Fatty acids profiling of avocado seed and pulp using gas chromatography–mass spectrometry combined with multivariate chemometric techniques

In the present study, the profiling of 17 fatty acids (FAs) in avocado seed and pulp was investigated. The fatty acids were extracted with vortex-assisted extraction, methyl esterified and finally preconcentrated by dispersive liquid–liquid microextraction. The preconcentrated fatty acid methyl esters (FAMEs) were analyzed using gas chromatography–mass spectrometry (GC–MS) to obtain qualitative and quantitative information. The GC–MS data were analyzed using multivariate curve resolution-alternating least squares (MCR-ALS) method to overcome general chromatographic problems such as overlapped peaks, background interference and peak shifts. The calibration data were prepared using pure analytical information obtained by MCR-ALS. The linear dynamic ranges and regression coefficients (R ²) for FAMEs were in the range of 0.19–65 mg L^?1 and 0.990–0.999, respectively. The relative standard deviation (RSD%) for determination of FAs in avocado seed and pulp was 0.17–8.84 and 0.64–17.93, respectively. The main FAs in the avocado pulp were: oleic acid (74.25 g Kg^?1), linoleic acid (26.87 g Kg^?1), palmitic acid (26.02 g Kg^?1), palmitoleic acid (1.22 g Kg^?1) and stearic acid (0.05 g Kg^?1). And, the main FAs in the avocado seed were: linoleic acid (1.09 g Kg^?1), palmitic acid (0.47 g Kg^?1), oleic acid (0.33 g Kg^?1), linolenic acid (0.12 g Kg^?1), and palmitoleic acid (0.04 g Kg^?1).     

Separation and identification of selenotrisulfides in epithelial cell homogenates by LC–ICP–MS and LC–ESI-MS after incubation with selenite

To elucidate how selenite is metabolised in the intestine after oral intake, it was incubated with homogenized epithelial cells from pigs. When the metabolites were analysed by LC–ICP–MS, two major selenium metabolites were separated in the supernatant from the homogenate. These metabolites were formed instantly but disappeared within 15 min. No other selenium-containing compounds appeared during this time. Hence, the secondary reaction products were either volatilised or precipitated. To verify the identity of the compounds, a larger amount of selenite was incubated with epithelial cells. The presence of Cys-Se-SG and GS-Se-SG was verified by LC–ESI-MS. Selenotrisulfides were synthesized by reaction of L-cysteine and L-glutathione with sodium selenite. The reaction mixture contained three main products: selenodicysteine (Cys-Se-Cys), selenocysteine glutathione (Cys-Se-SG), and selenodiglutathione (GS-Se-SG). The two transient selenium compounds in the epithelial cell incubation mixture co-eluted with the synthesized Cys-Se-SG and GS-Se-SG, respectively. The identities of these compounds were verified by LC–ESI-MS. Hence, these selenium metabolites have now been identified by ESI-MS after isolation from epithelial cells.     

Structural characterization and electrical conductivity studies of BaMoO4 nanofibers prepared by sol–gel and electrospinning techniques

Scheelite type BaMoO₄ nanofibers were prepared by using acrylamide assisted sol–gel process and electrospinning technique. The prepared Scheelite BaMoO₄ nanofibers were characterized by using TG/DTA, XRD, FTIR, FT-Raman and SEM–EDX techniques. Thermal behavior, crystalline phase and structure of the prepared BaMoO₄ nanofibers samples were confirmed from the analysis of the obtained results of TG/DTA, XRD, FTIR and FT-Raman respectively. SEM micrographs along with EDX showed the formation of one dimensional (1D) nanofibers 100–350 nm diameters and existence of Ba, Mo and O elements in the BaMoO₄ nanofibers sample. The electrical conductivity of BaMoO₄ nanofibers as a function of temperature 200–400 °C under air was evaluated by analyzing the measured impedance data using the winfit software. The newly prepared Scheelite type BaMoO₄ nanofibers showed electrical conductivity of 0.92 × 10^?3 S/cm at 400 °C.     

Evaluation of Sempervivum tectorum L. Flavonoids by LC and LC–MS

A reversed-phase high-performance liquid chromatography method with UV detection was developed for determination of [(N-morpholine)methylene]daunorubicin hydrochloride (DD-M) during studies of its stability. In this LC method the following were used: an RP-column, the mobile phase—acetonitrile:methanol:solution A (9:1:10 v/v/v) [solution A contains 2.88 g of sodium laurilsulfate and 1.6 mL of phosphoric acid(V)] with a flow rate of 1.4 mol L⁻¹ and quinine hydrochloride as an internal standard. The detection wavelength was 254 nm. The method was validated with regard to linearity, limit of detection, limit of quantitation, selectivity and precision. Hydrolysis of the DD-M catalyzed by hydrogen ions in hydrochloric acid and a spontaneous reaction of the DD-M degradation under the influence of the water in sodium hydroxide took place. The thermodynamic parameters of these reactions—energy, enthalpy and entropy of activation—were calculated. It was observed that a positive salt effect occurred in hydrochloric acid.

     

Simultaneous kinetic–spectrophotometric determination of mycophenolate mofetil and mycophenolic acid based on complexation with Fe(III) using chemometric techniques

Determination of pharmaceutical analytes has been subjected to many investigations, especially in transplantations in which accurate and precise detection of drugs is of importance. In this study, a simple and fast complexation reaction has been employed for simultaneous kinetic–spectrophotometric determination of two immunosuppressant drugs, mycophenolate mofetil and its active metabolite mycophenolic acid, which is based on the reaction between drugs and Fe(III) ions in the presence of sodium dodecyl sulfate as anionic surfactant by standard addition method. The effect of influential parameters including type of surfactant, concentration of Fe(III) ions and pH of the solution on the complexation reaction has been studied, and SDS was chosen as suitable surfactant, while reaction proceeds with 0.1 M Fe(III) at pH 4. Multivariate curve resolution-alternating least squares has been employed for analyzing the multiset data obtained from augmentation of resulting standard addition matrices. Values for limit of detection of method have been calculated as 4.88 and 1.62 µg mL^?1 for mycophenolic acid and mycophenolate mofetil, respectively, and Beer’s law is obeyed over the concentration ranges 10–200 µg mL^?1 for MPM and 50–250 µg mL^?1 for MPA. The proposed method was successfully applied for determination of drugs in plasma serum samples. The accuracy and reliability of the method was further ascertained by recovery studies via standard addition procedure.     

Determination of Fenofibric Acid in Human Plasma by LC–MS/MS and LC–UV

A sensitive, high-throughput and economic liquid chromatographic method for determination of fenofibric acid in human plasma was developed and validated by ultraviolet detection and tandem mass spectrometry, then applied in pharmacokinetic study to investigate Lipanthyl™ 200 mg MC bioavailability under food and fasting conditions. Fenofibric acid with 2-chloro fenofibric acid-d6 (internal standard) was extracted from 100 µL of human plasma by acetonitrile in a single extraction step. 25 and 2 µL from supernatant were injected onto ACE column, 50 mm, 5 micron with 4.6 mm inner diameter for LC–UV and 2.1 mm for LC–MS/MS, and both systems were eluted isocratically by water:methanol:formic acid (35:65:0.1, v/v/v), with a constant flow rate of 1 mL min⁻¹. The established calibration curve was linear between 0.05–20 µg mL⁻¹, and the within- and between-day precisions were all below 13 % in both LC–MS/MS and LC–UV systems during validation, and accuracies ranged between 91 and 112 %. Twenty-eight healthy adult subjects participated in this clinical study, and the pharmacokinetic parameters including coefficient of variation were calculated and discussed. A dramatic decrease in C _max and AUC0-72 (3.63- and 1.85-fold, respectively) were observed for Lipanthyl™ MC under fasting conditions with more variable inter subject measurements comparing to the fed state.

     

Fingerprint Analysis of Euonymus alatus (Thuhb) siebold by LC–DAD and LC–ESI–MS

A liquid chromatography coupled with photodiode array detection and electrospray ionization tandem mass spectrometry method was first developed for a chemical fingerprint analysis of Euonymus alatus (Thuhb) siebold (EAS) and rapid identification of major compounds in the fingerprints. Fingerprint profiles were found to be consistent for the herbs acquired from different locations, but the relative abundance of peaks was varied. Twelve peaks were chosen as the common peaks. Quercetin and rutin were detected by comparing the retention times, MS and UV spectra with the standards. The relative retention time and relative peak area of the 12 peaks in the fingerprint were calculated by setting the quercetin as the reference peak. The experimental data were used for similarity calculation and hierarchical clustering analysis. By comparing the UV and MS spectra data with those of the authentic standards and literature, five main peaks in the fingerprints were identified. Finally, five medicinal portions of the herb (leaf, fruit, stem, pterygium and root) were also analyzed by this method. It was found that there were similar chemical components in different parts of this herb but the contents were very different. The developed fingerprint assay was specific and could be readily utilized for comprehensive evaluation of EAS, as well as to distinguish different medicinal portions.     

Modification of composites of block copolymers–gold nanoparticles with enzymes and their characterization by electrochemical techniques

In this work, the poly(styrene-vynil pyridine) block copolymer was used as a porous pattern to study the electrodeposition of gold inside the pores, as a new method to obtain gold nanoparticles. The porous pattern left by the copolymer film onto a conductive glass surface was characterized by atomic force microscopy (AFM), evidencing pores of 30 nm diameter. After the electrodeposition, 30 nm diameter gold nanoparticles were obtained and they were characterized by cyclic voltammetry (CV) and AFM, and then used to study the adsorption of glucose oxidase enzyme. The adsorption process of glucose oxidase on gold nanowires was investigated by CV and electrochemical impedance spectroscopy. The morphological and capacitance results indicate that the block copolymer–gold nanoparticle composite seems to be a good candidate to design biosensors and immunosensors.     

In vivo quantification and pharmacokinetic studies of cotinine in mice after smoke exposure by LC–MS/MS

A sensitive analytical method was developed and validated for the quantification of cotinine in mouse plasma after exposure to smoke of 0.5, 1.0, and 1.5 commercially available cigarettes, using liquid chromatography tandem mass spectrometry. The method was validated over a linear concentration range of 0.075–20.0 ng/mL with the R² value being higher than 0.99. Both the precision (coefficient of variation; %) and accuracy (relative error; %) were within acceptable criteria of <15%. The lower limit of quantification (LLOQ) for cotinine was 0.075 ng/mL with sufficient specificity, accuracy, and precision. Following exposure to 0.5, 1.0, and 1.5 cigarette smoke, it was observed that the AUC and the C_max increased linearly as the doses increased. The pharmacokinetics of cotinine was found linear for the range of 0.5–1.5 commercial cigarette smoke. The quantification of the concentration of cotinine in mouse plasma after smoke exposure will facilitate future behavioral and toxicological experiments in animals and may prove useful in predicting cotinine levels in humans during smoking.     

Anthocyanin identification and composition of wild Vitis spp. accessions by using LC–MS and LC–NMR

The composition and concentration of anthocyanins of grape berry skins were analyzed in order to assess phenotypic variation between four grape wine varieties belonging to 4 different species: Vitis vinifera, Vitis amurensis, Vitis cinerea and Vitis X champinii. High-performance liquid chromatography coupled to mass spectrometry (LC–MS) and NMR spectroscopy (LC–NMR) were used to separate and identify the structure of anthocyanins present in these species. Combination of LC–MS and LC–NMR data resulted in the identification of 33 anthocyanins. In particular, newly reported cis isomers of p-coumaric-derivatives were identified (petunidin-, peonidin- and malvidin-3-(6-p-coumaroyl)-5-diglucoside). In V. cinerea and V. vinifera, anthocyanins were monoglucoside derivatives whereas in V. amurensis and V. X champinii, both mono- and diglucoside derivatives were identified. Malvidin-, delphinidin- and petunidin-derivatives were, respectively, the most abundant components in V. cinerea and V. vinifera, V. amurensis and V. X champinii.     

Efficient and rapid method for extraction of intact phospholipids from sediments combined with molecular structure elucidation using LC–ESI-MS–MS analysis

This paper presents the application of an efficient method for extraction and fractionation of intact phospholipids (PLs) from complex sediment matrices and elucidation of their molecular structure by normal-phase HPLC–ESI-MS–MS. Flow-blending extraction was tested with different solvent mixtures and the best recovery of all PLs classes from the sediment matrix was achieved by using methanol–dichloromethane–buffer, 2:1:0.8. The applied LC–ESI-MS system has linearity of R²=0.98 and a detection limit of 0.5 ng/PL, sufficient for reliable identification of complex mixtures of PLs. MS–MS analyses using a triple-quadrupole mass spectrometer enables detection of individual PL side-chain composition and, hence, characterization of the living organisms contributing to the sedimentary organic material. Parallel GC–MS analysis of the hydrolysed phospholipid fatty acids supports the characterized fatty acid patterns determined from intact PLs. The PL inventory of different investigated lacustrine surface sediments shows predominantly high abundance of phosphatidylglycerols and phosphatidylethanolamines and phosphatidyl-mono- and dimethyl-ethanolamines with fatty acyl side-chains typically known from bacteria. In a sample from Lake Baikal intense signals of bacterial 14:0-acyl-PGs were also identified, for the first time in sediments as far as we are aware.     

Determination of atorvastatin and metabolites in human plasma with solid-phase extraction followed by LC–tandem MS

The aim of the present study was to develop a chromatographic method for the analysis of atorvastatin, o- and p-hydroxyatorvastatin (acid and lactone forms) in human plasma after administration of atorvastatin at the lowest registered dose (10 mg) in clinical studies. Sample preparation was performed by solid-phase extraction and was followed by separation of the analytes on an HPLC system with a linear gradient and a mobile phase consisting of acetonitrile, water and formic acid. Detection was achieved by tandem mass spectrometry operated in the electrospray positive ion mode. Validation of the method for the compounds for which reference compounds were available (acid forms of atorvastatin, o- and p-hydroxyatorvastatin) showed linearity within the concentration range (0.2–30 ng/ml for atorvastatin acid and p-hydroxyatorvastatin acid, and 0.5–30 ng/ml for o-hydroxyatorvastatin acid) (r²0.99, n=5 for all analytes). Accuracy and precision (evaluated at 0.5, 3 and 30 ng/ml for atorvastatin, p-hydroxyatorvastatin and 1, 3 and 30 ng/ml for o-hydroxyatorvastatin) were both satisfactory. The detection limit was 0.06 ng/ml for atorvastatin and p-hydroxyatorvastatin, and 0.15 ng/ml for o-hydroxyatorvastatin. The method has been successfully applied in a clinical study where atorvastatin, o- and p-hydroxyatorvastatin (both acid and lactone forms) could be detected in a 24-h sampling interval after administration of the lowest registered dose of atorvastatin (10 mg) for one week.     

Therapeutic drug monitoring by LC–MS–MS with special focus on anti-infective drugs

Liquid chromatography coupled to mass spectrometry nowadays plays an important role in the field of therapeutic drug monitoring (TDM), especially of new compounds for which no immunoassays are available. This paper reviews LC–MS(–MS) methods published recently for anti-infective drugs: antiretroviral drugs, other antiviral drugs, antibacterial drugs, antihelmintic drugs, antimalarial drugs, and other antiprotozoal drugs. An overview of the different methods is given, with special focus on selection of the internal standard and validation procedures.     

Detection and Confirmation of Ginsenosides in Horse Urine by GC–MS and LC–MS

Ginseng has been used by the Chinese as a traditional herbal medicine for thousands of years. In view of the growing popularity in the use of ginseng preparations as natural remedies and food supplements worldwide, there is an increasing concern for their abuse in both human and animal sports. Ginsenosides are considered the major constituents of ginseng responsible for its pharmacological properties. In this study, a method was developed for the detection and confirmation of a number of ginsenosides in horse urine. The intact ginsenosides were detected and confirmed at 5–100 ng mL^?1 by LC–MS², and two deglycosylation metabolites, namely protopanaxadiol and protopanaxatriol, could both be detected and confirmed at 2 ng mL^?1 by GC–MS² after trimethylsilylation. The above GC–MS and LC–MS methods were then applied to study the in vitro metabolism of ginsenosides Rg1 and Rb1 and the in vivo urinary metabolites after oral administration of Rg1 to horses. Results obtained reveal the very first evidence for the existence of the metabolites, Rg1 and protopanaxatriol, as glucuronides in urine.     

Determination of Shikimic Acid in Fruits of Illicium Species and Various Other Plant Samples by LC–UV and LC–ESI–MS

A simple and specific analytical method for the quantitative determination of shikimic acid from the methanol extract of the fruits of Illicium species and from various plant samples was developed. The LC–UV separation was achieved by reversed-phase chromatography on a C18 column with potassium dihydrogen phosphate and methanol as the mobile phase. In the LC–MS method, the separation was achieved by a C12 column using water and acetonitrile, both containing 0.1% acetic acid as the mobile phase. The methods were successfully used to study the percentage compositions of shikimic acid present in nine species of Illicium and various other plant samples. The detector response was linear with concentrations of shikimic acid in the range from 1.0–500.0 μg mL^?1 by LC–UV and 100–1000 ng mL^?1 by LC–MS. Mass spectrometry coupled with electrospray ionization interface is described for the identification of shikimic acid in various plant samples. This method involved the use of the [M-H]^? ions of shikimic acid at m/z 173.0455 (calculated mass) in the negative ion mode with extractive ion monitoring.     

Synthesis of monoclinic BiVO4 microribbons by sol–gel combined with electrospinning process and photocatalytic degradation performances

Quasi one-dimensional (1D) BiVO₄ microribbons were prepared by sol–gel combined with electrospinning method. The prepared samples were characterized with thermogravimeter, differential scanning calorimeter, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and UV–vis absorbance spectroscopy. The as-prepared products showed a well-defined ribbon structure with 2–3 μm in width, tens of microns in length and about 0.4 μm in thickness, respectively and exhibited excellent photocatalytic activity in the photodegradation of methylene blue under visible light irradiation.     

Thermal investigation of heavy crude oil by simultaneous TG–DSC–FTIR and EDXRF

Present study investigates thermal behavior of two heavy crude oils with different °API values by simultaneous thermogravimetry–differential scanning calorimetry–fourier transform infrared spectroscopy (TG–DSC–FTIR), and an evaluation of the chemical element levels present in the oils’ ashes was done by energy dispersive X-ray fluorescence spectrometry. TG and DSC curves were obtained for two samples in nitrogen atmosphere. Among all inorganic components evaluated, the highest concentration in the two oils was SO₃. Thus this study may contribute to a better understanding of the thermal behavior of heavy crude oils and their composition.