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Carmen W Huie

Publications and source records attributed to Carmen W Huie.

18 recordsLinked to original sources
PubMed2006

Enantiomeric separation and quantification of ephedrine-type alkaloids in herbal materials by comprehensive two-dimensional gas chromatography.

The separation of ephedrine-type alkaloids and their enantiomers in raw herbs and commercial herbal products was investigated by carrying out enantioselective separation in the first-dimension column (containing beta-cyclodextrin as the chiral selector) of a comprehensive two-dimensional gas chromatography (GC x GC) system, whereas a polar polyethylene glycol capillary column was used for separation in the second dimension. Naturally occurring ephedrine-type alkaloids and their synthetic analogues (enantiomeric counterparts) were adequately resolved from each other, as well as from potential interference species in the sample matrix using GC x GC, whereas single column GC analysis was unable to separate all the alkaloids of interest. Detection limits in the order of 0.1-1.3 microg/mL and linearity of calibration with R(2)>or=0.999 over approximately the range of 0.5-100 microg/mL for the quantitative determination of various ephedrine-type alkaloids were obtained. The commercial herbal products tested contained mostly (-)-ephedrine, (+)-pseudoephedrine, (-)-N-methylephedrine and (-)-norephedrine, with concentrations in the range of 40-2100, 0-1,300, 15-300 and 0-30 microg/g of the product, respectively, and repeatability of analysis was generally in the range of 1-5%. The present GCxGC method is effective and useful for the determination of the dosage levels of the principle ephedrine-type alkaloids in commercial health supplements and complex raw herb formulations, as well the differentiation of ephedrine-containing products that were derived from natural plant or synthetic sources, e.g., simply by visualizing the presence or absence of the enantiomeric pairs of (+/-) ephedrine and (+/-)-N-methylephedrine in the GC x GC chromatograms.

Alkaloids↗
PubMed2006

Recent applications of microemulsion electrokinetic chromatography.

Compared to MEKC, the presence of a water-immiscible oil phase in the microemulsion droplets of microemulsion EKC (MEEKC) gives rise to some special properties, such as enhanced solubilization capacity and enlarged migration window, which could allow for the improved separation of various hydrophobic and hydrophilic compounds, with reduced sample pretreatment steps, unique selectivities and/or higher efficiencies. Typically, stable and optically clear oil-in-water microemulsions containing a surfactant (SDS), oil (octane or heptane), and cosurfactant (1-butanol) in phosphate buffer are employed as separation media in conventional MEEKC. However, in recent years, the applicability of reverse MEEKC (water-in-oil microemulsions) has also been demonstrated, such as for the enhanced separation of highly hydrophobic substances. Also, during the past few years, the development and application of MEEKC for the separation of chiral molecules has been expanded, based on the use of enantioselective microemulsions that contained a chiral surfactant or chiral alcohol. On the other hand, the application of MEEKC for the characterization of the lipophilicity of chemical substances remains an active and important area of research, such as the use of multiplex MEEKC for the high-throughput determination of partition coefficients (log P values) of pharmaceutical compounds. In this review, recent applications of MEEKC (covering the period from 2003 to 2005) are reported. Emphases are placed on the discussion of MEEKC in the separation of chiral molecules and highly hydrophobic substances, as well as in the determination of partition coefficients, followed by a survey of recent applications of MEEKC in the analysis of pharmaceuticals, cosmetics and health-care products, biological and environmental compounds, plant materials, and foods.

Animals↗
PubMed2006

Fluorescence imaging of sample zone narrowing and dispersion in a glass microchip: the effects of organic solvent (acetonitrile)-salt mixtures in the sample matrix and surfactant micelles in the running buffer.

A mismatch in the EOF velocities between the sample zone and running buffer region is known to generate pressure-driven, parabolic flow profile of the sample plug in electrokinetic separation systems. In the present study, video fluorescence microscopy was employed to capture real-time dynamics of the sample plug (containing fluorescein as the probe molecule) in a discontinuous conductivity system within a glass microchip, in which the sample matrix consisted of a mixture of ACN and salt (NaCl), and the running buffer contained sodium cholate (SC) micelles as the pseudo-stationary phase (i.e., performing "ACN stacking" in the mode of MEKC). Upon application of the separation voltage, the video images revealed that zone narrowing and broadening of the probe molecules occurred as the sample plug headed toward the cathode during the initial time period, probably resulting in part from the stacking/sweeping, and destacking of the SC micelles at the boundaries between the sample zone and running buffer. Interestingly, a second sample zone narrowing event can be observed as the sample plug moved further toward the cathode, which could be attributed to the sweeping of the slower moving probe molecules by the faster moving SC micelles that originated from the anode. This phenomenon was studied as a function of pH, sample plug length, as well as the concentration of organic solvent and salt in the sample matrix. The data suggested that the presence of large amounts of an organic solvent (such as ACN or methanol) and salts in the sample matrix not only induces sample dispersion due to the formation of a pressure-driven (hydrodynamic) flow, but may also lead to the formation of a double sample zone narrowing phenomenon by altering the local EOF dynamics within the separation system.

Acetonitriles↗
PubMed2006

Coupling of acetonitrile deproteinization and salting-out extraction with acetonitrile stacking for biological sample clean-up and the enrichment of hydrophobic compounds (porphyrins) in capillary electrophoresis.

A new sample pretreatment approach in CE was developed for concurrent biological sample clean-up and the concentration of hydrophobic compounds based on the combination of ACN deproteinization with salting-out extraction. Further enhancement in concentration detection sensitivity was achieved by coupling (offline) salting-out extraction with an online CE sample enrichment technique known as "ACN stacking". By optimizing the pH of salting-out extraction, a number of model compounds (hydrophobic porphyrins with clinical significances), i.e. zinc-protoporphyrin, protoporphyrin, and coproporphyrin (CP) III and I, can be efficiently extracted from the aqueous sample into a smaller volume organic solvent (ACN) phase and an enrichment factor of ca. 100 can be obtained. The pressure injection of the enriched ACN phase (containing ca.1% NaCl) into the CE capillary at 10% capillary volume resulted in additional concentration of the various hydrophobic porphyrins, allowing for a combined enrichment factor of ca.1000 to be obtained. Calibration curves obtained for the determination of a pair of positional isomers with significant diagnostic value, urinary CPIII and CPI, were found to be linear between 10-300 ng/mL (with R2 = 0.999), and LODs (absorbance detection at 400 nm) were ca. 0.8 ng/mL (1.1 nmol/L of CPIII or CPI). Based on a single salting-out extraction, intraday precisions (nine consecutive injections) for both CPIII and CPI (at spiked concentrations of 10-300 ng/mL into urine) in terms of migration time and peak area were found to be within the range of 0.2-0.5 and 0.8-2.9%, respectively.

Acetonitriles↗
PubMed2005

Microemulsion and micellar electrokinetic chromatography of Hematoporphyrin D: a starting material of hematoporphyrin derivative.

An investigation of the basic factors which govern the microemulsion electrokinetic chromatography (MEEKC) and micellar electrokinetic chromatography (MEKC) separation of Hematoporphyrin D and its base hydrolysis product, hematoporphyrin derivative (HpD), was performed. These model compounds contain a complex mixture of porphyrin monomers, dimers and/or oligomers, and were utilized to gain insights into the MEEKC/micellar electrokinetic chromatography (MEKC) separation of samples containing highly lipophilic substances. For example, the organic modifier/cosurfactant (1-butanol) and/or oil phase (e.g., 1-octanol in comparison to ethyl acetate) were found to have an apparent influence on the separation selectivity of Hematoporphyrin D, the extent of which was dependent on the chemical nature of the surfactant employed (e.g., sodium dodecyl sulfate vs. sodium cholate). An interesting and important finding was that the presence of an organic modifier (methanol or acetonitrile at a concentration of 20% or higher) in the sample matrix as well as in the run buffer was essential for the optimal MEEKC or MEKC separation of a number of porphyrin monomers (including hematoporphyrin IX and its acetates, most likely hydroxyacetate, diacetate, and vinyl acetate, as well as its dehydration products, hydroxyethylvinyldeuteroporphyrin and protoporphyrin) contained in Hematoporphyrin D. On the other hand, the use of these optimized conditions for the MEEKC or MEKC separation of various oligomeric porphyrin species in HpD were unsatisfactory. As HpD is a well-known and effective photosensitizing agent in photodynamic therapy (a new approach for cancer treatment), the improved separation and characterization of various monomeric and oligomeric porphyrin species in HpD and its starting material, such as Hematoporphyrin D, is a challenging and important task.

1-Butanol↗
PubMed2005

Investigation of solvent effects in capillary electrophoresis for the separation of biological porphyrin methyl esters.

The effects of organic solvents on the capillary electrophoresis (CE) separation of a number of important biological porphyrin methyl esters - six weakly basic, hydrophobic cyclic tetrapyrroles possessing two and four to eight methyl ester groups around the periphery of the porphyrin ring - were investigated in the mode of micellar electrokinetic chromatography (MEKC), microemulsion electrokinetic chromatography (MEEKC), and nonaqueous CE. In aqueous MEKC, partial separation of the six neutral porphyrin methyl esters was obtained with an organic modifier (acetonitrile) in the concentration range between 20 and 40%, in which sodium dodecyl sulfate (SDS) molecules might be present in the form of SDS micelles and/or SDS micelle-like aggregates. Relatively stable SDS micelles can be formed in nonaqueous MEKC using formamide as the separation medium, but the separation of the target analytes remained unsatisfactory. Improved resolution of all six porphyrin methyl esters was obtained using MEEKC with the running buffer consisting of 0.8% w/w n-heptane (oil phase), 2.25% w/w SDS and 1.0% w/w Brij 35 (mixed surfactant), 6.6% w/w 1-butanol (cosurfactant), and 30% v/v 2-propanol (second cosurfactant), but reproducibility in terms of peak areas for certain porphyrins (especially uroporphyrin I octamethyl ester) was found to be very poor. Best separation performances were achieved with nonaqueous CE separations in which the weakly basic porphyrin methyl esters were protonated under strongly acidic conditions (e.g., using 10 mM perchloric acid) in mixed organic solvents. For example, using a 50:50 mixture of methanol and acetonitrile as the separation medium, baseline separation of all six (positively charged) porphyrin methyl esters can be obtained within 3 min and the average precision (RSD, N = 13) in terms of migration time and peak area were 0.55 and 2.16%, respectively.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2004

Chromatographic and electrophoretic methods for Lingzhi pharmacologically active components.

Lingzhi is the Chinese name given to the Ganoderma family of mushrooms, which was considered the most valuable medicine in ancient China and was believed to bring longevity, due to its mysterious power of healing the body and calming the mind. Today, Lingzhi is still widely revered as a valuable health supplement and herbal medicine worldwide, as studies (mostly conducted in China, Korea, Japan and the United States) into the medicinal and nutritional values of Lingzhi revealed that it does indeed contain certain bioactive ingredients (such as triterpenes and polysaccharides) that might be beneficial for the prevention and treatment of a variety of ailments, including important diseases such as hypertension, diabetes, hepatitis, cancers, and AIDS. As research into the biological activities of Lingzhi, as well as the quality assurance and quality control of Lingzhi products, require the isolation/purification of active ingredients from Lingzhi, followed by subsequent analytical and/or preparative separations, the present review summarizes the various chromatographic and electrophoretic methods (as well as sample pretreatment methods) typically employed to achieve such extraction/separation procedures.

Alkaloids↗
PubMed2004

Separation of enantiomers in microemulsion electrokinetic chromatography using chiral alcohols as cosurfactants.

A novel chiral microemulsion, which involved the use of chiral alcohols as cosurfactants, was demonstrated for the enantiomeric separation of a number of pharmaceutical drugs in microemulsion electrokinetic chromatography (MEEKC). The chiral alcohols investigated were optically active 2-alkanols, with the alkyl chain length having carbon number ranging from 4 to 7. The data indicated that, except for R-(-)-2-butanol, the use of R-(-)-2-pentanol, R-(-)-2-hexanol or R-(-)-2-heptanol as the chiral cosurfactant resulted in the baseline or partial resolution of most of the test solutes, i.e., (+/-)-norephedrine, (+/-)-ephedrine, DL-nadolol, and DL-propranolol. In addition to the chain length of the chiral 2-alkanols, the effects of other experimental conditions, such as the concentration and chirality of the 2-alkanols, as well as the pH of the run buffer and the oil phase of the microemulsion, on the enantiomeric separation of the test solutes were also investigated. An interesting finding was that the water-immiscible organic solvent (oil core) within the microemulsion droplets appeared to play an important role in the chiral separation mechanism. Also, the importance of hydrogen bonding between the test solutes ((+/-)-ephedrine and related compounds) and the chiral microemulsion was demonstrated, as it was not possible to resolve a pair of enantiomers which lacked a beta-amino proton (i.e., (+/-)-N-methyl ephedrine) under optimized run buffer conditions (e.g., 5.0% R-(-)-2-hexanol, 0.8% n-octane, and 3.5% SDS in 90.7% borate buffer at pH 9.2).

Chromatography, Micellar Electrokinetic Capillary↗
PubMed2004

Application of headspace solid-phase microextraction (HS-SPME) and comprehensive two-dimensional gas chromatography (GC x GC) for the chemical profiling of volatile oils in complex herbal mixtures.

The coupling of headspace solid-phase microextraction (HS-SPME) with comprehensive two-dimensional gas chromatography (GC x GC) was shown to be a powerful technique for the rapid sampling and analysis of volatile oils in complex herbal materials. When compared to one-dimensional (1-D) GC, the improved analytical capabilities of GC x GC in terms of increased detection sensitivity and separation power were demonstrated by using HS-SPME/GC x GC for the chemical profiling (fingerprinting) of essential/volatile oils contained in herbal materials of increasing analytical complexity. More than 20 marker compounds belonging to Panax quinquefolius (American ginseng) can be observed within the 2-D contour plots of ginseng itself, a mixture of ginseng and another important herb (P. quinquefolius/Radix angelicae sinensis), as well as a mixture of ginseng and three other herbs (P. quinquefolius /R. angelicae sinensis/R. astragali/R. rehmanniae preparata). Such analytical capabilities should be important towards the authentication and quality control of herbal products, which are receiving increasing attention as alternative medicines worldwide. In particular, the presence of Panax in the herb formulation could be readily identified through its specific peak pattern in the 2-D GC x GC plot.

Chromatography, Gas↗
PubMed2003

Fingerprint profiling of acid hydrolyzates of polysaccharides extracted from the fruiting bodies and spores of Lingzhi by high-performance thin-layer chromatography.

Modern extraction and planar chromatographic instrumentation were employed for the fingerprint profiling of carbohydrates from an important and popular medicinal mushroom commonly known as Lingzhi. For the first time, the feasibility of employing the high-performance thin-layer chromatography (HPTLC) peak profiles (fingerprints) of carbohydrates for the screening of various Lingzhi species/products was demonstrated. An analytical procedure was developed such that upon acid hydrolysis of the polysaccharides extracted from various Lingzhi samples, fingerprint profiles that reveal the relative amounts of the degradation products, such as mono- and oligosaccharides, can be obtained using HPTLC plates (Si 50000) for separation and 4-aminobenzoic acid as the post-chromatographic derivatization reagent for detection. Also, using automated multiple development (AMD), the acid hydrolyzates from Lingzhi, consisting of simple and more complex sugars, can be separated simultaneously with high degree of automation. An important finding was that unique fingerprint patterns were observed in the monosaccharide profiles between two highly valued Lingzhi species, Ganoderma applanatum and Ganoderma lucidum, under total or partial acid hydrolysis conditions. Additionally, the HPTLC fingerprint profiles of carbohydrates were obtained from the extracts of the spores and fruiting bodies of Lingzhi and compared.

Acids↗
PubMed2003

Pressurized liquid extraction of active ingredients (ginsenosides) from medicinal plants using non-ionic surfactant solutions.

The feasibility of employing aqueous non-ionic surfactant solutions as an alternative solvent system in pressurized liquid extraction (PLE) is demonstrated for the first time using the roots of American ginseng as model solid samples. When compared to the use of pure water or methanol, the presence of a common non-ionic surfactant (Triton X-100) in water at a concentration above its critical micelle concentration was shown to enhance the amount of pharmacologically active ingredients (ginsenosides) extracted from ginseng roots. The advantages of using aqueous non-surfactant solutions were also demonstrated by comparing extraction performances between ultrasonic-assisted extraction and PLE methods. Furthermore, the combination of PLE and cloud point extraction was shown to be a new and effective approach for the rapid sample preconcentration of herbal materials prior to analysis by high-performance liquid chromatography.

Chromatography, High Pressure Liquid↗
PubMed2003

Effects of organic solvents on sample pretreatment and separation performances in capillary electrophoresis.

A review of recent developments in theoretical as well as application studies concerning the use of organic solvents, either as purely nonaqueous solvents, hydro-organic mixtures, or a combination of an organic solvent with another organic modifier(s), in the sample matrix and/or separation buffer for effecting sample pretreatment and/or improving separation performances in capillary electrophoresis (CE) is presented. In particular, recent advances made in furthering the basic understanding of selectivity changes that occur in capillary zone electrophoresis due the presence of organic solvents in the separation medium, based on in-depth studies of fundamental processes, such as acid-base chemistry, ion-ion and ion-solvent interactions, were discussed in detail. The utilization of organic solvents for improving the resolution of highly challenging and important separations, i.e., those involving the separation of positional and optical isomers, was also critically reviewed. Furthermore, a comprehensive survey of the use of organic solvents for on-line sample pretreatment, e.g., minimizing aggregation and maximizing solubilization of hydrophobic analytes, improving concentration detection sensitivity for analytes via the use of sample stacking, was presented and discussed. Moreover, recent applications involving the use of organic solvents for improving the CE separations of a variety of molecular species with significance in various disciplines, including biological, environmental and pharmaceutical areas, were summarized and tabulated.

Electrophoresis, Capillary↗
PubMed2003

Investigation of the effects of wall adsorption of the visualization agent on baseline noise characteristics for indirect UV detection in capillary electrophoresis.

New insights into the effects of the wall adsorption of the visualization agent on baseline noise characteristics in indirect UV detection in capillary electrophoresis were provided. When compared to relatively small, hydrophilic cationic (1-(4-pyridyl)pyridinium chloride hydrochloride) or anionic chromophores (bromide and benzoate), the use of a UV-absorbing long-chain cationic surfactant (benzyldimethylhexadecylammonium chloride) as a probe (visualization agent) for studying baseline noise characteristics as a function of various experimental conditions, such as applied voltage, pH or buffer composition, was found to provide noise data that were very different under certain conditions. For cationic visualization agents that have a strong tendency of adsorbing onto the capillary surfaces due to electrostatic and/or hydrophobic interactions, it appeared that the interplay of both thermal as well as adsorption/desorption events occurring within the capillary is likely responsible for a fluctuation of the visualization agent concentration at the detector.

Acetonitriles↗
PubMed2003

Stacking and separation of enantiomers by acetonitrile-salt mixtures in micellar electrokinetic chromatography.

The feasibility of employing the "acetonitrile stacking" method in micellar electrokinetic chromatography (MEKC) for the on-line preconcentration and separation of enantiomers is demonstrated for the first time. The effects of various experimental parameters on the stacking and separation of three different pairs of optical isomers, i.e., two substituted naphthyl enantiomers and one dansylated-DL-amino acid, were examined. In particular, the effectiveness of the addition of acetonitrile and salt in the sample matrix to induce narrowing of the analyte bands was investigated in the presence of sodium cholate as the chiral surfactant micelle in the separation buffer. For example, it was found that the presence of both acetonitrile and 1% NaCl in the sample matrix (volume ratio = 2:1) led to a significant improvement of the peak height and resolution for the MEKC separation of a pair of R(-)/S(+)-1,1'-binaphthyl diyl hydrogen phosphate enantiomers when the injection sample size was relatively large (e.g., 12% capillary volume). Furthermore, the feasibility of combining salting-out solvent extraction (off-line) and acetonitrile stacking (on-line) as a novel approach for sample preconcentration in capillary electrophoresis was also demonstrated.

Acetonitriles↗
PubMed2003

Simultaneous determination of copper(II) and cobalt(II) by ion chromatography coupled with chemiluminescent detection.

In the absence of any special luminescent reagents, a weakly chemiluminescent emission was observed during the decomposition of hydrogen peroxide, catalyzed by transition-metal ions, such as Cu(II) and Co(II), in basic aqueous solution. The chemiluminescent intensity was significantly enhanced by the addition of ethyldimethylcetylammonium bromide and uranine. The signal-to-noise ratio (S/N) was proportional to the concentrations of Cu(II) and Co(II). Based on these phenomena, a flow-injection chemiluminescent method for the simultaneous separation and determination of Cu(II) and Co(II) was developed. The detection limits of the present chemiluminescent method for Cu(II) and Co(II) were 7.5 and 0.01 ng/ml, respectively. After ion chromatographic separation of Cu(II) and Co(II) by an IonPac CS5A column with oxalic acid and lithium hydroxide monohydrate as the eluent, the present chemiluminescent system was used as a post-column detector for these two transition metal ions in natural water samples.

Journal Article↗
PubMed2002

A review of modern sample-preparation techniques for the extraction and analysis of medicinal plants.

Sample preparation is the crucial first step in the analysis of herbs. In recent years there has been increasing interest worldwide in the use of alternative/herbal medicine for the prevention and treatment of various illnesses. Currently, however, quality-related problems (lack of consistency, safety, and efficacy) seem to be overshadowing the potential genuine health benefits of various herbal products. Thus, the development of "modern" sample-preparation techniques with significant advantages over conventional methods for the extraction and analysis of medicinal plants is likely to play an important role in the overall effort of ensuring and providing high-quality herbal products to consumers worldwide. In this article, recent developments and applications of modern sample-preparation techniques for the extraction, clean-up, and concentration of analytes from medicinal plants or herbal materials are reviewed. These modern techniques include solid-phase microextraction, supercritical-fluid extraction, pressurized-liquid extraction, microwave-assisted extraction, solid-phase extraction, and surfactant-mediated extraction.

Plant Extracts↗