scholarly journals A New Definition of the Stationary Phase Volume in Mixed-Mode Chromatographic Columns in Hydrophilic Liquid Chromatography

Molecules ◽  
2021 ◽  
Vol 26 (16) ◽  
pp. 4819
Author(s):  
Pavel Jandera ◽  
Tomáš Hájek
Keyword(s):  
Liquid Chromatography ◽  
Stationary Phase ◽  
Mobile Phase ◽  
Dominant Role ◽  
Accurate Determination ◽  
Adsorbed Water ◽  
Retention Data ◽  
Phase Volume ◽  
Mobile Phases

Polar columns used in the HILIC (Hydrophilic Interaction Liquid Chromatography) systems take up water from the mixed aqueous–organic mobile phases in excess of the water concentration in the bulk mobile phase. The adsorbed water forms a diffuse layer, which becomes a part of the HILIC stationary phase and plays dominant role in the retention of polar compounds. It is difficult to fix the exact boundary between the diffuse stationary and the bulk mobile phase, hence determining the column hold-up volume is subject to errors. Adopting a convention that presumes that the volume of the adsorbed water can be understood as the column stationary phase volume enables unambiguous determination of the volumes of the stationary and of the mobile phases in the column, which is necessary for obtaining thermodynamically correct chromatographic data in HILIC systems. The volume of the aqueous stationary phase, Vex, can be determined experimentally by frontal analysis combined with Karl Fischer titration method, yielding isotherms of water adsorbed on polar columns, which allow direct prediction of the effects of the composition of aqueous–organic mobile phase on the retention in HILIC systems, and more accurate determination of phase volumes in columns and consistent retention data for any mobile phase composition. The n phase volume ratios of 18 columns calculated according to the new phase convention strongly depend on the type of the polar column. Zwitterionic and TSK gel amide and amine columns show especially strong water adsorption.

Determination of Reserpine, Hydralazine HCl, and Hydrochlorothiazide in Tablets by Liquid Chromatography on a Short, Normal-Phase Column

1994 ◽  
Vol 77 (5) ◽  
pp. 1104-1108 ◽  
Author(s):  
Ugo R Cieri
Keyword(s):  
Liquid Chromatography ◽  
Mobile Phase ◽  
Normal Phase ◽  
Uv Absorbance ◽  
Commercial Sample ◽  
Second Stage ◽  
Mobile Phases ◽  
Acid Sodium Salt ◽  
Phase Column

Abstract A procedure is presented for the determination of reserpine, hydralazine HCI, and hydrochlorothiazide in tablets by liquid chromatography. The sample is extracted with methanol, and the extract is filtered through paper. Chromatography is performed in 2 stages, each using a 7.5 cm-long normal-phase column but different mobile phases. In the first stage, intended exclusively for reserpine, the mobile phase consists of methanol containing 2% aqueous 1-pentanesulfonic acid sodium salt at 4 parts/1000. Detection and quantitation of reserpine was by fluorescence at 280 nm (excitation) and 360 nm (emission). In the second stage, the amount of the salt solution in the mobile phase was increased to 5%. Detection and quantitation of hydrochlorothiazide and hydralazine HCI was by UV absorbance at 260 nm. One commercial sample of tablets was analyzed by the proposed method. Two determination of each ingredient were made on a ground composite. Ten individual tablets also were examined.

scholarly journals Development of Micellar HPLC-UV Method for Determination of Pharmaceuticals in Water Samples

2018 ◽  
Vol 2018 ◽  
pp. 1-12 ◽  
Author(s):  
Danielle Cristina da Silva ◽  
Cláudio Celestino Oliveira
Keyword(s):  
Liquid Chromatography ◽  
Mobile Phase ◽  
Solid Phase ◽  
Sodium Dodecyl ◽  
Micellar Liquid Chromatography ◽  
Phase Extraction ◽  
Mobile Phases ◽  
Concentration Factors ◽  
Better Than

Method for extraction and determination of amoxicillin, caffeine, ciprofloxacin, norfloxacin, tetracycline, diclofenac, ibuprofen, nimesulide, levonorgestrel, and 17α-ethynylestradiol exploiting micellar liquid chromatography with PDA detector and solid-phase extraction was proposed. The usage of toxic solvents was low; the chromatographic separation of the medicaments was performed using a C18 column and mobile phases A and B containing 15.0% (v/v) ethanol, 3.0% (m/v) sodium dodecyl sulfate (SDS), and 0.02 mol·L−1 phosphate at pHs 7.0 and 8.0, respectively. The method is simple, selective, and fast, and the analytes were separated in 23.0 min. For extraction, 1000 mL of sample containing 2.0% (v/v) ethanol and 0.002 mol·L−1 citric acid at pH 2.50 was loaded through a 1000 mg of C18 cartridge. The analytes were eluted using 3.0 mL of ethanol, which were evaporated and redissolved in 0.5 mL of mobile phase. Concentration factors better than 1200, except amoxicillin (224), were obtained. The analytical curves were linear (R2 better than 0.992); LOD and LOQ n=10 presented values in the range of 0.019–0.247 and 0.058–0.752 mg·L−1, respectively. Recoveries of 99% were obtained, and the results are in agreement with those obtained by the comparative methods.

Separation and Determination of Some Aromatic Sulfones by Reversed-Phase High-Performance Liquid Chromatography

1994 ◽  
Vol 59 (3) ◽  
pp. 569-574 ◽  
Author(s):  
Josef Královský ◽  
Marta Kalhousová ◽  
Petr Šlosar
Keyword(s):  
High Performance Liquid Chromatography ◽  
Liquid Chromatography ◽  
Mobile Phase ◽  
High Performance ◽  
Reversed Phase ◽  
Uv Spectra ◽  
Optimum Conditions ◽  
Linear Calibration ◽  
Technical Grade

The reversed-phase high-performance liquid chromatography of some selected, industrially important aromatic sulfones has been investigated. The chromatographic behaviour of three groups of aromatic sulfones has been studied. The optimum conditions of separation and UV spectra of the sulfones and some of their hydroxy and benzyloxy derivatives are presented. The dependences of capacity factors vs methanol content in mobile phase are mentioned. The results obtained have been applied to the quantitative analysis of different technical-grade samples and isomer mixtures. For all the separation methods mentioned the concentration ranges of linear calibration curves have been determined.

scholarly journals Analysis of Some Biogenic Amines by Micellar Liquid Chromatography

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
Irena Malinowska ◽  
Katarzyna E. Stępnik
Keyword(s):  
Liquid Chromatography ◽  
Sodium Dodecyl Sulfate ◽  
Biogenic Amines ◽  
Physicochemical Parameters ◽  
Mobile Phase ◽  
Sodium Dodecyl ◽  
Micellar Liquid Chromatography ◽  
Ionic Surfactant ◽  
Mobile Phases ◽  
Dodecyl Sulfate

Micellar liquid chromatography (MLC) with the use of high performance liquid chromatography (HPLC) was used to determine some physicochemical parameters of six biogenic amines: adrenaline, dopamine, octopamine, histamine, 2-phenylethylamine, and tyramine. In this paper, an influence of surfactant’s concentration and pH of the micellar mobile phase on the retention of the tested substances was examined. To determine the influence of surfactant’s concentration on the retention of the tested amines, buffered solutions (at pH 7.4) of ionic surfactant—sodium dodecyl sulfate SDS (at different concentrations) with acetonitrile as an organic modifier (0.8/0.2 v/v) were used as the micellar mobile phases. To determine the influence of pH of the micellar mobile phase on the retention, mobile phases contained buffered solutions (at different pH values) of sodium dodecyl sulfate SDS (at 0.1 M) with acetonitrile (0.8/0.2 v/v). The inverse of value of retention factor () versus concentration of micelles () relationships were examined. Other physicochemical parameters of solutes such as an association constant analyte—micelle ()—and partition coefficient of analyte between stationary phase and water (hydrophobicity descriptor) () were determined by the use of Foley’s equation.

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