 54 and 81 °C. For a 50% mixture at 25 °C with a column pressure drop of 0.1 bar, the values of t
step are 257 and 254 seconds for the nitrogen and argon perturbations. The values of t
step are different because addition of the perturbation flow causes a very small increase in average column pressure (about 0.5 mbar), which causes the binary isotherm gradients to be measured in (slightly) different
directions along the isotherm surface. The intention is to determine the value of t
step for the case of a zero change in the average column pressure: experimentally, this would require a column with a zero pressure drop. The material balance
shows that t
step for a column with a zero pressure drop is obtained from a simple weighted function of the values of t
step for the two pure-component perturbations. Accurate determination is essential because the “zero pressure drop” values are
used to determine binary adsorption isotherms which are, of course, at a fixed pressure. 相似文献
3.
The dependence of retention factork
i
, relative retention time α
i
, and retention indexI
i
of organic compounds on the average pressure (p
av) of the carrier gas (helium) was studied experimentally using a long narrow-bore capillary column with the SE-30 nonpolar
phase at 120°C. The linear dependencesk
i
=f(p
av), α
i
=φ(p
av), andI
i
=φ(p
av) obtained previously were found to be in good agreement with experimental data. Invariant relative retention valuesk
0,i
, α
0,i
, andI
0,i
, which do not depend on the helium pressure, were determined for some organic compounds of various chemical classes. The
dependence of the relative retention on the carrier gas pressure needs to be taken into account in precision measurements
and in experiments with narrow-bore capillary columns.
Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 314–316, February, 1998. 相似文献
4.
Berezkin V. G. Korolev A. A. Malyukova I. V. Mardanov R. G. Khotimskii V. S. Yampol"skii Yu. P. 《Russian Chemical Bulletin》2001,50(7):1228-1232
The retention factor and height equivalent of a theoretical plate for gaseous hydrocarbons C1—C4 were studied on capillary columns with the layer of the new polymeric adsorbent polytrimethylsilylpropyne (PTMSP) as functions of the nature and pressure of the carrier gas. The retention factor k increases in the series helium < nitrogen < carbon dioxide. The k values depend linearly on the average pressure of the carrier gas in a capillary column with the adsorption PTMSP layer. 相似文献
5.
Chun-lan Yuan 《Kinetics and Catalysis》2011,52(5):697-701
A closed oscillation system comprised of alanine, KBrO3, H2SO4 and acetone catalyzed by tetraazamacrocyclic nickel(II) complex is introduced, and quantitatively characterized with kinetic
parameters, namely the rate constant (k
in, k
p), the apparent activation energy (E
in, E
p) and pre-exponential constant (A
in, A
p) and thermodynamic functions (ΔH
in, ΔG
in, ΔS
in and ΔH
p, ΔG
p, ΔS
p), where indexes “in” and “p” mean “induction period” and “oscillation period,” respectively. The results indicate that tetraazamacrocyclic
nickel(II) complex can catalyze alanine oscillating reaction and the reaction corresponds exactly to the feature of irreversible
thermodynamics as the entropy of system is negative. 相似文献
6.
Densities of glycerol (1) + tert-butanol (2) mixtures were measured over the temperature range 293.15 to 348.15 K at atmospheric pressure, over the entire
composition range, with a vibrating tube densimeter. Excess molar volumes, apparent and partial molar volumes of glycerol
and tert-butanol, thermal isobaric expansivities of the mixture and partial molar expansivities of the components were calculated.
The excess molar volumes of the mixtures are negative at all temperatures, and deviations from ideality increase with increasing
temperature. Excess molar volumes were fitted to the Redlich–Kister equation. Partial molar volumes of glycerol decrease with
increasing tert-butanol concentration. The temperature dependence of the partial molar volumes of glycerol is characterized by an inversion
at x
2≈0.7. “Negative expansion” of the limiting partial volumes of glycerol was observed. 相似文献
7.
Yanbao Zhao Li Yao Yuanchun Qi Lei Sun Zhishen Wu 《Journal of Sol-Gel Science and Technology》2009,50(1):3-7
Micrometer-sized flowerlike FeS/poly(vinyl pyrrolidone)(PVP) architectures were synthesized by solvothermal process with the
aid of thiourea, in which PVP may serve as soft templates. The FeS/PVP flowers have uniform morphologies with an average diameter
of 5 μm, made of several nanopetals. The formation of FeS/PVP flowers is a new kinetic control process. In this process, thiourea
molecules would be decomposed to produce “gas bubble”, and the “gas bubble” could make PVP chain segment rearrange along exterior
force, resulting in the morphology evolution. The higher “gas bubble” pressure would produce 3D flowers, and the lower pressure
would give a hollow structure. The evolution process from particles to 3D flowers is observed for the first time. In addition,
the hollow FeS/PVP and Cu2S/PVP spheres are also obtained by this technique. 相似文献
8.
Peter Korytr Eva Matisov Henrieta Lefflerov Jaroslav Slobodník 《Journal of separation science》2000,23(2):149-155
In this work a fast gas chromatography set‐up with on‐column injection was optimized and evaluated with a model mixture of C8–C28 n‐alkanes. Usual injection volumes when using narrow‐bore (e. g., 0.1 mm i.d.) analytical columns are ca. 0.1 μL. The presented configuration allows introduction of 10–30‐fold larger sample volumes without any distortion of peak shapes. In the set‐up a normal‐bore retention gap (1 m×0.32 mm i. d.) was coupled to a narrow‐bore (4.8 m×0.1 mm i. d.×0.4 μm film thickness) analytical column using a low dead volume column connector. The effects of the experimental conditions such as inlet pressure, sample volume, initial injection temperature, and oven temperature on a peak focusing are discussed. H‐u curves for helium and hydrogen are used to compare their suitability for high speed gas chromatography and to show the dependence of separation efficiency on the carrier gas velocity at high inlet pressures. In the fast gas chromatography system a baseline separation of C10–C28 n‐alkanes was achieved in less than 3 minutes. 相似文献
9.
Zusammenfassung Die Metathese-Reaktion von 1,4-Polybutadien mit 4-Octen wurde unter Anwendung eines WCl6/C2H5AlCl2
2-Katalysators kinetisch untersucht. Das Gemisch niedermolekularer Produkte wurde gaschromatographisch analysiert. Die Ergebnisse
wurden mit einer vonW. Kuhn angegebenen Gleichung berechnet. Hieraus und nach der Methode der „Gleichwertszeit” wurde die experimentelle Aktivierungsenergie
bestimmt. Der Abbau ist eine statistische Spaltung.
Mit 3 Abbildungen und 1 Tabelle 相似文献
Summary The metathesis reaction of 1,4-polybutadiene with 4-octene was investigated kinetically, using a WCl6/C2H5AlCl2 catalyst. The mixture of low molecular products was analysed by gas chromatography. Results were calculated with an equation developed byW. Kuhn. From this and with the method of “equivalent time” the experimental activation energy was calculated. The degradation is a random scission.
Mit 3 Abbildungen und 1 Tabelle 相似文献
10.
Glenn A. Harris Dana M. Hostetler Christina Y. Hampton Facundo M. Fernández 《Journal of the American Society for Mass Spectrometry》2010,21(5):855-863
The internal energy (Eint) distributions of a series of p-substituted benzylpyridinium ions generated by both direct analysis in real time (DART) and electrospray ionization (ESI)
were compared using the “survival yield” method. DART mean Eint values at gas flow rates of 2, 4, and 6 L min−1, and at set temperatures of 175, 250, and 325 °C were in the 1.92–2.21 eV range. ESI mean Eint at identical temperatures in aqueous and 50% methanol solutions ranged between 1.71 and 1.96 eV, and 1.53 and 1.63 eV, respectively.
Although the results indicated that ESI is a “softer” ionization technique than DART, there was overlap between the two techniques
for the particular time-of-flight mass spectrometer used. As a whole, there was an increase in Eint with increasing reactive and drying gas temperatures for DART and ESI, respectively, indicating thermal ion activation. Three
dimensional computational fluid dynamic simulations in combination with direct temperature measurements within the DART ionization
region revealed complex inversely coupled fluid-thermal phenomena affecting ion Eint values during atmospheric transport. Primarily, that DART gas temperature in the ionization region was appreciably less than
the set gas temperature of DART due to the set gas flow rates. There was no evidence of Eint deposition pathways from metastable-stimulated desorption, but fragmentation induced by high-energy helium metastables was
observed at the highest gas flow rates and temperatures. 相似文献
11.
V. A. Davankov L. A. Onuchak S. Yu. Kudryashov Yu. I. Arutyunov 《Chromatographia》1999,49(7-8):449-453
Summary A systematic derivation of corresponding equations shows that averaging the pressure and the flow rate of the mobile phase
in a gas chromatographic column over the column length and over the time that an unretained component resides in the column,
requires the use of three different compressibility correction factors,j
2
1
,j
3
2
, andj
4
3
. When multiplied by the adjusted retention volume,V
R-VM, the Martin and James mobile phase compressibility correction factorj
3
2
, only, produces the value of specific retention volume,V
g
T
, which is connected unambiguously with the thermodynamic phase distribution coefficient,K, of the sorbate. 相似文献
12.
A. A. Korolev V. E. Shiryaeva T. P. Popova A. V. Kozin A. A. Kurganov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(4):670-676
The influence of carrier gas pressure on the retention factor k′ of light hydrocarbons C1–C4 in a monolithic capillary column based on divinylbenzene was studied. It was shown that, for monolithic columns and nonideal
carrier gases, the pressure dependence of lnk′ was nonlinear over a wide pressure range and could be described by the classic Everett equation. It was concluded that the
competitive adsorption model failed to describe the experimental data correctly, especially for strongly retained sorbates
and/or heavy carrier gases.
Original Russian Text ? A.A. Korolev, V.E. Shiryaeva, T.P. Popova, A.V. Kozin, A.A. Kurganov, 2009, published in Zhurnal Fizicheskoi
Khimii, 2009, Vol. 83, No. 4, pp. 776–783. 相似文献
13.
E. V. Blynskaya K. V. Alekseev S. E. Kondakov R. N. Alyautdin V. Yu. Balaban’yan 《Moscow University Chemistry Bulletin》2011,66(2):129-132
Pharmacokinetics of nanoparticles loaded with the antituberculosis drug gatifloxacine, as a new delivery system, was studied.
In vivo experiments performed in laboratory animals showed that the dosage form of gatifloxacine incorporated into nanoparticles
of poly(DL-lactic-co-glycolic acid) has a different pharmacological pattern as compared with the dosage form manufactured in industry. An increase
in half-life (T
1/2) and in mean residence time (MRT) was observed for gatifloxacine nanoparticles in blood plasma. The area under the “concentration
versus time” pharmacological curve (AUC(0→36) was shown to increase mostly owing to the terminal part of the curve. 相似文献
14.
Liquid crystalline(LC) polymers with a shish-kebab-type moiety on their cross-conjugated(p-phenylene)s-poly(p-phenylenevinylene) s main chains were synthesized through Gilch polymerization in order to develop a kind of polymers available for linearly polarized white-light-emitting from single chain.In this system,the 2,5-bis(4’-alkoxyphenyl)benzene as the "kebabs" connects with poly(p-phenylenevinylene)(PPV) main chain backbone using its molecular gravity center and the PPV as the "shish" or "skewer"(the "shish-kebab").The polymers possess desirable properties such as excellent solubility and liquid crystalline properties.To drop the "kebabs" of the 2,5-bis(4’-alkoxyphenyl)benzene into the orientation microgroove of aligned polyimide film,not only the "shish" of polymer main chain can be aligned by the virtue of orientation of "kebabs" but also the uniform cross-conjugated structure between the "kebabs" and "shish" can be broken. Then,the alignment of the polymer main chain showed yellow light emission and was also accompanied by orientation of the LC side chains showing blue light emission,this gave rise to a notable linearly polarized white fluorescence. 相似文献
15.
Steven Ray Wilson Mikolai Jankowski Milaim Pepaj Albena Mihailova Fernando Boix Gabriel Vivo Truyols Elsa Lundanes Tyge Greibrokk 《Chromatographia》2007,66(7-8):469-474
A 2D liquid chromatography (LC) system using hydrophilic interaction chromatography (HILIC) and reversed phase columns has
been employed for comprehensive (LC × LC) separation of rat muscle tissue micro-dialysate. Incorporation of an on-line reverse-phase
solid phase extraction (SPE) enrichment column in front of the first dimension enabled aqueous samples with high salt concentrations
to be injected directly without compromising the chromatographic performance of the HILIC column. Since the SPE enrichment
column allowed injection of large sample volumes (e.g. 450 μL), a capillary HILIC column (inner diameter 0.3 mm) could be
employed instead of a larger column which is often used in the first dimension to load sufficient amounts of sample. The two
chromatographic dimensions were connected using a column selector system with 18, 1.0 mm I.D. C18 “transition” SPE columns. A PLRP C18 column was used in the second dimension. The 2D LC system’s performance was evaluated with a tryptic digest mixture of three
model proteins. Good trapping accuracy (HILIC→transition SPE→RP recovery >95%) and repeatability (within-and between day retention
time RSDs of first and second dimension chromatography >1%) was achieved. A dialysis sample of rat muscle tissue was separated
with the 2D system, revealing complexity and large differences in concentrations of the various compounds present, factors
which could potentially interfere with the quantification and monitoring of two target analytes, arg-bradykinin and bradykinin.
Subsequently, “Heart-cut” 2D LC-electrospray–mass spectrometry (ESI–MS) with post-column on-line standard injection was employed
to monitor arg-bradykinin and bradykinin levels as a function of various muscle conditions. The method’s quantification precision
was RSD = 3.4% for bradykinin. 相似文献
16.
G. I. Egorov D. M. Makarov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2011,85(2):171-178
Compressibility coefficients k were measured for binary ethylene glycol (EG)-dimethyl sulfoxide (DMSO) mixtures over the whole composition range at pressures
of 0.1–100 MPa and temperature 308.15 K. Excess molar volumes of mixtures, partial molar volumes of EG and DMSO, and changes
in the excess molar Gibbs energy were calculated. The concentration dependences of compressibility factors k passed a minimum at pressures of ∼10 MPa. The k coefficient increased as the pressure grew, and the dependence became linear. The composition dependences of the specific
volumes of mixtures passed minima at x ∼ 0.5 as the pressure increased (x is the mole fraction of dimethyl sulfoxide). The excess molar volumes were negative (EG-DMSO mixtures formed with compression).
Changes in the excess molar Gibbs energy characterized the stabilizing action of pressure on the EG-DMSO system. 相似文献
17.
Liquid and solid cyclic peroxides derived from aliphatic ketones are explosive materials so their enthalpies of vaporization
and other thermodynamic or condensed-phase properties cannot be measured directly. In this work the enthalpies of vaporization
of peroxides at 298.15 K were estimated simply from gas chromatographic retention times measured at different temperatures.
The technique correlates changes in the retention times of compounds whose enthalpies of vaporization are known (called the
reference series), with those of the compounds of interest. If t
R′ is the adjusted retention time (retention time of each compound minus the retention time of unretained diethyl ether, used
as solvent) a plot of ln t
R′ against 1/T for each compound (reference compounds and cyclic peroxides) results in a straight line (r
2 > 0.99 for all compounds). The enthalpy of transfer from solution to the vapor state (Δsolg
H
m) can be obtained by multiplying the slope by the gas constant (R). A second plot correlates the enthalpies of transfer from
solution to the vapor state (Δsolg
H
m), as measured by gas–liquid chromatography (GLC), with enthalpies of vaporization of reference materials (Δvap
H
m at 298.15 K) available in the literature. C9–C15 fatty acid methyl esters and hydrocarbons were used as reference compounds. The enthalpies of vaporization of the cyclic
organic peroxides were calculated from the equation of the line obtained in this second correlation, the slope of which was
Δvap
H
m (at 298.15 K)/Δg
sol
H
m. The experiments were performed under isothermal conditions with a DB-5 capillary column, flame-ionization detection (FID),
and nitrogen as carrier gas. The column temperature was varied over a range of at least 30–70 K between 403 and 473 K, with
chromatograms being acquired at 10 K intervals. Enthalpies of vaporization of cyclic organic peroxides are not available in
the literature, and the values given in this paper, obtained by gas chromatography, are the first to be reported. 相似文献
18.
Among physical and nutritional parameters optimized by “one variable at a time” approach, four cultural variables (sucrose,
MgSO4
.7H2O, inoculum size, and incubation period) significantly affected glucoamylase production. These variables were, therefore,
selected for optimization using response surface methodology. The p-values of the coefficients for linear effect of sucrose and inoculum size were less than 0.0001, suggesting them to be the
key experimental variables in glucoamylase production. The enzyme production (34 U/ml) attained under optimized conditions
(sucrose, 2%; MgSO4
.7H2O, 0.13%; yeast extract, 0.1%; inoculum size, 5 × 106 spores per 50 ml production medium; incubation time, 48 h; temperature, 40°C; and pH 7.0) was comparable with the value predicted
by polynomial model (34.2 U/ml). An over all 3.1-fold higher enzyme titers were attained due to response surface optimization.
The experimental model was validated by carrying out glucoamylase production in shake flasks of increasing capacity (0.25–2.0 l)
and 22-l laboratory bioreactors (stirred tank and airlift), where the enzyme production was sustainable. Furthermore, the
fermentation time was reduced from 48 h in shake flasks to 32 h in bioreactors. 相似文献
19.
Paul J. Trim Marie-Claude Djidja Sally J. Atkinson Keith Oakes Laura M. Cole David M. G. Anderson Philippa J. Hart Simona Francese Malcolm R. Clench 《Analytical and bioanalytical chemistry》2010,397(8):3409-3419
A commercial hybrid quadrupole time–of–flight mass spectrometer has been modified for high-speed matrix-assisted laser desorption
ionisation (MALDI) imaging using a short-pulse optical technology Nd:YVO4 laser. The laser operating in frequency-tripled mode (λ = 355 nm) is capable of delivering 1.5-ns pulses of energy at up to 8 μJ at 5–10 kHz and 3 μJ at 20 kHz. Experiments to improve
beam homogeneity and reduce laser speckle by mechanical vibration of the fibre-optic laser delivery system are reported along
with data from trial and tissue imaging experiments using the modified instrument. The laser appeared to yield best results
for MALDI-MS imaging experiments when operating at repetition rates 5–10 kHz. Combining this with raster imaging allowed images
of rat brain sections to be recorded in 37 min. Similarly, images of the distribution of peptides in “on-tissue” digest experiments
from tumour tissues were recorded in 1 h and 30 min rather than the 8-h acquisition time previously used. A brief investigation
of targeted protein analysis/imaging by multiple reaction monitoring experiments “on-tissue” is reported. A total of 26 transitions
were recorded over a 3-s cycle time and images of abundant proteins were successfully recorded. 相似文献
20.
Joint results of the differential scanning calorimetry (DSC) and thermogravimetry (TG) experiments were the basis for the
fusion enthalpy and temperature determination of the biuret (NH2CO)2NH (synthesis by-product of the urea fertilizer (NH2)2CO). Recommended values are Δm
H = (26.1 ± 0.5) kJ mol−1, T
m = (473.8 ± 0.4) K. The DSC method allowed for the phase diagrams of “water–biuret,” “water–urea,” “urea–biuret” binary systems
to be studied; as a result, liquidus and solidus curves were precisely defined. Stoichiometry and decomposition temperature
of the biuret hydrate identified, composition of the compound in “urea–biuret” system was suggested. 相似文献