Detection of Synthetic Antioxidants: What Factors Affect the Efficiency in the Chromatographic Analysis and in the Electrochemical Analysis?

Antioxidants are food additives largely employed to inhibit oxidative reactions in foodstuffs rich in oils and fat lipids, extending the shelf life of foodstuffs and inhibiting alterations in color, flavor, smell, and loss of nutritional value. However, various research has demonstrated that the inadequate use of synthetic antioxidants results in environmental and health problems due to the fact that some of these compounds present toxicity, and their presence in the human body, in high concentrations, is related to the development of some cancer types and other diseases. Therefore, the development of analytical methods for identifying and quantifying synthetic antioxidants in foodstuffs is fundamental to quality control and in ensuring consumer food safety. This review describes the recent chromatographic and electrochemical techniques used in the detection of synthetic phenolic antioxidants in foodstuffs, highlighting the main characteristics, advantages and disadvantages of these methods, and specific typical features, which include extraction methods for sample preparation and materials used in the working electrode construction, considering chromatographic and voltammetric methods, since these specific features influence the efficiency in the analysis.     

High-Performance Liquid Chromatographic Determination of the Metabolites of the Potato Glycoalkaloids, α-Chaconine and α-Solanine,in Potato Tubers and Potato Products

Abstract

A high-performance liquid chromatographic method has been developed to separate and quantify the metabolites, γ-chaconine, β₁-and β₂-chaconine, γ-solanine and β₂-solanine, of the potato gly-coalkaloids α-chaconine and α-solanine in potatoes and potato products. A carbohydrate analysis column and a solvent system of tetrahydrofuran-water-acetonitrile (55:8:37) were employed for the separation. Flow rate was 1.1 ml/min and the compounds were monitored at 215 nm. β₂-chaconine (0.63 mg to 29.75 mg/100 g dried weight) was present in all samples whereas the other glycosides of α-chaconine were only detectable in the animal feed products. It appears that some of the animal feeds may contain trace amounts of γ-solanine and an unknown which maybe β₁-solanine. Limit of detection for all glycosides was 0.05 μg/μl. Elution time for all the lower glycosides of α-chaconine was 8 min versus 16 min for the α-solanine group. These metabolic compounds were confirmed using thin-layer chromatography.     

Identification of the Major Constituents in Zhimu–Huangqi Herb-Pair Extract and Their Metabolites in Rats by LC–ESI-MSn

The Zhimu–Huangqi herb-pair is a famous Chinese herbal formula with a combination of Rhizoma Anemarrhenae (Zhimu in Chinese) and Radix Astragali (Huangqi in Chinese). This work describes a sensitive and specific LC–ES-MSⁿ methodology for identification of the major constituents in Zhimu–Huangqi herb-pair extract and their metabolites in rats after oral administration. A total of 30 compounds have been identified or tentatively characterized from the herb-pair extract, and 13 of them were unambiguously identified by comparing the retention times and mass spectra with those of reference standards, while the other 17 compounds were tentatively identified on the basis of their MSⁿ fragmentation behaviors and exact mass information from literature. Moreover, the metabolites in vivo were also identified. The Zhimu–Huangqi herb-pair extract was actively metabolized in rats, including four parent compounds and 8 metabolites in serum and seven parent compounds and 23 metabolites in urine. This study proposed a good example for the rapid identification of major constituents in complex systems such as herbal extract or traditional Chinese medicine formula, which facilitated the clarification of the metabolic pathway of the herbs in the body to better understand the action mechanism.

     

Identification of the Major Constituents in Zhimu–Huangqi Herb-Pair Extract and Their Metabolites in Rats by LC–ESI-MSn

The Zhimu–Huangqi herb-pair is a famous Chinese herbal formula with a combination of Rhizoma Anemarrhenae (Zhimu in Chinese) and Radix Astragali (Huangqi in Chinese). This work describes a sensitive and specific LC–ES-MSⁿ methodology for identification of the major constituents in Zhimu–Huangqi herb-pair extract and their metabolites in rats after oral administration. A total of 30 compounds have been identified or tentatively characterized from the herb-pair extract, and 13 of them were unambiguously identified by comparing the retention times and mass spectra with those of reference standards, while the other 17 compounds were tentatively identified on the basis of their MSⁿ fragmentation behaviors and exact mass information from literature. Moreover, the metabolites in vivo were also identified. The Zhimu–Huangqi herb-pair extract was actively metabolized in rats, including four parent compounds and 8 metabolites in serum and seven parent compounds and 23 metabolites in urine. This study proposed a good example for the rapid identification of major constituents in complex systems such as herbal extract or traditional Chinese medicine formula, which facilitated the clarification of the metabolic pathway of the herbs in the body to better understand the action mechanism.     

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.     

SPE–LC Multi-Residue Analysis of Mebendazole and its Metabolites in Grass Carp and Shrimp

An analytical method was developed to detect the residue of mebendazole and its metabolites (hydroxymebendazole and aminomebendazole) in the muscle of grass carp and shrimp by LC–UV detection. Mebendazole and its metabolites were extracted with water and ethyl acetate, defatted with hexane, and purified with MCX solid phase extraction column. The intra- and inter-batch precision (measured by CV%) was <9.0%. The accuracy (measured by relative error, %) was <12%. The LODs were 2.5 μg kg^?1 for mebendazole and hydroxymebendazole, 5 μg kg^?1 for aminomebendazole; the LOQs were 5 μg kg^?1 for mebendazole and hydroxymebendazole, 10 μg kg^?1 for aminomebendazole. The mean recoveries of mebendazole and its metabolites from grass carp and shrimp muscle at a concentration range of 5.0–500.0 μg kg^?1 were 90.7–97.0% with relative standard deviations below 10%.     

Metabolites of A Novel Antibiotic Bitespiramycin in Rat Urine and Bile

A sensitive analytical method to identify active metabolites of bitespiramycin in rat urine and bile was developed by liquid chromatography-electrospray ionization tandem mass spectrometry(LC/ESI-MS^n).Bitespiramycin and its major active metabolites in rat urine and bile were isolated and identified as M1 serial(spiramycin Ⅰ，Ⅱ，Ⅲ),M2 serial(platenomycin A1,josamycin and leucomycin A1) and M3 serial(deisovalerylplatenomycin A1,deisovaleryljosamycin,deisovalerylleucomycin A1).     

Liquid Chromatographic Resolution of the Enantiomers of Metoprolol and Carvedilol in Pharmaceutical Formulations by use of Marfey’s Reagent and its Variants

JPC – Journal of Planar Chromatography – Modern TLC - A simple and rapid method has been established for indirect separation of the enantiomers of (R,S)-metoprolol and (R,S)-carvedilol...     

A Highly Sensitive Kinetic Spectrophotometric System and Its Analytical Potential for Chromatographic Detection of Metal Ions

Micelles,microemulsions.vesicles,etc.,areorganicmicroheterogeneousmedia.Useofthesemediainanalyticalreactionsfordevelopingnewkinetic-baseddeterminationsorimprovingpreviouslyestablishedkineticmethodshasbeenreported"2.Inrecentyears,amixedmicellarmediumc...     

Identification of Acepromazine and Its Metabolites in Horse Plasma and Urine by LC–MS/MS and Accurate Mass Measurement

Acepromazine maleate (Sedalin^®) was administered orally to six thoroughbred horses at a dose of 0.15 mg kg⁻¹. Urine and blood samples were collected up to 412 h post-administration. Plasma and urine were hydrolysed; plasma samples were then processed using liquid–liquid extraction and urine samples using solid-phase extraction. A sensitive tandem mass spectrometric method was developed in this study, achieving a lower limit of quantification for acepromazine of 10 pg mL⁻¹ in plasma and 100 pg mL⁻¹ in urine. Acepromazine, hydroxyethylpromazine, hydroxyacepromazine, hydroxyethylpromazine sulphoxide, hydroxyethylhydroxypromazine, dihydroxyacepromazine and dihydroxyhydroxyethylpromazine were detected in the post-administration samples. The parent drug and its metabolites were identified using a combination of UPLC–MS/MS and accurate mass measurement. Separation of the structural isomers hydroxyethylpromazine sulphoxide and hydroxyethylhydroxypromazine was another significant outcome of this work and demonstrated the advantages to be gained from investing in chromatographic method development.

     

Identification of Acepromazine and Its Metabolites in Horse Plasma and Urine by LC–MS/MS and Accurate Mass Measurement

Acepromazine maleate (Sedalin^?) was administered orally to six thoroughbred horses at a dose of 0.15?mg?kg^?1. Urine and blood samples were collected up to 412?h post-administration. Plasma and urine were hydrolysed; plasma samples were then processed using liquid–liquid extraction and urine samples using solid-phase extraction. A sensitive tandem mass spectrometric method was developed in this study, achieving a lower limit of quantification for acepromazine of 10?pg?mL^?1 in plasma and 100?pg?mL^?1 in urine. Acepromazine, hydroxyethylpromazine, hydroxyacepromazine, hydroxyethylpromazine sulphoxide, hydroxyethylhydroxypromazine, dihydroxyacepromazine and dihydroxyhydroxyethylpromazine were detected in the post-administration samples. The parent drug and its metabolites were identified using a combination of UPLC–MS/MS and accurate mass measurement. Separation of the structural isomers hydroxyethylpromazine sulphoxide and hydroxyethylhydroxypromazine was another significant outcome of this work and demonstrated the advantages to be gained from investing in chromatographic method development.     

Reversed–Phase Liquid Chromatographic Determination of Zaleplon in Human Plasma and its Pharmacokinetic Application

Abstract

A simple, rapid, specific, and reliable high performance liquid chromatographic assay of zaleplon in human plasma has been developed. Reversed‐phase chromatography was conducted using a mobile phase of methanol∶ammonium acetate buffer (50∶50) v/v, pH 3.2 adjusted with orthophosphoric acid, UV detection at 232 nm. After extraction from plasma by precipitation the drug was chromatographed using a C₁₈ reversed‐phase analytical column. The average recoveries of zaleplon from spiked plasma in the concentration range from 0.005–0.2 µg/ml were 93.29%, and their respective CV% was 2.557%. Regression analysis for the calibration plot for plasma standards obtained on three different days for the drug concentrations between 0.005–0.2 µg/ml indicated excellent linearity (r>0.999) and the coefficient of variation of the slopes of the three lines was less than 2%. The limit of detection was 5 ng/ml. Analysis of variance of the data showed no detectable difference in the slopes of the three standard plots (F=3.1, P>0.01). The high correlation coefficients and the similarities in the slopes are good indications of the excellent reproducibility and linearity of the proposed method. The proposed method was applied to study the bioequivalence of a commercial product of zaleplon, using as reference standard the innovator drug product. The study was conducted by using one capsule (1×10 mg) of each of the commercial product and the reference standard in a two‐way open randomized crossover design involving 24 volunteers. The criteria used to assess bioequivalence of the products were AUC (0?∞), C_max, t_max, t_1/2, and K. The obtained values for these parameters were 0.246±0.03 µg h/ml, 0.150±0.013 µg/ml, 1 h, 1.26±0.36 h, and 0.5928±0.1732 h^?1 for product A whereas, for product B they were 0.256±0.044 µgh/ml, 0.142±0.014 µg/ml, 1 h, 1.18±0.33 h, and 0.63±0.1747 h^?1, respectively.     

Quantitative Analysis of Terbutaline (Bricanyl®) in Human Plasma with Liquid Chromatography and Electrochemical Detection Using On-Line Enrichment

Abstract

A liquid chromatographic method with electrochemical detection (LC-EC) has been developed for the quantitative analysis of terbuta-line in the range 5–50 pmole ml^?1 of human plasma. Terbutaline is isolated from 2 ml of plasma on an ion-exchange column and the eluate is concentrated on a hydrophobic precolumn on-line in the chromatographic system. The precolumn is then back-flushed for further separation onto a hydrophobic analytical column. The mobile phase is a methanol-aqueous buffer to which sodium perchlorate is added to achieve resolution from interfering peaks. A glassy carbon electrode is used for detection. Comparison has been made with gas chromatography-mass spectrometry (GC-MS) to examine the accuracy of the method.     

Simultaneous Determination of Flonicamid and its Metabolites in Tea by Liquid Chromatography–Tandem Mass Spectrometry

An analytical method was established to simultaneously quantify flonicamid and its metabolites 4-trifluoromethylnicotinic acid (TFNA), N-(4-trifluoromethylnicotinoyl) glycine (TFNG), and 4-trifluoromethylnicotinamide (TFNA-AM) in tea using orthogonal experimental design and liquid chromatography–tandem mass spectrometry (LC–MS/MS). Residues were extracted from the samples with acetonitrile containing 1% acetic acid and were purified with graphitized carbon black. The linearity of the method was excellent in the concentration range of 0.01–10?µg/mL, producing correlation coefficients greater than 0.996 for the target compounds. The limits of detection and quantification of all analytes in tea were 0.0013–0.013?mg/kg and 0.004–0.040?mg/kg, respectively. The average recoveries of flonicamid, TFNA, TFNG, and TFNA-AM ranged from 75.14 to 92.72%, with intra- and interday relative standard deviations of 1.07–9.75%. The proposed method was successfully applied to the terminal residue determination of flonicamid and its metabolites in dry tea processed from three field trials’ fresh samples. The determined total terminal residue concentrations of flonicamid 10?days after the last application at all three sites were below the maximum residue limit (MRL) set by the European Union (0.1?mg/kg) and the residues in all samples were lower than the MRL established by the United States Environmental Protection Agency (EPA) (8?mg/kg). This method may be used to meet the requirements for the determination of flonicamid and its metabolites that could provide guidance for establishing a MRL for flonicamid in tea in China.     

Detection and Determination of Released Ions in the Presence of Nanoparticles: Selectivity or Strategy?

Metallic nanoparticles can release ionic species, but also both species can occur in the same samples. Therefore, there is a need of efficient and cost‐effective methods to determine these ionic species in the presence of the corresponding nanoparticles. Electroanalytical techniques open the door to this selective detection of NPs and their ions. In this work, a methodology that allows the direct determination of ionic silver (Ag⁺) in the presence of silver nanoparticles based on anodic stripping voltammetry was implemented. Silver nanoparticles were determined, after acidic digestion of the sample, by difference with respect to the total content of silver. The method was validated in terms of specific identification of silver ions, linearity, working range, limit of detection, limit of quantification, recovery, repeatability and ruggedness. All parameters are adequate for an analytical method following Eurachem recommendations. The validated method was used to determine the concentration of Ag⁺ and total silver in two commercial products of colloidal silver. The results were compared with those obtained by atomic absorption spectrometry in combination with an ultrafiltration step for isolation of ionic silver. There were no significant differences in the results. The proposed methodology benefits from the intrinsic selectivity of the electroanalysis methods, allowing to eliminate the steps of pretreatments of the samples, which are necessary in other techniques. The novelty of the article lies in the direct determination of Ag (I) ions in the presence of AgNPs, without the use of previous separation steps.     

Preliminary results of the positron annihilation in zeolites: Peak shape and 3γ-decay

In many sorts of zeolites long-living positron components are manifested, connected presumably with Ps-formation in various kinds of free space in the zeolite structure. Literature values demonstrate, however, a broad scasttr of data obtained for assumedly on the same composition of zeolite indicating the possible influence of tehnology, adsorbates, impurities, water content, etc. In the present work spectral changes of the 511 keV annihilation peak and its vicinity are evaluated, applying for the first time a combination of theS and W parameters and the 3-specific left plateau region measured in zeolites. To ensure reproducible experimental conditions, evaluated samples were measured. The data show individual temperature behaviours of the annihilation parameters in the studied temperature range of 90–450 K for each kind of samples. The temperature dependence becomes reproducible after the first heating run. The results are discussed with respect to the evolution of long-living positron and positronium components.     

Advances in the chemistry of β-lactam and its medicinal applications

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Changes in the Inter- and Intra- Fibrillar Structure of Lyocell (TENCEL®) Fibers after KOH Treatment

Lyocell fibers were treated with KOH up to 8 M which was demonstrated to distribute homogeneously at the outer zones of fiber cross section compared to NaOH which accesses more deeply but less homogenously. Both NaOH and KOH solutions can be used to lower significantly the fibrillation of lyocell fibers. However, due to intrafibrillar swelling together with deep penetration ability of alkali seen for NaOH treatments results in great fiber tensile strength loss which is not observed for KOH treatments due to its inability to penetrate the fiber completely. The porous structure of fibers was studied by inverse size exclusion chromatography (ISEC) to identify mean pore diameter, total pore area and accessible pore volume (APV). Mean pore diameter of fibers decreased after KOH treatments which did not change after NaOH treatments. Wide angle X-ray diffraction analyses (WAXD) were applied to identify the crystallinity index and crystallite size. In general, fiber properties such as water retention value, carboxyl content using methylene blue sorption method, depth of color measured after dyeing with C.I. Direct Red 81 and weight loss were distinctly different in the ranges up to 2 M, 2-5 M and 5 to 8 M KOH. KOH treatment suggests new possibilities for the pretreatment of lyocell fibers to lower fibrillation while slightly lowering elongation at break without a distinct loss in tensile strength and with less decrease in carboxyl content and weight loss without changing dyeing properties of fibers compared to NaOH treatment.     

Changes in the intra- and inter-fibrillar structure of lyocell (TENCEL®) fibers caused by NaOH treatment

Some effects of NaOH treatment at concentrations of up to 8 M on (1) the porous structure, (2) the degree of swelling, (3) carboxyl content using methylene blue sorption and 9H-fluoren-2-yl-diazomethane (FDAM) methods, (4) dyeing, (5) the molecular weight distribution measured by gel permeation chromatography (GPC), (6) crystallinity determined by wide angle X-ray diffraction (WAXD) and (7) the tensile properties of lyocell fibers were investigated. The porous structure of fibers was visualised using fluorescence microscopy and transmission electron microscopy (TEM) on fiber cross-sections and was also studied by inversion size exclusion chromatography (ISEC). Mean pore diameter and pore area of fibers were not changed by NaOH treatments. The pore volume increased above 2.5 M NaOH. NaOH-treated samples showed higher dye uptake, higher swelling, but lower carboxyl and moisture content and increased crystallinity. As the NaOH concentration increased, the depth of colour following dyeing with C.I. Direct Red 81 also increased due to deep penetration of alkali into the fiber. In general, fiber properties were distinctly different in the ranges 0 to approximately 3 and 3–8 M NaOH. A part of this paper was presented at the 5th Central European Conference 2007, Fiber Grade Polymers, Chemical Fibers and Special Textiles, Krakow-Bielsko-Biala, Poland, 5–8 September 2007. Hale Bahar ?ztürk, Antje Potthast, Thomas Rosenau, Bill MacNaughtan, John R. Mitchell, Thomas Bechtold—Members of European Polysaccharide Network of Excellence (EPNOE), .