Changing the Electrophoretic Mobility of Phenols Using Ionenes as Additives in the Buffer Electrolyte

Water-soluble polymers of the ionene class with increased hydrophobicity (2-10-, 6-9-, and 3-X-ionenes) are used as modifiers in capillary electrophoresis in the determination of p-nitrophenol, phenol, and resorcinol. It is shown that 2-10-ionene provides the highest selectivity of phenol separation among all of the selected ionenes. The application of this polymer increases the selectivity of determination compared to commercially available 3-6-ionene (Polybrene) and poly(diallyldimethylammonium chloride). Under optimum conditions (a phosphate buffer solution, pH 11, U = –15 kV, l _cap = 50 cm), the separation efficiency of more than 40000 theoretical plates per capillary has been achieved with an analysis time of about 8 min. Using a stacking procedure, the efficiency of more than 250000 theoretical plates per capillary has been achieved. Changes have been introduced into the design of the capillary cartridge of a Kapel'-103R instrument. As a result, it has been possible to increase the field strength up to 1180 V/cm and, thus, to decrease the analysis time down to 2.5 min. The sensitivity of the instrument is mainly determined by the quality of the equipment used. The limits of detection of phenols are about 40 g/mL for a Kapel'-103R instrument and 0.05–0.1 g/mL for a Hewlett-Packard HP^3D CE.     

Determination of D- and L-amino acids in biological samples by two-dimensional column liquid chromatography

Summary A two-dimensional, column liquid chromatographic system is used for the determination of the D- and L-enantiomers of amino acids in biological samples. Separation of the amino acids is first on ion-exchange column by gradient elution with a sodium citratesodium chloride buffer. Enantioseparation is by subsequent injection of 3 l heart-cuts of the individual amino acids onto a second column with a chiral crown ether stationary phase. Finally, fluorescence detection is after post-column labelling of the amino acids using ano-phthalaldehyde-2-mercaptoethanol reagent solution. The high separation power and selectivity of the system allow processing of complex samples with hardly any additional treatment and the determination of small quantities of D-amino acids in the presence of excess L-form. Applicability of the system is illustrated by the determination of D- and L-aspartate, serine, glutamate and alanine in various complex biological samples, such as protein hydrolysates, urine and biotechnological and food samples. Data are given on detectability, repeatability and linearity.     

Trennung, Nachweis und Bestimmung von Benzidin, α- und β-Naphthylamin

Summary Three methods (photometry, TLC, HPLC) are proposed for the separation, detection and determination of the cancerogenic compounds benzidine, - and -naphthylamine in drinking water. The necessary detection limit of 0.1 g/l has been achieved.     

Quantitation of aniline in water,urine and serum by isotopic dilution mass fragmentography

Summary A method for trace analysis of aniline in water, urine and serum samples is presented. Internal standardisation with d₅-aniline, extraction, derivatisation with dimethylthiophosphinic chloride, gas chromatographic separation on a glass capillary column and mass fragmentographic quantitation are essential steps of the analytical procedure. A detection limit of 20 pg/ml in water and 500 pg/ml in urine or serum is achieved.Presented at the 14th International Symposium on Chromatography London, September, 1982     

HPLC-Methode zur simultanen Bestimmung von Harnstoff, Kreatinin und Harns?ure in Serum und Urin

Summary A simple, rapid, and reproducible method for the determination of urea, creatinine, and uric acid in human serum and urine by ion-pair reversed-phase high-performance liquid chromatography with UV detection (196 nm) has been developed. The method involves the pretreatment of serum samples with trichloroacetic acid and centrifugation followed by the isocratic separation of compounds on a -Bondapak C18 column using a mobile phase consisting of 1.25 mmol/l tetrabutylammonium phosphate. For urine samples no special pretreatment is necessary. In addition, this method allows, with some limitations, the determination of creatine in serum.     

Use of the sol-gel technique to prepare capillary columns coated with a macrocyclic dioxopolyamine for open-tubular capillary electrochromatography

Summary Columns for open-tubular (OT) capillary electrochromatography (CEC), coated with 1,4,7,10-tetraazacyclotridecane-11,13-dione (dioxo[13]aneN₄) by use of the sol-gel technique, have been investigated for the first time. Dioxol[13]aneN₄ was reacted with 3-(2-cyclooxypropoxy)propyltrimethoxysilane and the product was then mixed with tetraethoxysilane (TEOS) and water to form a glass matrix as a network in which the stationary phase (dioxo[13]aneN₄) was incorporated. In comparison with OTCEC columns prepared by the sol-gel process with TEOS only, the sol-gel-derived macrocyclic dioxopolyamine columns enabled better separations of a mixture of isomeric nitrophenols and benzenediols, a mixture of isomeric aminophenols and diaminobenzenes, and a mixture of four biogenic monoamine neurotransmitters. High efficiencies (60 000—340 000 plates m⁻¹) were achieved for isomeric benzenediols, aminophenols, nitrophenols, and diaminobenzenes. Migration time and theoretical plate number reproducibility was satisfactory;RSD was <2% for one column and <8.5% from column to column.     

Optimized Separation of cis-trans Isomers and Enantiomers of Sertraline Using Cyclodextrin-Modified Micellar Electrokinetic Chromatography

Micellar electrokinetic chromatography has been investigated for the separation of cis-trans isomers and enantiomers of sertraline. The effects of various separating factors were studied. Optimum separation was achieved using a buffer (pH 11.5) of 35 mM sodium borate containing 30 mM sodium deoxycholate and 20 mM hydroxypropyl –-cyclodextrin; the optimum voltage and temperature were 25 kV and 20 °C, respectively. A detection wavelength of 210 nm was used. The analytical performance of the method was discussed in terms of linearity response, precision, detection limits, quantification limits and recoveries. The method developed was successfully applied to the determination of sertraline in bulk drug, tablets and capsules.Revised: 1 April and 18 May 2004     

The determination of platinum in biotic and environmental materials,I. μg/kg- to g/kg-range

A simple and reliable procedure for the determination of platinum including high pressure ashing, separation and detection by graphite furnace AAS has been developed. It was put to practical use in the analysis of biotic and environmental materials polluted with platinum in the concentration rangeg/kg to g/kg.     

Separation of phenol and cresols by crystalline complexation with 1,1-di(p-hydroxyphenyl)cyclohexane,and crystal structure analyses of the complexes

This paper is concerned with 11 inclusion complexes of the 1,1-di(p-hydroxyphenyl)cyclohexane host with either phenol or one of the cresol derivatives as guest. Selectivity studies showed preferential complexation with a guest according to the sequence;m-cresol > p-cresol > phenol > o-cresol. Crystallographic analyses of the four complexes revealed isomorphous structures [crystal data for the phenol complex:a=6.232,b=10.849,c=14.845 Å, =95.69, =93.49, =104.31°, space groupPl,Z=2]. The intermolecular arrangements are characterized by layers of efficiently hydrogen bonded entities (host-to-host, host-to-guest and guest-to-host) parallel toab, every OH group being involved in two H-bonds. Organization of the layers alongc is stabilized by weak dispersion forces, thus being most sensitive to structural variation of the guest component. The observed features of selectivity upon crystalline complexation are related to differences in topological complementarity between the constituents of each structure. Supplementary Data relating to this article are deposited with the British Library as Supplementary Publication No. SUP 82052 (4 pages).     

Determination of galanthamine in Bulbus Lycoridis Radiatae by coupling capillary electrophoresis with end‐column electrochemiluminescence detection

A novel method for the determination of galanthamine (GAL) in Bulbus Lycoridis Radiatae has been developed based on coupling CE with an end‐column tris(2,2′‐bipyridyl)ruthenium(II) electrochemiluminescence (ECL). Parameters affecting CE separation and ECL detection were investigated and optimized. Baseline separation of GAL from other components in the Bulbus Lycoridis Radiatae sample was achieved with an 18 mmol/L phosphate running buffer at pH 9.0. Under the optimized conditions: 12 kV CE‐separation voltage, ECL detection potential at 1.25 V with 5 mmol/L and 50 mmol/L phosphate buffer at pH 7.5 in the detection reservoir, the linear range of GAL concentration was from 0.8 ng/mL to 2 μg/mL, whereas the detection limit was 0.25 ng/mL (S/N=3). The proposed method was successfully demonstrated for the determination of GAL in Bulbus Lycoridis Radiatae.     

The theory and practice of liquid-liquid partition chromatography of phenols

An equation is given for the design of liquid-liquid partition Chromatographie columns which relates the separation factors and column, characteristics with the number of theoretical plates required for a desired separation. This equation should be applicable to the separation of acids or bases when a buffered stationary phase is used, thus permitting a more rational approach to this technique.Using this approach a complete separation of the three isomeric cresols has been achieved. Methods are given for this determination and also for the determination of phenol in tar acid mixtures.     

Qualitative and quantitative chromatographic analysis of plant leaf waxes

Summary Plant leaf waxes can be characterised by HPLC eitherin toto or after separation into acidic and neutral fractions using DEAE Sephadex A-25. Group separation of acidic fraction components is easy using reversed phase systems; this method is also applicable but not recommended for the characterisation of unfractionated wax samples. Separation and quantitation of wax neutral fractions is easier by adsorption HPLC systems but solvent composition is critical and normally involves use of tetrahydrofuran. The replacement of a sample loop of the injector by a short column permits injection of larger volumes as well as separate elution of the most polar components. Examples are presented using mass and UV detectors as well as gravimetric analysis of wax from several plant species.Presented at the 14th International Symposium on Chromatography London, September, 1982     

Simultaneous determination of isomeric substituted anilines by imidization with benzaldehyde and gas chromatography–mass spectrometry

The chromatographic separation of several isomeric anilines is a challenging issue. Herein, a simple method for the simultaneous determination of four groups of isomeric primary aromatic amines, including chloroanilines, methylanilines, methoxylanilines, and dimethylanilines, was presented. In this method, all of the 15 primary aromatic amines were easily transformed into the corresponding imine derivative by treatment with benzaldehyde under mild conditions. The formed isomeric imine derivatives were completely separated on a commercial capillary gas chromatography column. The effects of several derivatization parameters were investigated and optimized. Linearity in the optimized method ranged from 0.050 to 50 μg/mL with the squared correlation coefficients (R²) between 0.9981 and 0.9999. Reasonable reproducibility was obtained, with the intraday relative standard deviation (N = 5) ranging from 0.89 to 4.57% and interday relative standard deviation ranging from 2.26 to 7.69% at the concentration of 5.0 μg/mL. The developed method has been successfully applied to determine these isomeric aromatic amines in real samples.     

Trace-level determination of polar phenolic compounds in aqueous samples by high-performance liquid chromatography and on-line preconcentration on porous graphitic carbon

The use of porous graphitic carbon (PGC) was investigated for the trace enrichment and the on-line liquid chromatographic separation of polar phenolic compounds (phenol, di- and trihydroxybenzenes, aminophenols, etc.) from aqueous samples. Comparison between retentions obtained with PGC and with the copolymer-based sorbent PRP-1 showed similar variations of the capacity factors with the mobile phase composition, but an inverse retention order. The capacity factor of a very polar analyte, such as 1,3,5-trihydroxybenzene (phloroglucinol), is 1000 in pure water, whereas this analyte is not retained by C₁₈-silica and is poorly retained by PRP-1 (k′ = 3 in water). A precolumn packed with PGC can be coupled to a PGC analytical column for simple separation in the reversed-phase mode. This methodology has been applied to the direct determination of pyrocatechol, resorcinol and phloroglucinol below the 0.1 μg/1 level in a 50-ml sample.     

Thermochemistry of Aniline Solution in Isomeric Butyl Alcohols and Their Aqueous Solutions

The enthalpies of solution (_s H ⁰) of aniline in isomeric butyl alcohols and their aqueous solutions at 25°C were determined. The dissolution of aniline becomes more endothermic with increasing content of alcohol in aqueous solution. The enthalpy coefficients of pair interaction alcohol-aniline in aqueous solution were calculated. This interaction is enhanced in the order tert-butanol-sec-butanol-iso-butanol-n-butanol. The correlations of these characteristics with physicochemical properties of solvents were revealed.     

The interaction of polar aromatic molecules with neutral (polar) polymers and polyanions in aqueous solution

The interaction of aniline, pyridine and its homologues, phenol and benzamide with a series of neutral polar polymers and polyanions in aqueous solution has been studied by the equilibrium dialysis method. The interaction isotherms were generally sigmoidal. Significant association between polymer and organic molecule was only observed beyond some specific free organic molecule-polymer concentration ratio; i. e., after inter-chain attractive forces and solvation have been partially weakened by preliminary absorption of a surface layer of organic molecules. Benzamide, in fact, shows practically no interaction with neutral ‘coiled’ polymers. Maximum interaction is reached at up to thirty percent utilisation of ‘polar’ sites on the polymer chain. Klotz's method was modified to correct for these weak interactions at low organic molecule concentration. Equilibrium constants and free energies for the main association were then determined. Equilibrium constants are low;K=5–50 (g. moles per l.)^?1 for interaction with neutral polymers andK=20–120 (g. moles per l.)^?1 for interaction with polyions. The free energies are (?δG)=1–3RT and 3–5RT calories per g. mole respectively. Complexing is due to dipole-dipole and/or ion-dipole type interaction and is greatest for aniline, pyridine and phenol with fully extended polyion chains. Van der Waals' interaction between the aromatic ring and the organic section of the polymer backbone augments the dipole-dipole or ion-dipole binding with pyridine homologues, especially with acridine.     

Sol-gel technique for the preparation of beta-cyclodextrin derivative stationary phase in open-tubular capillary electrochromatography

A novel open-tubular capillary electrochromatography (OT-CEC) column coated with 2,6-dibutyl-beta-cyclodextrin (DB-beta-CD) was prepared using sol-gel technique. In the sol-gel approach, owing to the three-dimensional network of sol-gel and the strong chemical bond between the stationary phase and the surface of capillary columns, good chromatographic characteristics and unique selectivity in separating isomers were shown. We achieved high efficiencies of 5-14 x 10(4) plates/m for the isomeric nitrophenols using the sol-gel-derived DB-beta-CD columns. The migration time reproducibility of the separation of the isomeric nitrophenols was better than 2.2% over five runs and 4.5% from column to column. These sol-gel-coated DB-beta-CD columns have shown improved separations of isomeric aminophenols, isomeric dihydroxybenzenes and isomeric nitrophenols, in comparison with the sol-gel matrix capillary column. The influences of buffer pH and methanol solvent on separation were investigated. The chiral resolution of enantiomers such as ibuprofen and binaphthol was explored primarily.     

Anwendung einer S?ule zur Extraktion, Trocknung und Reinigung von Retinol und α-Tocopherol bei deren Bestimmung in Milch und Milchprodukten mit Hilfe der HPLC

Summary An already described HPLC method for the determination of retinol and -tocopherol has been improved by development of the simple column serving simultaneously for the extraction, drying and purification of these compounds. This column contains alumina, extrelut and sodium sulphate. After saponification of the sample the solution is neutralized and applied to the column. Hexane is employed for extracting the vitamins. Preparation of the column and of a suitable rack are described in detail.     

Liquid chromatographic determination of aniline and derivatives in environmental waters at nanogram per litre levels using fluorescamine pre-column derivatization

Summary Fluorescamine (fluram) has been used as a fluorogenic compound for pre-column derivatization of aniline and some derivatives. Anilines were derivatized with fluram in citrate buffer media (pH 5.5) to form pyrrolinones. The highly fluorescence pyrrolinones were isolated and pre-concentrated by solid phase extraction. A reversed phase, Spherisorb RP-8 column and tetrahydrofuran: water:formic acid (42:56:2) mobile phase was used for separation. Detection method was by a sensitive fluorimetric method and quantitation was at 395 and 495 nm. The various parameters such as reaction conditions between anilines and fluram, solid phase extraction and chromatographic separation were optimized. Calibrations were linear over the range considered with excellent correlation coefficients (r>0.999). Relative standard deviations are less than 2.5 % and detection limits for aniline,p-toluidine, 4-chloroaniline and 4-bromoaniline were 6, 30, 6 and 8 ng L⁻¹, respectively. This method has been used successfully for the determination of anilines in environmental waters.     

Separation and Determination of the Structural Isomers of Madecassoside by HPLC Using β-Cyclodextrin as Mobile Phase Additive

A reversed phase HPLC method has been investigated for separation and determination of the structural isomers of madecassoside (madecassoside and asiaticoside-B). The isomeric compounds can be isolated with high resolution by adding β-CD in mobile phase on a C₁₈ column. The effect of β-CD concentration on resolution is discussed. The functional group in the separation process is investigated. The correlation coefficient (R ²) of the calibration was 0.9995 over the range of 0.1–5.0 mg mL⁻¹. The method was successfully applied to characterize and determine the madecassoside in Centella extract.