Showing papers in "Journal of Liquid Chromatography & Related Technologies in 1987"
TL;DR: In this paper, Okamoto et al. compared the optical resolving power of chiral stationary phases with cellulose triphenylcarbamate derivatives coated on silica gel and showed that cellulose is more sensitive to 3,5-dimethylphenyl- or 3, 5-dichlorophenylisocyanate.
Abstract: Cellulose was bonded chemically to 3-aminopropyl silica gel with diisocyanates and then allowed to react with a large excess of 3,5-dimethylphenyl- or 3,5-dichlorophenylisocyanate. Optical resolving power of these chiral stationary phases was compared with that of the cellulose triphenylcarbamate derivatives coated on silica gel. ∗Chromatographic Resolution XV, for part XIV, see Y. Okamoto, R. Aburatani, and K. Hatada, J. Chromatogr., in press.
149 citations
TL;DR: In this article, the transcarotenoids, β-carotene, lutein and lycopene, were isomerized with light energy under iodine catalysis and the isomeric mixtures were subjected to reverse phase chromatography on a 5μ VYDAC TP-201 column with mobile phases of methanol-chloroform to separate the major isomers.
Abstract: Four trans-carotenoids, β-carotene, α-carotene, lutein and lycopene, were isomerized with light energy under iodine catalysis and the isomeric mixtures were subjected to reverse phase chromatography on a 5μ VYDAC TP-201 column with mobile phases of methanol-chloroform to separate the major isomers. The amounts and properties of the cis-compounds conformed with separations obtained by others from lime and alumina columns. In each case, the predominant isomers behaved as 13-cis-and 9-cis-isomers, except for the lycopene set which included isomers not previously separated. Use of the system for rapid analysis of 13-cis, 9-cis-and trans-β-carotene in some common food materials was demonstrated. The percentage of cis-isomers in the β-carotene fraction ranged from 1.6 in raw carrot to 29.6 in canned peach.
95 citations
TL;DR: In this paper, an evaporative light scattering detector enables the detection and quantification of all relatively non-volatile lipids, including polar and non-polar lipids.
Abstract: The evaporative light scattering detector enables the detection and quantitation of all relatively non-volatile lipids. The mixtures of polar and non-polar lipids were separated in one run, in 20 to 25 minutes on Silica Si-100 columns, using consecutive gradients of pentane to diethylether, to chloroform, to methanol containing a large concentration of ammonia. The flexibility of the method is illustrated by the change in elution patterns following the treatment of the packing material by ammonia. For example, the elution order of phosphatidyl inositol and phosphatidyl choline is reversed and the separation of the former compound from phosphatidyl serine, which is generally difficult, is now accomplished readily. The weak dependence of the detector sensitivity on the nature of the analytes permits an easy quantitation, as illustrated by the results of the analyses of lipid classes in blood serum, amniotic fluid, beef brain and other natural samples. The method is particularly useful for the analy...
88 citations
TL;DR: The most active catalyst in many cases has been p-toluene sulfonic acid, however, for silanes with basic groups triethylamine gives better coverages as discussed by the authors.
Abstract: For preparation of polar bonded phases with alkoxy silanes an activator and a catalyst are required to achieve surface coverages comparable to those obtained with chlorosilanes. For activation a monolayer of water on the silica surface is sufficient. The most active catalyst in many cases has been p-toluene sulfonic acid, however, for silanes with basic groups triethylamine gives better coverages. Silanes with polar groups tend to adsorb also with this group onto the surface thus preventing chemical binding via alkoxy groups. Long time experiences in the preparation of amino phases, anion and cation exchangers and hydrophilic bonded phases for protein analysis are summarized.
84 citations
TL;DR: In this paper, surface tension data of binary mixtures of methanol, acetonitrile, tetrahydrofuran, isopropanol, tertiary butanol and dimethylsulfoxide with water have been measured.
Abstract: Surface tension data of binary mixtures of methanol, acetonitrile, tetrahydrofuran, isopropanol, tertiary butanol and dimethylsulfoxide with water have been measured. Best fit polynomal functions are reported for in [sgrave] vs. volume fraction of an organic modifier. The reported data is precise and accurate to about 2% and is consistent with the available literature data. The sequence of eluotropic strength based on the solvophobic theory in RP-HPLC should be dimethylsulfoxide < methanol < acetonitrile
77 citations
TL;DR: In this paper, a multi-step gradient system of two solvents (0.1M sodium acetate, pH 7.2/methanol:tetrahydrofuran) was developed for rapid analysis of amino acids in biological samples using Ophthaldialdehyde as a precolumn derivatizing agent and fluorescence detection.
Abstract: A suitable gradient system has been developed for rapid analysis of amino acids in biological samples using O-phthaldialdehyde as a precolumn derivatizing agent and fluorescence detection. Resolution of 21 amino acids has been accomplished with 3 μm Ultrasphere ODS column by using a multi-step gradient system of two solvents (0.1M sodium acetate, pH 7.2/methanol:tetrahydrofuran) in less than 1 hour. Within-assay and between-assay coefficients of variation of retention times and fluorescence yield show good reproducibility. The fluorometric detection response is linear from 25 to 500 pmoles with a minimum detection limit of less than 1 pmol. High resolution, rapid analysis and high sensitivity of this method facilitates amino acid analysis in samples of less than 1 mg of tissue.
68 citations
TL;DR: In this paper, the authors used two experimental HPLC runs to allow prediction of sample retention as a function of mobile phase composition or gradient conditions, and they found that small deviations in this relationship can lead to error in predicted retention times.
Abstract: Computer simulation uses two experimental HPLC runs to allow prediction of sample retention as a function of mobile phase composition or gradient conditions. The general approach is rigorous, but it is assumed that reversed-phase retention obeys the relationship log k' = log kw - S 0. Small deviations in this relationship can lead to error in predicted retention times. We have studied this error empirically for several different reversed-phase systems. This provides a basis for partially correcting these errors, and suggests recommendations for avoiding significant errors during computer simulation.
67 citations
TL;DR: In this article, a method for resolution of amino acid enantiomers was described, where D- and L-amino acids were reacted with o-phthalaldehyde (OPA) and the optically active 2,3,4,6-tetra-O-acetyl-1-thio-β-glucopyranoside (TATG).
Abstract: A method is described for resolution of amino acid enantiomers. The D- and L-amino acids were reacted with o-phthalaldehyde (OPA) and the optically active 2,3,4,6-tetra-O-acetyl-1-thio-β-glucopyranoside (TATG). The reaction was complete in a few minutes at room temperature and the derivatives were quite stable. The formed diastereomers were separated by reversed phase chromatography and the selectivity was generally good, except for lysine and ornithine. A mean separation factor (α) of 1.27 was obtained with acetonitrile as an organic modifier. The fluorescence excitation and emission maxima were at 342 nm and 410 nm respectively, and the electrochemical half-wave potential E½ ≡ 0.65–0.75 V. The detection limits (for L-leucine) were 23 pmol and 1 pmol (S/N 3:1) in the respective detection modes. With laser-induced fluorescence detection (He-Cd laser, 325 nm) and microcolumns, a detection limit in the fmol range is obtainable.
67 citations
TL;DR: An HPLC/UV system for the analysis of drugs and toxic compounds is presented in this paper, where the usefulness of a computer search routine, utilizing UV and HPLC retention data, is discussed.
Abstract: An HPLC/UV system for the analysis of drugs and toxic compounds is presented. Retention data for 157 compounds in an acid HPLC system and 144 compounds in a basic HPLC system are listed. UV spectral data for 25 compounds from each system are listed. The usefulness of a computer search routine, utilizing UV and HPLC retention data, is discussed.
55 citations
TL;DR: A combination of ion suppression reverse phase high pressure liquid chromatography and differential radioimmunoassay was used to identify and quantify ecdysteroids from Drosophila melanogaster during the development of the white puparium to the adult.
Abstract: A combination of ion suppression reverse phase high pressure liquid chromatography (RP-HPLC) and differential radioimmunoassay (RIA) was used to identify and quantify ecdysteroids from Drosophila melanogaster during the development of the white puparium to the adult. The whole body ecdysteroid titer revealed a large peak approximately 30 hours after pupariation. RP-HPLC-RIA analysis of the brain-ring gland complex secretion in vitro revealed the presence of: ecdysone, 20-deoxymakisterone A, and a yet uncharacterized low polarity ecdysteroid (LP-1). The metabolism of ecdysone and 20-deoxymakisterone A was followed by analysis of the ecdysteroids during development. The white puparium (0 hour) yielded a four-fold greater quantity of free 20-hydroxyecdysone and makisterone A than ecdysone and 20-deoxymakisterone A, respectively, indicating high 20-monooxygenase activity during this stage. Another metabolite of ecdysone, 20,26-dihydroxyecdysone, was present at a quantity intermediate between that of ...
55 citations
TL;DR: The Py values for aqueous cyclodextrins are reported and compared to those of organic solvents in this paper, and the combined fluorescence and Py data indicates that marked sensitivity improvements in fluorescence chromatographic detection may result from using cyclodesxtrin aqueously mobile phase modifiers which allow moderate inclusion of the analytes (presumably other polycyclic aromatic hydrocarbons).
Abstract: The Py values for aqueous cyclodextrins are reported and compared to those of organic solvents. The data indicates that the cavities of the cyclodextrins have about the same polarity as n-octanol for Pyrene, and fluorescence intensity data confirms that pyrene does not completely fit into the cavity of the smaller cyclodextrins. The combined fluorescence and Py data indicates that marked sensitivity improvements in fluorescence chromatographic detection may result from using cyclodextrin aqueous mobile phase modifiers which allow moderate inclusion of the analytes (presumably other polycyclic aromatic hydrocarbons, etc.).
TL;DR: In this article, a wide-pore silica for HPLC (SBET = 360 m2 g−1, D = 20 nm, Vp = 2.1 cm3 g− 1) was silanized with n-octadecyl dimethylchlorosilane in the presence of several base activators.
Abstract: A wide-pore silica for HPLC (SBET = 360 m2 g−1, D = 20 nm, Vp = 2.1 cm3 g−1) was silanized with n-octadecyl dimethylchlorosilane in the presence of several base activators. It has been found that the density of bonded octadecyl ligands is not only a function of reaction time and temperature, but also depends upon the structure of the organic base used as reaction activator. The reproducible synthesis of silica bearing more than 4/umol m–2 of octadecyl ligands is described.
TL;DR: In this article, a unified theory for the solute capacity factor of supercritical fluid chromatography has been proposed, based on a simple theoretical model which exploits the isomorphism pervading critical phenomena.
Abstract: Based on a simple theoretical model which exploits the isomorphism pervading critical phenomena, a general equation is derived for the solute capacity factor, k′, in a chromatographic system where the stationary phase is an absorbent and the mobile-phase fluid may be an ideal gas, moderately nonideal gas, supercritical fluid or liquid. This comprehensive equation is in the form 2nk′ = 2nk′o + F(TR, ρR), where TR and ρR are the reduced temperature and reduced density of the mobile phase and where 2nk'o, the stationary-phase contribution, corresponds to ideal gas-liquid chromatography (ρR = 0) and F(TR, ρR), the mobile-phase contribution (eqn. 14), is a quadratic function of [sgrave]R and a linear function of TR -1 and solute carbon number (homologous solute series). The limitations and advantages, molecular interpretation, predictions, practical implications and applications, and general utility of this unified theory are discussed, with special emphasis on supercritical fluid chromatography (and ...
TL;DR: In this article, an optimization problem in (capillary) supercritical fluid chromatography is discussed as a practical example and the results of an optimization process depend on the optimization criterion selected.
Abstract: Optimization procedures in chromatography require clear and unambiguous goals. Optimization criteria express such goals in mathematical terms. If the capacity factors vary as a function of the parameters to be optimized, criteria should be selected that allow the simultaneous optimization of the retention and the selectivity. It is demonstrated that the result of an optimization process depends on the optimization criterion selected. For a simple (fictive) example five different criteria are seen to result in five different locations for the optimum. This example will be used to compare the different criteria and to formulate general recommendations for two different situations. An optimization problem in (capillary) supercritical- fluid chromatography is discussed as a practical example.
TL;DR: In this paper, a quantitative measure for characterizing structural similarity of compounds on the basis of their reversed-phase liquid chromatographic retention data was developed for characterising the structural similarity.
Abstract: A quantitative measure has been developed for characterizing the structural similarity of compounds on the basis of their reversed-phase liquid chromatographic retention data. Reversed-phase retention data (expressed by log k' values) of 59 compounds of various types (aniline, phenol, morphine, barbiturate, xantine, sulfonamide, steroid, benzoic acid derivatives) have been investigated as a function of organic modifier concentration (OP%) in the mobile phase. The effect of acetonitrile and methanol concentration in the mobile phase on the log k' values was measured. High correlation was found between the slope and the intercept values of the log k' vs OP% straight lines for only structurally related compounds. In view of these results, the correlation coefficient between the slope and the intercept values of the linear section of the log k' vs OP% straight lines is suggested as a measure of structural similarity of compounds with regard to their partition behaviour in a reversed-phase chromatogra...
TL;DR: The physical and chromatographic properties of two types of non-porous HPLC support materials were examined in this paper, and it was shown that such materials appeared to be less suitable for low-molecular-weight solutes, except for fundamental retention studies.
Abstract: The physical and chromatographic properties of two types of non-porous HPLC support materials were examined. Loading capacities of non-porous supports were about 10 fold less than of wide-pore gels, while their physical strength was much greater, suggesting that non-porous supports could be useful for polymer separations. Such materials appeared to be less suitable for low-molecular-weight solutes, except for fundamental retention studies, where the absence of pore structure offers a less ambiguous support matrix.
TL;DR: A simple and rapid method of purification of coupling factor CF1 from spinach chloroplast crude extracts, involving anion exchange HPLC on DEAE Pak, is described in this paper.
Abstract: A simple and rapid method of purification of coupling factor CF1, from spinach chloroplast crude extracts, is described, involving anion exchange HPLC on DEAE Pak. Separation of β, CF1 - δ, CF1-e subunits is performed on the same column, after dissociation of the bound enzyme by extensive washing at low ionic strength. Purity of the fractions is checked by urea-SDS polyacrylamide electrophoresis and by fluorescence spectrometry.
TL;DR: The original mixture-design statistical software has been expanded and enhanced to accomodate data from both isocratic and gradient elution separations, single or multiple stationary phases, and other variables, such as temperature or pH.
Abstract: Optimization of separations in high-performance liquid chromatography (HPLC) is dependent on several factors: the proper choice of variables; a definition of criteria for a suitable separation; a rational strategy for examining the effects of these variables; and an efficient analysis of the data using manual methods or computer software. The selection of variables and, strategy for optimization is discussed in this paper, and a detailed description of a versatile software package for data analysis is presented along with provisions for obtaining the actual FORTRAN source code. The original mixture-design statistical software has been expanded and enhanced to accomodate data from both isocratic and gradient elution separations, single or multiple stationary phases, and other variables, such as temperature or pH. The software can be used to predict a single optimum set of conditions for a particular separation, and also to calculate the actual separation quality under any set of conditions bounded...
TL;DR: In this paper, a simple method for determination of ACh, Ch, NA, DA, 5-HT and their related metabolites on the same brain tissue sample was developed by HPLC-ED.
Abstract: A simple method for determination of ACh, Ch, NA, DA, 5-HT and their related metabolites on the same brain tissue sample was developed by HPLC-ED. The electrochemical detection system is equipped with a platinum electrode for ACh and Ch detection, or a glassy carbon electrode for CA and 5-HT detection. ACh and Ch can be separated with bonded silica or polystyrene reverse phase columns, using a pH 7 mobile phase. They are converted to H2O2 by the passage of the effluent through an in line post column reactor with covalently bonded ACh esterase and Ch oxidase. This step ensures sensitivity, reliability and enzyme economy. Tissue preparation consists of formic acid/acetone extraction and purification by tetraphenyl boron exchange with high reproductible recoveries. The time necessary for the whole procedure is short, making it well adapted to large series. CA, 5-HT and related metabolites can be simply analysed on an aliquot of the tissue extract.
TL;DR: In this article, a specific, sensitive and quantitative method for measuring tissue sulfhydryl (SH) and disulfide levels in nonprotein, protein, and protein-bound fraction has been developed by using HPLC with electrochemical detection.
Abstract: A specific, sensitive and quantitative method for measuring tissue sulfhydryl (SH) and disulfide levels in nonprotein, protein, and protein-bound fraction has been developed by using HPLC with electrochemical detection. Protein and nonprotein fractions are separated through perchloric acid precipitation. The protein fraction is divided into two aliquots: one which undergoes protein hydrolysis in HCl and the other which undergoes sodium borohydride reduction. The nonprotein, protein and protein-bound fractions generated are then separated by HPLC and the various sulfhydryls (e.g., cysteine, glutathione) and disulfides (e.g., cystine, glutathione disulfide) are measured directly by a dual gold mercury electrode thin layer electrochemical cell. The chromatography takes less than 15 min to separate cystine, cysteine, glutathione, and glutathione disulfide. This assay is more specific and as sensitive as other assays employing 5,5′-dithiobis (2-nitrobenzoic acid) (DTNB). Furthermore, this procedure al...
TL;DR: The ET(30) polarity values of binary methanol-water, acetonitrile-water and tetrahydrofuran-water mobile phases used in reversed phase liquid chromatography are reported in this article.
Abstract: The ET(30) polarity values of binary methanol-water, acetonitrile-water and tetrahydrofuran-water mobile phases used in reversed phase liquid chromatography are reported, and equations are presented for the calculation of polarity values for any composition of these solvents. We summarize previously reported comparisons of these measured polarities with both chromatographic retention and methylene selectivity. Plots of log k' vs. ET(30) polarity were generally found to be better descriptors of retention than commonly used plots of log k' vs. percent organic modifier. For 332 data sets examined, the average r2 value for plotting log k' vs. percent organic modifier was 0.9783 while plotting vs. ET(30) polarity gave a value of 0.9910. Retention in acetonitrile-water mixtures is also compared with theory developed by Dill using binary interaction parameters. Variation in methylene selectivity was found to correlate best with percent organic modifier in methanol-water mixtures, while the ET(30) polari...
TL;DR: The compositions of ethanolamine glycerophospholipids from rat brain and of choline and ethanolamine Glyceroph phospholipid from human platelets agreed well with previous results obtained with much longer procedures.
Abstract: The 1-alkyl-2-acyl, 1-alk-1'-enyl-2-acyl, and 1,2-diacyl-snglycerol moieties of choline and ethanolamine glycerophospholipids were converted to the dinitrobenzoyl derivatives. These compounds were separated by high performance liquid chromatography and quantitated by their absorbance at 235 nm. Peak areas were proportional to the amount injected. Separations were optimal for the derivatives from 5 to 30 nmol of the glycerophospholipids. The compositions of ethanolamine glycerophospholipids from rat brain and of choline and ethanolamine glycerophospholipids from human platelets agreed well with previous results obtained with much longer procedures.
TL;DR: In this article, a new application of HPLC analysis to assay for all the enzymes involved in regulation of adenine nucleotide pool metabolism is described, which can be routinely used to determine adenosine levels within 3-4 minutes, using a single solvent HPLC system.
Abstract: A new application of HPLC analysis to assay for all the enzymes involved in regulation of adenine nucleotide pool metabolism is described. In vitro, enzymatic reactions were carried out in buffered reaction media containing appropriate concentrations of metal ions, specific substrate, inhibitors and enzymes. Following an incubation period, the enzymatic reactions were terminated and extracted with cold trichloroacetic acid. The soluble acid extracts were neutralized and injected in a HPLC system. Using a C18-Nova Pak reverse phase column, we were able to separate, identify and quantify the substrate, products and their possible catabolites and UV-detectable inhibitors. A complete separation and quantitation of metabolites was accomplished within 16-18 minutes. However, rapid and simple HPLC runs were also developed which can be routinely used to determine adenosine levels within 3-4 minutes, using a single solvent HPLC system. This procedure is extremely reproducible and very reliable as demonstr...
TL;DR: In this article, the authors compared the performance of the traditional break-through and the system peak technique for the adaption of a secondary amine, protriptyline, as phosphate ion-pair to Nucleosil C18.
Abstract: Adsorption of a secondary amine, protriptyline, as phosphate ion-pair, to Nucleosil C18, was studied. Two different techniques were compared; the traditional break-through and the system peak technique. Both techniques indicated that the adsorption of the ion-pair was best fitted to a 2-site adsorption model of the Langmuir type, indicating a heterogenous solid phase surface. The reliability of the system peak technique was tested by comparing the retention volumes of the system peaks for different kind of equilibrium disturbances introduced into the system. When injecting finite amounts of analytes the system peak retention was affected by the analyte concentration, charge and hydrophobicity, keeping the eluent composition constant. The effects could qualitatively be explained in light of the developed model for the retention.
TL;DR: In this article, expressions for retention time and fractionating power Fd for linear and two types of parabolic programmed field decay were derived for sedimentation field-flow fractionation.
Abstract: Following an earlier treatment of exponentially programmed field decay in field-flow fractionation (FFF), expressions have been derived for retention time and fractionating power Fdfor linear and two types of parabolic programmed field decay. The particular case of sedimentation FFF has been considered and plots of both retention time and Fdas functions of particle diameter are generated by computer in order to illustrate the influence of the various experimental parameters. Approximate analytical expressions have been derived for retention time and Fd in each case, and from these the means of calculating both the initial field strength and the program time necessary to obtain a desired level of Fd at some particular particle size have been obtained. Finally the special properties and possible uses of these programs have been discussed.
TL;DR: Capacity ratios (k') for a set of small organic compounds of miscellaneous structure were measured under a variety of reversed-phase liquid chromatoghraphic conditions and the null hypothesis was applied to compare the correlation of the best chromatographic data with binding to the correlations of the binding data with the octanol-water partition coefficients of these compounds.
Abstract: Capacity ratios (k') for a set of small organic compounds of miscellaneous structure were measured under a variety of reversed-phase liquid chromatoghraphic conditions. The capacity ratios from these experiments were correlated with the binding of these solutes to bovine serum albumin (BSA). Hydrophobic binding of small molecules to BSA is considered to be a nonspecific process (i.e., requiring no special orientation or restriction of movement of the solute molecules) and serves as a model for the hydrophobic binding of small molecules to other macromolecules, such as hemoglobin and ribonuclease. Standard deviations from these correlations were compared using the null hypothesis to determine the set of chromatographic conditions giving the best correlation with the binding constants. The null hypothesis was again applied to compare the correlation of the best chromatographic data with binding to the correlation of the binding data with the octanol-water partition coefficients of these compounds. ...
TL;DR: In this article, a computational technique using a combination of molecular mechanics, MO and intermolecular interaction energy calculations was developed that is capable of predicting the possibility of chiral separation in liquid chromatography, the most retained enantiomer and the orientations between the enantiomers and the chiral stationary phase.
Abstract: A computational technique using a combination of molecular mechanics, MO and intermolecular interaction energy calculations has been developed that is capable of predicting the possibility of chiral separation in liquid chromatography, the most retained enantiomer and the orientations between the enantiomers and the chiral stationary phase.
TL;DR: In this paper, a universal calibration curve based on hydrodynamic volume [η]M was obtained for PVP using both SEC/LALLS and universal calibration, showing good agreement between the two methods.
Abstract: Poly(vinylpyrrolidone) and poly(ethylene oxide) separate by hydrodynamic volume on Toyo Soda TSK-PW columns in a mixed solvent mobile phase of 50:50 (v/v) MeOH/H2O containing 0.1M LiNO3. From this separation a single universal calibration curve based on hydrodynamic volume [η]M can be obtained. Accurate weight average molecular weights of PVP were obtained by both SEC/LALLS and universal calibration showing good agreement between the two methods. SEC/LALLS overestimates the number average molecular weight for broad distribution polymers due largely to the lack of sensitivity of the LALLS detector to the low molecular weight portion of the polymers, while the universal calibration method slightly underestimates the number average molecular weight as compared to osmometric values.
TL;DR: In this paper, the authors described the hydrocarbon group types analysis of a large number of petroleum products by HPLC equipped with columns of suitable selectivity, and an effective approach to the factors influencing the specificity of the columns was developped and stationary phases were synthetised in fonction of the products to be separated.
Abstract: The hydrocarbon group types analysis of a large number of petroleum products by HPLC equipped with columns of suitable selectivity is described. An effective approach to the factors influencing the specificity of the columns was developped and stationary phases were synthetised in fonction of the products to be separated. All new phases were characterized by elemental, 29Si and 13C NMR analyses. The potentialities of theses phases were illustrated by analysis of selected samples either of fundamental or of industrial interest.