共查询到20条相似文献,搜索用时 0 毫秒
1.
P. L. Zhu 《Chromatographia》1985,20(7):425-433
Summary In RPLC the dead volume can be defined as the difference between the maximum column hold-up volume and the volume of the adsorbed phase. The composition of the adsorbed phase depends on the composition of the mobile phase and therefore, the dead volume also varies with it. In this work, the alkyl bonded phase acetonitrile (ACN)-water mobile phase system is investigated. In the system, deuterated water (D2O) and deuterated acetonitrile (D-ACN) are retained due to the isotopic dilution effect. By means of D2O and D-ACN, the absolute adsorption isotherm of the organic modifier ACN is measured. Based on the isotherm, the chromatographic behaviour of ACN, D-ACN and D2O, the variation of the dead volume with the composition of the mobile phase, and the approach to determine the maximum column hold-up volumn are explained. In addition, the various approaches to determine the dead volume are compared and the recommendations are given for the case of common unbuffered binary systems (MeOH/H2O, THF/H2O and ACN/H2O). 相似文献
2.
Summary For the evaluation of reversed phase packing materials a mixture of acetylacetone, I-nitronaphthalene and naphthalene is proposed. This will reveal the usual optimum kinetic chromatographic parameters (the naphthalene peak), the degree of activity or endcapping status of the column (the ratio of the I-nitronaphthalene and naphthalene retention times) and trace metal activity (the shape and intensity of the acetylacetone peak). 相似文献
3.
Summary Modification of silica gel with thiophene-propyl-trichlorosilane is described as well as the synthesis of the silane. The
chromatographic performance and selectivity are demonstrated with various polyaromatic compounds. Thiophene-modified silica
gel was found to exhibit a selectivity comparable with both ODS-and amino-phases. 相似文献
4.
Summary A new method for the determination of the mobile phase volume (V
m) in liquid chromatography is presented based on the model regarding the retention of ionic solutes in the presence of eluent
electrolytes. TheV
m value can be determined by measuring the retention volumes of two ions that have the same charge in two eluent electrolyte
systems. Compared with the methods using isotopically labelled eluent components or inorganic salts asV
m markers, the method presented is proved to give more reasonableV
m values for both normal and reversed-phase liquid chromatography. As well as in binary mixed solvent systems, theV
m values in single solvent systems can be determined by this method. 相似文献
5.
J. P. Bianchini E. M. Gaydou A. M. Siouffi G. Mazerolles D. Mathieu R. Phan Tan Luu 《Chromatographia》1987,23(1):15-20
Summary An optimization procedure for the chromatographic separation of polymethoxylated flavones is described. A polyhedron working volume is drawn from a truncated tetrahedron constructed from the four solvents selected. The response function is an n'th degree polynomial the coefficients of which are calculated through the least squares method by means of B=(XX)–1XY in which XX is the information matrix (XX)–1 the variance covariance matrix. X is the matrix of the model (polynomial built from the selected experiments) and X the transposed matrix. Y is the quality of the chromatogram defined by the resolution of each pair of solutes. An exchange algorithm matrix yields the minimum number of runs necessary to obtain a correct B. Isoresponses curves are drawn by intersection of a cubic volume which includes the polyhedron to give a better insight. An optimal zone is then determined and provides the solvent composition. An optimized chromatogram of 8 methoxylated flavones demonstrates the application of the method. 相似文献
6.
7.
The multi-component isotherms for human insulin (HI) and desamido human insulin (dHI) over reversed phase packing (C18) and with 29.8% (w/w) ethanol-water as mobile phase have been determined experimentally. The isotherms of HI in ethanol-water differ from those obtained with the more commonly applied methanol-water and acetonitrile-water mobile phase, as described in this paper. The isotherm exhibits anti Langmuirian behavior and can be very well modeled by an anti Langmuir isotherm presented in this paper. The HI and dHI anti Langmuir isotherm are determined as: qHI = (8.4C(HI) + 3C(HI)CdHI)/(1 - 0.05C(HI) - 0.14CdHI + 0.04C(HI)CdHI) and qdHI = (11.4CdHI + 2C(HI)CdHI)/ (1 - 0.05C(HI) - 0.14CdHI + 0.04C(HI)CdHI) 相似文献
8.
A new stationary phase demonstrated effective separation towards polar analytes or their counterions within a single run. 相似文献
9.
10.
Ehab F. Elkady 《Talanta》2010,82(4):1604-1607
New, simple, rapid and precise reversed phase liquid chromatographic (RP-LC) method has been developed for the simultaneous determination of diclofenac potassium (DP) and methocarbamol (MT) in ternary mixture with guaifenesin (GF), degradation product of methocarbamol. Chromatographic separation was achieved on a Symmetry® Waters C18 column (150 mm × 4.6 mm, 5 μm). Gradient elution based on phosphate buffer pH (8)-acetonitrile at a flow rate of 1 mL min−1 was applied. The UV detector was operated at 282 nm for DP and 274 nm for MT and GF. Linearity, accuracy and precision were found to be acceptable over the concentration ranges of 0.05-16, 0.5-160 and 0.5-160 μg mL−1 for DP, MT and GF, respectively. The optimized method proved to be specific, robust and accurate for the quality control of the cited drugs in pharmaceutical preparation. 相似文献
11.
Fotios Tsopelas Maria Ochsenkühn-Petropoulou Anna Tsantili-Kakoulidou 《Journal of chromatography. A》2010,1217(17):2847-2854
A comparative investigation of 15 void volume marker candidates was carried out on two reversed-phase (RP), two immobilized artificial membrane (IAM) and two immobilized protein columns, namely Human Serum Albumin (HSA) and α1-acid-glycoprotein (AGP), using different mobile phases in respect to pH and buffer composition. Pycnometric analysis of the 6 chromatographic columns was also employed for reasons of comparison. The results revealed the possible overestimation of stationary phase void volume if a general void volume marker is used under different chromatographic conditions. In particular, overestimation of the investigated columns’ void volumes was a common phenomenon when using acidic eluents or High Purity Water (HPW) as mobile phase. For this purpose, a classification of the recommended chemicals according to the column type or the pH of the mobile phase is suggested for the accurate determination of retention factors. 相似文献
12.
Summary A brief critique on the existing methods for the determination of LC column dead volume is presented. The dispute and controversy among scientists regarding the definition of column void volume, as well as the methods for its determination are pointed out. Difficulties arising in connection with the determination of the dead volume of cyclodextrin columns are discussed; it seems that the applicability of conventional methods is questionable. The necessity for further research in this field is stressed. 相似文献
13.
P. L. Zhu 《Chromatographia》1986,21(4):229-233
Summary An equation is derived which can describe how the retention of solutes is influenced by the composition of the mobile phase
in reversed-phase liquid chromatography, the retention of solutes in alkyl bonded stationary phase regarded as the complexation
between solute molecule and the active sites on the surface of the stationary phase. When the stationary phase is not fully
saturated by the organic modifier, the activity of the active sites, the activity coefficient of the adsorbed solute as well
as the activity coefficient of the solute in the mobile phase depend on the composition of the mobile phase. However, when
the stationary phase is fully saturated, the composition of the mobile phase mainly influences the activity coefficient of
the solute in the mobile phase. In addition, the selectivity of retention is discussed in terms of the derived equation. 相似文献
14.
Comparative study on determination of fumagillin in fish by normal and reversed phase chromatography
Summary Fumagillin is an antibiotic agent mostly used in the veterinary profession. A normal-phase liquid chromatographic method was
developed for the determination of this drug in fish matrices. A hexane-dichloromethanedioxan-2-PrOH-acetic acid (43:43:9:5:0.1
v/v %) eluent was used on a Perkin Elmer silica gel column. For validation of the process a reversed-phase HPLC method was
also developed (eluent: acetonitrile-water-bicyclohyxylamine 70:30:0.05 v/v %, with Spherisorb ODS, as stationary phase).
Recovery is about 100% and the limit of detection is 5 ng g−1 for meat samples.
Presented at: Balaton Symposium on High-Performance Separation Methods, Siófok, Hungary, September 3–5, 1997. 相似文献
15.
16.
A systematic study of the behavior of several common mobile‐phase volume markers using traditional and polar‐group‐containing reversed‐phase stationary phases is presented. Examined mobile‐phase volume markers include two neutral molecules, uracil and thiourea, concentrated (0.10 M) and dilute (0.0001 M) KNO3, and D2O. Mobile‐phase volumes are examined over the entire reversed‐phase mobile‐phase range of 100% water to 100% methanol or acetonitrile. The behavior of these mobile‐phase volume markers is compared with a maximum theoretical value (i.e. the void volume), as determined by pycnometry. The data suggest that: (i) uracil begins to fail as a mobile‐phase volume marker in mobile phases below about 40% strong solvent for polar group containing phases; (ii) in nearly all cases, the mobile‐phase volume measured dynamically is smaller than the pycnometric void volume; (iii) a significant dependence of measured mobile‐phase volume on salt concentration is seen on the polar endcapped phase, which is not observed on the traditional and embedded polar group phase; and (iv) D2O does not work well as a mobile‐phase volume marker with polar‐group‐containing phases, possibly due to interaction with the stationary phase polar group. 相似文献
17.
18.
Summary The retention of positively and negatively charged and neutral solutes was studied in an aqueous phosphate buffer eluent, with constant inorganic-counterion concentration, on ODS-Hypersil stationary phase in the presence of various sulfonic acid ion-pairing reagents. The adsorption isotherms of the ion-pairing reagents d-camphor-10-sulfonic acid, sodium cyclohexylsulfamic acid and sodium alkylsulfonates (butyl-, hexyl- and octyl-) were determined by the breakthrough method.Dedicated to Professor J. F. K. Huber on the occasion of his 60th birthday. 相似文献
19.
Summary Ultra high molecular mass (> 7 million dalton) polystyrenes are prone to degradation in size exclusion chromatography. In gradient elution reversed phase HPLC they do not elute visibly on small particle size porous supports. However, large diameter C18 pellicular particles were successfully employed for reversed phase study of ultra high molecular mass (15 million dalton) polystyrenes without polymer degradation during elution. Although retention for the lower molecular mass polystyrenes was lower than on small diameter porous particles, the medium high molecular mass polystyrenes (0.5–1 million dalton) showed similar retention. The addition of small diameter porous particles in small quantities, to the large diameter pellicular particles, increased the amount of retention of the low molecular mass polystyrenes without affecting the higher molecular mass polystyrenes. 相似文献
20.
Summary The molecular-shape recognition of polycyclic aromatic hydrocarbons has been studied on various stationary phases in reversed-phase high-performance liquid chromatography. The examined stationary phases were phenyl-, diphenyl-, triphenyl- and benzyl-bonded silicas. The results of regression analysis inidcated that triphenylsilica is the best packing material to recognize the difference in the molecular-shape of structural isomers. This fact was confirmed by the separation of 4-ring isomers. 相似文献