Determination of Phthalate Esters in Wine Using Dispersive Liquid–Liquid Microextraction and Gas Chromatography

A simple and rapid efficient method was developed for the determination of phthalate esters using dispersive liquid–liquid microextraction followed by gas chromatography with flame ionization detection. A mixture of isopropanol (0.75 mL, dispersant) and carbon tetrachloride (30 µL, extractant) with sodium chloride (1%, w/v) was used for extraction. Under optimum conditions, the method provided linear calibration curves between 0.5 and 200 µg L^?1 for dibutyl phthalate, and 1.0 and 200 µg L^?1 for butyl benzyl phthalate, diethyl phthalate, and diisooctyl phthalate. The relative standard deviations for intra-day and inter-day analyses were less than 5.8% and 6.9%, respectively, with enrichment factors between 229 and 424. Two wine samples were analyzed with recoveries between 70.1% and 119.3%.     

Determination of γ-Aminobutyric Acid in the Mouse Hypothalamus and Hippocampus Using Liquid Chromatography/Electrochemistry

Abstract

A method is described for the rapid detection and measurement of γ-aminobutyric acid (GABA) in crude extracts of mouse brain. This study includes optimisation of the pre-column derivatization of GABA by o-phthalaldehyde in the presence of ethylmercaptan as well as of the chromatographic and electrochemical conditions. The GABA levels have been measured in the hypothalamus and hippocampus of control mice and mice treated with three compounds known for their activity on brain GABA levels.     

Identification Markers of Adulteration in Korean Red Ginseng (Panax Ginseng) Products Using High-Performance Liquid Chromatography (HPLC) and Liquid Chromatography–Mass Spectrometry (LC-MS)

The commercial products of Panax ginseng have increasing market demand and high prices due to the pharmacological activities. To obtain high profits, P. ginseng may be adulterated with lower priced morphologically similar species such as Platycodon grandiflorum, Codonopsis lanceolata, and Pueraria lobata. This study was designed to validate accurate methods for the analysis of adulteration in P. ginseng products. High-performance liquid chromatography (HPLC) and ultraperformance liquid chromatography–diode array detector–electrospray ionization–ion trap–time of flight–mass spectrometry (UPLC–DAD–ESI-IT-TOF-MS) were validated to analyze the raw plant materials, self-prepared formulations, and commercial products of P. ginseng, C. lanceolata, P. grandiflorum, and P. lobata. The developed analytical methods were confirmed by quality assurance parameters such as linearity, sensitivity, precision, and accuracy. Lobetyolin and ononin were identified as marker compounds by HPLC and confirmed by accurate mass measurement with ESI-IT-TOF-MS. HPLC analysis of self-prepared formulations indicated that by increasing the ratio of C. lanceolata, P. grandiflorum, and P. lobata in P. ginseng extracts, the peak area is increased at the same retention time. The limits of detection and quantification for lobetyolin and ononin were 0.098 and 0.171, and 0.108 and 0.726?mg/kg, respectively. Furthermore, the intraday precision (<1.0%) measurements confirmed that the developed analytical methods fulfill the required criteria for characterization of these products. The results demonstrated that the developed liquid chromatographic and mass spectrometric methods accurately characterized adulteration in P. ginseng commercial products.     

Determination of Promedol (Trimeperidine) and Ketamine in Blood Using Gas Chromatography–Mass Spectrometry

A procedure was developed for the gas-chromatographic determination of promedol (trimeperidine) and ketamine in whole blood with mass-selective detection. The detection limit for trimeperidine and ketamine in blood is 0.05 g/mL. The analytical range is 0.1–5.0 g/mL. The maximum within-series errors in the determination of the studied compounds are no higher than 14.1% for concentrations of 0.10 g/mL and 7.47% for concentrations of 1.0 g/mL. The maximum between-series relative errors are 5.75% for concentrations of 0.10 g/mL and 2.7% for concentrations of 1.0 g/mL. The procedure can be used in toxicological and clinical analyses.     

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

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 C 18 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.     

Simultaneous Determination of Phenylpropanolamine Hydrochloride and Isopropamide in Capsule∗ by High Performance Liquid Chromatography Using CROWNPAK Column

Abstract

A procedure is described for the assay of phenylpropanolamine hydrochloride & isopropamide by HPLC using CROWNPAK column and detection at 200 nm. The system was aqueous perchloric acid as mobile phase containing 5 % methanol. Linearity studies were carried out using peak height measurements. There was > 99 % recovery and coefficient of variation was < 2% for formulation. The procedure was rapid, accurate, precise and specific for the assay of phenylpropanolamine HCl in presence of isopropamide.     

“True” Concentration Determination Using a Concentration and Composition Sensitive Infrared Detector for Molecular Weight Characterization of Polyolefins

Summary: The infrared detector with a composition channel provides the ability to construct “true” concentration of the polyethylene-polypropylene copolymer and polymer blends to compensate the different infrared responses to each component. Using this “true” concentration constructed by the infrared detector, triple detector gel permeation chromatography (GPC) could generate conventional (by column calibration) and absolute (by laser light scattering) molecular weight and molecular weight distribution data comparable to data obtained by using the concentration obtained by a differential reflex index concentration detector. In addition to its unique feature of in-situ composition detection, the infrared detector in its mass detection mode possesses the advantages of faster equilibrium time, more stable baseline, less effect from temperature variation, and low sensitivity to moisture or air in the solvent.     

Determination of Mycotoxins Using Hollow Fiber Dispersive Liquid–Liquid–Microextraction (HF-DLLME) Prior to High-Performance Liquid Chromatography – Tandem Mass Spectrometry (HPLC - MS/MS)

A modified hollow-fiber-supported dispersive liquid-liquid microextraction (HF-DLLME) method was developed for the determination of aflatoxins and ochratoxin A in food samples. The various parameters affecting the efficiency of extraction, such as pH, salt addition, extraction time, stirring rate, desorption time, type and volume of extractant and disperser solvents were carefully studied and optimized using two step strategies. The linearity of the evaluated results was 0.1 to 30?μg L^?1 for aflatoxins and 0.1 to 20?μg L^?1 for ochratoxin A, with regression coefficients (R²) exceeding 0.9990. The precision was satisfactory with relative standard deviation values less than 11%. The method accuracy was within the recommended range from 70% to 120% and analyte accuracy between 83% and 101%. The limits of detection and quantification were in the range from 0.04 to 0.06?μg L^?1 and 0.08 to 0.13?μg L^?1, respectively, for multi-aflatoxins, and 0.02 to 0.04?µg L^?1 and 0.08 to 0.10?µg L^?1, respectively, for ochratoxin A. The developed method was successfully applied for the determination of mycotoxins in food samples.     

Determination and Characterization of the Uptake of Voriconazole in Human Lung Epithelial Cells by High-Performance Liquid Chromatography–Tandem Mass Spectrometry

Voriconazole is used to prevent invasive pulmonary aspergillosis. However, little is known about the concentrations of voriconazole in human lung epithelial cells (A549), which is the target for preventing invasive pulmonary aspergillosis. The goal of this study was to develop a high-performance liquid chromatography–tandem mass spectrometry method to quantify voriconazole in A549 cells. A triple-quadrupole mass spectrometer in selected reaction monitoring mode was used with positive electrospray ionization. The total duration of each run was 5?min. The calibration curves fit a least squares model for the voriconazole concentration ranging from 0.625 to 160?ng/mL. Intraday and interday coefficients of variation were less than 10%. Recoveries at the concentrations of the quality control samples where greater than 85%, and the matrix effects showed that the ratios of the peak response exhibited a 15% suppression of the signal in the matrix compared to water. Voriconazole may penetrate A549 cells. However, the voriconazole uptake was slow in A549 cells, reaching a plateau at 2?h, where the dose-dependent intracellular voriconazole concentrations were 1.98?±?0.38, 4.43?±?0.54, and 8.14?±?0.52?ng/mg protein for extracellular voriconazole concentrations of 5, 10, and 20?µg/mL, respectively. The uptake of voriconazole by A549 cells was linear at extracellular concentrations from 0 to 20?µg/mL. This study established a rapid and sensitive method suitable for determining voriconazole in A549 cells and described the kinetic properties of the absorption of voriconazole by A549 cells.     

Simultaneous Determination of Diethylstilbestrol, Testosterone, and 17β-Estradiol Residues in Meat and Meat Products Using Gas–Liquid Chromatography

A gas-chromatographic procedure was developed for the simultaneous determination of hormones (diethylstilbestrol, testosterone, and 17-estradiol) as heptafluorobutyric anhydride derivatives. A mid-polarity HP-50 capillary column (silicone liquid phase containing 50% phenyl groups) and an electron-capture detector were used. The detection limits were 0.3–0.6 mg in a sample of 2 L. The applicability of this procedure for the determination of hormone residues in meat and meat products was demonstrated.     

Complexometric Determination of Zinc(II) Using 2,2′-Bipyridyl as Selective Masking Agent

 An indirect complexometric method is described for the determination of zinc(II) using 2,2′-bipyridyl as masking agent. Zinc(II) in a given sample solution is initially complexed with an excess of EDTA and surplus EDTA is titrated with lead nitrate solution at pH 5.0–6.0 (hexamine), using xylenol orange as indicator. An excess of 2,2′-bipyridyl is then added, the mixture shaken well and the EDTA released from the Zn-EDTA complex is titrated with standard lead nitrate solution. Results are obtained for 3–39 mg of Zn with relative errors ≤ 0.5% and standard deviations ± 0.06 mg. The interference of various ions are studied. The method is applied for the determination of zinc in its alloys and ores. Received October 27, 1998. Revision June 10, 1999.     

Speciation Study of Trace Elements by Reversed Phase-High Performance Liquid Chromatography ( Ⅰ )——Simultaneous Determination of Cr( Ⅲ ) and Cr( Ⅵ )

Reported here is the Cr-speciation study by High Performance Liquid Chromatography (HPLC) using precolumn derivatization with ammonium pyrolidinyldithiocarbamate (APDC) and spectrophotometric detection. The rapid and sensitive method has been successfully applied to the analysis of environmental water. The chromatographic behavior of the two Cr-APDC chelates are illustrated with "Solvophobic Theory".     

A Short Synthesis of Benzomorphane Analgesics (±)-Metazocine and (±)-Phenazocine

A three step synthesis of (±)-metazocine and (±)-phenazocine starting with 3,4-lutidine is described. The key step involves Lewis acid promoted lithiation/electrophilic substitution reaction of N-alkyl-3,4-dimethyl-1,2,5,6- tetrahydropyridine.     

A highly diastereoselective total synthesis of (±)-heritonin and (±)-heritol

A highly diastereoselective synthesis of heritol and heritonin by intramolecular cyclization on a preformed sensitive butenolide functionality is described.     

Total Synthesis of (±)‐Infuscol A and (±)‐Cuprenenol

Abstract

Total synthesis of the nonaromatic cuparenoid sesquiterpenes (±)‐infuscol A and cuprenenol, and (±)‐infuscol B and neocuprenenol isolated from the Japanese liverwort Jungermannia infusca has been accomplished. Two ring‐closing metathesis reaction based strategies have been developed for the generation of the key intermediate of the sequence.