bluuebunny/crossref_metadata_2025 huggingface dataset:
Determination of Fruit Juice Authenticity by Capillary Gas Chromatography with Flame Ionization Detection
Authors: Low Nicholas H
Published: February 2020

A method using capillary gas chromatography with flame ionization detection was developed to determine the addition of high�fructose syrup and beet or cane invert syrup to apple or orange juice. Fingerprint oligosaccharides in these inexpensive sweeteners were not detectable (area < 1000) in pure apple or orange juice. One hundred twenty- three pure apple juice and 60 pure orange juice samples representing growing regions around the world were analyzed. Ten samples were intentionally adulterated with each sweetener at levels of 5, 10, and 15%. The detection limit for each sweetener was 5%.
Determination of Selenium in Urine by Hydride Generation Atomic Absorption Spectrometry
Authors: Navarro Miguel , Lopez Herminia , Lopez Maria C , Perez Vidal
Published: February 2020

A procedure has been developed for determination of total selenium in urine by hydride generation atomic absorption spectrometry. Mineralization was performed with a nitric acid–perchloric acid mixture on a thermostated digestion block. The method was validated by comparison with the method involving mineralization in a microwave acid digestion bomb containing nitric acid and small amounts of vanadium pentoxide. Se(VI) was reduced to Se(IV) by dissolution in 7N HCI. Sample recoveries, precision studies, and analyses of a certified reference material demonstrated the reliability and accuracy of this technique. Urine samples had selenium concentrations ranging from 4.6 to 50.3 μg/L. These values correspond to an average of 54.9 μg per person per day total ingested and bioavailable Se in the daily diet.
Determination of Bensulfuron Methyl in Rice and Crayfish by Liquid Chromatography with a Column- and Eluant-Switching System and UV Detection
Authors: Zhou In , Bramble Fred Q , Devine Tim J , Norwood Gwen I
Published: February 2020

Bensulfuron methyl (an active ingredient of Londax herbicide) was determined in rice and crayfish by liquid chromatography with column switching (LCCS), using a simple extraction and cleanup scheme. After bensulfuron methyl was extracted from sample with methylene chloride, the extract was concentrated, cleaned up, and reconstituted into acetonitrile–water (1+1, v/v). The extract was further cleaned up chromatographically, and then bensulfuron methyl was quantitatively determined by reversed-phase LC using a column- and eluantswitching system and UV detection at 254 nm. Bensulfuron methyl was recovered at 90 ± 8% over a range of 0.008 to 1.0 ppm from fortified samples of polished rice, rice grain, rice straw, rice hull, rice bran, aspirated grain fractions, and crayfish. Method quantitation limits were 0.008 ppm for polished rice and rice grain; 0.02 ppm for rice hull, rice bran, aspirated grain fractions, and crayfish; and0.05 ppm for rice straw.
Emergence of Rapid Methods for Identifying Microbial Pathogens in Foods
Authors: Feng Peter
Published: February 2020

Because of the complexities of food analysis, conventional microbiological methods must use timeconsuming enrichment steps for culturing viable bacterial cells in foods. With rapid advancements in technology, however, numerous so-called rapid methods were introduced into the field of food microbiology in a relatively short time. Culture methods that were once used to obtain profiles for bacterial identification were simplified or automated. Many microbiological procedures were also streamlined or automated to reduce assay time, labor, and materials. Nucleic acid-based assays are used to identify gene sequences in foodborne bacteria, and antibody-based assays are used in numerous formats to detect bacterial pathogens and toxins in foods. The difficulties of analyzing food, however, remain challenging, and rapid methods need to be evaluated thoroughly before they are used for routine food analysis.
Indirect Spectrophotometric Determination of Chromium
Authors: Balasubramanian N , Maheswari V
Published: February 2020

A sensitive spectrophotometric method for determining trace amounts of chromium(VI) is described. In the presence of acetate buffer, chromium(VI) oxidizes hydroxylamine quantitatively to nitrite at pH 4.0 ± 0.5. The nitrite diazotizes p-nitroaniline to form a diazonium salt that, in acidic medium, couples with N-(1-naphthyl)ethylenediamine dihydrochloride to form an azo dye with a molar absorptivity of 4.1 x 104 L/mol-cm at 545 nm. The color is stable for 5 h, and the system obeys Beer's law in the range 0-8 μg chromium(VI) in a final volume of 10 mL. The detection limit of chromium(VI) is 0.6 μg. Chromium(lll) can be determined after it is oxidized with bromine water in alkaline medium to chromium(VT). Extraction of the azo dye in alkaline medium with methyl isobutyl ketone followed by addition of methanolic hydrochloric acid permitted determination of chromium(VI) down to 10 ng/mL. The method has been used to determine chromium in alloy steels, pharmaceutical preparations, and industrial effluents.
Determination of Citrinin in Barley by Indirect and Direct Enzyme Immunoassay
Authors: Abramson David , Usleber Ewald , Martlbauer Erwin
Published: February 2020

Polyclonal antibodies against the mycotoxin citrinin were raised in rabbits after immunization with citrinin conjugated to keyhole limpet hemocyanin. The antibodies were used in a competitive indirect enzyme immunoassay (EIA) with citrinin coupled to glucose oxidase as the solid-phase antigen for coating microtiter plates. Detection limits of this indirect EIA for citrinin ranged from 0.4 to 0.8 ng/mL for buffer solutions. Recoveries of citrinin added to ground barley at 100–2000 ng/g ranged from 105 to 112%, with coefficients of variation between 4.5 and 12%. A direct competitive EIA also was established, with citrinin coupled to horseradish peroxidase as the labeled antigen. Detection limits of this direct EIA for citrinin ranged from 2 to 4 ng/mL for buffer solutions. Recoveries of citrinin added to ground barley at 500–2000 ng/g ranged from 108 to 111%, with coefficients of variation between 8.4 and 26.9%. In naturally contaminated barley samples assayed with the indirect EIA, optimum extraction of citrinin was obtained in 30 min, and only one extraction was necessary to recover 72–76% of the analyte.
Modification of AOAC Multiresidue Method for Determining Synthetic Pyrethroid Residues in Fruits, Vegetables, and Grains. Part III: Studies of Analyte Stability and Method Ruggedness
Authors: Pang Guo-Fang , Cao Yan-Zhong , Fan Chun-Lin , Zhang Jin-Jie , Li Xue-Min
Published: February 2020

The stability of 8 synthetic pyrethroids in 9 crops during storage for 90 days were studied. The 8 pyrethroid insecticides were highly persistent in the 6 grains during storage. But their stabilities in 3 kinds of fruits and vegetables were different from those in the 6 grains: Most of them were degraded. Florisil purification conditions were studied with 6 batches of Florisil from 3 countries at various extents of deactivation and amounts. The best conditions of Florisil purification found in this present research agree with those found 1 year ago. The efficiencies of acetonitrile and acetone to extract the 8 pyrethroids from 6 fruit and vegetable samples were compared. The extraction efficiency of acetone was competitive with that of acetonitrile for the 6 fruit and vegetable samples. Method performance was evaluated by 6 analysts from different areas. The ruggedness tests demonstrate further that the proposed method is simple, accurate with good precision, and suitable for multiresidue analysis of pyrethroids in various agriculture products.
Determination of Chlordane and Chlorpyrifos in Ambient Air at Low Nanogram-Per-Cubic Meter Levels by Supercritical Fluid Extraction
Authors: Swami Kamal , Narang Amarjit S , Narang Rajinder S
Published: February 2020

A method for the determination of termiticides present in ambient air was simplified by modifying the extraction thimbles used in the Hewlett-Packard supercritical fluid extractor so they could be used for collection as well as extraction of termiticides. The method was applied to the determination of chlorpyrifos and technical chlordane. The termiticides were trapped on cartridges containing Florisil and foam plugs, extracted with carbon dioxide in the supercritical fluid extractor, and determined by capillary gas chromatography with electron capture detection. On the basis of a 20 m3 sample, detection limits were 0.1 ng/m3 for chlorpyrifos and 1.0 ng/m3 for technical chlordane.
Fine Tuning a Bile-Enzymatic-Gravimetric Total Dietary Fiber Method
Authors: Cranker Kenneth J , Phillips Katherine M , Gonzales Maria Carmen Rita V , Stewart Kent K
Published: February 2020

A recently proposed bile-enzymatic-gravimetric total dietary fiber (TDF) method was modified and the new procedure was compared with the original method, the traditional AOAC enzymatic-gravimetric determination (AOAC Official Method 985.29), and another simplified AOAC procedure by analyzing several diet composites, including National Institute of Standards and Technology 1548 total diet reference material. The original and modified bile-enzymatic-gravimetric procedures also were compared by analyzing 9 food samples from a collaborative study of the original method. The modified method consistently yielded values about 10% lower than the original method but closer to reference values and to values from AOAC Offical Method 985.29, suggesting results that are more in line with accepted TDF standard methodology. Our modified method was used to analyze 180 fresh-frozen diet composites with TDF values ranging from 0.6 to 3.2 g/100 g wet weight. Samples were from 2 multicenter feeding studies sponsored by the National Heart, Lung and Blood Institute: DELTA (Dietary Effects on Lipoproteins and Thrombogenic Activity) and DASH (Dietary Approaches to Stop Hypertension). The mean relative standard deviation (RSD) for duplicate analyses was 1.1%. For 40 assays of a quality control diet composite over 9 months, the standard deviation was 0.1 g/100 g wet weight (4.9% RSD), indicating the method’s excellent precision for routine use.
Chiral Gas Chromatographic Determination of Ephedrine-Type Alkaloids in Dietary Supplements Containing Má Huáng
Authors: Betz Joseph M , Gay Martha L , Mossoba Magdi M , Adams Sarah , Portz Barbara S
Published: February 2020

Má Huáng is a traditional Chinese medicine derived from the aerial parts of several Ephedra species (Ephedraceae). These plants produce (–)-ephed- rine, (+)-pseudoephedrine, (–)-norephedrine, (+)- norpseudoephedrine, (–)-N-methylephedrine, and (+)-N-methylpseudoephedrine. Racemic and (–)- ephedrine, (+)-pseudoephedrine, and (±)-norephe- drine (phenylpropanolamine) are used clinically in the United States and are largely synthetic in origin. Current interest in Má Huáng is spurred by reports describing a “thermogenic” (calorie burning) effect provided by mixtures of ephedrine, caffeine, and aspirin. Products providing the key thermogenic compounds from natural sources are available as dietary supplements in retail outlets. Reports of potentially unsafe levels of the alkaloids, as well as possible fortification of Má Huáng-containing products with synthetic Ephedra alkaloids, prompted the development of a chiral gas chromatographic (GC) method that allows determination of alkaloid patterns and identification of isomerically impure synthetic alkaloids. Nine products were analyzed on a γ-cyclodextrin capillary GC column. Identity of the alkaloids was verified by GC/mass spectrometry (MS) and GC/matrix isolation/Fourier transform infrared spectroscopy. No synthetic isomers were found in the dietary supplements analyzed. Three products contained only one of the ephedrine-type alkaloids. One product that listed Má Huáng as an ingredient contained no detectable ephedrine-type alkaloid. In products containing measurable quantities of these compounds, total alkaloid levels ranged from 0.3 to 56 mg/g.
Spectrophotometric Method for Determination of Paraquat in Food and Biological Samples
Authors: Kesari Ritu , Rai Manish , Gupta Vinay Kumar
Published: February 2020

A sensitive spectrophotometric method was developed for determination of paraquat, a widely used herbicide. Paraquat was reduced with glucose in an alkaline medium, and the blue radical ion obtained was measured at 600 nm. Beer’s law was obeyed at 0.1–1.2 ppm paraquat. The molar absorptivity was 1.26 × 105 L mol-1 cm-1. The standard deviation and relative standard deviation were ± 0.007 and 2.0%, respectively, for 5 μg paraquat/10 mL analyzed over 7 days. The method was free from interference by other commonly used pesticides and metal ions. The method may be used to the determine paraquat in plants, fruits, grains, water, blood, and urine.
Quantitative Analysis of Aloe vera Mucilaginous Polysaccharide in Commercial Aloe vera Products
Authors: Ross Samir A , Elsohly Mahmoud A , Wilkins Scott P
Published: February 2020

A quantitative method using size exclusion chromatographic (SEC) analysis was performed to determine the concentration of Aloe vera mucilaginous polysaccharide (AVMP) in 18 selected commercial preparations. Of the 18 preparations studied, 9 contained quantitatable amounts of AVMP at 0.22 to 1.30 mg/mL, and 2 showed trace amounts (<0.2 mg/mL). Seven preparations showed no detectable levels of AVMP. The method may be adapted to standardize these and similar preparations.
Simultaneous Determination of Alliin and Allicin in Allium Plants and Their Products by Liquid Chromatography
Authors: Mochizuki Emiko , Yamamoto Takao , Horie Masakazu , Ikai Yoshitomo , Nakazawa Hlroyuki
Published: February 2020

Alliin and allicin in garlic and their products are determined simultaneously by ion-pair reversedphase liquid chromatography (LC) with diode array UV detection. Alliin is extracted from fresh garlic, purified by ion-exchange chromatography, and appliedas external standard. Allicin is generated enzymatically from alliin, confirmed by LC, and applied as external standard. Compounds areextracted from samples with water and chromatographed on an octadecylsilane column with gradient elution from 0.01 M phosphate buffer (pH 2.5) with 5 mM heptanesulfonic acid (A) to 0.01 M phosphate buffer (pH 2.5)-acetonitrile (1 + 1; B). Themethod can be used to analyze fresh garlic, spices, garlic preparations, and health foods.
Determination of Phosphorus, Potassium, and Magnesium in Fertilizers by Inductively Coupled Plasma–Atomic Emission Spectroscopy and Comparison with Other Techniques
Authors: Hamalovâ Martina , Hodslavská Jiřina , Janos Pavel , Kanický Viktor
Published: February 2020

Phosphorus, potassium, and magnesium in 12 fertilizers were determined by inductively coupled plasma–atomic emission spectroscopy (ICP–AES), and results were compared with those obtained by standard gravimetry (phosphorus) and atomic absorption spectrometry (AAS) (potassium and magnesium). ICP–AES and gravimetry were also used to determine water- and citrate-soluble phosphorus in fertilizers. In all cases, precision and accuracy of the ICP–AES method were satisfactory. Certain differences, probably not significant for routine analyses, were observed between ICP–AES and gravimetry in determinations of total and citrate-soluble phosphorus when the measurements were performed strictly under conditions of repeatability.
Multiresidue Method for Quantitative Gas Chromatographic Determination of Pesticide Residues in Sweet Cherries
Authors: Bicchi Carlo , D’Amato Angela , Balbo Cristina
Published: February 2020

A multiresidue method is described for determination of acephate, diazinon, dimethoate, fenitrothion, malathion, pirimicarb, trichlorfon, bromopropylate, dicofol, and tetradifon in sweet cherries for baby food at a limit of 0.01 ppm. Sweet cherry samples were extracted through a selective Extrelut column with methylene chloride and cleaned up with quaternary aminesilane-silica-dichloromethane. Extracts were then analyzed by gas chromatography (GC)/electron capture detection/flame photometric detection (FPD) and GC/nitrogen-phosphorous detection/FPD. Recoveries were determined by spiking sweet cherry homogenates with 10 pesticides at 0.1, 0.05, 0.02, and 0.01 ppm. Six determinations were performed at each level for each pesticide. Recoveries were 70% or better at the 0.01 ppm level.
Procedure for Detecting and Confirming Pentobarbital Residues in Dog Food by Gas Chromatography/Mass Spectrometry
Authors: Adam Laura A , Reeves Valerie B
Published: February 2020

abstract

The method described detects and confirms presence of pentobarbital residues in dry, extruded feeds at concentrations of 5-20 ppb. Dried feed is ground to a uniform powder and shaken overnight in methanol. A portion of the methanolic extract is evaporated, and the residue is reconstituted in phosphate-buffered saline. The aqueous extract is cleaned with a solid-phase extraction cartridge designed to extract barbiturate residues from biological matrixes. Dimethyl sulfoxide, tetramethylammonium hydroxide, and iodomethane are added to derivatize pentobarbital. 1,3-Dimethylpentobarbital is then acidified with dilute hydrochloric acid and extracted with isooctane. The organic layer is transferred and evaporated under a stream of nitrogen. The residue is reconstituted in a small volume of ethyl acetate for analysis by gas chromatography/mass spectrometry. The limit of detection is approximately 0.7 ppb. The method was validated with pentobarbital-fortified feed samples containing high concentrations of meat and bone meal.
Comparison of SimPlate TotalTM Plate Count Test with Plate Count Agar Method for Detection and Quantitation of Bacteria in Food
Authors: Townsend David E , Naqui Ali
Published: February 2020

abstract

The SimPlateTM Total Plate Count (TPC) test, developed by IDEXX Laboratories, Inc., detects and quantitates total bacterial concentration in food after 24 h of incubation. The performance of SimPlate TPC was compared with that of the plate count agar (PCA) method for enumerating total bacterial concentration of 255 food samples representing 15 different food matrixes. Total bacterial counts on SimPlate TPC were measured after 24 h of incubation and plotted against values obtained from PCA after 48 h. Simple regression analysis of the data showed strong correlation between the methods (r = 0.95); the sensitivity of SimPlate TPC for foodborne bacteria was 96% relative to PCA (slope = 0.96). It was concluded that SimPlate TPC is a suitable alternative for the detection and quantitation of foodborne bacteria. The method has been granted Performance Tested Certification by the AOAC Research Institute.
Liquid Chromatographic Method for Analysis of All-rac-α-Tocopheryl Acetate and Retinyl Palmitate in Milk-Based Infant Formula Using Matrix Solid-Phase Dispersion
Authors: William Chase G , Long Austin R
Published: February 2020

abstract

A liquid chromatographic method is described for analysis of all-rac-α-tocopheryl acetate, tocopherols, and retinyl palmitate in milk-based infant formula. The vitamins are extracted from infant formula without saponification by matrix solid-phase dispersion and quantitated by normal-phase chromatography with fluorescence detection. Retinyl palmitate and vitamin E are quantitated isocratically with mobile phases of 0.125% (v/v) and 0.5% (v/v) isopropyl alcohol in hexane, respectively. Results were similar to the certified and non-certified ranges for all-rac-α-tocopheryl acetate, retinyl palmitate, and tocopherols in the infant formula standard reference material (SRM) 1846. Results also compared favorably with the label declaration on a retail infant formula. Recoveries were determined on an analyte-fortified zero control reference material for milk-based infant formula and averaged 96.8% (n = 30) for retinyl palmitate and 91.5% (n = 25) for all-rac-α-tocopheryl acetate. Examination of 5 concentrations for each analyte gave results that were linear (r = 0.999) over the concentration examined, with coefficients of variation ranging from 1.02 to 5.86%. The method provides a rapid, specific, and easily controlled assay for analysis of retinyl palmitate and vitamin E in fortified infant formula. Additionally, the method minimizes solvent use by using only 14 ml_ solvent per extraction.
Gas Chromatographic Determination Of Diphenylamine In Apples And Pears: Method Validation And Results Of Spanish Official Residue Monitoring Program 1995
Authors: Garrido Juan , Alba Mercedes De , Jimenez Irene , Cadado Elisa , Folgeiras Maria Luz
Published: February 2020

abstract

A simple, fast, and inexpensive method is described for the determination of diphenylamine residues in apples and pears. The diphenylamine is extracted with acetone, and the extraction is followed by liquid-liquid partitioning and further analysis by gas chromatography with nitrogen-phosphorous detection. The method was validated with fortified samples at 4 concentration levels. A gas chromatographic/ mass spectrometric confirmatory procedure was developed and applied in routine analysis. The detection level of the proposed method is 0.005 mg/kg, and recoveries ranged from 80 to 100℅. The method was used to analyze 100 apple and pear samples from the Residue Monitoring of Hygiene Food Program 1995 of the Spanish Ministry of Health, which is conducted by our laboratory. The results obtained confirmed the viability of the method for routine analysis for this compound. A first evaluation was completed for the presence of diphenylamine residues in apples and pears produced in Spain.
Release of Fumigant Residues from Grain by Microwave Irradiation
Authors: Ren Yong-Lin , Desmarchelier James M
Published: February 2020

abstract

Multiresidue analysis of fumigants is important because of their widespread use on staple foodstuffs, such as grain. Fumigants are usually extracted from grain either by solvent extraction or by purgeand- trap techniques. In this paper, fumigant residues in wheat were "extracted" by a microwave procedure. Wheat, in gas-tight Erlenmeyer flasks, was placed in a domestic microwave oven, and fumigants were released into the headspace by microwave irradiation. Power settings for maximum release of fumigants were determined for CH3Br PH3, CS2, and COS. Recoveries of fortified samples were >90%. Completeness of extraction was assessed from the amount of fumigant retained by the microwave-irradiated wheat. This amount, determined from both solvent extraction and from further microwave irradiation, was always small(<5℅ of the amount obtained from the initial procedure). Limits of quantitation were <1 ng/g for ChhBr, PH3, and CS2. These low limits were essentially due to the absence of interference from solvents. The microwave method is rapid and solvent-free. However, care is required in selecting the appropriate power setting. The safety implications of heating sealed flasks in microwave ovens should be noted.
pH-Metric Determination of the Acid Value of Vegetable Oils without Titration
Authors: Kuselman Ilya , Tur’yan Yakov I , Berezin Oleg Y , Kogan Lina , Shenhar Avinoam
Published: February 2020

The acid value (AV) of vegetable oils is determined without titration by using a new reagent consisting of triethanolamine in a solution of water and isopropyl alcohol. When the oil sample is mixed with the reagent in the pH-metric cell, free fatty acids from the sample are extracted into the reagent ( 3 - 4 min). The initial pH, called conditional pH´, is measured, a standard acid (HC1) is added, and the final pH, pH´2, is measured. AV is calculated from the difference between pH´! and pH´2. The method is applicable for quality control of vegetable oils during their production, trade, and use
Identification of the Source of Reagent Variability in the Xanthydrol/Urea Method
Authors: Biles Patricia Valdes , Ziobro George C
Published: February 2020

Contamination of food and food packaging material by rodent urine is evidence of insanitary conditions. Urea from rodent urine is used as a chemical indicator of contamination. The limit of detection of the xanthydrol/urea AOAC Method 959.14 by formation of dixanthylurea crystals is 4 μg urea isolated from urine on packaging material. Six different lots of xanthydrol from 5 different manufacturers were compared. Differences in urea detection sensitivity of the xanthydrol of up to 1000-fold were observed. Melting points showed further evidence of variability and impurities in xanthydrol lots. A liquid chromatographic method was developed to separate and identify the impurities. Confirmation of analytes was performed by gas chromatography/mass spectrometry.
Determination of (+/−) Elution Orders of Chiral Organochlorines by Liquid Chromatography with a Chiral Detector and by Enantioselective Gas Chromatography
Authors: Wetter Walter , Klobes Ulrike , Luckas Bernd , Hottinger Georg , Schmidt Gabi
Published: February 2020

Enantioselective gas chromatography (GC) with 5 modified cyclodextrins was applied to chiral organochlorines. A prerequisite for determining GC elution orders of enantiomers is the availability of enantioenriched standard solutions. In addition to compounds reported before (e.g., α-HCH, PCB 174, oxychlordane), we determined the sign of optical rotation of enantioenriched solutions of e-aeee-pentachlorocyclohexene-1 (β-PCCH), perdeuterated α-HCH (α-PDHCH), perdeuterated β-PCCH, and the persistent compound of technical toxaphene—2-exo,3-endo,5-exo,9,9,10,10-heptachlorobornane (B7-1453)—by liquid chromatography (LC) with a chiral detector. An enantioenriched solution of (β-PCCH was obtained by enantioselective degradation of α-HCH with (-)-brucine. In addition to forming an enantiomeric excess of (-)-α- HCH, we formed enantioenriched (+)-(α-PCCH. In a similar study, α-PDHCH showed the same behavior with respect to enantioselectivity. Dextrorotation of an enantioenriched solution of B7-1453 was also confirmed by LC with a chiral detector. Enantioseparation of chiral organochlorines on 5 chiral stationary phases resulted in several reversed elution orders. These results indicate that a careful check of elution orders of organochlorine enantiomers is necessary prior to comparison of literature data for the study of enantioselective processes in the environment.
Liquid Chromatographic Determination of Carotenoids and Vitamins A and E in Multivitamin Tablets
Authors: Sun Jidong
Published: February 2020

Carotenoids and vitamins A and E in multivitamin tablets can be determined simultaneously by reversed-phased liquid chromatography (LC) with a programmable UV detector. Samples were dissolved in dimethyl sulfoxide and thenextracted with hexane. A portion was injected onto a SymmetryC18,150 × 4.6 mm id, 5 μm column and chroma tographed with a mobile phaseof acetonitrile–0.25% ammonium acetate in methanol and 0.05% triethylamine in dichloromethane. A step gradient was used. The system was operated at 25°C with a flow rate of 1.5 mL/min. UV detection was at 325 nm for retinols, 285 nm for tocopherols, and 450 nm for carotenoids. Detection limits were less than 0.3 ng for retinol and retinyl acetate; 2 ng for α-tocopherol acid succinate; 10 ng for α-tocopherol, γ-tocopherol, and α-tocopherol acetate; and 0.4 ng for α-carotene and β-carotene. Intraday and interday coefficients of variation ranged from 1.40 to 5.20%. The sample preparation method and LC assay are practical for quality control and routine analysis of multivitamin tablets.
Fast Determination of Lead and Copper in Dairy Products by Graphite Furnace Atomic Absorption Spectrometry
Authors: Viñas Pilar , Pardo-Martí Mercedes , Campillo Natalia , Hernández-Córdoba Manuel
Published: February 2020

A rapid and direct procedure for determining lead and copper in dairy products by electrothermal atomic absorption spectrometry (ETAAS) is described. Samples are slurried in a medium containing 50% v/v hydrogen peroxide, 1 % v/v nitric acid, 0.5% w/v dihydrogen phosphate, and 20% v/v ethanol and directly injected into the furnace with no previous mineralization. Calibration is performed with aqueous standards. Limits of determination were 0.4 and 2.4 ng/mL for copper and lead, respectively. The reliability of the procedure was checked by comparison with the acid mineralization procedure and by analyzing 3 certified reference milk samples.
Principles To Guide International Standard Tests for Liquid Chemical Germicides: A Proposal
Authors: Miner Norman
Published: February 2020

This review discusses issues involved in developing standard tests for liquid chemical germicides and suggests some guiding principles to be considered for future development of harmonized international standard methods for testing disinfectants and sterilants. A published test method to measure sporicidal activity is used as an example of the implementation of these principles.
Multiresidue Determination of Pesticides in High-Organic-Content Soils by Solid-Phase Extraction and Gas Chromatography/Mass Spectrometry
Authors: Mogadati Paul , Louis Judith B , Rosen Joseph D
Published: February 2020

A multiresidue method based on solid-phase extraction cleanup and gas chromatography/ion trap mass spectrometry was developed to analyze 120 pesticides and pesticide metabolites in 2 soils with organic matter contents of 4.0 and 5.2%. Among the pesticides and the pesticide metabolites studied (almost all of which were spiked into soils at 0.075 ppm in triplicate), 107 (89%) of those spiked in soil containing 4.0% organic matter showed recoveries of 70–130%, as did 98 (82%) of those spiked in soil containing 5.2% organic matter. At a signal-to-noise ratio of 5 for all pesticides except chlorothalonil in soil containing 5.2% organic matter, limits of detection ranged from <1 to 15 ng/g.
Quantitative Analysis of Sulpiride and Impurities of 2-Aminomethyl-1-Ethylpyrrolidine and Methyl-5-Sulphamoyl-2-Methoxybenzoate in Pharmaceuticals by High-Performance Thin-Layer Chromatography and Scanning Densitometry
Authors: Agbaba Danica , Miljkovic Tatjana , Marinkovic Valentina , Zivanov-Stakic Dobrila , Vladimirov Sote
Published: February 2020

A simple and reliable thin-layer chromatographic method for determining sulpiride and impurities of 2-aminomethyl-1-ethylpyrrolidine and methyl-5-sulphamoyl-2-methoxybenzoate was developed and validated. A methylene chloride–methanol–ammonia solution (25%; 18 + 2.8 + 0.4, v/v) solvent system is used for separation and quantitative evaluation of chromatograms. The chromatographic plate is first scanned at 240 nm to locate chromatographic zones corresponding to sulpiride and methyl-5-sulphamoyl-2-methoxybenzoate. Then 2-aminomethyl-1-ethylpyrrolidine is derivatized in situ with ninhydrin, and resulting colored spots are measured at 500 nm. The method is reproducible and convenient for quantitative analysis and purity control of sulpiride in its raw material and in its dosage forms.
Simultaneous Determination of Water and Enediols or Thiols in Chemical Products and Drugs Not Amenable to Direct Karl Fischer Titration
Authors: Kuselman Ilya , Sherman Felix , Bourenko Tat’Yana , Shenhar Avinoam
Published: February 2020

A method proposed for determining water and enediols or thiols is based on consecutive titration of the enediols or thiols by a novel reagent and of water by the conventional Karl Fischer reagent in the same cell. The time for both titrations is 8–20 min. The novel reagent consists of iodine, sodium acetate as a base, and potassium iodide in a nonaqeous solvent system. The method is applicable for quality control of chemical products and drugs during their production and trade.
Analysis of Pesticide Residues in Fruits, Vegetables, and Milk by Gas Chromatography/Tandem Mass Spectrometry
Authors: Sheridan Robert S , Meola John R
Published: February 2020

A method for detection, quantitation, and confirmation of more than 100 pesticides by gas chromatography (GC) with ion trap mass spectrometry (MS/MS) has been developed. The sensitivity of this method for many analytes is equal to or lower than those of selective GC detectors such as flame photometric detectors and electrolytic conductivity detectors. Using MS/MS, very low detection limits and good confirmation (1 precursor ion and 2 or more product ions) are achieved simultaneously. The entire list of pesticides is screened with 2 injections per sample. Samples are introduced onto the column by a temperature-programmed cold injection to maximize response. Each pesticide is run with its own unique set of parameters, which fragment the compound, retaining only the precursor ion. This ion is then refragmented to create a product spectrum. The selectivity of MS/MS gives a very clean spectrum, making compound identification and confirmation clear, even with a relatively dirty food matrix. If care is taken to maintain the injection port and guard column, this method can reliably identify and confirm more than 100 pesticides at the low parts-per-billion range.
Multiresidue Analytical Method for the Determination of Eight Penicillin Antibiotics in Muscle Tissue by Ion-Pair Reversed-Phase HPLC after Precolumn Derivatization
Authors: Verdon Eric , Couëdor Pierrick
Published: February 2020

A high-performance liquid chromatographic multiresidue method was developed for the determination of 8 penicillin compounds (benzylpenicillin, phenoxymethylpenicillin, ampicillin, amoxicillin, nafcillin, oxacillin, cloxacillin, and dicloxacillin) at trace levels in muscle tissue. This method involves extraction of the penicillins with phosphate buffer pH 9 followed by cleanup and concentration on a C18 solid¯phase extraction column and reaction with benzoic anhydride at 50°C for 5 min and with 1,2,4-triazole and mercury(II) chloride solution pH 9 at 65°C for 10 min. The derivatized compounds are eluted on a C18 column with a mobile phase containing acetonitrile and phosphate buffer (pH 6; 0.1 mol/L) loaded with sodium thiosulfate and ion-pairing tetrabutylammonium hydrogenosulphate. The method detection limit is approximately 3-11 μg/kg and the limit of determination was evaluated down to 25 μg/kg in line with the criteria of the EU decision No. 93/256/EEC.
A Test Strip for Diamines in Tuna
Authors: Hall Margot , Sykes Paul A , Fairclough Diane L , Lucchese Leonard J , Rogers Patricia , Staruszkiewicz Walter , Bateman Robert C
Published: February 2020

This study describes the production of a solid-phase assay (test strip/dipstick test) for putrescine and cadaverine in tuna based on the coupling of an amine oxidase to a peroxidase/dye system. The assay was linear to 75 μM in phosphate buffer, and the minimum detectable concentration was 0.5 μM (<0.1 ppm), corresponding to 0.01 mg% in spiked extracts. Intra- and interassay precisions were <20%. Test strips were stable at 4°C for at least 12 months. Lysine, ornithine, and histidine did not react with the assay, and histamine reacted only minimally. Sixteen fish samples were tested by test strip and the standard AOAC protocol, and results were in good agreement.
Liquid Chromatographic Analysis of Vitamin K1 in Milk-Based Infant Formula with Matrix Solid-Phase Dispersion
Authors: Chase G William , Eitenmiller Ronald R , Long Austin R
Published: February 2020

A liquid chromatographic method for vitamin K1 in milk-based infant formula is described. The vitamins are extracted from infant formula by matrix solid-phase dispersion and quantitated by reversed-phase chromatography with fluorescence detection. Vitamin K1 is converted to the fluorescent hydroquinone with a postcolumn zinc reductive reactor. The limit of detection is 12 pg, and the limit of quantitation is 38 pg on-column. Linear responses were obtained in the range 0.55-22.1 ng/mL (r2 = 0.9998). Recoveries of vitamin K1 from an analyte-fortified blank material for milk-based infant formula averaged 91.7% (n = 25). The method provides a rapid, specific, and easily controlled assay for vitamin K1 in fortified infant formula.
Isolation of Chloramphenicol from Whole Eggs by Supercritical Fluid Extraction with In-Line Collection
Authors: Pensabene John W , Fiddler Walter , Donoghue Dan J
Published: February 2020

Egg consumption, at more than 65 billion per year in the United States, represents a potentially significant source of exposure to drug residues, particularly if the laying hens are treated with antimicrobial compounds or fed a diet containing medicated feed. Residues resulting from the use of chloramphenicol (CAP) is especially problematic if this compound is not used in accordance with national registration, e.g., for the control of Salmonella microorganisms in poultry. The most commonly used methods for the determination of CAP in biological samples require the use of large amounts of organic solvent. As a result, a less solvent intensive supercritical fluid extraction (SFE) method was developed for CAP in whole chicken eggs, and the results were compared with those for a solvent extraction procedure. In the SFE method, the egg sample is extracted with supercritical CO2 (without a modifier) at 10 000 psi (680 bar), 80°C, and an expanded gas flow rate of 3.0 L/min to a total volume of 150 L. The CAP is trapped in-line on a Florisil sorbent bed. The CAP is eluted post-SFE by using the liquid chromatographic mobile phase solvent (water-methanol), and determined on a C8 column with ultraviolet detection at 280 nm. Recovery from eggs fortified at the 10 ppb level (n = 6) was 81.2 ± 4.3%. To obtain eggs containing incurred CAP, hens were given a single daily dose of 75 mg CAP (orally by gelatin capsule) for 2 consecutive days, and the eggs were collected over a 12-day period. The mean value for “normally incurred” CAP in the eggs (n = 17) analyzed by SFE ranged from none detected to 174.5 ppb, with an overall mean of 60.5 ppb, compared with a mean of 60.4 ppb for the solvent extraction method. No significant difference in results was found between methods. However, the SFE method is more rapid, uses less solvent, and gives recoveries similar to those for the solvent extraction method, making it ideal for regulatory monitoring.
Indirect Determination of the Pesticide Dimethoxydithiophosphate by Flow Injection Analysis with Liquid-Liquid Extraction and Atomic Absorption Spectrometry with Hydride Generation
Authors: Blas Oroncio Jiménez de , Paz Josë Luis Pereda de
Published: February 2020

We developed a new procedure for the indirect determination of the organophosphorus pesticide dimethoxydithiophosphate (DDTP) by coupling, in continuous mode, flow injection analysis (FIA) with liquid-liquid extraction and atomic absorption spectrometry with hydride generation in the organic phase. Both continuous-mode extraction of the species Bi(DDTP)3 in isobutylmethylketone (IBMK) organic medium and the process of hydride(BiH3) generation in the same organic medium were optimized. The most suitable solvent of the reducing agent, NaBH4, was a 1 % solution of N,N-dimethylformamide in glacial acetic acid medium. Phase separation was accomplished with an original design that has been patented for use (Spain patent 10,118,929 Y). The hydride generated is transported by the FIA setup in continuous mode to the quartz cell where the analytical signal was measured. The procedure developed was rapid, continuous, and involved little manipulation, thus avoiding possible errors and contamination. Moreover, only small amounts (250 μL) of sample were required in the injection of the aqueous sample, and a volume of 30 μL was used in the injection of the organic phase extracted. The values obtained for the detection limit (5 ppb DDTP in the aqueous phase injected) and for precision (3.0%, expressed as coefficient of variation) are very acceptable in comparison with other procedures described in the literature. The accuracy obtained was in agreement with the imprecision of the method when it was applied to the aqueous samples. The procedure can be used for the analysis of surface waters subject to different types of treatment prior to their use for human consumption. For this type of water, European legislation permits pesticide concentrations up to 5 ppb, which is the value of the detection limit obtained in the proposed procedure.
Statistical Verification of Parameters Describing Liquid Adsorption on Heterogeneous Solid Surfaces
Authors: Podkościelny Przemysław , Dąbrowski Andrzej
Published: February 2020

A new approach is presented for determining the surface phase capacity and the distribution function in liquid adsorption on heterogeneous solid surfaces. This approach deals with statistical analysis of the errors made by applying the so-called exponential equation of the adsorption isotherm. It is proved that such an analysis, which is suitable for all types of excess experimental isotherms, gives the answer to the dilemma of the reliability of the results obtained by means of the assumed adsorption model. Several experimental systems were analyzed to demonstrate the advantage of our approach.
Abduction and diagrams
Authors: Pietarinen Ahti-Veikko
Published: February 2020

Abductive conclusions are drawn in a special, co-hortative mood (Peirce’s ‘investigand’). Abductive conclusions are representative interpretants that represent abduction (or retroduction) as a form of reasoning that can convey a general conception of the truth. The truth is not asserted; abduction merely delivers the idea of a matter of course, rendering that idea comparatively simple and natural, hence assuring us of its justified assertibility. Hence abductive reasoning is at home in addressing ‘How Possible’-questions in science. Abductive reasoning concerns the question of how things might, could or would conceivably be such that they can be plausibly asserted. Peirce took all reasoning to be diagrammatic and representable using the graphical method of logic. Yet no examples have previously been found in his large manuscript corpus of what such non-deductive graphs might look like. This paper proposes a new interpretation of a sole exception, a sketch of two graphs from a rejected page from 1903, which might be the only surviving example of Peirce’s abductive graphs. The proposed interpretation takes them to be representative interpretants of this special inverse type of inference.
On carbon nanotubes in the interstellar medium
Authors: Li Qi , Li Aigen , Jiang B W , Chen Tao
Published: February 2020

Since their discovery in 1991, carbon nanotubes (CNTs) – a novel one-dimensional carbon allotrope – have attracted considerable interest worldwide because of their potential technological applications such as electric and optical devices. In the astrophysical context, CNTs may be present in the interstellar space since many of the other allotropes of carbon (e.g. amorphous carbon, fullerenes, nanodiamonds, graphite, polycyclic aromatic hydrocarbons, and possibly graphene as well) are known to be widespread in the Universe, as revealed by pre-solar grains in carbonaceous primitive meteorites and/or by their fingerprint spectral features in astronomical spectra. In addition, there are also experimental and theoretical pathways to the formation of CNTs in the interstellar medium (ISM). In this work, we examine their possible presence in the ISM by comparing the observed interstellar extinction curve with the ultraviolet/optical absorption spectra experimentally obtained for single-walled CNTs of a wide range of diameters and chiralities. Based on the absence in the interstellar extinction curve of the ${\sim}$4.5 and 5.25 ${\rm eV} \ \pi$-plasmon absorption bands that are pronounced in the experimental spectra of CNTs, we place an upper limit of ${\sim}10\, {\rm ppm}$ of C/H (i.e. ${\sim}$4 per cent of the total interstellar C) on the interstellar CNT abundance.
hybrid-lenstool: a self-consistent algorithm to model galaxy clusters with strong- and weak-lensing simultaneously
Authors: Niemiec Anna , Jauzac Mathilde , Jullo Eric , Limousin Marceau , Sharon Keren , Kneib Jean-Paul , Natarajan Priyamvada , Richard Johan
Published: February 2020

We present a new galaxy cluster lens modelling approach, hybrid-lenstool, that is implemented in the publicly available modelling software lenstool. hybrid-lenstool combines a parametric approach to model the core of the cluster, and a non-parametric (free-form) approach to model the outskirts. hybrid-lenstool optimizes both strong- and weak-lensing constraints simultaneously (Joint-Fit), providing a self-consistent reconstruction of the cluster mass distribution on all scales. In order to demonstrate the capabilities of the new algorithm, we tested it on a simulated cluster. hybrid-lenstool yields more accurate reconstructed mass distributions than the former Sequential-Fit approach where the parametric and the non-parametric models are optimized successively. Indeed, we show with the simulated cluster that the mass density profile reconstructed with a Sequential-Fit deviates from the input by 2–3σ at all scales while the Joint-Fit gives a profile that is within 1–1.5σ of the true value. This gain in accuracy is consequential for recovering mass distributions exploiting cluster lensing and therefore for all applications of clusters as cosmological probes. Finally we found that the Joint-Fit approach yields shallower slope of the inner density profile than the Sequential-Fit approach, thus revealing possible biases in previous lensing studies.
Doublesex Mediates the Development of Sex-Specific Pheromone Organs in Bicyclus Butterflies via Multiple Mechanisms
Authors: Prakash Anupama , Monteiro Antónia
Published: February 2020

The Bicyclus lineage of satyrid butterflies exhibits male-specific traits, the scent organs, used for chemical communication during courtship. These organs consist of tightly packed brush-like scales (hair-pencils) that rub against scent patches to disperse pheromones, but the evolution and molecular basis of these organ’s male-limited development remains unknown. Here, we examine the evolution of the number and location of the scent patches and hair-pencils within 53 species of Bicyclus butterflies, and the involvement of the sex determinant gene doublesex (dsx) in scent organ development in Bicyclus anynana using CRISPR/Cas9. We show that scent patches and hair-pencils arose via multiple, independent gains, in a correlated manner. Further, an initially nonsex-specific Dsx protein expression pattern in developing wing discs becomes male-specific and spatially refined to areas that develop the scent patches. Functional perturbations of dsx show that this gene activates patch development in males whereas hair-pencils develop in both sexes without Dsx input. Dsx in females is, instead, required to repress hair-pencils whereas Dsx in males regulates minor aspects of its development. These findings suggest that the patches and hair-pencils evolve as correlated composite organs presumably due to their functional integration. Divergence in the function of dsx isoforms occurred across the sexes, where the male isoform promotes patch development in males and the female isoform represses hair-pencil development in females, both leading to the development of male-limited traits. Furthermore, evolution in number of patches in males is due to the evolution of spatial regulation of dsx.