Simultaneous determination of aflatoxins, ochratoxin A and Fusarium toxins in maize by liquid chromatography/tandem mass spectrometry after multitoxin immunoaffinity cleanup

A liquid chromatography/tandem mass spectrometry method was developed for the simultaneous determination of aflatoxins (B(1), B(2), G(1), G(2)), ochratoxin A, fumonisins (B(1), B(2)), deoxynivalenol, zearalenone, T-2 and HT-2 toxins in maize. A double extraction approach, using a phosphate-buffered solution followed by methanol, was applied to achieve effective co-extraction of the 11 mycotoxins under investigation having quite different polarities and chemical structures. A new multitoxin immunoaffinity column containing antibodies for all these mycotoxins was used to clean up the extract. Detection and quantification of the 11 mycotoxins were performed by reversed-phase liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry (LC/ESI-MS/MS) using, as chromatographic mobile phase, a linear gradient of methanol/water containing 0.5% acetic acid and 1 mM ammonium acetate. Method performances were quite satisfactory for all tested mycotoxins at contamination levels close to or below the relevant EU maximum permitted or recommended levels. Limits of detection in maize ranged from 0.3 to 4.2 microg/kg. Recoveries higher than 79% were obtained for all tested mycotoxins with relative standard deviations less than 13%.     

Phase behavior of lyotropic rigid-chain polymer liquid crystal studied by dissipative particle dynamics

The phase behavior of lyotropic rigid-chain liquid crystal polymer was studied by dissipative particle dynamics (DPD) with variations of the solution concentration and temperature. A chain of fused DPD particles was used to represent each mesogenic polymer backbone surrounded with the strongly interacted solvent molecules. The free solvent molecules were modeled as independent DPD particles, where each particle includes a lump of solvent molecules with the volume roughly equal to the solvated polymer segment. The simulation shows that smectic-B (S(B)), smectic-A (S(A)), nematic (N), and isotropic (I) phases exist within certain regions in the temperature and concentration parameter space. The temperature-dependent S(B)∕S(A), S(A)∕N, and N∕I phase transitions occur in the high concentration range. In the intermediate concentration range, the simulation shows coexistence of the anisotropic phases and isotropic phase, where the anisotropic phases can be the S(B), S(A), or N phases. Mole fraction and compositions of the coexisted phases are determined from the simulation, which indicates that concentration of rigid rods in isotropic phase increases as the temperature increases. By fitting the orientational distribution function of the systems, the biphasic coexistence is further confirmed. From the parameter α obtained for the simulation, the distribution of the rigid rods in the two coexistence phases is quantitatively evaluated. By using model and simulation methods developed in this work, the phase diagrams of the lyotropic rigid-chain polymer liquid crystal are obtained. Incorporating the solvent particles in the DPD simulation is critical to predict the phase coexistence and obtain the phase diagrams.     

Chromatographic separation of tocopherols.

alpha-, beta-, gamma-, and delta-Tocopherols were separated by reversed-phase high-performance thin-layer chromatography (C18RP-HPTLC), normal-phase high-performance liquid chromatography (NP-HPLC), reversed-phase high-performance liquid chromatography (C18RP-HPLC), and gas chromatography (GC). The selected topological indices based on connectivity (M, 1chi(v)), on distance matrix (W, (o)B, MTI) and on information theory (I(AC), I(AC)) were calculated for these tocopherols. The observed chromatographic separations of investigated tocopherols were compared. This comparison indicated that the C18RP-HPTLC, NP-HPLC, and GC are the best techniques for the separation of these tocopherols. Topological index (o)B was the most significant. We obtained definite dependence between the numerical values of topological index (o)B and the chromatographic separation of the investigated tocopherols.     

Structural dependence of microwave dielectric properties of ixiolite structured ZnTiNb2O8 materials: crystal structure refinement and Raman spectra study

Structural and property relationships of ixiolite structured ZnTiNb(2)O(8) microwave dielectric materials were studied by structure refinement and Raman spectra analysis. The vibration modes which have Raman activities of the ixiolite structure were assigned for the first time. The bands with wavenumbers greater than 450 cm(-1) can be associated with several modes (A(g(2)), B(3g(1)), B(3g(2)), A(g(1)), B(1g(2)), A(g(3)), B(2g(2))) involving the stretching of the cation-O bonds. For wavenumbers between 250 and 450 cm(-1), the bands are due, principally, to the bending of O-cation-O (B(1g(1)), B(2g(1)), B(1g(3))). The origin of the bands with wavenumbers below 250 cm(-1) would be lattice vibrations (B(1g(4)), A(g(4)), B(3g(4)), B(2g(4))), mainly associated with cation ions. The correlation between bond strength and packing fraction, Raman shift, full width at half maximum (FWHM) of Raman spectra were discussed. With increase of bond strength, the oxygen octahedron became rigid, the Raman shift increased, and the damping behavior became weaker. With increase of Raman shift, the dielectric constant decreased. With increase of packing fraction and decrease of FWHM, the Q(f) (quality factor × resonance frequency) value increased. The τ(f) (temperature coefficient of resonance frequency) decreased with increase of bond strength. And there was no direct relationship between oxygen octahedron distortion and τ(f). The excellent microwave dielectric properties of ZnTiNb(2)O(8) in this work were: dielectric constant (ε) = 34.4, Q(f) = 56,900 GHz, τ(f) = -47.94 × 10(-6)/°C.     

Binuclear mesogenic copper(i) isocyanide complexes with an unusual inorganic core formed by two tetrahedra sharing an edge

The preparation of binuclear mesogenic copper(I) isocyanide complexes [CuX(CNR)(2)](2) (X = halogen; R = C(6)H(4)C(6)H(4)OC(10)H(21) (L(A)), C(6)H(4)COOC(6)H(4)OC(n)H(2n+1)((L(B)), C(6)H(2)(3,4,5-OC(n)H(2n+1))(3) (L(C))) with an unusual tetrahedral core is described. The copper complexes with L(A) are not liquid crystals, but the Cu-L(B) complexes show SmA mesophases and the Cu-L(C) derivatives display hexagonal columnar mesophases, some of them at room temperature. The relationship between the molecular structure of the complexes and their thermal behavior is discussed.     

Photoelectron spectroscopy of higher bromine and iodine oxide anions: electron affinities and electronic structures of BrO(2,3) and IO(2-4) radicals

This report details a photoelectron spectroscopy (PES) and theoretical investigation of electron affinities (EAs) and electronic structures of several atmospherically relevant higher bromine and iodine oxide molecules in the gas phase. PES spectra of BrO(2)(-) and IO(2)(-) were recorded at 12 K and four photon energies--355 nm/3.496 eV, 266 nm/4.661 eV, 193 nm/6.424 eV, and 157 nm/7.867 eV--while BrO(3)(-), IO(3)(-), and IO(4)(-) were only studied at 193 and 157 nm due to their expected high electron binding energies. Spectral features corresponding to transitions from the anionic ground state to the ground and excited states of the neutral are unraveled and resolved for each species. The EAs of these bromine and iodine oxides are experimentally determined for the first time (except for IO(2)) to be 2.515 ± 0.010 (BrO(2)), 2.575 ± 0.010 (IO(2)), 4.60 ± 0.05 (BrO(3)), 4.70 ± 0.05 (IO(3)), and 6.05 ± 0.05 eV (IO(4)). Three low-lying excited states along with their respective excitation energies are obtained for BrO(2) [1.69 (A (2)B(2)), 1.79 (B (2)A(1)), 1.99 eV (C (2)A(2))], BrO(3) [0.7 (A (2)A(2)), 1.6 (B (2)E), 3.1 eV (C (2)E)], and IO(3) [0.60 (A (2)A(2)), 1.20 (B (2)E), ～3.0 eV (C (2)E)], whereas six excited states of IO(2) are determined along with their respective excitation energies of 1.63 (A (2)B(2)), 1.73 (B (2)A(1)), 1.83 (C (2)A(2)), 4.23 (D (2)A(1)), 4.63 (E (2)B(2)), and 5.23 eV (F (2)B(1)). Periodate (IO(4)(-)) possesses a very high electron binding energy. Only one excited state feature with 0.95 eV excitation energy is shown in the 157 nm spectrum. Accompanying theoretical calculations reveal structural changes from the anions to the neutrals, and the calculated EAs are in good agreement with experimentally determined values. Franck-Condon factors simulations nicely reproduce the observed vibrational progressions for BrO(2) and IO(2). The low-lying excited state information is compared with theoretical calculations and discussed with their atmospheric implications.     

Electronic structure and stability of fullerene C82 isolated-pentagon-rule isomers

All nine isolated-pentagon-rule isomers of fullerene C(82) were investigated by the DFT method with the B3LYP functional at the 6-31G, 6-31G*, and 6-31+G* levels. The distribution of single, double, and delocalized π-bonds in the molecules of these isomers is shown for the first time. The obtained results are fully supported by DFT quantum-chemical calculations of electronic and geometrical structures of these isomers. The molecules of isomers 7 (C(3v)), 8 (C(3v)), and 9 (C(2v)) contain some radical substructures (such as the phenalenyl-radical substructure), which indicates that they are unstable and cannot be obtained as empty molecules. Thus, there is a possibility of obtaining them only as endohedral metallofullerenes or exohedral derivatives. Isomers 1 (C(2)), 2 (C(s)), 4 (C(s)), 5 (C(2)), and 6 (C(s)) with closed electronic shell are supposed to be stable, resembling isomer 3 (C(2)), which has just been extracted experimentally as an empty fullerene. We assume they can be produced as empty molecules.     

Simple derivatization of aldehydes with D-cysteine and their determination in beverages by liquid chromatography-tandem mass spectrometry

We describe a simple derivatization method to determine aldehydes. This method is based on derivatization with D-cysteine and consecutive liquid chromatography-tandem mass spectrometry (LC-MS/MS). The optimum derivatization conditions of aldehydes with D-cysteine were 10 min at 50°C and pH 7.0. The formed alkyl thiazolidine-4-carboxylic acid derivatives were directly injected in LC-MS/MS. In the established condition, the method was used to detect eight aldehydes in beverages. The limit of detection (LOD) and limit of quantification (LOQ) of the aldehydes were 0.2-1.9 μg L(-1) and 0.7-6.0 μg L(-1) and the relative standard deviation was less than 2.0% at concentrations of 0.1 mg L(-1) and 1.0 mg L(-1) with the exception of octanal. All the beverage samples had detectable levels of methanal (0.033-0.145 mg L(-1)), ethanal (0.085-2.12 mg L(-1)), propanal (ND to 0.250 mg L(-1)), butanal (ND to 0.003 mg L(-1)), pentanal (ND to 0.471 mg L(-1)), hexanal (ND to 0.805 mg L(-1)), heptanal (0.019-3.91 mg L(-1)) and octanal (0.029-0.118 mg L(-1)).     

Synthesis, structure, and spectroscopic properties of chiral oxorhenium(V) complexes incorporating polydentate ligands derived from L-amino acids: a density functional theory/time-dependent density functional theory investigation

The oxorhenium(V) complexes [Re (V)O(L A)Cl 2] bearing the (N-2-pyridylmethyl) of l-valine (HL A (1)), l-leucine (HL A (2)), and l-phenylalanine (HL A (3)) and [Re (V)O(L B)Cl] containing the {(N-2pyridylmethyl)-(N-(5-nitro-2-hydroxybenzyl)} of l-valine (H 2L B (1)), l-leucine (H 2L B (2)), and l-phenylalanine (H 2L B (3)) are presented in this article. The complexes are isolated in enantiomeric pure form examined from X-ray structure determination. The complexes are characterized by spectroscopic and electrochemical methods. The molecular structures observed in the solid state are grossly preserved in solution ( (1)H, (13)C, and circular dichroism spectra). Gas-phase geometry optimization and the electronic structures of [Re (V)O(L A (1))Cl 2], [Re (V)O(L A (2))Cl 2], and [Re (V)O(L B (2))Cl] have been investigated with the framework of density functional theory. The absorption and circular dichroism spectra of the complexes were also calculated applying time-dependent density functional theory (TDDFT) using the conductor-like polarizable continuum solvent model to understand the origin of the electronic excitations. The chemical shift ( (1)H and (13)C) as well as (1)H- (1)H spin-spin coupling constant were also computed by the gauge-independent atomic orbital method, and the computed values are consistent with the experimental data.     

An isocratic HPLC method for the quantitation of eicosanoids in human platelets

We describe here a modified protocol for the simultaneous quantification of specific eicosanoids formed during stimulation of human platelets in vitro with adenosine diphosphate. The eicosanoids thromboxane B(2) (TXB(2)), arachidonic acid (AA), 12-R-hydroxyeicosatetraenoic acid (12-R-HETE), 12-S-hydroxyheptadecatrienoic acid (12-S-HHTrE) and the internal standard prostaglandin B(1) (PGB(1)) were extracted from human platelets by liquid-liquid extraction using ethyl acetate. This was followed by derivatization and fluorescent detection prior to analysis by reversed phase liquid chromatography. The high-performance liquid chromatographic method consisted of ODS reversed-phase column (3 microm) and a mobile phase of acetonitrile-water (85:15). TXB(2) and AA plasma calibration curves were linear between 6.25 and 125 ng mL(-1) (r(2) > 0.997), whereas for 12-R-HETE and 12-S-HHTrE the curves were linear between 5.0 and 40 ng mL(-1) (r(2) > 0.998). All calibration curve standards had <15% CV (coefficient of variation) and between-run precision, and the percentage relative deviation for replicate (n = 6) quality controls was less than 5.5%. The method was adapted to allow the screening of drugs that may affect either one or both of the lipoxygenase and cyclo-oxygenase pathways.     

Analysis of fumonisins B(1), B(2) and B(3) in corn-based baby food by pressurized liquid extraction and liquid chromatography/tandem mass spectrometry

A sensitive and reliable method using pressurized liquid extraction (PLE) and liquid chromatography (LC)/electrospray ionization (ESI) tandem mass spectrometry with a triple quadrupole (QqQ) analyzer has been developed for the analysis of fumonisin B(1) (FB(1)), fumonisin B(2) (FB(2)) and fumonisin B(3) (FB(3)) in corn-based baby foods. Influence of several extraction parameters that affect PLE efficiency such as temperature, pressure, solvent extraction, number of cycles and dispersant/clean-up agents were studied. The selected PLE operating method was: 3g of sample was packed into 11 ml stainless-steel cell and fumonisins were extracted with methanol at 40 degrees C, 34 atm in one cycle of 5 min at 60% flush. The analytes were ionized in ESI operating with positive ion mode and identified by selecting two monitoring transitions, permitting quantification and confirmation in a single injection. Recoveries ranged from 68% to 83% at fortification levels of 200 microg kg(-1) with relative standard deviation (RSD) from 4% to 12%. The limits of quantification were from 2 microg kg(-1) for FB(1) and FB(2), and 5 microg kg(-1) for FB(3), which are below the maximum residue level established by the European Union legislation in infant formulas. The proposed method was successfully applied to the analysis of twenty seven samples of baby food products collected from different markets, and one positive sample with a content of 15.9 microg kg(-1) for FB(1), 9.2 microg kg(-1)for FB(2) and 5.8 microg kg(-1) for FB(3) was obtained. Given the simplicity and potential of the proposed procedure, its application for safety control is recommended.     

A reversed phase high performance liquid chromatography method for the determination of fumonisins B1 and B2 in food and feed using monolithic column and positive confirmation by liquid chromatography/tandem mass spectrometry

The development of a reversed phase high performance liquid chromatography fluorescence method for the determination of the mycotoxins fumonisin B(1) and fumonisin B(2) by using silica-based monolithic column is described. The samples were first extracted using acetonitrile:water (50:50, v/v) and purified by using a C(18) solid phase extraction-based clean-up column. Then, pre-column derivatization for the analyte using ortho-phthaldialdehyde in the presence of 2-mercaptoethanol was carried out. The developed method involved optimization of mobile phase composition using methanol and phosphate buffer, injection volume, temperature and flow rate. The liquid chromatographic separation was performed using a reversed phase Chromolith(?) RP-18e column (100 mm × 4.6 mm) at 30 °C and eluted with a mobile phase of a mixture of methanol and phosphate buffer pH 3.35 (78:22, v/v) at a flow rate of 1.0 mL min(-1). The fumonisins separation was achieved in about 4 min, compared to approximately 20 min by using a C(18) particle-packed column. The fluorescence excitation and emission were at 335 nm and 440 nm, respectively. The limits of detections were 0.01-0.04 μg g(-1) fumonisin B(1) and fumonisin B(2), respectively. Good recoveries were found for spiked samples (0.1, 0.5, 1.5 μg g(-1) fumonisins B(1) and B(2)), ranging from 84.0 to 106.0% for fumonisin B(1) and from 81.0 to 103.0% for fumonisin B(2). Fifty-three samples were analyzed including 39 food and feeds and 14 inoculated corn and rice. Results show that 12.8% of the food and feed samples were contaminated with fumonisin B(1) (range, 0.01-0.51 μg g(-1)) and fumonisin B(2) (0.05 μg g(-1)). The total fumonisins in these samples however, do not exceed the legal limits established by the European Union of 0.8 μg g(-1). Of the 14 inoculated samples, 57.1% contained fumonisin B(1) (0.16-41.0 μg g(-1)) and fumonisin B(2) (range, 0.22-50.0 μg g(-1)). Positive confirmation of selected samples was carried out using liquid chromatography-tandem mass spectrometry, using triple quadrupole analyzer and operated in the multiple reaction monitoring mode.     

Carrier-facilitated bulk liquid membrane transport of iron(III)-siderophore complexes utilizing first coordination sphere recognition

Carrier-facilitated bulk liquid membrane (BLM) transport from an aqueous source phase through a chloroform membrane phase to an aqueous receiving phase was studied for various hydrophilic synthetic and naturally occurring Fe(III)-siderophore complexes using first coordination sphere recognition. Iron transport systems were designed such that two cis coordination sites on a hydrophilic Fe(III) complex are occupied by labile aquo ligands, while the other four coordination sites are blocked by strong tetradentate ligands (siderophores). The labile aquo coordination sites can be "recognized" by a liquid membrane-bound hydrophobic bidentate ligand, which carries the hydrophilic Fe(III)-siderophore complex across the hydrophobic membrane to an aqueous receiving phase. The system is further designed for uphill transport of Fe(III) against a concentration gradient, driven by anti-port H(+) transport. Three tetradentate siderophore and siderophore mimic ligands were investigated: rhodotorulic acid (H(2)L(RA)), alcaligin (H(2)L(AG)), and N,N'-dihydroxy-N,N'-dimethyldecanediamide (H(2)L(8)). Flux values for the transport of Fe(L(x))(OH(2))(2)(+) (x = RA, AG, 8) facilitated by the hydrophobic lauroyl hydroxamic acid (HLHA) membrane carrier were the highest when x = 8, which is attributed to substrate lipophilicity. Ferrioxamine B (FeHDFB(+)) was also selectively transported through a BLM by HLHA. The process involves partial dechelation of ferrioxamine B to produce the tetradentate form of the complex (Fe(H(2)DFB)(OH(2))(2)(2+)), followed by ternary complex formation with HLHA (Fe(H(2)DFB)(LHA)(+)) and transport across the membrane into the receiving phase. Uphill transport of ferrioxamine B was confirmed by increased flux as [H(+)](source phase) < [H(+)](receiving phase). The membrane flux of ferrioxamine B occurs near neutral pH, as evidence that ternary complex formation and ligand exchange are viable processes at the membrane/receptor surface of microbial cells.     

Direct measurement of the energy thresholds to conformational isomerization in tryptamine: experiment and theory

The methods of stimulated emission pumping-hole filling spectroscopy (SEP-HFS) and stimulated emission pumping population transfer spectroscopy (SEP-PTS) were applied to the conformation-specific study of conformational isomerization in tryptamine [TRA, 3-(2-aminoethyl)indole]. These experimental methods employ stimulated emission pumping to selectively excite a fraction of the population of a single conformation of TRA to well-defined ground-state vibrational levels. This produces single conformations with well-defined internal energy, tunable over a range of energies from near the zero-point level to well above the lowest barriers to conformational isomerization. When the SEP step overcomes a barrier to isomerization, a fraction of the excited population isomerizes to form that product. By carrying out SEP excitation early in a supersonic expansion, these product molecules are subsequently cooled to their zero-point vibrational levels, where they can be detected downstream with a third tunable laser that probes the ground-state population of a particular product conformer via a unique ultraviolet transition using laser-induced fluorescence. The population transfer spectra (recorded by tuning the SEP dump laser while holding the pump and probe lasers fixed) exhibit sharp onsets that directly determine the energy thresholds for conformational isomerization in a given reactant-product conformer pair. In the absence of tunneling effects, the first observed transition in a given X-Y PTS constitutes an upper bound to the energy barrier to conformational isomerization, while the last transition not observed constitutes a lower bound. The bounds for isomerizing conformer A of tryptamine to B(688-748 cm(-1)), C(1)(860-1000 cm(-1)), C(2)(1219-1316 cm(-1)), D(1219-1282 cm(-1)), E(1219-1316 cm(-1)), and F(688-748 cm(-1)) are determined. In addition, thresholds for isomerizing from B to A(<1562 cm(-1)), B to F(562-688 cm(-1)), and out of C(2) to B(<747 cm(-1)) are also determined. The A-->B and B-->A transitions are used to place bounds on the relative energies of minima B relative to A, with B lying at least 126 cm(-1) above A. The corresponding barriers have been computed using both density functional and second-order many-body perturbation theory methods in order to establish the level of theory needed to reproduce experimental results. While most of the computed barriers match experiment well, the barriers for the A-F and B-F transitions are too high by almost a factor of 2. Possible reasons for this discrepancy are discussed.     

Structure and conformational properties of N-pentafluorosulfur(sulfuroxide difluoride imide) SF5N=S(O)F2: vibrational analysis, gas electron diffraction, and quantum chemical calculations

The molecular structure and conformational properties of N-pentafluorosulfur(sulfuroxide difluoride imide), SF5N=S(O)F2, have been studied by vibrational spectroscopy (IR (gas) and Raman (liquid)), by gas electron diffraction (GED), and by quantum chemical calculations (MP2 and B3LYP with (6-31G(d) and 6-311+G(2df) basis sets). According to GED, the prevailing conformer possesses a syn structure (N-SF5 bond synperiplanar with respect to the bisector of the SF2 group). Splitting of the symmetric N=S=O stretching vibration in gas and liquid spectra demonstrates the presence of a second conformer (11(5)%) with anticlinal orientation of the N-SF5 bond according to quantum chemical calculations. The geometric structure, conformational properties, and vibrational frequencies are well reproduced by quantum chemical calculations.     

Determination of selected human pharmaceutical compounds in effluent and surface water samples by high-performance liquid chromatography-electrospray tandem mass spectrometry

A simple method is presented for the analysis of 13 pharmaceutical and pharmaceutical metabolite compounds in sewage effluents and surface waters. The pharmaceutical compounds were extracted using a genetic solid-phase extraction (SPE) procedure using Phenomenex Strata X as a stationary phase. Extracts were quantitatively analysed by four separate reversed-phase high-performance liquid chromatography-electrospray tandem mass spectrometry (HPLC-ESI-MS/MS) techniques and quantified by comparison with an internal standard ([13C]-phenacetin). Recoveries and limits of detection (LOD) for sulfamethoxazole (120%, 50 ng l(-1)), acetyl-sulfamethoxazole (56%, 50 ng l(-1)), trimethoprim (123%, 10 ng l(-1)), erythromycin (73%, 10 ng l(-1)), paracetamol (75%, 50 ng l(-1)), ibuprofen (117%, 20 ng l(-1)), clofibric acid (83%, 50 ng l(-1)), mefenamic acid (24%, 50 ng l(-1)), diclofenac (62%, 20 ng l(-1)), propranolol (45%, 10 ng l(-1)), dextropropoxyphene (63%, 20 ng l(-1)) and tamoxifen (42%, 10 ng l(-1)) were all acceptable. The recovery of lofepramine (4%) was too low to be of use in a monitoring programme. Application of the method to samples collected from UK sewage effluents and surface waters showed detectable concentrations of mefenamic acid, diclofenac, propranolol, erythromycin, trimethoprim and acetyl-sulfamethoxazole in both matrices. Ibuprofen and dextropropoxyphene were detected in sewage effluents alone. All other pharmaceutical compounds were below the methods limits of detection.     

Comparison of pyrolysis-mass spectrometry with high performance liquid chromatography for the analysis of vancomycin in serum

Mass spectrometry coupled with a pyrolysis inlet system (Pyr-ms) is compared with high performance liquid chromatography (HPLC) for the determination of vancomycin and its crystal degradation products (CDP-Is) in human serum. Quantitative analysis of Pyr-ms was performed by selected ion monitoring (SIM) method at 108 mass:charge (m/z) of pyrolysis product of vancomycin. 3-Nitroaniline (138 m/z) was used as an internal standard. A mu-Bondapak C(18) column and the gradient mobile phase of triethylamine buffer (pH 6.2), acetonitrile and tetrahydrofuran and a photometric detection at 205 nm are found to be the optimum conditions for the HPLC determination of vancomycin and CDP-Is. The limit of detection (LOD=1 ng ml(-1)), linearity (1 ng ml(-1)-10 mg ml(-1)), relative standard deviation (R.S.D.=1%), time analysis (1/2 h) and sample volume (50 mul) of Pyr-ms are far better than of the HPLC method. However, the HPLC method can individually determine the concentration of vancomycin and its degradation products.     

Ternary cubic phases containing ionic liquid

The phase diagram of 1-butyl-3-methylimidazolium tetrafluoroborate (bmim-BF(4)) in aqueous solutions of oleyl polyoxyethylene (20) ether (C(18:1)E(20)) was determined at 25 degrees C by a combination of visual inspection and small-angle X-ray scattering (SAXS). The micellar cubic Im3m liquid crystalline phase found in the ternary system was investigated by means of SAXS and rheological techniques. The cubic samples show highly elastic gel-like properties indicated by their mechanical and discrete relaxation spectra. Moreover at a constant C(18:1)E(20)/bmim-BF(4) ratio, with decreasing water content the network strength increases. The internal structure apparently becomes more stable, as indicated by an increase in the storage and loss moduli and a decrease in the lattice parameter alpha and interfacial area of per surfactant a(S). Furthermore, investigations on the representative micellar Im3m cubic phases formed in a relatively hydrophobic ionic liquid bmim-PF(6) with C(18:1)E(20) and water ternary system (P(1)), a C(18:1)E(20)/water binary system (J(1)), and C(18:1)E(20)/water/bmim-BF(4) system (B(1)) were made in comparison. It can be clearly seen that appreciably different mechanical spectra and relaxation spectra are shown by the cubic phases investigated. B(1) exhibits a typical gel-like dynamic rheogram while P(1) exhibits fluid-like viscoelastic properties to some extent, and J(1) shows traits of the general Maxwell model. These differences are analyzed through SAXS data as the employment of ionic liquids and their different location in the cubic phases.     

Determination of RSD921 in human plasma by high-performance liquid chromatography-tandem mass spectrometry using tri-deuterated RSD921 as internal standard: application to a phase I clinical trial.

A fast, sensitive and specific method is presented for the quantification of RSD921 in human plasma by liquid chromatography coupled with tandem mass spectrometry using tri-deuterated RSD921 (3d-RSD921) as an internal standard. A single-step liquid/liquid extraction was performed with diethyl ether/hexane (80 : 20, v/v) using 0.5 ml of plasma. The plasma calibration curves were linear from 0.1 to 20 ng ml(-1) (r > 0.999). Between-run precision, based on the percent relative deviation for replicate (n = 40) quality controls, was < or =7.27% (0.5 ng ml(-1)), < or =7.39% (5.0 ng ml(-1)), and < or =5.06% (20.0 ng ml(-1)). Between-run accuracies, based on the relative error, were +/-2.59%, +/-1.23% and +/-1.64% respectively. The method was developed to evaluate the pharmacokinetic profile after 15 min of intravenous stepwise-ascending infusion dose of RSD921 in 18 healthy volunteers. A dissociation study of protonated RSD921 and 3d-RSD921 by collision-induced dissociation using in-source fragmentation and tandem mass spectrometry is also presented.     

Development and in-house validation of a robust and sensitive solid-phase extraction liquid chromatography/tandem mass spectrometry method for the quantitative determination of aflatoxins B1, B2, G1, G2, ochratoxin A, deoxynivalenol, zearalenone, T-2 and HT-2 toxins in cereal-based foods

A sensitive and robust liquid chromatography/tandem mass spectrometry (LC/MS/MS) method was developed for the simultaneous determination of aflatoxins (B(1), B(2), G(1), G(2)), ochratoxin A, deoxynivalenol, zearalenone, T-2 and HT-2 toxins in cereal-based foods. Samples were extracted with a mixture of acetonitrile/water (84:16, v/v) and cleaned up through a polymeric solid-phase extraction column. Detection and quantification of the nine mycotoxins were performed by reversed-phase liquid chromatography coupled with electrospray ionization triple quadrupole mass spectrometry (LC/ESI-MS/MS), using fully (13)C-isotope-labelled mycotoxins as internal standards. The method was validated in-house for five different cereal processed products, namely barley, oat and durum wheat flours, rye- and wheat-based crisp bread. Recoveries and repeatability of the whole analytical procedure were evaluated at contamination levels encompassing the EU maximum permitted levels for each tested mycotoxin. Recoveries ranged from 89 to 108% for deoxynivalenol, from 73 to 114% for aflatoxins, from 85 to 114% for T-2 and HT-2 toxins, from 64 to 97% for zearalenone, from 74 to 102% for ochratoxin A. Relative standard deviations were less than 16% for all tested mycotoxins and matrices. Limits of detection (signal-to-noise ratio 3:1) ranged from 0.1 to 59.2 μg/kg. The trueness of the results obtained by the proposed method was demonstrated by analysis of reference materials for aflatoxins, deoxynivalenol, zearalenone. The use of inexpensive clean-up cartridges and the increasing availability of less expensive LC/MS/MS instrumentation strengthen the potential of the proposed method for its effective application for reliable routine analysis to assess compliance of tested cereal products with current regulation.