JOURNAL OF FOOD QUALITY, Issue 3 2007
EKERO, LU GÜLTEN
ABSTRACT Analysis of 40 oil samples showed that 38 of them were contaminated with benzo(a)pyrene (BaP). Thirty of the 38 BaP-contaminated edible oil samples did not have any label of a brand name. BaP content for the 38 contaminated edible oil samples were in the range of 1.22,74.89 ppb. Sixteen of the contaminated oil samples had BaP content of more than 10 ppb, which is the maximum tolerable limit for the Turkish Food Codex Regulation. BaP contents of samples for each type of oil were significantly different (P < 0.05) from each other. [source]

DETERMINATION OF AFLATOXIN CONTAMINATION IN OLIVES BY IMMUNOAFFINITY COLUMN USING HIGH-PERFORMANCE LIQUID CHROMATOGRAPHY

JOURNAL OF FOOD QUALITY, Issue 2 2006
CAVIT BIRCAN
ABSTRACT Eighty-two whole black olive samples gathered from six different olive oil processing facilities were surveyed to determine levels of aflatoxins using immunoaffinity column extraction and reversed-phase high-performance liquid chromatography. Two different analytical procedures adopted for the analysis of aflatoxins were investigated for their suitability by spiking the blank olive samples with five different known levels of aflatoxins to determine which one had higher recovery rates. Although some of the olive samples had been exposed to adverse conditions, such as rain and high temperatures, none were found to contain aflatoxins at the determined detection limit. Although the samples were kept in high relative humidity (75%) and high temperature (30C) for 3 months and were tested at 1-month intervals, no aflatoxins were detected. In addition, the olives were inoculated on a potato dextrose agar medium and incubated for 7 days at 25C to characterize the microflora. Because there is no evidence of aflatoxins in fresh whole olives, the next step of processing the contaminated olives into olive oils and testing them for the aflatoxins was not pursued. [source]

Selective Analysis of Secondary Amines Using Liquid Chromatography with Electrochemical Detection (LC-EC)

ELECTROANALYSIS, Issue 21 2006
Celia
Abstract In a mixture of primary and secondary aliphatic amines, the primary amines were derivatized (masked) with o -phthalaldehyde (OPA) followed by derivatization of the remaining secondary amines with ferrocenecarboxylic acid chloride (FAC). The "tagged" amines were analyzed by LC-EC (liquid chromatography with electrochemical detection) using in-series dual electrode detection. Chemically-reversible oxidation of the FAC tagged secondary amines and their subsequent complementary oxidation and reduction signals coupled with chemically-irreversible oxidation of OPA tagged primary amines provided the selectivity for quantitative secondary amine analysis. The procedure was also applied for the selective identification of fragment 4,11 (N -terminus-proline) of Substance P in the presence of other Substance P fragments with primary amino acids as their N -termini. [source]

Routine Analyses of Trace Elements in Geological Samples using Flow Injection and Low Pressure On-Line Liquid Chromatography Coupled to ICP-MS: A Study of Geochemical Reference Materials BR, DR-N, UB-N, AN-G and GH

GEOSTANDARDS & GEOANALYTICAL RESEARCH, Issue 2-3 2001
Jean Carignan
géostandards; éléments traces; flow injection; chromatographie liquide; ICP-MS We describe analytical procedures for trace element determinations developed at the CNRS Service d'Analyse des Roches et des Minéraux (SARM) and report results obtained for five geochemical reference materials: basalt BR, diorite DR-N, serpentinite UB-N, anorthosite AN-G and granite GH. Results for rare earth elements, U and Th are also reported for other reference materials including dunite DTS-1, peridotite PCC-1 and basalt BIR-1. All rocks were decomposed using alkali fusion. Analyses were done by flow injection ICP-MS and by on-line low pressure liquid chromatography (LC)-ICP-MS for samples containing very low REE, U and Th concentrations. This latter method yielded limits of determination much lower than data by direct introduction and eliminated possible isobaric interference on these elements. Although results agree with most of the working values, when available, results for some elements differed slightly from the recommended concentrations. In these cases, we propose new values for Co, Y and Zn in basalt BR, Zr in diorite DR-N, Sr and U in granite GH, and Ga and Y in anorthosite AN-G. Furthermore, although the Sb concentration measured in AN-G was very close to our limit of determination, our value (0.3 ± 0.1 ,g g,1) is much lower than the reported working value of 1.4 ± 0.2 ,g g,1. These new values would need to be confirmed by a new inter-laboratory programme to further characterise these reference materials. Results obtained for REE, Th and U concentrations using the on-line low pressure LC-ICP-MS yielded good limits of determination (ng g,1to sub-ng g,1for rocks and ng l,1to sub-ng l,1for natural waters) and accurate results. The efficiency of the matrix separation allowed accurate measurements of Eu without the need to correct the BaO isobaric interference for samples having Ba/Eu ratios as high as 27700. For REE concentrations in PCC-1 and DTS-1, differences with values reported in the literature are interpreted as resulting from possible heterogeneity of the reference materials. Thorium and U values are proposed for these two samples, as well as for AN-G and UB-N. Nous rapportons les procédures d'analyse pour les éléments traces développées au Service d'Analyse des Roches et des Minéraux (SARM) du CNRS et les résultats obtenus pour 5 géostandards: le basalte BR, la diorite DR-N, la serpentinite UB-N, l'anorthosite AN-G et le granite GH. Des résultats obtenus pour les Terres Rares (REE), l'uranium et le thorium sont aussi rapportés pour d'autres matériaux de référence tels que la dunite DTS-1, la péridotite PCC-1 et le basalte BIR-1. Les roches ont été décomposées par fusion alcaline. Les analyses ont été faites par Flow Injection ICP-MS et par chromatographie liquide basse pression en ligne sur un ICP-MS pour les très faibles teneurs en REE, U et Th. Cette dernière méthode permet d'avoir une meilleure limite de détermination que celle par introduction directe et d'éliminer certaines interférences isobariques sur ces éléments. Bien que, dans la majorité des cas, nous ayons mesuré les valeurs de référence telles que rapportées dans la littérature, certaines concentrations mesurées diffèrent légèrement des valeurs recommandées. Ainsi, nous proposons de nouvelles valeurs de Co, Y et Zn pour le basalte BR, de Zr pour la diorite DR-N, de Sr et U pour le granite GH et de Ga et Y pour l'anorthosite AN-G. De plus, bien que la concentration en Sb mesurée pour AN-G soit très proche de notre limite de détermination, notre valeur (0.3 ± 0.1 ,g g,1) est bien inférieure à celle rapportée dans la littérature (1.4 ± 0.2 ,g g,1). Ces nouvelles valeurs devraient être confirmées par une nouvelle campagne de caractérisation inter laboratoire pour ces géostandards. Les résultats obtenus pour les REE, U et Th par chromatographie liquide basse pression en ligne sur un ICP-MS sont justes et livrent des limites de détermination faibles au niveau du ng g,1à sub-ng g,1pour les roches et ng l,1à sub-ng l,1pour les eaux naturelles. La séparation de la matrice est efficace et permet une mesure juste de Eu sans correction d'interférence générée par l'oxyde de Ba, et ce même pour des échantillons possédant des rapports Ba/Eu très élevés, de l'ordre de 27700. Les concentrations en REE mesurées pour les échantillons PCC-1 et DTS-1 peuvent être significativement différentes de celle rapportées dans la littérature, probablement à cause d'une hétérogénéité de ces échantillons. Des valeurs de concentrations en U et Th sont proposées pour ces deux échantillons ainsi que pour AN-G et UB-N. [source]

PURIFICATION AND CHARACTERIZATION OF BACTERIOCIN FROM WEISSELLA PARAMESENTEROIDES DFR-8, AN ISOLATE FROM CUCUMBER (CUCUMIS SATIVUS)

JOURNAL OF FOOD BIOCHEMISTRY, Issue 5 2010
AJAY PAL
ABSTRACT Bacteriocin from Weissella paramesenteroides DFR-8 isolated from cucumber (Cucumis sativus) was purified by using only two steps, viz., pH-mediated cell adsorption,desorption method and gel permeation chromatography. A single peak observed in the purity check by analytical Reverse Phase-High Performance Liquid Chromatography (Waters 600 analytical HPLC system, Milford, MA) and a single band (molecular weight,3.74 kDa) shown on SDS-PAGE analysis strongly indicated the homogeneity of the bacteriocin preparation. Treatment with proteolytic enzymes abolished the antimicrobial activity indicating the proteinaceous nature of bacteriocin. The purified bacteriocin exhibited a broad inhibitory spectrum against foodborne pathogens and spoilage microorganisms, including gram-negative bacteria such as Salmonella typhimurium, Vibrio parahaemolyticus, Aeromonas hydrophila and Listeria monocytogenes. Response surface methodology was employed to study the interactive effect of temperature and pH on bacteriocin activity, and a regression equation was developed. The bacteriocin retained full activity after storage at,20C for 90 days, while partial and complete activity loss was observed when stored at 4 and 37C, respectively. PRACTICAL APPLICATION In recent years, bacteriocins of lactic acid bacteria have gained much attention as food biopreservatives because of their origin from generally regarded as safe organisms. In spite of various bacteriocins studied worldwide, studies on bacteriocins of Weissella paramesenteroides remain rare. The present work involves the purification of bacteriocin up to absolute homogeneity from W. paramesenteroides, an isolate first time reported from cucumber (Cucumis sativus). The purified bacteriocin (molecular weight ,3.74 kDa) was found to inhibit a large number of foodborne pathogens, including Listeria monocytogenes, which is resistant to commercially available bacteriocin, i.e., nisin. The application of central composite rotatable design enabled us to design a regression equation from which the residual activity of bacteriocin can be predicted at any given conditions of temperature and pH within the experimental domain. The broad inhibitory spectrum and thermostability of bacteriocin suggest its potential application in food preservation. [source]

Isolation and Identification of Bitter Peptides of Tryptic Hydrolysate of Soybean 11S Glycinin by Reverse-phase High-performance Liquid Chromatography

JOURNAL OF FOOD SCIENCE, Issue 8 2003
I M.-R.
ABSTRACT: The 21 peptides purified from the bitter fraction of tryptic hydrolysates of soybean 11S glycinin by using gel-permeation high-performance liquid chromatography (HPLC) and a series of 3 C18 reverse phase (RP)-HPLC were in the molecular weight range of 200-1400 Da and showed mostly the hydrophobicity of less than 1400 cal/mol. Although the primary structures of the bitter peptides from 11S glycinin were not exactly the same as those of the proglycinin, many bitter peptides were basic mimics of the common structure, indicating the significance of the primary structure of a peptide playing a role in the bitter taste perception. [source]

Analyses of Glycolipids in Clove, Red Pepper, and Nutmeg by High-Performance Liquid Chromatography

JOURNAL OF FOOD SCIENCE, Issue 6 2000
H. Suzuki
ABSTRACT: To determine the existence of glycolipids (neutral glycosphingolipid and glycoglycerolipid) in clove, red pepper, and nutmeg, we performed silica gel chromatography and high-performance liquid chromatography (HPLC) using an Aquasil-SS column and a C8 -reversed-phase silica gel column. HPLC (Aquasil-SS column) with a UV absorption detector was used to analyze neutral glycosphingolipid. These chromatograms showed two typical peaks in clove lipids. UV-HPLC (C8 -reversed phase silica gel column) was also used to analyze glycoglycerolipid. The chromatograms indicated a small peak in clove lipids. Moreover, we observed the same two peaks in the glycolipid fraction of clove lipid when we used HPLC (Aquasil-SS column) with a differential refractometer detector. These results suggest that clove may contain new and plural neutral glycosphingolipids. [source]

Research Article: Fingerprinting Analysis of Saposhnikovia divaricata using 1H Nuclear Magnetic Resonance Spectroscopy and High Performance Liquid Chromatography

JOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 9 2010
Yue-Yang Xin
The 1H nuclear magnetic resonance (1H NMR) fingerprints of fractionated non-polar and polar extracts (control substance for plant drug [CSPD] A and B) from the roots of 12 specimens of Saposhnikovia divaricata (Turcz.) Schischk were achieved with Fourier Transform (FT)-NMR spectrometer and assigned by comparison to each other and to the 1H NMR spectra of the isolated individual compounds. These fingerprints were found to be uniform in terms of the specificity for the implication of all 12 specimens being systematically of the same origin. The uniformity was further affirmed by high performance liquid chromatography (HPLC), which also revealed exactly identical specificity for the identified S. divaricata species with the 1H NMR appearances of corresponding CSPD on the part of the composition of characteristic constituents when comparing to corresponding individual compounds. This investigation unambiguously shows that the specific signals from the chemotaxonomically significant compounds of chromones and coumarins in S. divaricata are exhibited distinctively in the composite features of both 1H NMR fingerprints and HPLC profiles. The 1H NMR and HPLC profiles established can successfully be used as reference for the authentication of the origin of S. divaricata species as well as for chemotaxonomic studies. [source]

Editorial: The Capillary Column in Liquid Chromatography

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 17-18 2004
Tyge Greibrokk
[source]

Fast Liquid Chromatography for High-Throughput Screening of Polymers

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 1 2003
Harald Pasch
Abstract Liquid chromatography of polymers is traditionally a slow technique with analysis times of typically 30 min per sample. For the application of liquid chromatographic techniques to combinatorial materials research the analysis time per sample must be reduced considerably. Analysis time in SEC can be reduced to about 2 min per sample when high-throughput columns are used. For HPLC small columns with improved separation efficiencies can be used. As compared to conventional technology, time savings of more than 80% are achieved. Chromatogram from conventional SEC column compared to high-speed SEC column tested on an identical instrument with polystyrene standards in THF. [source]

Characterization of Ethylene Copolymers with Liquid Chromatography and Melt Rheology Methods

MACROMOLECULAR SYMPOSIA, Issue 1 2009
Yefim Brun
Abstract Summary: Melt rheology and polymer chromatography methods were applied to characterize molecular heterogeneities in products of free radical copolymerization of ethylene with methyl acrylate and vinyl acetate comonomers performed in continuously stirred tank and tubular reactors. We found that the ethylene,vinyl acetate copolymers made in both reactors had similar linear viscoelastic properties typical to branched products of the high pressure process. But the ethylene,methyl acrylate copolymers obtained in the tubular reactor had unusually high melt viscosity at low shear rate and much lower onset of shear thinning despite the narrower molecular weight distribution and the lower overall amount of long-chain branches compare to their autoclave counterparts with similar average molecular weight and chemical composition. Using interaction polymer chromatography method called gradient elution at critical point of adsorption we found that ethylene-acrylate copolymers from the tubular reactor had very broad chemical composition distribution, which was consistent with a significant difference in reactivity ratios between ethylene and acrylate comonomers. Such chemical composition heterogeneity can be a reason for the observed unusual rheological properties of these copolymers. [source]

Liquid Chromatography of Synthetic Polymers under Limiting Conditions of Insolubility III

MACROMOLECULAR SYMPOSIA, Issue 1 2007
Application of Monolithic Columns
Abstract Summary Performance was evaluated of silica based commercial monolithic rod-like columns in liquid chromatography of synthetic polymers under limiting conditions of enthalpic interactions (LC LC). LC LC employs the barrier effect of the pore permeating and therefore slowly eluting small molecules toward the pore excluded, fast eluting macromolecules. Phase separation (precipitation) barrier action was applied in present study. The barrier was created either by the narrow pulse of an appropriate nonsolvent injected into the column just before the sample solution (LC LC of insolubility , LC LCI) or by the eluent itself. In the latter case, the polymer sample was dissolved and injected in a good solvent (LC LC of solubility , LC LCS). In LC LCI, polymer species cannot break thru the nonsolvent zone while in LC LCS they cannot enter eluent, which is their precipitant. Therefore, polymer species keep moving in the zone of their original solvent. Macromolecules eluting under the LC LC mechanism leave the column in the retention volume (VR) roughly corresponding to VR of the low molar mass substances and can be efficiently separated from the polymer species non-hindered by the barrier action. The known advantages of monoliths were confirmed. From the point of view of LC LCI and LC LCS the most important quality of monolithic columns represents their excellent permeability, which allows both working at high flow rates and injecting very high (in the range of 5%) sample concentrations. Monolithic column tolerate also extremely high molar mass samples (M>10,000 kg,·,mol,1). On the other hand, the mesopores (separation pores) of the tested monoliths exhibited rather small volume and wide size distribution. These shortcomings partially impair the permeability advantage of monoliths because in order to obtain high LC LC separation selectivity a tandem of several monolithic columns must be applied. Presence of large mesopores also reduces applicability of monolithic columns for molar masses below about 50 kg,·,mol,1 because VRs of polymers eluted behind the barrier are similar to that of freely eluting species. The non- negligible break-thru phenomenon was observed for the very high polymer molar masses largely eluting behind the barrier. It is assumed that the fraction of very large mesopores present in the monoliths or association/microphase separation of macromolecules may be responsible for this phenomenon. This is why the presently marketed SiO2 monolithic columns are mainly suitable for the fast purification of the LC LC eluting macromolecules from the polymeric admixtures non-hindered by the barrier-forming liquid. Still, monolithic columns have large potential in the LC LCI and LC LCS procedures provided size (effective diameter) of the mesopores can be reduced and their volume increased. [source]

Evaluation of a Non-Targeted "Omic" Approach in the Safety Assessment of Genetically Modified Plants

PLANT BIOLOGY, Issue 5 2006
S. B. Metzdorff
Abstract: Genetically modified plants must be approved before release in the European Union, and the approval is generally based upon a comparison of various characteristics between the transgenic plant and a conventional counterpart. As a case study, focusing on safety assessment of genetically modified plants, we here report the development and characterisation of six independently transformed Arabidopsis thaliana lines modified in the flavonoid biosynthesis. Analyses of integration events and comparative analysis for characterisation of the intended effects were performed by PCR, quantitative Real-time PCR, and High Performance Liquid Chromatography. Analysis by cDNA microarray was used as a non-targeted approach for the identification of potential unintended effects caused by the transformation. The results revealed that, although the transgenic lines possessed different types of integration events, no unintended effects were identified. However, we found that the majority of genes showing differential expression were identified as stress-related genes and that environmental conditions had a large impact on the expression of several genes, proteins, and metabolites. We suggest that the microarray approach has the potential to become a useful tool for screening of unintended effects, but state that it is crucial to have substantial information on the natural variation in traditional crops in order to be able to interpret "omics" data correctly within the framework of food safety assessment strategies of novel plant varieties, including genetically modified plant varieties. [source]

Selective extraction of polyunsaturated triacylglycerols using a novel ionic liquid precursor immobilized on a mesoporous complexing adsorbent

BIOTECHNOLOGY PROGRESS, Issue 5 2009
Patrisha J. Pham
Abstract Mesoporous silica (SBA-15) synthesized by using Pluronic123 as the structure-directing template was functionalized by imidazolium-based ionic liquid precursors. Silver salts were then immobilized onto the supported ionic liquids using the incipient wetness impregnation technique. The separation of unsaturated species was achieved through the reversible and specific interaction between silver ions and carbon,carbon double bonds. This adsorbent was examined for the selective separation of polyunsaturated triacylglycerols (PUTAG) using High Pressure Liquid Chromatography (HPLC) with Evaporative Light Scattering Detection (ELSD) as the quantification methodology. AgBF4/SBA15·HPSiOEtIM·PF6 showed an adsorption capacity for linolenin of about 217 mg adsorbed/gram of sorbent. This adsorbent had good selectivity and a high capacity for the most highly unsaturated triacylglycerol when applied to a mixture of triacylglycerols with varying degrees of unsaturation. Consequently, a stepwise methodology was also developed to increase the recovery of the adsorbed components. This adsorbent retained its selectivity and capacity when recycled up to five times. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009 [source]

Lornoxicam pharmacokinetics in the vitreous humor of albino rabbits

ACTA OPHTHALMOLOGICA, Issue 2009
C TSIKA
Purpose To assess the elimination half-life of intravitreal lornoxicam, a non-steroidal anti-inflammatory drug (NSAID). Methods Both eyes of 15 rabbits were intravitreally injected with 250 ,g of commercially available lornoxicam (for intravenous/intramuscular use, Xefo® 8 IV/IM Injection, Nycomed Hellas S.A.). Six eyes were enucleated at time points 0, 1, 2, 6 and 24 hours after the injection was performed. The eyes were immediately frozen at -80°C. The vitreous was eviscerated from the eye and the drug was liquid-liquid extracted from a 0.4 ml sample. Lornoxicam was isolated by a reversed-phase High Performance Liquid Chromatography (HPLC) method at retention time 10.7 min and detected at 372 nm. The data were statistically analyzed in order to evaluate the pharmacokinetic parameters of the drug. Results The recovery of lornoxicam after liquid-liquid extraction was calculated at 69.6% and the limit of determination was 0.1 ,g/ml. Statistical analysis revealed that lornoxicam concentrations followed first-order kinetics with an elimination rate constant of 0.235h-1 and a half-life of 3.0 h. Conclusion The determination of the pharmacokinetic characteristics of intravitreal lornoxicam allows the possibility for further investigation of the drug's intraocular behaviour and therapeutic potential. [source]

Chiral Separation of Calcium (,)-2(S)-2-Benzyl-4-oxo-4-(cis -hexahydro-2-isoindolinyl)butyrate Enantiomers by High-performance Liquid Chromatography,

CHINESE JOURNAL OF CHEMISTRY, Issue 1 2009
Zhefeng ZHANG
Abstract A chiral high-performance liquid chromatographic method was developed for the enantioseparation of a new insulinotropic drug of the glinide class with rapid onset. The chiral separation was performed on a Sumichiral OA-3300 column (250 mm×4.6 mm, 5 µm) with methanol containing 0.05 mol/L ammonium acetate as the optimized mobile phase at detection wavelengh 210 nm. Baseline separation of the two enantiomers was obtained in 22 min with a resolution of 3.01. Calibration graphs were constructed in a range of 0.028,5.6 µg·mL,1 for S - and 0.03,6.0 µg·mL,1 for R -(,)-enantiomer, respectively. The linear correlation equations are: y=1.32×103x,2.54 (r=0.9997) for S -enantiomer and y=1.15×103x,1.78 (r=0.9998) for R -enantiomer, respectively. The limits of detection obtained by S/N=3 were 0.15 ng for S - and 0.10 ng for R -enantiomer, respectively. RSD of the method was below 1.0% (n=5). [source]

Determination of Tetracyclines in Honey Using Liquid Chromatography with Ultraviolet Absorbance Detection and Residue Confirmation by Mass Spectrometry

CHINESE JOURNAL OF CHEMISTRY, Issue 9 2007
Yan Liu
Abstract A determination method has been optimized and validated for the simultaneous analysis of tetracycline (TC), oxytetracycline (OTC), chlortetracycline (CTC) and doxycycline (DC) in honey. Tetracyclines (TCs) were removed from honey samples by chelation with metal ions bound to small Chelating Sepharose Fast Flow columns and eluted with Na2EDTA-Mcllvaine pH 4.0 buffers. Extracts were further cleaned up by Oasis HLB solid-phase extraction (SPE), while other solid-phase extraction cartridges were compared. Chromatographic separation was achieved using a polar end-capped C18 column with an isocratic mobile phase consisting of oxalic acid, acetonitrile, and methanol. LC with ultraviolet absorbance at 355 nm resulted in the quantitation of all four tetracycline residues from honey samples fortified at 15, 50, and 100 ng/g, with liner ranges for tetracyclines of 0.05 to 2 µg/mL. Mean recoveries for tetracyclines were greater than 50% with R.S.D. values less than 10% (n=18). Detection limits of 5, 5, 10, 10 ng/g for oxytetracycline, tetracycline, chlortetracycline and doxycycline, respectively and quantitation limits of 15 ng/g for all the four tetracyclines were determined. Direct confirmation of the four residues in honey(2,50 ng/g) was realized by liquid chromatography-tandem mass spectrometry (LC/MS/MS). The linear ranges of tetracyclines determined by LC/MS/MS were between 5 to 300 ng/mL, with the linear correlation coefficient r>0.995. The limits of detection of 1 to 2 ng/g were obtained for the analysis of the TCs in honey. [source]

Simultaneous Determination of Epinephrine, Noradrenaline and Dopamine in Human Serum Samples by High Performance Liquid Chromatography with Chemiluminescence Detection

CHINESE JOURNAL OF CHEMISTRY, Issue 7 2007
Fu-Nan Chen
Abstract A simple, rapid and accurate high performance liquid chromatographic (HPLC) technique coupled with chemiluminescence (CL) detection was developed for the simultaneous determination of epinephrine (E), noradrenaline (NA) and dopamine (DA). It was based on the analyte enhancement effect on the CL reaction between luminol and potassium ferricyanide. The effects of various parameters, such as potassium ferricyanide concentration, luminol concentration, pH value and component of the mobile phase on chromatographic behaviors of the analytes (E, NA and DA) were investigated. The separation was carried out on C18 column using the mobile phase of 0.01 mol/L potassium hydrogen phthalate solution and methanol (92:8, V/V). Under the optimum conditions, E, NA and DA showed good linear relationships in the range of 1×10,8,5×10,6, 5.0×10,9,1.0×10,6 and 5.0×10,9,1.0×10,6 g/mL respectively. The detection limits for E, NA and DA were 4.0×10,9, 1.0×10,9 and 8.0×10,10 g/mL. The proposed method has been applied successfully to the analysis of E, NA and DA in human serum samples. [source]

Optimizing the Quadruple-potential Waveform for the Determination of Gentamicin Sulfate by High Performance Liquid Chromatography with Pulsed Electrochemical Detection

CHINESE JOURNAL OF CHEMISTRY, Issue 9 2005
Ya-Qi Cai
Abstract In this paper, a quadruple-potential waveform was investigated and optimized for the determination of gentamicin by reversed phase ion-pair chromatography. Instead of a relatively high positive potential, a negative potential was adopted as a potential for the cleaning of gold working electrode. By this way, the formation of gold oxide resulting from the application of high positive potential during the analyte detection and electrode cleaning was greatly reduced, and therefore, the dissolution and recession of gold working electrode was also reduced. The good condition of gold working electrode achieved by this quadruple-potential waveform can help us to obtain a good reproducibility. In order to acquire signal-to-noise ratio as high as possible, several waveform parameters affecting the detection of gentamicin were carefully selected. The analytical method has been applied to the determination of two real gentamicin samples, and good results with low relative standard deviation not more than 4% were obtained. [source]

Historical review of sample preparation for chromatographic bioanalysis: pros and cons

DRUG DEVELOPMENT RESEARCH, Issue 3 2007
Min S. Chang
Abstract Sample preparation is a major task in a regulated bioanalytical laboratory. The sample preparation procedure significantly impacts assay throughput, data quality, analysis cost, and employee satisfaction. Therefore, selecting and optimizing an appropriate sample preparation method is essential for successful method development. Because of our recent expertise, this article is focused on sample preparation for high-performance liquid chromatography with mass spectrometric detection. Liquid chromatography with mass spectrometric detection (LC-MS) is the most common detection technique for small molecules used in regulated bioanalytical laboratories. The sample preparation technologies discussed are pre-extraction and post-extraction sample processing, protein precipitation (PPT), liquid,liquid extraction (LLE), offline solid-phase extraction (SPE), and online solid-phase extraction. Since all these techniques were in use for more than two decades, numerous applications and variations exist for each technique. We will not attempt to categorize each variation. Rather, the development history, a brief theoretical background, and selected references are presented. The strengths and the limitations of each method are discussed, including the throughput improvement potential. If available, illustrations from presentations at various meetings by our laboratory are used to clarify our opinion. Drug Dev Res 68:107,133, 2007. ©2007 Wiley-Liss, Inc. [source]

Liquid chromatography on chip

ELECTROPHORESIS, Issue 15 2010
Karine Faure
Abstract LC is one of the most powerful separation techniques as illustrated by its leading role in analytical sciences through both academic and industrial communities. Its implementation in microsystems appears to be crucial in the development of ,-Total Analysis System. If electrophoretic techniques have been widely used in miniaturized devices, LC has faced multiple challenges in the downsizing process. During the past 5 years, significant breakthroughs have been achieved in this research area, in both conception and use of LC on chip. This review emphasizes the development of novel stationary phases and their implementation in microchannels. Recent instrumental advances are also presented, highlighting the various driving forces (pressure, electrical field) that have been selected and their respective ranges of applications. [source]

,, ,-Unsaturated sulfophenylcarboxylates as degradation intermediates of linear alkylbenzenesulfonates: Evidence for ,-oxygenation followed by ,-oxidations by liquid chromatography-mass spectrometry

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2002
Peter Eichhorn
Abstract Liquid chromatography with an electrospray interface to a mass spectrometer (LC-ES-MS) and LC-ES coupled to a tandem MS (LC-ES-MS/MS) were used to detect and identify intermediates excreted transiently during the aerobic degradation of linear alkylbenzenesulfonates (LAS) in fixed-bed bioreactors (FBBR). The inoculum for the FBBR was the microflora of the River Rhine, Germany. Two major phenomena were observed on the addition of 100 mg/L LAS to the system, sorption and then biodegradation. Disappearance due to sorption was followed in an inhibited FBBR. Biodegradation of LAS started on day 7 and was accompanied by the transient excretion of intermediates, which were later largely degraded. We detected not only the sulfophenylcarboxylates (SPCs) observed previously but also the ,, ,-unsaturated SPCs (SPC-2H), which have not been reported before. Experiments with the (4-sulfophenyl)dodecanes (C12-LAS), which had minor contaminants of C11-LAS, showed C12-, C10-, C8-, C6-, and C4-SPCs when LAS was degraded as well as traces of C9-, C7-, and C5-SPCs. Signals from the SPC-2H species were usually some 10% of those from the corresponding SPCs. Samples from these experiments were also examined by gas chromatography-mass spectrometry (GC-MS), but no desulfonated intermediates were detected. We interpret the data to mean that the only attack on LAS was by ,-oxygenation; there was no visible initial desulfonation. The products of ,-oxygenation were oxidized to the corresponding SPC and subject to ,-oxidation, as evidenced not only by the pattern of C-2 units in the excreted SPCs but also in the corresponding series of SPC-2H, representing the intermediates in ,-oxidation. [source]

Matrix effects on accurate mass measurements of low-molecular weight compounds using liquid chromatography-electrospray-quadrupole time-of-flight mass spectrometry,

JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2006
F. Calbiani
Abstract Liquid chromatography (LC) with high-resolution mass spectrometry (HRMS) represents a powerful technique for the identification and/or confirmation of small molecules, i.e. drugs, metabolites or contaminants, in different matrices. However, reliability of analyte identification by HRMS is being challenged by the uncertainty that affects the exact mass measurement. This parameter, characterized by accuracy and precision, is influenced by sample matrix and interferent compounds so that questions about how to develop and validate reliable LC-HRMS-based methods are being raised. Experimental approaches for studying the effects of various key factors influencing mass accuracy on low-molecular weight compounds (MW < 150 Da) when using a quadrupole-time-of-flight (QTOF) mass analyzer were described. Biogenic amines in human plasma were considered for the purpose and the effects of peak shape, ion abundance, resolution and data processing on accurate mass measurements of the analytes were evaluated. In addition, the influence of the matrix on the uncertainty associated with their identification and quantitation is discussed. A critical evaluation on the calculation of the limits of detection was carried out, considering the uncertainty associated with exact mass measurement of HRMS-based methods. The minimum concentration level of the analytes that was able to provide a statistical error lower than 5 ppm in terms of precision was 10 times higher than those calculated with S/N = 3, thus suggesting the importance of considering both components of exact mass measurement uncertainty in the evaluation of the limit of detection. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Liquid chromatography,tandem mass spectrometry method for simultaneous determination of cyclosporine A and its three metabolites AM1, AM9 and AM4N in whole blood and isolated lymphocytes in renal transplant patients

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 15 2010
Hana Brozmanová
Abstract A LC-MS/MS method was developed and validated for the determination of cyclosporine A (CsA) and its three phase 1 metabolites AM1, AM9, and AM4N in whole blood and lymphocytes isolated on the Histopaque gradient. 200,,L of whole blood was precipitated with 10,mol/L zinc sulfate in acetonitrile/methanol (40:60, v/v) and lymphocytes isolated from 1.5,mL blood were extracted with acetonitrile/methanol (40:60, v/v). The analytes and internal standard cyclosporine D were separated on RP column BEH C18, 2.1×50,mm, 1.7,,m using gradient LC-MS/MS analysis in positive electrospray mode. Time of analysis was 5,min. Linearity in blood was 5,2000,,g/L for CsA, AM1, and AM9; 2,500,,g/L for AM4N; and 2,500,,g/L for all substances in lymphocytes. Coefficient of variations was 1.8,9.8% and recovery was 92.0,110.0%. The method was used in early and chronic renal transplant patients for therapeutic drug monitoring of CsA to compare either its share in lymphocytes as target organ or binding to one lymphocyte. The same parameters were calculated for all metabolites tested. [source]

Capillary columns in liquid chromatography: between conventional columns and microchips

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 17-18 2004
Yoshihiro Saito
Abstract Liquid chromatography on columns with small internal diameters has been reviewed as the intermediate technique between conventional liquid chromatography and microchip separations. The development of micro column separations in the early years has been described, starting with the papers of Horváth and co-workers and Ishii and co-workers, continuing into the first part of the eighties, then making a leap in time to recent innovations with small-bore columns. Based on internal diameters a classification of the different analytical HPLC columns has been suggested. The advantages of small-bore columns have been discussed, with particular emphasis on the advantage of coupling to concentration sensitive detectors when the sample amount is limited. Open tubular columns are treated as a part of the historic background. The recent developments include a brief look into the current status of monolithic columns, the use of packed nano columns and micro columns with electrospray mass spectrometry, and the potential of two-dimensional comprehensive liquid chromatography. Finally, the coupling of sample preparation to analytical columns and the future applications of the novel technological improvements to the microchip separation methods have been discussed. [source]

Liquid chromatography coupled to nuclear magnetic resonance spectroscopy for the identification of isoflavone glucoside malonates in T. pratense L. leaves.

JOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2004
Eva de Rijke
Abstract Previous studies revealed that the main isoflavones in extracts of leaves of T. pratense L. are biochanin A and formononetin, their 7- O -glucosides, and two glucoside malonate isomers of each of them. Since LC,MS(/MS) did not provide sufficient information to distinguish the glucoside malonate isomers, in the present paper LC,NMR as well as off-line two-dimensional NMR were used to obtain further structural information. Matrix solid-phase dispersion (MSPD) was applied to obtain sufficiently high analyte concentrations to perform LC,NMR. Stop-flow reversed-phase LC,NMR was performed using a gradient of deuterated water and deuterated acetonitrile. Off-line COSY and NOESY experiments were carried out to determine the positions of the glucose moiety on the flavonoid aglycone, and of the malonate moiety on the glucose. Based on the fragmentation patterns in MS/MS and the NMR spectra, the two formononetin glucoside malonate isomers were identified as 7- O -,-D-glucoside 6´´- O -malonate and 7- O -,-D-glucoside 4´´- O -malonate; i.e. they only differ in the substitution position of the malonate group on the glucoside ring. The biochanin A glucoside malonate isomers, however, have quite different structures. The main and later eluting isomer is biochanin A 7- O -,-D-glucoside 6´´- O -malonate, and the minor and earlier eluting isomer is 5-hydroxy-7-methoxyisoflavone 4´- O -,-D-glucoside 4´´- O -malonate: the positions of the methoxy group and the glucoside 6´´- O -malonate group on the flavonoid skeleton are interchanged. [source]

Fast Liquid Chromatography for High-Throughput Screening of Polymers

Liquid chromatography,tandem mass spectrometry applications in endocrinology

MASS SPECTROMETRY REVIEWS, Issue 3 2010
Mark M. Kushnir
Abstract Liquid chromatography,tandem mass spectrometry (LC,MS/MS) has been recognized as a primary methodology for the accurate analysis of endogenous steroid hormones in biological samples. This review focuses on the use of LC,MS/MS in clinical laboratories to assist with the diagnosis of diverse groups of endocrine and metabolic diseases. Described analytical methods use on-line and off-line sample preparation and analytical derivatization to enhance analytical sensitivity, specificity, and clinical utility. Advantages of LC,MS/MS as an analytical technique include high specificity, possibility to simultaneously measure multiple analytes, and the ability to assess the specificity of the analysis in every sample. All described analytical methods were extensively validated, utilized in routine diagnostic practice, and were applied in a number of clinical and epidemiological studies, including a study of the steroidogenesis in ovarian follicles. © 2009 Wiley Periodicals, Inc. Mass Spec Rev 29:480-502, 2010 [source]

Liquid chromatography combined with mass spectrometry for 13C isotopic analysis in life science research

MASS SPECTROMETRY REVIEWS, Issue 6 2007
Jean-Philippe Godin
Abstract Among the different disciplines covered by mass spectrometry, measurement of 13C/12C isotopic ratio crosses a large section of disciplines from a tool revealing the origin of compounds to more recent approaches such as metabolomics and proteomics. Isotope ratio mass spectrometry (IRMS) and molecular mass spectrometry (MS) are the two most mature techniques for 13C isotopic analysis of compounds, respectively, for high and low-isotopic precision. For the sample introduction, the coupling of gas chromatography (GC) to either IRMS or MS is state of the art technique for targeted isotopic analysis of volatile analytes. However, liquid chromatography (LC) also needs to be considered as a tool for the sample introduction into IRMS or MS for 13C isotopic analyses of non-volatile analytes at natural abundance as well as for 13C-labeled compounds. This review presents the past and the current processes used to perform 13C isotopic analysis in combination with LC. It gives particular attention to the combination of LC with IRMS which started in the 1990's with the moving wire transport, then subsequently moved to the chemical reaction interface (CRI) and was made commercially available in 2004 with the wet chemical oxidation interface (LC-IRMS). The LC-IRMS method development is also discussed in this review, including the possible approaches for increasing selectivity and efficiency, for example, using a 100% aqueous mobile phase for the LC separation. In addition, applications for measuring 13C isotopic enrichments using atmospheric pressure LC-MS instruments with a quadrupole, a time-of-flight, and an ion trap analyzer are also discussed as well as a LC-ICPMS using a prototype instrument with two quadrupoles. © 2007 Wiley Periodicals, Inc., Mass Spec Rev 26:751,774, 2007 [source]

Time of flight mass spectrometry applied to the liquid chromatographic analysis of pesticides in water and food

MASS SPECTROMETRY REVIEWS, Issue 6 2006
Sílvia Lacorte
Abstract Liquid chromatography coupled to mass spectrometry (LC-MS) is an excellent technique to determine trace levels of polar and thermolabile pesticides and their degradation products in complex matrices. LC-MS can be equipped with several mass analyzers, each of which provides unique features capable to identify, quantify, and resolve ambiguities by selecting appropriate ionization and acquisition parameters. We discuss in this review the use of LC coupled to (quadrupole) time-of-flight mass spectrometry (LC-(Q)ToF-MS) to determine the presence of target and non-target pesticides in water and food. This technique is characterized by operating at a resolving power of 10,000 or more. Therefore, it gives accurate masses for both parent and fragment ions and enables the measurement of the elemental formula of a compound achieving compound identification. In addition, the combination of quadrupole-ToF permits tandem mass spectrometry, provides more structural information, and enhances selectivity. The purpose of this article is to provide an overview on the state of art and applicability of liquid chromatography time-of-flight mass spectrometry (LC-ToF-MS), and liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QToF-MS) for the analysis of pesticides in environmental matrices and food. The performance of such techniques is depicted in terms of accurate mass measurement, fragmentation, and selectivity. The final section is devoted to describing the applicability of LC-(Q)ToF-MS to routine analysis of pesticides in food matrices, indicating those operational conditions and criteria used to screen, quantify, and identify target and "suspected" pesticides and their degradation products in water, fruits, and vegetables. The potential and future trends as well as limitations of LC-(Q)ToF-MS for pesticide monitoring are highlighted. © 2006 Wiley Periodicals, Inc. [source]