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PubMed1976

Reverse-phase chromatography of polar biological substances: separation of catechol compounds by high-performance liquid chromatography.

Catecholamines and their metabolites have been separated isocratically by reverse-phase chromatography with aqueous (no organic solvent admixed) eluents. Unlike ion-exchange or ion-pair chromatography, mixtures of both acidic and basic substances can be separated in a single chromatographic run, because the retention is governed by hydrophobic interactions between the nonpolar moiety of the solute molecules and the octadecyl-silica stationary phase. The relative retention values strongly depend on the pH of the eluent, which governs the degree of dissociation of ionogenic solutes. The reproducibility of the results and the stability and efficiency of the chromatographic systems make this approach particularly attractive for use in clinical analysis.

3,4-Dihydroxyphenylacetic Acid↗
PubMed1993

Analysis of polycyclic aromatic hydrocarbon-DNA adducts by postlabelling with the weak beta-emitters 35S-phosphorothioate and 33P-phosphate, immobilized boronate chromatography and high-performance liquid chromatography.

The wide range of carcinogenic activities of optical isomers of bay-region diol-epoxides of polycyclic aromatic hydrocarbons (PAHs) demands analytical techniques capable of distinguishing both the diastereoisomer and enantiomers of the PAH diol-epoxide (PAH-DE) responsible for DNA adduct formation. Our laboratory recently developed postlabelling procedures using the radioisotope 35S for HPLC analysis of benzo[a]pyrene (BaP)-DNA adducts formed in BaP-treated hamster cell cultures. To allow identification and complete separation of anti-PAH-DE-DNA adducts from syn-PAH-DE-DNA adducts, an immobilized boronate chromatography procedure was developed using a high-capacity boronate column. Analysis of 7,12-dimethyl-benz[a]anthracene (DMBA)-DNA adducts formed in treated hamster embryo cells by this boronate chromatography procedure and 35S-postlabelling demonstrated that both anti- and syn-DMBA-DE were bound to DNA. These analytical techniques also provided evidence that the potent carcinogen and environmental PAH dibenzo[a,l]pyrene was metabolized in cells to a DNA-binding intermediate with structural characteristics of an anti-PAH-DE. Conditions were also developed for using 33P-labelled ATP in the postlabelling assay. The use of [33P] instead of [35S]ATP offers the advantages of ease of labelling and greater sensitivity while still using a weak beta-emitter. The development of PAH-DNA adduct analysis techniques with improved sensitivity allows more detailed studies of how PAHs interact with DNA and how this leads to cancer induction.

9,10-Dimethyl-1,2-benzanthracene↗
PubMedDate not supplied

Comparison of cyclodextrin modified micellar electrokinetic capillary chromatography and reversed-phase liquid chromatography for separation of polycyclic aromatic hydrocarbons.

The elution mechanism of polycyclic aromatic hydrocarbons (PAHs) in cyclodextrin modified micellar electrokinetic capillary chromatography (CD-MEKC) has been compared to that in reversed-phase liquid chromatography (RPLC). The contribution of the inner surface of the capillary has been discussed mainly pertaining to the migration mechanism of PAHs. As a result, the C18-coated capillary can produce a separation field similar to that which is generally found in RPLC with the C18 alkyl bonded stationary phase, and the main migration mechanism is thought to be facilitated by the hydrophobic interaction between the solutes and the cyclodextrins (CDs). Very high linear relationships were found for log k1 versus log P in both CD-MEKC with the C18-coated capillary and RPLC with the C18 stationary phase using sodium dodecyl sulfate (SDS) as the mobile phase additive.

Chromatography, Liquid↗
PubMed1976

Application of gas-liquid chromatography and high-performance liquid chromatography to the analysis of trace amounts of salicylic acid, acetylsalicylic anhydride and acetylsalicylsalicylic acid in aspirin samples and aspirin formulations.

The gas-liquid chromatographic (GLC) determination of salicylic acid (SA) in 12 commercial acetylsalicylic acid (aspirin, ASA) samples and 12 ASA formulations is reported. The GLC determination of SA as an impurity in ASA, utilising methylation with methyl iodide in the presence of potassium carbonate, requires a column chromatographic separation of SA prior to derivatization. Trace amounts of SA in ASA have also been determined by high-performance liquid chromatography (HPLC) on a Sil-X-I adsorption column using light petroleum-ethyl acetate-acetic acid as the mobile phase. Acetylsalicylic anhydride (ASN) and acetylsalicylsalicylic acid (ASSA) were determined by HPLC on a reversed-phase C18 column with water-methanol mixtures as the mobile phase. GLC was also applied to the determination of ASN as an impurity in ASA formulations.

Anhydrides↗
PubMed1999

Quantitation of N epsilon-(dichloroacetyl)-L-lysine in proteins after perchloroethene exposure by gas chromatography-mass spectrometry using chemical ionization and negative ion detection followingimmunoaffinity chromatography.

An antibody specific to N epsilon-(dichloroacetyl)-L-lysine (DCA-Lys) was immobilized to immunoaffinity columns for the use in selective enrichment of dichloroacetylated proteins. These result from the reaction with dichlorothioketene the beta-lyase cleavage product of the perchloroethene metabolite S-(trichlorovinyl)-L-cysteine. Dichloroacetylated proteins from rat kidney mitochondria, rat plasma and human blood plasma were isolated after exposure to 40 ppm tetrachloroethene (PER) for 6 h. After acid hydrolysis of the protein fraction, DCA-Lys was derivatized with 1,3-dichloro-1,1,3,3-tetrafluoroacetone using N epsilon-(trifluoroacetyl)-L-lysine as internal standard. Recovery of dichloroacetylated reference proteins from immunoaffinity columns was about 73%. Samples were analyzed by GC-MS with chemical ionization and negative ion (NCI) detection showing DCA-Lys in proteins with 2.26 (+/- 0.02) pmol/mg protein in male rat kidney mitochondria and 1.92 (+/- 0.05) pmol/mg total mitochondrial protein in female rats. In rat plasma 0.47 (+/- 0.006) pmol DCA-Lys/mg protein in male and 0.34 (+/- 0.02) in female animals were found. DCA-Lys could not be detected in blood plasma of human volunteers exposed to PER with a detection limit of 20 fmol for the DCA-Lys derivative 2,2-bis(chlorodifluoromethyl)-4-(1-dichloroacetamido)-butyl- 1,3-oxazolidine-5-one. Immunoaffinity chromatography with specific antibodies provides a powerful tool for the enrichment of minor quantities of dichloroacetyled proteins in biological samples for GC-NCI-MS analysis of the modified amino acid lysine having broad utility in the biomonitoring of PER exposure.

Adult↗
PubMed1989

Screening and confirmation of thyreostatics in urine by gas chromatography with nitrogen-phosphorus detection and gas chromatography-mass spectrometry after sample clean-up with a mercurated affinity column.

Methods are described for the screening and confirmation of residues of the thyreostatics thiouracil, methylthiouracil and propylthiouracil in urine samples of cattle at levels down to 25 micrograms/l. After a selective preconcentration of the thiol-containing thyreostatics on a mercurated affinity column, the analytes are derivatized by extractive alkylation and analysed by gas chromatography with nitrogen-phosphorus or mass spectrometric detection.

Animals↗
PubMed1997

Use of immobilized metal ion affinity chromatography and dye-ligand chromatography for the separation and purification of rainbow trout pituitary gonadotropins, GTH I and GTH II.

A new procedure is described for the purification of gonadotropic hormones (GTHs) from the pituitary glands of vitellogenic rainbow trout. The procedure utilizes immobilized metal ion affinity chromatography (IMAC) on a column containing immobilized iminodiacetic acid (Toyopearl AF Chelate) charged with Cu2+ ions as a critical step for the efficient separation of GTH I and GTH II. Further purification of both GTH fractions on Cibacron Blue F3GA immobilized on Toyopearl was followed by HPLC size-exclusion for GTH II. The resulting electrophoretically homogeneous preparations possessed a characteristic range of biological activity in the stimulation of steroidogenesis in vitro. N-Terminal sequences of the GTH I and GTH II subunits purified using reversed-phase HPLC revealed a high level of homology with those of GTH subunits found in three other salmonid fish species. In contrast to salmon GTH II, two different alpha-subunits were observed in trout GTH II. The cross-reactivity between GTH I and GTH II was studied in radioimmunoassay using antibodies against Chinook salmon GTH II beta-subunit and rainbow trout GTH I dimer.

Amino Acid Sequence↗
PubMed2003

Structural identification of nonvolatile dimerization products of glucosamine by gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, and nuclear magnetic resonance analysis.

The degradation profile of glucosamine bulk form stressed at 100 degrees C for 2 h in an aqueous solution was studied. Column chromatography of acetylated product mixture led to isolation of two pure compounds (1b and 2b) and a mixture of at least three isomers (3b). 1a and 2a were identified as 5-(hydroxymethyl)-2-furaldehyde (5-HMF) and 2-(tetrahydroxybutyl)-5-(3',4'-dihydroxy-1'-trans-butenyl)pyrazine, respectively, by utilizing a variety of analytical techniques, such as GC-MS, LC-MS, on-line UV spectrum, (1)H and (13)C NMR, and DEPT, as well as (1)H-(1)H COSY. 3a was identified as 2-(tetrahydroxybutyl)-5-(2',3',4'-trihydroxybutyl)pyrazine, commonly known as deoxyfructosazine. In addition, glucosamine solid dosage form was exposed to 40 degrees C/75% relative humility for 10 weeks. Methanol extract of glucosamine solid dosage form was analyzed after acetylation by LC-MS, resulting in degradants 3b and 4b. 3a and 4a were, therefore, determined as deoxyfructosazine and 2,5-bis(tetrahydroxybutyl)pyrazine (fructosazine), respectively. Furthermore, the mechanisms of formation of identified degradation products are proposed and briefly discussed.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Sample preparation improvement in polycyclic aromatic hydrocarbons determination in olive oils by gel permeation chromatography and liquid chromatography with fluorescence detection.

The determination of 15 polycyclic aromatic hydrocarbons (PAHs) in olive oil samples has been improved in order to obtain a fast methodology with a low limit of detection through the combination of liquid-liquid extraction with acetonitrile and preparative gel permeation chromatography (GPC) prior to the injection of purified extracts into a C18 column. Acetonitrile-water was used as the mobile phase with a gradient from 50 to 95%, w/w, acetonitrile in 30 min. The oven temperature was maintained at 15 degrees C, and fluorometric detection was made at a fixed excitation wavelength of 264 nm and variable, optimal emission wavelength for each analyte ranging from 352 nm for 11-H-benzo(b)fluorene to 500 nm for indeno(1,2,3-cd)pyrene. Recovery for all the compounds studied varied from 75 to 111%, and limit of detection values from 0.05 ng/g for benzo(k)fluoranthene to 0.48 ng/g for indeno(1,2,3-cd)pyrene, corresponding to 0.09 ng/g benzo(a)pyrene. Results were compared with those obtained by liquid-liquid extraction followed by a cleanup on silica and a direct GPC treatment of oil samples diluted in dichloromethane, 2 other methodologies that are appropriate for quantifying PAHs in olive oils. However, the proposed method improves the determination limits, reduces the time of analysis, and provides a highly stable baseline for sample chromatograms.

Acetonitriles↗
PubMed1997

Separation of cardiac glycosides by micellar electrokinetic chromatography and microemulsion electrokinetic chromatography.

The interest of micellar electrokinetic chromatography (MEKC) and microemulsion electrokinetic chromatography (MEEKC) for the resolution of four cardiac glycosides is demonstrated. First, the influence of some parameters on the resolution of the solutes in MEKC such as the concentration of the surfactant, pH, addition of organic modifiers and urea is discussed. Then, results are compared with those obtained in MEEKC using different microemulsion compositions. Results indicate that MEEKC possesses several advantages over MEKC for the separation of relatively hydrophobic compounds such as digitalic compounds. First, microemulsions allow a better manipulation of the migration time window and of the retention of the solutes. Moreover, efficiency is improved with shorter analysis time.

Acetyldigitoxins↗
PubMedDate not supplied

Differentiation of coloured inks of inkjet printer cartridges by thin layer chromatography and high performance liquid chromatography.

Document examiners are frequently asked to determine whether or not a colour printout has originated from a particular inkjet printer. The printer can rarely be identified unless some unique defects or irregularities of the printer are present on the printout. However, it is possible to decipher the make and/or model of the printer by comparing the ink-profile of the questioned printout with that of a seized inkjet printer cartridge or from one in a database. This paper presents an overview of a systematic approach to characterising and discriminating the inks of different inkjet printer cartridges using thin layer chromatography (TLC) and high pressure liquid chromatography (HPLC) with multi-wavelength ultra-violet/visible (UV/Vis) detection. Ink samples from 23 different inkjet printer cartridges (including originals and substitutes) of different brands and colour printouts, printed by known printers were examined with newly developed chromatographic methods. Subsequently, a database of the ink-profiles was generated. The methods provide a useful tool for discriminating coloured inks in inkjet printer cartridges of different brands.

Journal Article↗
PubMed2003

Initial characterization of humic acids using liquid chromatography at the critical condition followed by size-exclusion chromatography and electrospray ionization mass spectrometry.

Structural information on humic acids is difficult to obtain because of the heterogeneity of the acids. Herein liquid chromatography at the critical condition, LCCC, is used to provide a sorting mechanism for the diverse types of molecules contained in humic acids. The critical condition of polymers that are believed to model some subunit of the humic acid is determined. Humic acids from three different terrestrial sources (soil, compost, and peat) are then separated under these chromatographic conditions. The portion of the humic acid that has structure similar to that of the model polymer elutes at the retention volume of the critical condition of the model. Next, fractions are collected and further characterized. This detailed characterization includes high-efficiency size-exclusion chromatography and electrospray mass spectrometry. The size-exclusion chromatograms of the fractions were found to be markedly different from that of the original humic acid sample. This is strong evidence that the LCCC separation mechanism is different from size fractionation. The mass spectra of the humic acid fractions were also markedly different from those of the bulk humic acids previously reported. The mass spectra of specific fractions collected had repeating clusters of m/z values, which is more evidence that the critical condition separation is a powerful sort function.

Journal Article↗
PubMedDate not supplied

Hard modeling methods for the curve resolution of data from liquid chromatography with a diode array detector and on-flow liquid chromatography with nuclear magnetic resonance spectroscopy.

Hard modeling methods have been performed on data from high-performance liquid chromatography with a diode array detector (LC-DAD) and on-flow liquid chromatography with 1H nuclear magnetic spectroscopy (LC-NMR). Four methods have been used to optimize parameters to model concentration profiles, three of which belong to classical optimization methods (the simplex method of Nelder-Mead, sequential quadratic programming approach, and Levenberg-Marquardt method), and the fourth is the application of genetic algorithms using real-value encoding. Only classical methods worked well for LC-DAD data, while all of the methods produced good results when LC-NMR data were divided into small spectral windows of peak clusters and parameters were optimized over each window.

Journal Article↗
PubMed2001

Potential for the speciation of Zn using fast protein liquid chromatography (FPLC) and convective interaction media (CIM) fast monolithic chromatography with FAAS and electrospray (ES)-MS-MS detection.

Analytical procedures were developed for the speciation of Zn using fast protein liquid chromatography (FPLC), flame atomic absorption spectrometry (FAAS) and convective interaction media (CIM) fast monolithic chromatography with FAAS and electrospray (ES)-MS-MS detection. The investigation was performed on synthetic solutions (2 microg cm-3 Zn) of hydrated Zn2+ species and Zn complexes with citrate, oxalate and EDTA (ligand-to-Zn molar ratio 100:1) over a pH range from 5.4 to 7.4. It was found that Zn interacts with various buffers and the careful adjustment of the pH with diluted solutions of KOH is, therefore, required. FPLC separations were carried out on a Mono Q HR 5/5 strong anion-exchange column, applying an aqueous 1 mol dm(-3) NH4NO3 linear gradient elution over 15 min, at a flow rate of 1.0 cm3 min(-1). The separated Zn species were determined in 1.0 cm3 eluate fractions "off line" by FAAS. Speciation of Zn was also performed on a weak anion-exchange CIM DEAE fast monolithic disc by applying an aqueous 0.4 mol dm(-3) NH4NO3 linear gradient elution over 7.5 min, at a flow rate of 2.0 cm3 min(-1) and determination of the separated Zn species in 1.0 cm3 eluate fractions "off line" by FAAS. Zn-binding ligands in separated fractions were also characterized by electrospray (ES)-MS-MS analysis. The CIM DEAE disc was found to be more efficient in the separation of negatively charged Zn complexes than the Mono Q FPLC column. On the CIM DEAE disc Zn-citrate was separated from both Zn-oxalate and from Zn-EDTA. All these species were also separated from hydrated Zn2+, which was eluted with the solvent front. This method has an advantage over commonly used analytical techniques for the speciation of Zn which are only able to distinguish between labile and strong Zn complexes. Good repeatability of the measurements (RSD 2-4%), tested for six parallel determinations (2 microg cm(-3) Zn) of Zn-EDTA, Zn-citrate and Zn-oxalate was found at a pH of 6.4 on a CIM DAEA disc. The limit of detection (3s) for the separated Zn species was 10 ng cm(-3). The proposed analytical procedure was applied to the speciation of Zn in aqueous soil extracts and industrial waste water from a lead and zinc mining area.

Journal Article↗
PubMed2003

Stereodifferentiation of chiral compounds using reversed-phase liquid chromatography coupled with capillary gas chromatography.

A method is described for the enantiomeric quantitation of some chiral compounds via online coupling of reversed-phase liquid chromatography-gas chromatography. The evaluation of some variables affecting the experimentation (i.e., the packing material used in the interface, volume of the transferred fraction, desorption time, initial temperature of the interface, and purge time) makes it possible to optimize the recoveries obtained for some chiral terpenes and lactones using a capillary column of beta-cyclodextrin dissolved in OV-1701. The proposed method allows the enantiomeric analysis of aqueous matrices obtaining relative standard deviations lower than 9% and detection limits ranging from 0.26-0.93 ppm for the investigated compounds.

Journal Article↗
PubMed2006

[Preparative separation of aloin diastereoisomers by high-speed countercurrent chromatography combined with silica gel column chromatography].

Aloin, naturally a mixture of two diastereoisomers, aloin A and aloin B, is the major anthraquinone in aloe, and now served as one of the important control constituents in most of the commercial aloe products. High-speed countercurrent chromatography (HSCCC) combined with silica gel column chromatography was developed for the preparative separation of the two individual aloins. Aloin A (98%) and aloin B (96%) were obtained. Fast atom bombardment mass spectrometry (FAB-MS), 1H nuclear magnetic resonance (1H NMR) and GOESY (gradient-enhanced nuclear Overhauser effect spectroscopy) were employed for the elucidation of their structure conformation. The developed method is of high preparative capacity and high efficiency in resolution.

Aloe↗
PubMed2006

Characterization of in vitro metabolites of toad venom using high-performance liquid chromatography and liquid chromatography-mass spectrometry.

The characterization of the in vitro metabolites of toad venom, which has been widely used as a traditional Chinese drug, Ch'an Su, has been completed. Toad venom contains bufotoxins (such as marinobufotoxin; marinobufagin 3-suberoylarginine ester) and bufogenins (such as marinobufagin and bufalin) as the main cardiac steroids. An in vitro experiment using the rat or human liver cytosolic fraction disclosed that marinobufotoxin produced marinobufagin, but not its 3-hemisuberate. Marinobufagin was subjected to the enzyme reaction using the rat or human liver microsomal fraction together with NADPH and NAD, which produced 3-dehydromarinobufagin and 3-epimarinobufagin. Marinobufagin produced its 3-sulfate upon treatment with the rat or human liver cytosolic fraction and 3'-phosphoadenosine 5'-phosphosulfate. Bufalin was also subjected to the above enzyme reactions and showed almost the same results except for the result that the hydroxylation occurred at the 5beta-position. On the other hand, small amounts of marinobufagin 3-glucuronide were obtained only by treatment with the human liver microsomal fraction and uridine 5'-diphosphoglucuronic acid. The structures of these metabolites were confirmed using authentic samples regarding their high-performance liquid chromatographic behavior and/or liquid chromatography-mass spectrometry analysis.

Amphibian Venoms↗