Showing papers in "Journal of Liquid Chromatography & Related Technologies in 1999"
TL;DR: The assay combines the isolation and separation of curcuminoids on silica gel 60F254 high performance thin layer chromatographic plates, followed by scanning of the spots at 366 nm using a UV detection mode.
Abstract: A rapid and simple high performance thin layer chromatographic method has been developed for the simultaneous quantitation of pharmacologically important diaryl heptanoids curcumin, demethoxy curcumin, and bis-demethoxy curcumin in Curcuma longa and C. amada. The assay combines the isolation and separation of curcuminoids on silica gel 60F254 high performance thin layer chromatographic plates, followed by scanning of the spots at 366 nm using a UV detection mode.
133 citations
TL;DR: In this article, thin-layer chromatography and high-performance liquid chromatography were used for qualitative and quantitative analysis of phenolic acids in Ginkgo biloba leaves, and the amounts of both free and bound phenolic acid were determined within the whole vegetative period.
Abstract: In this paper, thin-layer chromatography and high-performance liquid chromatography for the qualitative and quantitative analysis of phenolic acids in Ginkgo biloba L. leaves are described. The amounts of both free and bound phenolic acids were determined within the whole vegetative period. For this purpose, a special extraction procedure, comprising acid and alkaline hydrolyses, was used. The described method allowed us to identify and estimate the concentration levels of eight phenolic acids: protocatechuic, para-hydroxybenzoic, vanillic, caffeic, isovanillic, para-coumaric, ferulic, and sinapic. Depending on the part of the plant vegetation, significant differences in the content of the compounds examined were observed and discussed. The elaborated method could be used in studies on the seasonal distribution of phenolic acids in plant material.
95 citations
TL;DR: The α-diketones glyoxal, methylglyoxal and diacetyl were determined in selected beer and wine using a procedure involving the use of C18 solid phase extraction columns to remove interferences and derivatization of the compounds with o-phenylenediamine to form quinoxalines.
Abstract: The α-diketones glyoxal, methylglyoxal, and diacetyl were determined in selected beer and wine using a procedure involving the use of C18 solid phase extraction columns to remove interferences and derivatization of the compounds with o-phenylenediamine to form quinoxalines, which are separated by HPLC and detected using UV spectrophotometric detection. Interferences were more difficult to remove in the case of beer, due to the higher complexity of the matrix and because the concentrations of the compounds were lower (higher for methylglyoxal and lower for diacetyl, but all in the 10−7 M region). The determination was easier to implement in the case of wine as the typical concentrations of the compounds were about ten times higher, with methylglyoxal being the more abundant compound found.
76 citations
TL;DR: In this paper, a low capacity strong anion exchange PRP-X100 Hamilton, 150 × 4.1 mm, 10 μm, with exchange capacity 0.19 ± 0.02 meq/g, analytical column was used, with a mixture of 0.1 M NaCl-CH3OH, at a volume ratio 45:55.
Abstract: A rapid, accurate, and sensitive method has been developed for the simultaneous determination of nitrite and nitrate. A low capacity strong anion exchange PRP-X100 Hamilton, 150 × 4.1 mm, 10 μm, with exchange capacity 0.19 ± 0.02 meq/g, analytical column was used, with a mixture of 0.1 M NaCl-CH3OH, at a volume ratio 45:55. The flow rate of 2 mL/min, lead to a pressure of 150 kg/cm2. Detection was performed with a variable wavelength UV-visible detector, at 230 nm, resulting in detection limits of 0.1 ng and 0.2 ng for nitrite and nitrate, respectively, per 20 μL injection. For the quantitative determination, iodide was used as internal standard, at a concentration of 7.0 ng/μL. A rectilinear relationship was observed up to 12 ng/μL for nitrite and up to 25 ng/μL for nitrate. Analysis time was less than 6 min. The statistical evaluation of the method was examined performing intra–day (n = 8) and inter-day calibration (n = 8) and was found to be satisfactory, with high accuracy and precision results. The m...
69 citations
TL;DR: A high performance thin layer chromatography technique was developed and applied successfully to birds found dead after a known exposure to the compound and indicates that imidacloprid accounts for the majority of the toxic residues detected in the tissues and organs of affected animals.
Abstract: Several accidents were reported in France, in domestic and wild animals, involving the potential ingestion of imidacloprid-coated seeds. Imidacloprid is a new insecticide which acts as a nicotinic blocker. Since there was very limited published information regarding this compound, its toxicity to wild birds, and potential routine analytical techniques, this study was designed to set up and validate a method for the detection and quantification of imidacloprid and its primary metabolite, 6-chloronicotinic acid, in tissues and organs of affected animals. A high performance thin layer chromatography (HPTLC) technique was developed to quantify both compounds. The method is repeatable, reproducible, and sensitive enough to investigate potential poisoning cases (limits of quantification between 0.25 and 0.5 μg/g). The technique was also applied successfully to birds found dead after a known exposure to the compound and indicates that imidacloprid accounts for the majority of the toxic residues detected in the l...
66 citations
TL;DR: An isocratic high performance liquid chromatographic (HPLC) method with run times of less than 22 min has been developed for simultaneous analysis of carotenoids and tocopherols in corn as mentioned in this paper.
Abstract: An isocratic high performance liquid chromatographic (HPLC) method with run times of less than 22 min has been developed for simultaneous analysis of carotenoids and tocopherols in corn. The reverse phase system utilizes a nonaqueous mobile phase in combination with a polymeric C18 column coupled to a monomeric C18 column to separate lutein, zeaxanthin, β-cryptoxanthin, α-carotene, β-carotene, and the α-, δ- and γ- forms of tocopherol. The detector was a multi-channel UV-VIS. One channel was used to monitor carotenoid absorption at 450 nm while another monitored tocopherols at 290 nm. Retention times and spiked tests with known standards validated peak identification. Linear regressions of external standards generated coefficients of determination (R2) that were in the ninety-ninth percentile for all compounds tested. Using the same samples, concentrations generated from our protocol and compared with results from other laboratories suggest that this procedure is relatively accurate.
62 citations
TL;DR: In this paper, a comprehensive analysis of interactive polymer chromatography is presented, where the authors provide the quantitative condition for statistical copolymer chains to have a single adsorption-desorption transition point and for non-random copolymers this condition includes the comparison between the mean length of chain segments connecting the attractive walls of the pore and the chemical correlation segment characterizing the randomness of th...
Abstract: A comprehensive analysis of interactive polymer chromatography is presented. Isocratic liquid chromatography of polymers at the critical eluent composition (the transition point where size-exclusion and adsorption interactions completely compensate each other) is currently used to separate functional oligomers and block copolymers. We have extended the concept of this critical elution chromatography to the cases of statistical copolymers as well as porous stationary phases with heterogeneous surfaces (viz., surfaces with both inert and active groups). The theory provides the quantitative condition for statistical copolymer chains to have a single adsorption-desorption transition point. The random copolymers with narrow chemical composition distribution (CCD) always posses such a point. For non-random copolymers this condition includes the comparison between the mean length of chain segments connecting the attractive walls of the pore and the chemical correlation segment characterizing the randomness of th...
60 citations
TL;DR: In this article, the molecular-statistical theory of polymer solutions in confined media is applied to the conventional chromatographic theory of gradient elution, which leads to the prediction of the special mode of interactive polymer chromatography, which occurs at the critical point of adsorption.
Abstract: The molecular-statistical theory of polymer solutions in confined media is applied to the conventional chromatographic theory of gradient elution. This approach leads to the prediction of the special mode of interactive polymer chromatography: gradient elution at critical point of adsorption. We demonstrate theoretically and experimentally that under appropriate conditions elution of each compositionally homogeneous fraction of copolymer occurs at the critical mobile phase composition. This critical mobile phase composition depends only on the local structure of the copolymer chain and is independent of its molecular weight. As a consequence, gradient elution produces the chemical composition distribution of the copolymer. The theory provides the quantitative conditions for statistical copolymer chains to have a single transition point. Equations describing relationships between the critical eluent composition and the chemical composition and microstructure of macromolecules are developed. The experimenta...
59 citations
TL;DR: A new HPLC-DAD method for separation and identification of the main phenolics present in in vivo and in vitro biomass of Hypericum perforatum and Hypericum androsaemum has been developed, achieving the direct identification of 22 compounds including flavonoids, hypericins, phloroglucinols, and phenolic acids.
Abstract: A new HPLC-DAD method for separation and identification of the main phenolics present in in vivo and in vitro biomass of Hypericum perforatum and Hypericum androsaemum has been developed. This method accomplished the direct identification of 22 compounds including flavonoids, hypericins, phloroglucinols, and phenolic acids. The HPLC profiles obtained in the course of this work clearly evidenced a distinct phenolic production between in vivo and in vitro biomass. For example calli and suspended cells produced mainly xanthones while in in vivo plants of both species these compounds were not detected. Some luteolin flavone type compounds were identified in calli and suspended cells of H. perforatum while quercetin was found in suspended cells of H. androsaemum. Flavonoids, namely those related to quercetin, were the major metabolites in methanolic extracts from in vivo plants. Hypericins were detected in in vivo plants and in in vitro shoots of H. perforatum but not in calli or suspended cells of the same sp...
54 citations
TL;DR: To meet the requirement of quantitative analysis, this work re-investigated the parameters relevant to the separation of seven fluoroquinolone antibacterials, ciprofloxacin, enoxac in, lomefloxain, norfloxACin, ofloxacIn, peflox ACin, and sparfloxAcin, based on the method developed previously in the laboratory.
Abstract: To meet the requirement of quantitative analysis, this work re-investigated the parameters relevant to the separation of seven fluoroquinolone antibacterials, ciprofloxacin, enoxacin, lomefloxacin, norfloxacin, ofloxacin, pefloxacin, and sparfloxacin, based on the method developed previously in our laboratory. With the optimum conditions obtained: electro- phoretic media - 65 mM sodium borate, 35 mM sodium dihydrogen phosphate, 60 mM sodium cholate, pH 7.3 / acetonitrile (72 : 28, v/v); fused silica capillary - 50 μm I.D., total length 67 cm, detection length 52 cm; hydrodynamic injection - 60 mbar, 3 sec; voltage - 27 kV; temperature - 25°C and detection wavelength - 275 nm, the fluoroquinolones were well separated within 8.5 min. After being validated the method was used for the assay of the formulation products. The assay results were within 95∼105 % of their label claims. The method should be applicable to the analysis of these and other similar formulation products containing these drugs.
50 citations
TL;DR: In this paper, a rapid analytical method is proposed for the determination of PAHs (fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzos[e]pyrene, dibenzo [a,h]anthricene and benzo [g,h,i]perylene) in coffee brew samples, based on solid phase extraction with SepPak Vac tC-18 cartridges and elution with ethyl ether.
Abstract: A rapid analytical method is proposed for the determination of PAHs (fluoranthene, pyrene, benzo[a]anthracene, chrysene, benzo[e]pyrene, benzo[a]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene) in coffee brew samples The method is based on solid phase extraction with Sep-Pak Vac tC-18 cartridges and elution with ethyl ether The extracts were analyzed by RP-HPLC with a Green PAH column and fluorescence detection under an acetonitrile-water mobile phase gradient Some PAHs were detected in the samples studied and their mean contents were 165–287 ng/L coffee brew The relative standard deviations were in the range 2–13% for four replicates
TL;DR: This work suggests a strategy, which offers the possibility of having the first simple tool for ceramide structural identification in the absence of a ceramide standard, based on various theories: the linear progression of t'R in a linear gradient, methylene selectivity and the incrementation on homol...
Abstract: Ceramides constitute the major group of lipids in the Stratum Corneum where they play a crucial role in maintaining the water permeability barrier of the mammalian epidermis. Cutaneous ceramides are highly heterogeneous in structure. Consequently commercial standards of all these molecules are not available and no simple analytical system supports this magnitude at this time. Our work suggests a strategy, which offers the possibility of having the first simple tool for ceramide structural identification in the absence of a ceramide standard. The ceramide separation is done in NARP (non-aqueous reverse phase) liquid chrom-atography and the ceramide structural identification in GC/MS (gas chromatography / mass spectrometry). The correlation between these two methods establishes the retention behaviour of ceramides. This retention has been shaped into abacuses. This approach is based on various theories: the linear progression of t'R in a linear gradient, methylene selectivity and the incrementation on homol...
TL;DR: A review on the quantitative structure-retention relationship (QSRR) in TLC is given in this article, where the establishment of QSRR equations is described, which is based on physico-chemical parameters, non-specific parameters, topological indices, and a combination of physicochemical parameters.
Abstract: A review is given on the quantitative structure-retention relationship (QSRR) in TLC. The establishment of QSRR equations is described, which is based on physico-chemical parameters, non-specific parameters, topological indices, and a combination of physico-chemical parameters. The application of QSRR for prediction of retention, determination of lipophilicity, evaluation of some physico-chemical parameters of chemicals, evaluation of biological activity of compounds, and explanation of separation mechanisms are also reviewed.
TL;DR: In this paper, the molecular weight distributions of dissolved and residual lignins from different delignification phases during flow-through kraft cooking of birch have been studied and the fundamental characteristics of the isolated lignin samples were evaluated by size exclusion chromatography using lithium chloride/N,N-dimethylacetamide (LiCl/DMAc).
Abstract: The molecular weight distributions (MWDs) of dissolved and residual lignins from different delignification phases during flow-through kraft cooking of birch have been studied. The fundamental characteristics of the isolated lignin samples were evaluated and the lignins were characterised by size exclusion chromatography using lithium chloride/N,N-dimethylacetamide (LiCl/DMAc) not used for isolated lignin samples before. The MWDs of underivatized and acetylated samples were compared with the MWDs of acetylated samples obtained by using tetrahydrofuran (THF) as mobile phase in a similar chromatographic system. The results indicate that removal of pulp lignin during the initial phase of kraft cooking of birch is restricted partly because of the large size of the lignin polymer. However, at the end of the cook no such restrictions remain. The apparently larger molecular size obtained with the LiCl/DMAc-system compared to the THF-system, may be due to interactions between the polystyrene standards and column m...
TL;DR: In this paper, the retention behavior of substituent aliphatic carboxylic acids was evaluated on titania synthesized in this laboratory and compared with those of zirconia provided by the manufacturer.
Abstract: For demonstrating the presumption that on the hydrous zirconium oxide loaded porous polymer resin (Zr-gel) under alkaline pH the recognition of a position of hydroxyl or carboxyl group was ascribed to formation of a chelate ring, the retention behaviors of hydroxyl and other substituent aliphatic carboxylic acids were evaluated on titania synthesized in this laboratory and compared with those of zirconia provided by the manufacturer. The retention behavior supported the formation of chelate ring and suggested the priority of forming a five-membered ring. On comparison titania and zirconia, the distinct elution order was shown in retention behavior of 2-hydroxycarboxylic acids. It might be ascribed to the difference in the bond angle and distance between metal ion and two oxygen atoms of hydroxyl group and carboxylate anion on formation of chelate ring.
TL;DR: A review of HPLC methodologies for total vitamin C activity with references to their applications mainly in citrus juices and related drink products can be found in this paper, where the authors define the total activity as the sum of both reduced and oxidized forms of vitamin C.
Abstract: The reduced form of vitamin C is referred to as L-ascorbic acid (AA), and the oxidized form is referred to as L-dehydroascorbic acid (DHAA). In humans, both forms are biologically active. The total vitamin C activity is defined as the sum of both forms. This review discusses HPLC methodologies for total vitamin C activity with references to their applications mainly in citrus juices and related drink products.
TL;DR: In this paper, a novel separation method for macromolecules, viz. liquid chromatography under limiting conditions of adsorption (LC LCA), is presented, where the column packing attracts macromoles and, if the sample were dissolved and injected in eluent, it would be retained within column.
Abstract: A novel separation method for macromolecules, viz. liquid chromatography under limiting conditions of adsorption (LC LCA), is presented. LC LCA is designed for discrimination of complex polymers. It combines exclusion and adsorption mechanisms so that they mutually compensate. This results in the absence of separation of macromolecules according to their size or molar mass. In LC LCA, the eluent is a liquid moderately promoting adsorption of polymer species. The column packing attracts macromolecules and, if the sample were dissolved and injected in eluent, it would be retained within column. Therefore, the polymer is injected in a solvent that effectively suppresses adsorption. Experimental conditions can be identified with regard to the eluent, column packing, temperature as well as sample solvent, and injected sample volume under which macromolecules of various molar masses are eluted together with their initial solvent. in this way, binary polymer blends, with components exhibiting different adsorptiv...
TL;DR: Application of the HPLC method to chondroitin sulfate and dermatan sulfate revealed that the first uronic acid after the -Gal-Gal-Xyl linkage trisaccharide is always glucuronic acid and the next galactosamine res...
Abstract: The linkage-region oligosaccharides of chondroitin sulfate and dermatan sulfate, produced by the action of various chondroitinases, as well as of heparan sulfate, produced by the combined action of heparin-lyases I, II, and III, have been separated and characterized according to their size, number of sulfate residues, and the presence of phosphorylated xylose by HPLC. Glycosaminoglycans and/or proteoglycans were treated by tritiated borohydride and the [3H]-labeled xylitole-containing glycan chains were degraded by the various chondro/dermato-lyases (chondroitinases ABC, AC and B) and/or heparin-lyases. The produced linkage-region Δ-oligosaccharides have been completely separated by ion-pair reversed phase HPLC, using tetrabutylammonium as ion-pairing reagent, and detected by a radiochemical detector. Application of the method to chondroitin sulfate and dermatan sulfate revealed that the first uronic acid after the -Gal-Gal-Xyl linkage trisaccharide is always glucuronic acid and the next galactosamine res...
TL;DR: The structural composition of sardine oil triacylglycerols (TAGs) has been studied in this paper, with the result of 65 chromatographic peaks resolved.
Abstract: The nutritional benefits attributed to fish oils have been the basis for the study of the structural composition of Sardine oil triacylglycerols (TAGs). TAGs were separated reversed-phase high performance liquid chromatography (RP-HPLC) with the result of 65 chromatographic peaks resolved. The problem of identification was avoided by the use of two more chromatographic techniques. Separation of the sardine oil TAGs into fractions by silver-ion thin layer chromatography (TLC) and its subsequent fatty acid analysis by gas chromatography allowed identification of 59 of the 65 chromatographic peaks. From those peaks, the major was trimyristin (MMM), with 8.22 % of the total. Dioleoyl-acyl-glycerol (OPO, OOE), dipalmitoyl-acyl-glycerol (PPO, PPPo), dipalmitoleoyl-acyl.glycerol (PoPoO) and dieicosapentaenoyl-acyl-glycerol (EEP) species were found in important amounts.
TL;DR: In this paper, a simple and rapid isocratic high-performance liquid chromatographic method has been developed for the simultaneous analysis of the non-steroidal anti-inflammatory drugs tenoxicam, piroxicam, meloxicam and lornoxicam using isoxicam as an internal standard.
Abstract: A simple and rapid isocratic high-performance liquid chromatographic method has been developed for the simultaneous analysis of the non-steroidal anti-inflammatory drugs tenoxicam, piroxicam, meloxicam, and lornoxicam using isoxicam as an internal standard. The analyte was chromatographed using a Lichrosphere RP18 column, a Tris acetic acid buffer-tetrabutylammonium reagent-tetrahydrofuran-acetonitrile as the mobile phase, and UV detection at 360 nm. The separation obtained was very good. The method was applied to pharmaceutical formulations containing a single active ingredient and was shown to be linear, sensible, accurate, and reproducible. A very small modification of the mobile phase enabled the separation of tenoxicam, piroxicam, isoxicam, cinnoxicam,meloxicam, and lornoxicam with symmetrical and well resolved peaks.
TL;DR: In this paper, a solid phase extraction procedure using strong cation exchange (SCX, benzenesulfonic acid) cartridges followed by a reversed-phase HPLC assay was applied to the analysis of hyoscine n-butylbromide and lidocaine hydrochloride in injection forms.
Abstract: A solid phase extraction procedure using strong cation exchange (SCX, benzenesulfonic acid) cartridges followed by a reversed-phase HPLC assay was applied to the analysis of hyoscine n-butylbromide and lidocaine hydrochloride in injection forms. The chromatographic separation was performed on a BDS C-18 column. The mobile phase consisted of a mixture of acetonitrile: ammonium acetate 0.2M, (30:70, v/v) pumped at a flow rate 1.2 mL/min. The UV detector was operated at 254 nm. A UV-Vis spectrophotometric method was also developed for the determination of paracetamol in the injection forms. The method consists of subsequent dilution of the injection forms and measure of the absorbance value at 242.7 nm. Relative standard deviation was less than 0.95% for HPLC and less than 0.78% for the spectrophotometric method. Detection limits were 1.05, 0.96 and 0.67 μg/mL for hyoscine n-butylbromide, lidocaine hydrochloride and paracetamol, respectively.
TL;DR: A “quick” HPLC method using a diode array detector for the spectral analysis and quantitation of adenosine and its derivatives in less than two hours following sampling, providing values that are on average 30% higher than those obtained with the classical method.
Abstract: Assays of adenosine and its derivatives in biological fluids involve fluorimetric, radioimmunological or chromatographic analyses. Techniques currently used are tedious because they involve either an extraction using immunological methods or one or two freeze drying cycles when using high performance liquid chromatography (HPLC). In this context, we describe a “quick” HPLC method using a diode array detector for the spectral analysis and quantitation of adenosine and its derivatives in less than two hours following sampling. We compared our results to those obtained with an HPLC technique coupled to UV detection. Although there is a good correlation between the two techniques, the“quick” method provide values that are on average 30% higher than those obtained with the classical method. The absence of a lyophilization step in the classical method could explain this difference. The utilization of an HPLC system coupled to a diode array detector leads to a rapid and reliable assay of adenosine and its deriva...
TL;DR: In this article, the mass spectra obtained at different voltages of the sample cone have been used to build a library of citrus essential oils (lemon, mandarin, sweet orange, bitter orange, bergamot, grapefruit, and lime).
Abstract: The oxygen heterocyclic compounds (coumarins, psoralens, and polymethoxylated flavones (PMFs)) present in citrus essential oils (lemon, mandarin, sweet orange, bitter orange, bergamot, grapefruit, and lime) were analysed by an HPLC-MS system equipped with an APcI source. The mass spectra obtained at different voltages of the “sample cone” have been used to build a library. Citrus essential oils have been analysed with this system, using an optimised normal phase HPLC method, and the mass spectra were compared with those of the home made library. This method allowed the rapid identification and the characterisation of the oxygen heterocyclic compounds of citrus oils, the detection of some minor components for the first time in some oils, and the detection of authenticity and possible adulteration of the oils.
TL;DR: The efficiency of silver ion and reversed-phase thin layer chromatography in the analysis of triacylglycerols is discussed in this paper and examples are presented that demonstrate the achievements of thin-layer Chromatography in elucidating the triplets structure of natural and modified lipid samples.
Abstract: The efficiency of silver ion and reversed-phase thin layer chromatography in the analysis of triacylglycerols is discussed in this paper. The experimental conditions that allowed for the conversion of these techniques into full-scale quantitative analytical methods are presented and details of the respective protocols are given. Examples are presented that demonstrate the achievements of thin-layer chromatography in elucidating the triacylglycerol structure of natural and modified lipid samples.
TL;DR: In this article, the direct resolution of nineteen structurally related racemic flavanones was evaluated by reversed-phase planar chromatography using both home-made microcrystalline cellulose triacetate (MCTA) layers and mobile phase modifiers, such as β-cyclodextrin and bovine serum albumin, on commercially available Sil C18-50/UV254 plates.
Abstract: The direct resolution of nineteen structurally related racemic flavanones was evaluated by reversed-phase planar chromatography using both home-made microcrystalline cellulose triacetate (MCTA) layers and mobile phase modifiers, such as β-cyclodextrin and bovine serum albumin, on commercially available Sil C18-50/UV254 plates. Except for the two glycosides, 5-methoxy-, 7-hydroxy- and 5-hydroxy-7-methoxyflavanone, the enantiomers of other flavanones were all resolved by at least one of the three chiral phases tested. Densitograms of racemic flavanones were measured on MCTA layers developed with alcohol-water mixtures and on Sil C18-50/UV254 plates after elution with chiral mobile phases.
TL;DR: A new procedure for the amino acid analysis of peptides has been devised utilizing high performance liquid chromatography (HPLC) with evaporative light scattering detection (ELSD), which eliminates the need for complex derivatization schemes inherent of previous amino acids analysis procedures.
Abstract: A new procedure for the amino acid analysis of peptides has been devised utilizing high performance liquid chromatography (HPLC) with evaporative light scattering detection (ELSD). This procedure eliminates the need for complex derivatization schemes inherent of previous amino acid analysis procedures since the ELSD detects the amino acids directly. This quantitative method detects and separates 18 of the common amino acids in a one hour run time using cation exchange chromatography coupled with ELSD. The procedure was tested by analyzing the hydrolysate of human parathyroid hormone 1–34 (PTH), a synthetic polypeptide. A standard digestion consisting of 24 hour hydrolysis at 110°C in 6 N hydrochloric acid with 3% phenol was used. Validation data reveal this is an accurate and precise procedure for the amino acid analysis of peptides. The sensitivity of this technique is low compared to other state-of-the-art analytical techniques. Detection limits varied depending on the amino acid being analyzed and were...
TL;DR: In this article, a method of analysis using high performance liquid chromatography (HPLC) was developed for the separation and quantitation of the metabolites of stevioside: steviol-16,17α-epoxide, 15α-hydroxysteviol, stevio-bioside, isosteviol and stebiol.
Abstract: A method of analysis using high performance liquid chromatography (HPLC) was developed for the separation and quantitation of the metabolites of stevioside: steviol-16,17α-epoxide, 15α-hydroxysteviol, steviolbioside, isosteviol, and steviol. The separation was carried out on a reversed-phase C18 Nova-Pack column with gradient elution of acetonitrile/water mixture. The applicability of the method was demonstrated in the detection and separation of stevioside and its metabolites found in blood, feces, and urine of hamsters after ingestion of stevioside.
TL;DR: In this article, the mechanism of chiral selectivity of a difunctional polymer imprinted with dansyl-L-phenylalanine was investigated using the polymer as an HPLC stationary phase.
Abstract: The mechanism of chiral selectivity of a difunctional polymer imprinted with dansyl-L-phenylalanine was investigated using the polymer as an HPLC stationary phase. Temperature studies revealed that the mass transfer of the imprinted enantiomer with the polymer was sluggish at low temperatures, leading to a non-equilibrium migration down the column. Conversely, retention of the non-imprinted enantiomer was controlled by a thermodynamic equilibrium over the entire temperature range of the study. Variation of the structure of the analyte indicated a single leading interaction between both enantiomers of dansyl-phenylalanine and the polymer phase; a hydrogen bonding interaction between the carboxylic acid group of dansyl-phenylalanine and pyridinyl sites on the polymer. Secondary processes contributing to enantioselectivity were also deduced; a hydrogen bonding interaction occurring between the imprinted enantiomer and carboxyl sites on the polymer and a precise steric fit of the amino acid side chain into th...
TL;DR: In this paper, the best mobile phase, benzene-chloroform-acetone-methanol (20:92.5:15:7.5) used twice over a distance of 15 cm was applied for isolation of analyzed taxoids by preparative TLC in connection with RP-HPLC.
Abstract: Many mobile phases, including solvent systems with one and two polar modifiers as well as some multiple development techniques and gradient elutions, were examined to select the best thin-layer chromatographic conditions on silica gel F254 plates for micropreparative isolation of 10-deacetylbaccatin III (10-DAB III), baccatin III, paclitaxel, and cephalomannine from methanolic extracts obtained from fresh and dried needles and stems of Taxus baccata L. In case of each solvent system and development technique, R F , k, and α values of 10-DAB III and paclitaxel were determined as well as the separation of compounds coextracted with taxoids, and the whole yew extract. The best mobile phase, benzene-chloroform-acetone-methanol (20:92.5:15:7.5) used twice over a distance of 15 cm was applied for isolation of analyzed taxoids by preparative TLC in connection with RP-HPLC, (C-18) quantitative determination using two mobile phases (30% acetonitrile in water to measure of 10-DAB III levels and 50% acetonitrile in ...
TL;DR: In this paper, the enantioselectivity of the amylose tris(3,5-dimethoxyphenyl carbamate) phase towards some β-blockers was investigated.
Abstract: The enantioselectivity of the amylose tris(3,5-dimethoxyphenyl carbamate) phase towards some β-blockers was investigated. A sensitive HPLC method was developed for the enantiomers of metoprolol and betaxolol. The validated methods were suitable for the analysis of enantiomeric composition in a variety of pharmaceutical formulations of both drugs.