bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of Glyphosate Residues in Plants by Precolumn Derivatization and Coupled-Column Liquid Chromatography with Fluorescence Detection
Authors: Hernández Félix , Hidalgo Carmen , Sancho Juan V 
Published: February 2020

Abstract
A rapid method was developed for the trace-level determination of glyphosate in olives. After extraction of the glyphosate with water–dichloromethane and simultaneous removal of the olive oil, an aliquot of the aqueous extract is derivatized with 9-fluoroenylmethyl chloroformate (9-fluorenylmethoxycarbonyl chloride; FMOC-Cl) to produce a highly fluorescent derivative. A 2 mL aliquot of this extract is injected directly into a coupled-column liquid chromatography system with fluorimetric detection (LC/LC–FD). The procedure was validated by recovery experiments at 3 spiking levels; recoveries ranged from 80 to 97% with relative standard deviations of 3–6%. The limits of detection and quantitation were estimated to be 0.01 and 0.05 mg/kg, respectively. The method was also applied to other plant materials, i.e., tomato plants, strawberry plants, and pear trees (branches, leaves, and fruits) suspected to be contaminated by glyphosate. In all these cases, the extraction was performed in aqueous media. The derivatization reaction was modified by increasing the FMOC-Cl concentration, to ensure a quantitative reaction between analyte and reagent in the presence of high levels of coextractives, which also react with FMOC-Cl. The final determination was by LC/LC–FD, yielding a rapid, selective, and sensitive method for the determination of glyphosate residues in these samples. The method was tested with real-world samples after application of glyphosate to the surrounding area of crops.
New Method for Determining Total Dietary Fiber by Liquid Chromatography
Authors: Ohkuma Kazuhiro , Matsuda Isao , Katta Yasuo , Tsuji Keisuke 
Published: February 2020

Abstract
The molecular weight limit of water-soluble dietary fiber (SDF) determined by the Prosky method was studied by liquid chromatography (LC). It was confirmed that only SDF with an average degree of polymerization of 12 or higher can be determined by the Prosky method. Total dietary fiber (TDF) was determined by 2 additional methods using LC. In the first method, the total quantity of insoluble dietary fiber (IDF) and high molecular weight SDF (HMSDF) was determined according to the modified Prosky method (MES-TRIS buffer-based). The quantitatively collected final filtrate was analyzed by LC for the quantity of low molecular weight SDF (LMSDF), and the 2 quantities were totaled to obtain TDF. TDF values thus determined for rice, polished or unpolished, soybean flour, and pressed barley were higher than those determined by the Prosky method by approximately 6, 3.5, and 3.5%, respectively. In the second method, direct determination by LC analysis was done on samples after enzymatic treatment according to the Prosky method. Results showed that the determination of LMSDF, in particular, was highly accurate and more effective. In both of these methods, the quantity of LMSDF was determined from its chromatographic peak area ratio to glucose as an internal standard, which was produced by hydrolysis.
Liquid Chromatographic Determination of Dehydroepiandrosterone (DHEA) in Dietary Supplement Products
Authors: Thompson Richard D , Carlson Marvin 
Published: February 2020

Abstract
A liquid chromatographic (LC) method was developed to assess the potency of products that contain dehydroepiandrosterone (DHEA), a precursor hormone synthesized from cholesterol by the human adrenal cortex and converted to potent androgens and/or estrogens in peripheral tissues. Forty-five commercial products (both single and multi-ingredient) were subjected to analysis by the proposed method. A Zorbax Rx C18 column with a mobile phase containing acetonitrile–0.025M phosphate buffer (60 + 40), pH 3.50, and UV detection at 292 nm was used for 87% of the products. An alternative mobile phase containing methanol–0.025M phosphate (75 + 25), pH 3.50, was used to isolate DHEA from more complex product mixtures. Assay values varied from 0 to 109.5% of the declared amount with an overall mean value of 91.1%. The recoveries based on fortified products ranged from 96.4 to 101.2%, and the intraday precision (RSD, n = 5) varied from 0.50 to 1.66%.
Simultaneous Determination of the Predominant Hyperforins and Hypericins in St. John's Wort (Hypericum perforatum L.) by Liquid Chromatography
Authors: Gray Dean E , Rottinghaus George E , Gene Garrett H E , Pallardy Stephen G 
Published: February 2020

Abstract
Hypericin and hyperforin are believed to be among the active constituents in common St. John's wort (Hypericum perforatum L.). Presently, dietary supplements are generally standardized to contain specified levels of hypericin and hyperforin, and the related compounds, pseudohypericin and adhyperforin. A rapid method was developed for simultaneous determination of these 4 active constituents by liquid chromatography (LC). A 1 g portion of dried, finely ground leaf/flower sample is extracted with 20 mL methanol for 2 h. A 0.6 mL aliquot of the crude extract is combined with 5.4 mL acetonitrile–methanol (9 + 1) and passed through a mixed solid-phase cleanup column. The eluate is examined by LC for hyperforin, adhyperforin, hypericin, and pseudohypericin on a Hypersil reversed-phase column by using simultaneous ultraviolet (284 nm) and fluorescence detection (excitation, 470 nm; emission, 590 nm). The compounds are easily separated isocratically within 8 min with a mobile phase of acetonitrile–aqueous 0.1M triethylammonium acetate (8 + 2). Average recoveries of hyperforin and adhyperforin were 101.9 and 98.4%, respectively, for 3 sample mixtures containing concentrations ranging from approximately 0.2 to 1.5% combined hyperforins per gram dry weight. Average relative standard deviation (RSD) values for hyperforin and adhyperforin for all 3 mixtures were 18.9 and 18.0%, respectively. Average recoveries of hypericin and pseudohypericin were 88.6 and 93.3% respectively, from 3 sample mixtures containing concentrations ranging from approximately 0.2 to 0.4% combined hypericins per gram dry weight. Average RSD values for hypericin and pseudohypericin for all 3 mixtures were 3.8 and 4.2%, respectively.
Determination of Vitamin K1 in Medical Foods by Liquid Chromatography with Postcolumn Reduction and Fluorometric Detection
Authors: Ware George M , Chase G William , Eitenmiller Ronald R , Long Austin R 
Published: February 2020

Abstract
A liquid chromatographic (LC) method is described for the determination of vitamin K1 in medical foods. The sample is enzymatically digested with lipase and α-amylase and extracted with 1% sodium bicarbonate solution–isopropanol (1 + 1). After C18 solid-phase extraction, vitamin K1 is separated by nonaqueous reversed-phase LC, converted to the hydroquinone by postcolumn zinc reduction, and quantitated by fluorescence detection. The limit of detection is 8 pg (3 σ), and the limit of quantitation is 27 pg (10 σ) on column. Linear response ranged from 0.1 to 1.0 ng vitamin K1 (r = 0.9999). The mean recovery (n = 38) for all spiking levels was 101.6 ± 2.85%. Analysis of Standard Reference Material 1846, Infant Formula, gave a mean value of 0.95 ± 0.088 mg vitamin K/kg (K or K1?)(n = 31) with a coefficient of variation of 9.26.
Determination of Binary and Ternary Mixtures of Pesticides in Wetland Waters by Gas Chromatography Using Partial Least-Squares Analysis
Authors: García María Dolores Gil , Galera María Martínez , Espada Maria Del Carmen Pablos , Frenich Antonia Garrido , Vidal José Luis Martínez 
Published: February 2020

Abstract
Partial least-squares (PLS) analysis was applied for the first time to ternary and binary mixtures of pesticides producing overlapping peaks in gas chromatograms. Several preprocessing algorithms for pretreatment of data were tested for optimization of the PLS models, and the most advantageous were used in each case. Three different mixtures of pesticides were resolved with satisfactory results: parathion-methyl, chlorpyrifos-methyl, and vinclozolin; parathion-ethyl, chlorpyrifos, and triadimefon; and endosulfan sulfate and carbophenothion. The proposed models were applied to the determination of 3 mixtures of pesticides at levels of 0.02–1.00 ng/mL in wetland water samples after a preconcentration step with C18 cartridges, with recoveries ranging from 82.7 to 117.4%. The reported method is sufficiently sensitive to measure pesticide residues at the maximum allowable concentrations given in the European Union Drinking Water Directive.
Determination of Inorganic Cations by Capillary Ion Electrophoresis in Ilex paraguariensis (St. H.), a Plant Used to Prepare Tea in South America
Authors: Carducci Clyde N , Dabas Paula C , Muse Jorge O 
Published: February 2020

Abstract
A practical and economical capillary ion electrophoresis method with indirect UV detection at 214 nm was developed for determination of inorganic cations in plants of Ilex paraguariensis (St. H.) and their infusion known as mate tea, a very popular beverage in South America. A microwave digestion procedure was used to prepare the herbal plants, but the infusion was only diluted. The background electrolyte contained 6mM imidazole and 10mM α-hydroxyisobutyric acid, pH 4.0. The running voltage was 20 kV and temperature was 25°C. K, Na, Ca, Mg, and Mn ions were quantitated, and linearity was demonstrated between 0.6 and 120 ppm. The results were in good agreement with those obtained by flame atomic absorption and emission spectrometry. Accuracy of the method was verified by comparison with Beech leaves CRM 100, a standard reference material. The high content of minerals and several oligoelements, especially Mn in mate tea, is considered to be of nutritional interest.
Determination of Two Oxy-Pyrimidine Metabolites of Diazinon in Urine by Gas Chromatography/Mass Selective Detection and Liquid Chromatography/Electrospray Ionization/Mass Spectrometry/Mass Spectrometry
Authors: Yokley Robert A , Shen Nanzhu , Cheung Max W 
Published: February 2020

Abstract
An analytical method was developed for the determination in urine of 2 metabolites of diazinon: 6-methyl-2-(1-methylethyl)-4(1H)-pyrimidinone (G-27550) and 2-(1-hydroxy-1-methylethyl)-6-methyl-4(1H)-pyrimidinone (GS-31144). Two of the urine sample preparation procedures presented rely on gas chromatography/mass selective detection (GC/MSD) in the selected ion monitoring mode for determination of G-27550. For fast sample preparation and a limit of quantitation (LOQ) of 1.0 ppb, urine samples were purified by using ENV+ solid-phase extraction (SPE) columns. For analyte confirmation at an LOQ of 0.50 ppb, classical liquid/liquid partitioning was used before further purification in a silica SPE column. An SPE sample preparation procedure and liquid chromatography/electrospray ionization/mass spectrometry/mass spectrometry (LC/ESI/MS/MS) were used for both G-27550 and GS-31144. The limit of detection was 0.01 ng for G-27550 with GC/MSD, and 0.016 ng when LC/ESI/MS/MS was used for both G-27550 and GS-31144. The LOQ was 0.50 ppb for G-27550 when GC/MSD and the partitioning/SPE sample preparation procedure were used, and 1.0 ppb for the SPE only sample preparation procedure. The LOQ was 1.0 ppb for both analytes when LC/ESI/MS/MS was used.
Performance of Three Pneumatic Probe Samplers and Four Analytical Methods Used to Estimate Aflatoxins in Bulk Cottonseed
Authors: Park Douglas L , Whitaker Thomas B , Giesbrecht Francis G , Njapau Henry 
Published: February 2020

Abstract
The requirement by the U.S. Food and Drug Administration that agricultural products susceptible to aflatoxin contamination contain aflatoxin at levels ≤20 parts per billion for consumer-ready products has led to the establishment of inspection programs by various industries. In Arizona, cottonseed samples from 100 ton piles are collected by an accumulation of 3 or more probings with a pneumatic probe. When sampling compacted cottonseed piles, the large official pneumatic probe (7.6 × 127 cm) decreases in efficiency. Two smaller probes (1.9 × 127 cm and 1.9 × 254 cm ) were therefore developed and tested for their suitability for sampling cottonseed piles. Three rapid analytical methods (one thin-layer chromatographic and 2 immunochemical) were tested for suitability as on-site assay systems. An analysis of variance of the analytical test results showed no differences between the various probes tested. Of the rapid methods, however, only the AflaTest-P immunoaffinity column gave results similar to those of the official AOAC thin-layer chromatography method. In terms of safety, however, all methods prevent material contaminated above regulatory limits from reaching the consumer.
Multiresidue Determination of Fluoroquinolones in Eggs
Authors: Schneider Marilyn J , Donoghue Dan J 
Published: February 2020

Abstract
A multiresidue method was developed for the determination of fluoroquinolones in eggs. Extraction of eggs with ammoniacal acetonitrile was followed by liquid–liquid defatting, solvent evaporation, and redissolution in a small volume of buffer. The fluoroquinolones were further purified by on-line microdialysis, concentrated on a trace enrichment column, and separated by reversed-phase liquid chromatography with fluorescence detection. Norfloxacin (NOR), ciprofloxacin (CIP), and sarafloxacin (SAR) were extracted from fortified eggs over a range of 2–200 μg/kg, with recoveries of 65.7–78.9%, 65.6–77.1%, and 67.6–110%, respectively. Enrofloxacin (ENRO) was extracted over a range of 1–100 μg/kg, with recoveries of 71.5–86.7%, whereas desethylene ciprofloxacin (DCIP) and danofloxacin (DANO) were extracted over a range of 0.2–20 μg/kg, with recoveries of 68.7–90.7% and 76.0–93.8%, respectively. The limits of quantitation for the 6 fluoroquinolones were as follows: DCIP and DANO, 0.3 μg/kg; ENRO, 1 μg/kg; NOR and CIP, 2 μg/kg; and SAR, 3 μg/kg. Both SAR and ENRO incurred eggs were also successfully analyzed using this method.
Measurement of Voltammetric Peak Area and Resolution of Overlapping Peaks in the Simultaneous Determination of Copper, Lead, Cadmium, and Nickel in Environmental Matrix
Authors: Locatelli Clinio 
Published: February 2020

Abstract
Peak area was used for the simultaneous determination of copper(II), lead(II), cadmium(II), and nickel(II) in environmental matrixes by differential pulse voltammetry. The voltammetric measurements were performed with a conventional 3-electrode cell and an ammonia–ammonium chloride buffer, pH 9.1, as the supporting electrolyte. The analytical procedure was verified first in aqueous reference solutions and later by analysis of the standard reference materials Estuarine Sediment BCR-CRM 277 and River Sediment BCR-CRM 320. The precision and accuracy of the method, expressed as the relative standard deviation and the relative error, respectively, were &lt;5% in all cases; the detection limit for each element under the experimental conditions used was in the range 1–5 μg/L. In the case of mutual interference between neighboring elements, an analytical procedure is proposed that is based on the standard additions technique, which allows the resolution of the overlapping voltammetric peaks.
Determination of Domoic Acid in Japanese Mussels by Enzyme Immunoassay
Authors: Kawatsu Kentaro , Hamano Yonekazu , Noguchi Tamao 
Published: February 2020

Abstract
Ten samples of commercial blue mussels (Mytilus edulis) from Japan were analyzed for domoic acid by an indirect competitive enzyme immunoassay (idc–EIA) based on an anti-domoic acid monoclonal antibody. Domoic acid was found in all samples at low concentrations (0.11–1.81 ng/g mussel tissue). The presence of domoic acid was confirmed by liquid chromatography coupled with immunoaffinity chromatography using an anti-domoic acid monoclonal antibody as ligand. To our knowledge, this is the first reported detection of domoic acid, a causative agent of amnesic shellfish poisoning, in Japanese mussels.
Resistance of Pseudomonas aeruginosa to Liquid Disinfectants on Contaminated Surfaces before Formation of Biofilms
Authors: Sagripanti Jose-Luis , Bonifacino Aylin 
Published: February 2020

Abstract
A comparison was made of the effectiveness of popular disinfectants (Cavicide, Cidexplus, Clorox, Exspor, Lysol, Renalin, and Wavicide) under conditions prescribed for disinfection in the respective product labels on Pseudomonas aeruginosa either in suspension or deposited onto surfaces of metallic or polymeric plastic devices. The testing also included 7 nonformulated germicidal agents (glutaraldehyde, formaldehyde, peracetic acid, hydrogen peroxide, sodium hypochlorite, phenol, and cupric ascorbate) commonly used in disinfection and decontamination. Results showed that P. aeruginosa is on average 300-fold more resistant when present on contaminated surfaces than in suspension. This increase in resistance agrees with results reported in studies of biofilms, but unexpectedly, it precedes biofilm formation. The surface to which bacteria are attached can influence the effectiveness of disinfectants. Viable bacteria attached to devices may require dislodging through more than a one-step method for detection. The data, obtained with a sensitive and quantitative test, suggest that disinfectants are less effective on contaminated surfaces than generally acknowledged.
Determination of Hydrocarbon Types in Petroleum and Coal-Derived Products by Thin-Layer Chromatography/Densitometry
Authors: Cebolla Vicente L , Membrado Luis , Vela Jesús , Garriga Rosa , Henrion Patrick , Domingo María P , González Paula 
Published: February 2020

Abstract
Different methodologies based on thin-layer chromatography (TLC)/densitometry were used to separate and quantitate hydrocarbon types in middle distillates (gas oil), heavy distillates (lubricant) from petroleum, and coal-derived products. Thus, petroleum products were separated into saturates and aromatics by development, using n-hexane (9 min) followed by dichloromethane (4.5 min), of silica gel plates impregnated with berberine sulfate. Detection of saturates and aromatics was performed by fluorescence scanning using 365 nm as the excitation wavelength. Alternative detection of aromatics can be performed on either silica gel or berberine-impregnated plates by using ultraviolet (UV) densitometry at 250 nm. On the other hand, polar coal-derived products were separated into aromatics, polar compounds, and uneluted components by using silica gel plates and development with toluene (12 min), followed by dichloromethane–methanol (95 + 5, v/v), with detection by UV densitometry at 250 nm. In all cases, external standard calibration was used for quantitation. Results were validated by using standard methods or well-established techniques of the petrochemical industry. The potential usefulness of TLC/densitometry is discussed.
Determination of Phenylephrine Hydrochloride by Flow Injection Analysis with Chemiluminescence Detection
Authors: Mestre Yolanda Fuster , Zamora Luis Lahuerta , Calatayud José Martínez 
Published: February 2020

Abstract
A new method is proposed for the determination of phenylephrine hydrochloride by flow injection analysis with direct chemiluminescence detection. The method is based on the oxidation of the drug by potassium permanganate in sulfuric acid medium at 80°C. The calibration graph is linear over the range 0.03–8 ppm phenylephrine hydrochloride, with a relative standard deviation (n = 51, 0.5 ppm) of 1.1% and sample throughput of 134/h. The influence of 38 different foreign compounds was tested, and the method was applied to the determination of phenylephrine hydrochloride in 8 different pharmaceutical formulations.
Long-Term Monitoring of Atrazine Contamination in Soil by ELISA
Authors: Kramer Karl , Lepschy Johann , Hock Bertold 
Published: February 2020

Abstract
An enzyme-linked immunoassay (ELISA) was used for screening atrazine residues in soil. Samples were annually collected in Southern Germany between 1993 and 1998. An average of 419.5 samples was analyzed per year amounting to 2517 samples. The fraction of positive samples defined by atrazine concentrations &gt;100 μg/kg soil decreased successively from 8% (corresponding to 33 samples) in 1993 to 0.6% (corresponding to 2 samples) in 1998. All positive samples and a selection of negative samples were subsequently validated by HPLC. Comparison of ELISA and HPLC data yielded correlation coefficient values of r= 0.958–0.981 (n= 18–47), except for 1995 when only a correlation of r= 0.864 (n= 18) was obtained. Four samples were overestimated and another 4 were underestimated with respect to the atrazine threshold value of 100 μg/kg soil as revealed by HPLC validation. Thus, 99.68% of 2517 analyzed samples were correctly evaluated. The precision and reproducibility of the ELISA were adequate for a prescreening tool. The low cost per sample and the high sample throughput are not yet achievable by conventional analytical methods. The described combination of ELISA and HPLC has the potential to take advantage of both methods and to restrict determination errors to a minimum.
Simultaneous Determination of E- and Z-Guggulsterones in Dietary Supplements Containing Commiphora mukul Extract (Guggulipid) by Liquid Chromatography
Authors: Nagarajan Mythili , Waszkuc Ted W , Sun Jidong 
Published: February 2020

Abstract
Guggulipid, the standardized product from the extraction of the ole-gum-resin from the Commiphora mukul plant, has been marketed as a hypolipidemic agent. The ketosteroids, cis- and trans-4,17(20)-pregnadiene-3,16-dione, known as E- and Z-guggulsterones, respectively, are the main ingredients in guggulipid. A liquid chromatographic method was developed for simultaneous determination of E- and Z-guggulsterones in guggulipid preparations using synthetic E- and Z-guggulsterone standards. Realtively low amounts of guggulsterones (E and Z) were found in commercial guggulipid preparations in comparison with the manufacturer's claim of 2.5%. The mixture of E- and Z-guggulsterones was extracted and separated on a Symmetry C18 reversed-phase column, with a mobile phase of acetonitrile–water (46 + 54, v/v) and detected at 242 nm. The retention times of E- and Z-guggulsterones are approximately 8 and 11 min, respectively. Assay quantitation was based on the calibration curve obtained from a mixture of synthetic standard E- and Z-guggulsterones. Experimental data on selectivity, linearity, accuracy, and recoveries are presented.
Sensitive Spectrophotometric Determination of Nitrite in Human Saliva and Rain Water and of Nitrogen Dioxide in the Atmosphere
Authors: Helaleh Murad I H , Korenaga Takashi 
Published: February 2020

Abstract
A new simple, sensitive, and selective spectrophotometric method was developed for the determination of nitrite. The method is based on the reaction of nitrite with sulfathiazole in acidic medium to form a diazonium cation, which is subsequently coupled with N-(1-naphthyl)ethylenediamine dihydrochloride to form a highly stable, violet azo dye. The reaction product has an absorption maximum at 546 nm and obeys Beer's law over a nitrite range of 0.054–0.816 μg/mL. The molar absorptivity of the colored compound is 4.61 × 104 L/(mol·cm). The detection limit is 12.1 μg/L. The relative standard deviation is 0.85% for 5 determinations of nitrite at 0.27 μg/mL. The reproducibility and validity of the proposed method are discussed in the present paper. The simplicity of the method is demonstrated by the high stability of the azo-dye product as well as the short time required for its complete formation in a reaction at room temperature without pH control or extra extraction. The sensitivity of the method is shown by the successful determination of nitrite in human saliva and rain water, and of nitrogen dioxide in the atmosphere. The results compare favorably with those obtained by the reference method. The selectivity of the method is indicated by its freedom from most interferences, even at high concentrations of nitrate (500 μg/mL).