bluuebunny/crossref_metadata_2025 huggingface dataset:
Rapid Spectrophotometric Method for Analyzing Natamycin in Cheese and Cheese Rind
Authors: Fletouris Dbvutrios J , Botsoglou Nickos A , Mantis Antonios J
Published: February 2020

A rapid spectrophotometric method for determining natamycin in cheese and cheese rind has been developed. Samples are homogenized with acidified aqueous acetonitrile and homogenates are filtered. Natamycin is directly quantitated in filtered extracts on the basis of the characteristic thirdderivative trough at 322.6 nm. Additional cleanup of extracts is not required because derivative transformation of the conventional analytical band at around 319 nm eliminates spectral interferences from other compounds. The analysis is simple and can be completed in 6 min. The equipment is easily accessible because most modern spectrophotometers allow instant generation of derivative spectra. The method needs small amounts of solvents and has good analytical characteristics. Overall recovery was 98.4 ± 0.7%, and linearity was excellent (r= 0.9998) in the range examined (0.5–20 mg/kg). Quantitation and detection limits were estimated at 0.5 and 0.25 mg/kg, respectively. Precision statistics based on within-day and between-days variations suggest an overall relative standard deviation of 1.4%.
Determination of Methylmercury After Supercritical Fluid Extraction
Authors: Holak Walter
Published: February 2020

A method, using supercritical fluid extraction, for determining methylmercury in seafood has been developed to eliminate use of toxic organic solvents. Seafood samples were treated with 1N NaOH and then acidified with HCI to release CH3HgCI. After mixing the sample with cellulose powder (40 mesh) containing stearic acid modifier at 5 mg/g, the extraction was performed with supercritical CO2 under the following conditions: pressure, 200 atm; temperature, 50°C; time, 20 min; and trap, 0.01N Na2S2O3 in a conical tube immersed in a flask of warm water to prevent freezing. The extract was then analyzed by a suitable method, such as cold-vapor atomic absorption spectrophotometry. The accuracy of the procedure was verified by analyzing biological standard reference materials. Several commercial seafood samples and spikes have been analyzed.
Determination of Ajmalicine in Reserpine Raw Materials by Liquid Chromatography with Fluorescence Detection
Authors: Cieri Ugo R
Published: February 2020

A method is presented for determination of ajmalicine in reserpine raw materials by liquid chromatography (LC) with fluorescence detection. The sample is dissolved in a very small volume of chloroform, and the resulting solution is diluted with methanol. The reference solution of ajmalicine is prepared directly in methanol. For LC, a 30 cm long normal-phase column is used. The mobile phase is methanol containing a small volume of an aqueous solution of 1-pentanesulfonic acid, sodium salt. Detection is by fluorescence with excitation at 280 nm and emission at 360 nm. In 3 samples, the ajmalicine contents ranged from 1.2 to 1.9%.
Isolation, Purification, and Liquid Chromatographic Determination of Stilbene Phytoalexins in Peanuts
Authors: Sobolev Victor S , Cole Richard J , Dorner Joe W , Yagen Boris
Published: February 2020

A liquid chromatographic (LC) method for determination of stilbene phytoalexins (SPs) in peanuts has been developed. SPs were extracted with acetonitrile–water (90 + 10, v/v) by high-speed blending. An aliquot of extract was applied to a minicolumn packed with AI2O3–ODS (C18) mixture and eluted with acetonitrile-water (90 + 10, v/v). Eluate was evaporated under nitrogen, and residue was dissolved in LC mobile phase. SPs in an aliquot of purified extract were quantitated by normal-phase partition LC on silica gel with n-heptane–2-propanol–water–acetonitrile–acetic acid (1050 + 270 + 17 + 5 + 1, v/v) as mobile phase. Recoveries of SPs [frans-4-(3-methyl-but-1-enyl)-3,5,4′-trihy-droxystilbene (trans-arachidin-3; t-Ar-3), trans-3-isopentadienyl-4,3′,5′-trihydroxystilbene (t-IPD), and trans-3,5,4′-trihydroxystilbene (trans-resveratrol; t-Res)] from peanuts spiked at 300 ppb were 96.05 ± 2.8%. Limits of quantitation for t-Ar-3 and t-IPD were about 100 ppb. t-Ar-3, t-IPD, and t-Res were found in all parts of the peanut plant as major SPs produced in response to fungal invasion.
Determination of Honey Authenticity by Capillary Gas Chromatography
Authors: Low Nicholas H , South Wendy
Published: February 2020

Methodology using capillary gas chromatography was developed to determine addition of invert syrups (beet or cane) to honey. Fingerprint oligosaccharides, which were either not detectable or present in low concentrations in pure honey, were found in these inexpensive sweeteners. Oligosaccharides were analyzed as their trimethylsilyl ethers. Sixty-eight pure honey samples produced in continental North America, Hawaii, China, and Australia were analyzed. The detection limit for invert sugar addition was 5%.
Determination of Dithiocarbamate and Its Breakdown Product Ethylenethiourea in Fruits and Vegetables
Authors: Ahmad Nazir , Guo Lin , Mandarakas Peter , Appleby Sevieone
Published: February 2020

Improved methods for determination in fruits and vegetables of ethylene bisdithiocarbamate (EBDC) residues as carbon disulfide by gas–liquid chromatographic headspace analysis and of othylenethio-urea (ETU) residues by liquid chromatography (LC) are described. Improvements to the EBDC procedure include increased sensitivity by use of 140 mL crimp seal samples bottles fitted with silicone seals, which are leak-proof and reduce headspace volume; use of a Porapak column, which allows use of higher column temperature for better residue separation; and inclusion of thiopheno as an internal standard for bettor quality control. The relationship between the logarithm of the response of carbon disulfide divided by the thiophene response versus concentration of carbon disulfide is expressed by the regression equation Y = 1.011 X + 0.008, with a correlation coefficient r2 = 0.993. Mean recoveries from 8 commodities spiked with mancozcb at 1 and 3 mg/kg, equivalent to 0.473 and 1.419 mg/kg carbon disulfide, are 94.2 ±10 and 98.3 ± 13%, respectively. The Improved LC procedure for ETU residue analysis requires minimal cleanup of sample extract, no derivatization prior to injection, and no specialized LC detectors for quantitation. The UV detector response at 240 nm Is linearly related to ETU concentration [Y = (3.18X – 0.778) × 1000. r2 = 0.997]. Moan ETU recovery from 5 commodities spiked at 0.2 to 5 mg/kg is 93.9 ± 6%. ETU residues of 0.02 to 0.25 μg/g were detected in macerated samples of fruits and vegetables spiked with man-cozeb at 5 μg/g and incubated at room temperature for 3 days. The improved procedures were used to analyze EBDC and ETU residues in fruits and vegetables sampled at a wholesale Sydney produce market. Approximately 30% of samples tested contained EBDC residues, whereas ETU residues in the same samples were below the detection limit of the analytical method (<0.02 mg/kg).
Determination of 2-Ethylhexyl 4-(N-Methyl-N-Nitrosamino) Benzoate in Commercial Sunscreens and Cosmetic Products
Authors: Chou Hardy J , Yates Ronald L , Havery Donald C , Wenninger John A
Published: February 2020

An analytical method has been developed for determination of 2-ethylhexyl 4-(N-methyl-N-nitrosamino) benzoate (NMPABAO), a nitrosamine contaminant in sunscreen products containing 2-ethylhexyl 4-(N,N-dimethylamino) benzoate (Padimate O). The method involves extraction of NMPABAO by column chromatography followed by liquid chromatographic separation and analysis with a nitric oxide detector. To confirm the presence of NMPABAO in sunscreen products, the N-nitrosamine was synthesized and its structure was determined by infrared spectrophotometry, nuclear magnetic resonance spectrometry, and mass spectrometry (MS). For method validation, recovery studies were performed on a commercial suntan lotion, cream, and gel. Recoveries of NMPABAO added to representative test samples averaged 83%. The method has an estimated detection limit of 30 ppb. The method was used to analyze 25 commercial cosmetic and sunscreen products containing Padimate O. Eleven products contained NMPABAO at levels ranging from 160 to 21 000 ppb. NMPABAO presence in 4 products was confirmed by MS at levels ≥4000 ppb. The highest levels of NMPABAO were associated with products that contained the nitrite-releasing preservative 2-bromo-2- nitro-1,3-propanediol.
Determination of Combined Residues of Metalaxyl and 2,6-Dimethylaniline Metabolites in Urine byGas Chromatography/Mass Spectrometry
Authors: Headley John V , Maxwell Donald B , Swyngedouw Christopher , Purdy John R
Published: February 2020

A gas chromatographic/mass spectrometric (GC/MS) method for determination of combined residues of the fungicide metalaxyl and its metabolites in urine containing the 2,6-dimethylaniline moiety is described. The method is a modification of a method of Balasubramanian and Perez for analysis of metalaxyl invegetables. Noted modifications include replacement of steam extraction with extraction by methylene chloride and use of electron impact ionization GC/MS in the selected-ion mode. The method is linear over the range of 0.1-5 μg 2,6- dimethylaniline/g urine and has a detection limit of 0.025 μg/g.
Comparison of Cleanup Techniques for Simple Method for Analysis of Selected Organophosphorus Pesticide Residues in Molluscs
Authors: Hernández Félix , Serrano Roque , Beltran Joaquim , López Francisco J
Published: February 2020

A simple method for determination of 5 organo phosphorus pesticides (dimethoate, chlorfenvin phos, chlorpyrifos, methidathion, and phosmet) in molluscs (Mytilus galloprovincialis and Venus gallina) was developed, with special attention to cleanup. Organophosphorus pesticides were extracted with acetonitrile-acetone (90 + 10, v/v) in a high-speed blender. Two cleanup procedures were used to defat extracts prior to injection into a gas chromatograph: liquid-liquid partition with acetoni trile-hexane and adsorption column chromatography with silica gel. The latter was more efficient for elimination of fat and fractionation of pesticides with different polarities. Limits of detection of the overall procedure including extraction and cleanup ranged from 0.2 to 1 ng/g. Quantitative recoveries for pesticide concentrations ranging from 1 to 10 000 ng/g were obtained.
Collection and Analysis of Butyltin Compounds in Air at Nanogram-Per-Cubic-Meter Levels
Authors: Swami Kamal , Narang Rajinder S
Published: February 2020

An analytical method for determining butyltin chlo rides in air at low nanogram-per-cubic-meter levels was developed. Butyltin chlorides investigated were mono-n-butyltin trichloride (MBTC),di-n-butyltin dichloride (DBTC), and tri-n-butyltin chlo ride (TBTC). These tin chlorides were trapped on cartridges packed with Porapak-N, eluted with methylene chloride containing 0.3% HCI, hy dridized with sodium borohydride, and analyzed by capillary gas chromatography with flame photometric detection. On the basis of a 20 m3 sample, a detection limit of 0.05 ng/m3 can be achieved.
Identification of Phylloquinone (Vitamin K1) as an Unknown Peak in Electron Capture Detection Gas Chromatograms of Pyrethroid Insecticide Residues
Authors: Imanaka Masaaki , Kadota Minoru , Kumashiro Kazuo , Mori Tadashige
Published: February 2020

An unknown peak was observed in spinach extract during routine analysis of 7 pyrethroid insecticides by gas chromatography with electron capture detection (GC-ECD) using a DB-1 column (20 m x 0.25 mm id, 0.1 μm film thickness). It eluted later than the 7 pyrethroids, and it was also found in other agricultural crops. The intensity of the unknown peak was related to the green color of the sample: It was absent in white vegetables such as radish root or onion. Data from GC/direct deposi- tion/Fourier-transform infrared spectroscopy (FTIR) suggested it might be phylloquinone (vitamin K1). The identity was confirmed also by using electron impact capillary GC/mass spectrometry (MS). Although phylloquinone has no halogens, it showed very high sensitivity by ECD (63Ni), responding to 10 pg.
Determination of Thiabendazole Residues in Whole Citrus Fruits by Liquid Chromatography with Fluorescence Detection
Authors: Arenas Rene V , Rahman Hafizur , Johnson Nelson A
Published: February 2020

An existing liquid chromatographic (LC) methodfor determination of thiabendazole (TBZ) residues inor on whole green bananas and potatoes was applied to whole, unwashed citrus fruits. The method is applicable for determining TBZ residues in whole oranges,grapefruits, tangerines, and lemons. TBZ is extracted from citrus homogenate with ethyl acetate, and theextract is cleaned up on a cation-exchange, solid-phase extraction column. The purified extract is analyzed by LC with a cation-ex change column and fluorescence detection. Average recovery of TBZ from whole citrus fruits fortified with TBZ at 0.05-20 ppm was 96%. The assay provides a simple, rapid, and sensitive method for monitoring TBZ residues in whole citrus fruit.
Gradient Liquid Chromatographic Method for Determination of Chlorhexidine and Its Degradation Products in Bulk Material
Authors: Doub William H , Ruhl Don D , Hart Brad , Mehelic Paul R , Revelle Larry K
Published: February 2020

A liquid chromatographic method was developed for determination of chlorhexidine and its degradation products in unformulated drug substance. A nonlinear gradient from 80% 0.1 M ammonium acetate buffer, pH 5.0, to 20% buffer over 90 min (balance is acetonitrile) is applied to a 3 μm octadecylsilane bonded-phase column. The drug and some of its degradation products are determined at 230 nm. Of 11 previously identified degradation products, 9 are determined with good precision (relative standard deviation of peak area is <2%).
Liquid Chromatographic Determination of Benzylpenicillin and Cloxacillin in Animal Tissues and Its Application to a Study of the Stability at –20°C of Spiked and Incurred Residues of Benzylpenicillin in Ovine Liver
Authors: Gee Hock-Eng , Ho Koon-Bay , Toothill John
Published: February 2020

A method was developed for determining benzylpenicillin and cloxacillin in animal tissues. Samples are extracted with acetonitrile, and the extract is cleaned up on a C18 solid-phase extraction (SPE) cartridge, derivatized, and quantitated by liquid chromatography with UV detection at 325 nm. The method was validated on spiked bovine kidney, liver, and muscle tissues. Kidney was spiked at 0.01,0.05, and 0.20 mg/kg; liver and muscle were spiked at 0.20 mg/kg. Recoveries were 75–100%, with coefficients of variation of 2–7%. The method was further validated on kidney, liver, and muscle tissues from 2 sheep dosed with Aquacaine G suspension (containing benzylpenicillin). Mean levels of benzylpenicillin in these tissues ranged from 0.02 to 4.06 mg/kg, with coefficients of variation of replicate analyses between 3 and 7%. The limit of detection was approximately 0.005 mg/kg for benzylpenicillin and cloxacillin in kidney, liver, and muscle tissues. This method was used to study the stability of both spiked and incurred residues of benzylpenicillin in ovine liver during storage at –20°C for 3 months. Assuming the rate of loss follows a first-order kinetic decay, the mean half-life of benzylpenicillin in liver is 62 days for spiked tissues and 71 days for tissues with incurred residues.
Analysis of Fermented Milk Products by Near-Infrared Reflectance Spectroscopy
Authors: Rodríguez-Oxero José L , Hermtoa Marià
Published: February 2020

Fat, protein, and total solids in fermented milk were determined by near-infrared reflectance spectroscopy (NIRS). A set of 107 samples from diverse types of fermented milk (whole, skimmed, with added flavors, and without added flavors) were used to calibrate the instrument by modified partial least-square regression. Global calibration, using all samples, was more effective than specific calibrations using fewer samples of each type. Standard errors of a calibration were 0.071 for fat, 0.075 for protein, and 0.083 for total solids. Values of the correlation coefficient square (R2) were 0.997 for fat, 0.981 for protein, and 1.000 for total solids. Calibration was validated with an independent set of 34 samples of the same types. Standard errors of validation were 0.08,0.14, and 0.25 for fat, protein, and total solids, respectively, and values of R2 for the regression of measurements by NIRS versus reference methods were 1.00 for fat and total solids and 0.94 for protein. When Standard 128 of the International Dairy Federation was used to compare NIRS results with those from reference methods, no significant differences were found (p = 0.05).
Liquid Chromatographic Determination of Fentin Acetate in Fentin and Maneb Formulations
Authors: Papadopoulou-Mourkidou Euphemia , Patsias John , Papadopoulos George , Galanis Costas
Published: February 2020

A normal-phase liquid chromatographic (LC) system is presented for determination of fentin acetate in fentin and fentin-maneb wettable powder formulations. Fentin acetate is extracted from both formulations with glacial acetic acid-hexane (20 + 80), and the extract is analyzed after appropriate dilution. An isocratic LC system equipped with a photodiode array detector and a silica gel column, which is eluted with glacial acetic acid-hexane (5 + 95), are used. Quantitation at 258.5 nm is based on an external standard calibration curve. Relative standard deviations were 0.2 and 2.3% for the mean levels (w/w) of fentin acetate determined in fentin and fentin-maneb formulations, respectively.
Determination of Low Concentrations of Acetochlor in Water by Automated Solid-Phase Extraction and Gas Chromatography with Mass-Selective Detection
Authors: Lindley Chris E , Stewart Jeff T , Sandstrom Mark W
Published: February 2020

A sensitive and reliable gas chromatographic/mass spectrometric (GC/MS) method for determining acetochlor in environmental water samples was developed. The method involves automated extraction of the herbicide from a filtered 1 L water sample through a C18 solid-phase extraction column, elution from the column with hexane-isopropyl alcohol (3 + 1), and concentration of the extract with nitrogen gas. The herbicide is quantitated by capillary/column GC/MS with selected-ion monitoring of 3 characteristic ions. The single-operator method detection limit for reagent water samples is 0.0015 μg/L Mean recoveries ranged from about 92 to 115% for 3 water matrixes fortified at 0.05 and 0.5 μg\L. Average single-operator precision, over the course of 1 week, was better than 5%.
Suitability of Several Statistical Models to Simulate Observed Distribution of Sample Test Results in Inspections of Aflatoxin-Contaminated Peanut Lots
Authors: Whitaker Thomas , Giesbrecht Francis , Wu Jeremy
Published: February 2020

The acceptability of 10 theoretical distributions to simulate observed distribution of sample aflatoxin test results was evaluated by using 2 parameter estimation methods and 3 goodness of fit (GOF) tests. All theoretical distributions were compared with 120 observed distributions of aflatoxin test results of farmers' stock peanuts. For a given parameter estimation method and GOF test, the negative binomial distribution had the highest percentage of statistically acceptable fits. The log normal and Poisson-gamma (gamma shape parameter = 0.5) distributions had slightly fewer but an almost equal percentage of acceptable fits. For the 3 most acceptable statistical models, the negative binomial had the greatest percentage of best or closest fits. Both the parameter estimation method and the GOF test had an influence on which theoretical distribution had the largest number of acceptable fits. All theoretical distributions, except the negative binomial distribution, had more acceptable fits when model parameters were determined by the maximum likelihood method. The negative binomial had slightly more acceptable fits when model parameters were estimated by the method of moments. The results also demonstrated the importance of using the same GOF test for comparing the acceptability of several theoretical distributions.
Determination of Phenylbutazone Residues in Bovine Milk by Liquid Chromatography with UV Detection
Authors: De Veau E J  Ian
Published: February 2020

A published liquid chromatographic (LC) method was modified for quantitation of phenylbutazone (PBZ) residues in the range of 25-300 ng/mL in bovine milk. Milk samples (1 m└) were diluted with absolute ethanol and 25% NH4OH. Diethyl ether and petroleum ether were added sequentially to the milk extract and the mixture was agitated on a Vortex mixer to partition out milk fat. The organic phase was removed and discarded. Tetrahydrofuran- hexane (1 + 4) was added to the aqueous phase and the extract was acidified with 3M HCI. The samples were mixed on a Vortex mixer for 30 min, and centrifuged. The organic layer, containing PBZ, was transferred to a clean test tube. The organic solvents were evaporated to dryness under a stream of N2 at room temperature. The resulting extract was dissolved in 1 m└ mobile phase and filtered before injection. The chromatographic system was a C18 reversed-phase column connected to a UV detector set at 264 nm. Recoveries of PBZ from raw bovine milk fortified at 25- 300 ng/mL ranged from 79 to 84%; relative standard deviations (RSDs) ranged from 6 to 7%. The RSDs for incurred PBZ quantitated from 34 to 229 ng/mL ranged from 1 to 4%.
Determination of Decarbamoyl Saxitoxin and Its Analogues in Shellfish by Prechromatographic Oxidation and Liquid Chromatography with Fluorescence Detection
Authors: Lawrence James F , Wong Barbara , Ménard Cathie
Published: February 2020

Oxidation and chromatographic conditions for detecting the decarbamoyl analogues of several paralytic shellfish poison (PSP) toxins were studied. Prechromatographic oxidation with periodate or hydrogen peroxide under slightly alkaline conditions was used as previously reported for the parent PSP toxins. Both periodate and hydrogen peroxide oxidations produced 2 fluorescent products separable by liquid chromatography for each decarbamoyl (dc) toxin (dc-saxitoxin, dc-neosaxatoxin and dcgonyautoxins 2 and 3). Decarbamoyl saxitoxin produced the same 2 products as did dc-neosaxitoxin but in different ratios. One of these products was the same as the one obtained with neosaxitoxin after periodate oxidation. Decarbamoyl gonyautoxins 2 and 3 (together) produced 2 products, one of which was the same as the major product obtained with gonyautoxins 1 and 4 (together) after periodate oxidation. Decarbamoyl gonyautoxins 1 and 4 were not available for study. The method was used to detect dc-saxitoxin and dc-gonyautoxins 2 and 3 in shellfish extracts
TCDD Residues in Fish and Shellfish from U.S. Waterways
Authors: Firestone David , Fehrtnger Norbert V , Walters Stephen M , Kozara Ronald J , Ayres Russell J , Ogger John D , Schneider Louis F , Glidden R Michael , Ahlrep James R , Brown Patrick J , Ford Susanna E , Davy Raphael A , Gulick Daniel J , Mccullough Bruce H , Sittig Robert A , Smith Paul V , Syvertson Carl N , Barber Mildred R
Published: February 2020

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin) in the edible portion of fish and shellfish from various U.S. waterways has been monitored since 1979. Analytical results for the period 1979-1994 are reported. Extracts obtained after column chromatographic and liquid chromatographic cleanup were examined by electron capture detection-gas chromatography (GC), and final quantitation and confirmation were performed by GC/mass spectrometry with multiple ion detection. Analyses of 1623 test samples indicated that TCDD residues in fish and shellfish were not widespread but rather were localized in areas near waste sites, chlorophenol manufacturers, and pulp and paper mills. Analytical results indicated that levels in aquatic species from these sites have been declining steadily. No TCDD (limit of detection and confirmation, 1 - 2 ppt) has been found in recent years in aquatic species from most Atlantic, Pacific, and Gulf of Mexico sites and Great Lakes other than Lake Ontario and Saginaw Bay (Lake Huron).
A Simplified Method for Determining Undeclared Sweeteners Added to Pure Orange Juice
Authors: Iuliano Theresa A
Published: February 2020

Previous research has described methods for monitoring unique oligosaccharides as indicators of adulteration of pure orange juice with undeclared sweeteners. Modifications are reported here that streamline the method for routine analysis of large numbers of samples. Sample preparation is faster and more efficient, allowing preparation of up to 24 samples at one time. Oligosaccharides are eluted isocratically at 30�C, decreasing retention times and eliminating the need for column reequilibration between injections. Oligosaccharide profiles of commercially available sweeteners and fortified orange juice samples analyzed under the modified conditions demonstrate that the method reduces analysis time by >50%, while at the same time improving resolution and maintaining established detection limits.
Escherichia coli 0157:H7 Visual Immunoprecipitate Assay: A Comparative Validation Study
Authors: Feldsine Philip T , Forgey Robin L , Falbo-Nelson Maria T , Brunelle Sharon L
Published: February 2020

A wide variety of food products, with emphasis on raw meat products, were analyzed simultaneously by 3 methods: the Assurance Escherichia coli 0157:H7 (EHEC) enzyme immunosorbent assay (EIA), the EHEC visual immunoprecipitate assay (VIP), and a modified Bacteriological Analytical Manual (BAM) culture method. This paper reports results of a comparative study of the Assurance and modified BAM methods. In this comparative study, 1050 samples and controls gave false-negative rates of 1.0 and 0%, respectively, for the Assurance EIA and the modified BAM culture methods. The overall agreement between the 2 methods was 99.4%. Cultural confirmation of presumptive positive samples was problematic because competitive flora were present in higher levels than EHEC in the enrichment broth after incubation and the target organism had nondescript characteristics on the primary selective agar, hemorrhagic coli agar, which necessitated picking of additional colonies in many instances.
Effect of Seeds on Bile-Enzymatic-Gravimetric Analysis of Total Dietary Fiber
Authors: Cranker Kenneth J , Phillips Katherine M , Gonzales Maria Carmen Rita V , Stewart Kent K
Published: February 2020

Dietary fiber sometimes is defined chemically as nonstarch polysaccharides plus lignin or as other specific chemical entities. Analysis of dietary fiber according to a chemical definition typically involves gas chromatography, which allows separation and quantitation of chemical constituents that are added to arrive at a dietary fiber value. Other definitions of fiber are broader, defining it to be whatever is not digested in the alimentary tract. Analytically, this definition translates into the gravimetric sum of the material remaining after a series of enzymatic and chemical treatments that simulate in vivo digestion. Various methods reflect the gravimetric definition, which might include as dietary fiber some protein, resistant starch, and even lipids that are not digested by particular assay conditions. We used a recently proposed bile-enzymatic-gravimetric assay for total dietary fiber on commonly consumed seeds (hulled and unhulled sesame, caraway, and poppy) and visually found these seeds to be undigested. We then determined the impact of the undigested seeds on measured dietary fiber content by spiking homogenized daily menus with 5% by weight of these seeds and calculating recoveries with 2 assumptions: seeds are 100% fiber because they are not digested, and the fiber content of seeds is as determined by assay. Calculated recoveries were very different depending on which assumption was made (71-90% or 99109%, respectively), and the difference was closely related to the seed’s protein content.
Determination of Calcium in Certain Fertilizers by Inductively Coupled Plasma Atomic Emission Spectrometry: Studies of Some Spectral and Interelement Effects at Different Wavelengths
Authors: Matilainen Rose , Tummavuori Jouni
Published: February 2020

Four analytical wavelengths (393.366, 396.847, 317.933, and 422.673 nm) were used to determine Ca in 2 fertilizers by inductively coupled plasma atomic emission spectroscopy (ICP-AES). Matrix effects were studied by adding to real fertilizer solutions fertilizer elements that are known or believed to interfere with Ca determination. Matrix effects were calculated by multiple linear regression. Interference was caused by S, K, or B. At 422.673 nm, the interference of B and K is a spectral effect, and at 396.847 and 317.933 nm, the interference of S and K is an interelement effect. At 393.366 nm, no linear interference was found. The best wavelength for determining Ca in fertilizers by ICP-AES is 396.847 nm.
Measurement of Total Starch in Cereal Products by Amyloglucosidase-α-Amylase Method: Collaborative Study
Authors: Mccleary Barry V , Gibson Trevor S , Mugford David C ,   Collaborators:, Lukow O , Jackson D S , Rabe E , Patel N , Williams P C , Gelroth J , Camire M E , Chibbar R N , Ingelin M , Niemann C , Grant L A , Peterson D M , Corke H , Sanders P , Muir J , Choct M , Schmidt J , Walker R , Blakeney A B , Logue S , Tarr A , Gibson T , Batey I , Dynes J , Miklaszewicz T , Panozzo J , McCleary B , Li B W , Hofer P , Arndt E , Thomas M , Depalo R
Published: February 2020

American Association of Cereal Chem- ists/AOAC collaborative study was conducted to evaluate the accuracy and reliability of an enzyme assay kit procedure for measurement of total starch in a range of cereal grains and products. The flour sample is incubated at 95°C with thermostable α-amylase to catalyze the hydrolysis of starch to maltodextrins, the pH of the slurry is adjusted, and the slurry is treated with a highly purified amyloglucosidase to quantitatively hydrolyze the dextrins to glucose. Glucose is measured with glucose oxidase-peroxidase reagent. Thirty-two collaborators were sent 16 homogeneous test samples as 8 blind duplicates. These samples included chicken feed pellets, white bread, green peas, high- amylose maize starch, white wheat flour, wheat starch, oat bran, and spaghetti. All samples were analyzed by the standard procedure as detailed above; 4 samples (high-amylose maize starch and wheat starch) were also analyzed by a method that requires the samples to be cooked first in dimethyl sulfoxide (DMSO). Relative standard deviations for repeatability (RSDr) ranged from 2.1 to 3.9%, and relative standard deviations for reproducibility (RSDr) ranged from 2.9 to 5.7%. The RSDr value for high amylose maize starch analyzed by the standard (non-DMSO) procedure was 5.7%; the value
Monitoring of Domestic and Imported Apples and Rice by the U.S. Food and Drug Administration Pesticide Program
Authors: Roy Ronald R , Wilson Patrick , Laski Ronald R , Roberts James I , Weishaar Joseph A , Bong Rodney L , Yess Norma J
Published: February 2020

In 1993-94, the U.S. Food and Drug Administration (FDA) conducted a statistically based study of pesticide residues in domestic and imported fresh apples and processed rice. For apples, 769 domestic and 1062 imported samples were collected and analyzed; 85% of the domestic and 86% of the imported samples had detectable residues. Benomyl, a widely used fungicide, was found with greatest frequency in domestic apples, while diphenylamine was found most often in imported apples. One domestic and 4 imported samples contained violative residues of pesticides for which there are no U.S. tolerances on apples. The statistically weighted (by domestic packer throughput or import shipment size) violation rates for domestic and imported apples were 0.30% (0.13 unweighted) and 0.41% (0.38 unweighted), respectively. For rice, 598 domestic and 612 imported samples were collected and analyzed; 56% of the domestic and 12% of the imported samples had detectable residues. Malathion had the greatest frequency of occurrence in both groups of rice. Eight domestic and 9 imported samples were violative, all as a result of use of pesticides for which there are no U.S. tolerances on rice. The statistically weighted violation rates for domestic and imported rice were 0.43% (1.3 unweighted) and 1.1% (1.5 unweighted), respectively. Results of the statistically based study show that, as in FDA’s regulatory monitoring, the levels of most pesticide residues found in these 2 commodities are generally well below U.S. tolerances, and few violative residues are found.
Analyses of Chlorothalonil and Dichlofluanid in Greenhouse Air
Authors: González Fj. Egea , Cano M L Castro , Vidal J L Martínez , Galera M Martínez
Published: February 2020

A method to sample and analyze chlorothalonil and dichlofluanid in greenhouse air was evaluated. Analysis was performed by gas chromatography with electron capture detection and gas chromatography- mass spectrometry. Solid sorbents such as Chromosorb 102, Porapak R, Supelpak-2, AmberliteXAD-2, Amberlite XAD-4, and polyurethane foam were studied. The use of Soxhlet extraction and solvent desorption with sonication to desorb the pesticides from these sorbents were compared.A procedure to generate atmospheres containing known concentrations of these fungicides was established to study sorption capacity and samplingconditions. Breakthrough and storage of pesticides also were studied. Dissipation of analytes in a 24 h period after application was studied by using personal samplers in a field experiment.
Determination of Four Fluoroquinolones in Milk by Liquid Chromatography
Authors: Roybal José E , Pfenning Allen P , Turnipseed Sherri B , Walker Calvin C , Hurlbut Jeffrey A
Published: February 2020

A liquid chromatographic (LC) method with fluorescence detection is presented for the analysis of 4 fluoroquinolones; enrofloxacin (ENRO), ciprofloxacin (CIPRO), sarafloxacin (SARA), and difloxacin (DIFLX) in milk. The procedure consists of extraction of milk with acidified ethanol, isolation and retention on a cation exchange solid-phase extraction column, elution with basic methanol, and LC analysis with fluorescence detection. LC analysis is performed by isocratic elution using an acetonitrile-2% acetic acid (15 + 85) mobile phase and an Inertsil phenyl column with fluorescence detection at excitation and emission wavelengths of 278 and 450 nm, respectively. A target level of 10 ppb for each of the 4 fluoroquinolones has been established for this method. Average recovery from fortified raw milk samples (5-100 ppb each) based on a 5-point standard curve calculation was 70-90%, with relative standard deviations of <15%.
Determination of Tilmicosin in Swine Feeds by Liquid Chromatography
Authors: Readnour Robin S , Helton-Groce Susan L , Dixon Sharon S
Published: February 2020

This method determines tilmicosin in feeds over a concentration range of 100 to 600 mg/kg. Tilmicosin is extracted from swine feeds by adding 200 mL of a swine feed extractant (20 + 80, acetonitrile–Millipore water, pH 2.5, with 25 mM dibutylammonium phosphate) to 20 g feed and placing on a shaker table for 1 h. This extractant is filtered and analyzed by liquid chromatography (LC). A gradient LC method is used to separate ilmicosin from the feed matrix in 30 min of run time. The recovery of tilmicosin from fortified feeds ranged from 96.7 to 112%, with the coefficients of variation (CVs) ranging from 1.4 to 3.9%. The determination of tilmicosin in medicated feeds resulted in an average recovery of 92.7% of labeled claim for pelleted feeds at 200 mg/kg and 99.1% of labeled claim for mash feeds at 400 mg/kg. Determination of tilmicosin in medicated feeds resulted in CVs ranging from 2.6 to 3.8%. The method has shown no interference with 18 other drugs.
Validated Method for Quantitation and Identification of 4,4-Desmethylsterols and Triterpene Diols in Plant Oils by Thin-Layer Chromatography–High Resolution Gas Chromatography–Mass Spectrometry
Authors: Reina Robert J , White Kevin D , Jahngen Edwin G E
Published: February 2020

Alkaline hydrolysis was performed on a series of different vegetable oils. The unsaponifiable lipid matter was extracted with ethyl ether, and the class of 4,4-desmethylsterols (sterols) plus the triterpene diols (diols) erythrodiol, uvaol, and betulinol were isolated by thin-layer chromatography. A validated method using the acetate derivatives of sterols instead of their silyl ethers is presented. The acetate derivatives were analyzed by high resolution gas chromatography (HRGC). Retention time, precision, recovery studies, and absolute response factors were calculated for these esters, and GC/mass spectrometric structure of the assigned retention times was confirmed for the sterols and triterpene diols.
Determination of Chlorinated Phenols in Water and Soil by Capillary Zone Electrophoresis
Authors: Rae Wayne E , Lucy Charles A
Published: February 2020

A capillary zone electrophoresis (CZE) method was developed to separate and determine chlorinated phenols in water and soil samples. A mixture of 16 chlorinated phenols was resolved in 25 min by using a 77 cm (70 cm to detector) × 75 μm fused silica capillary with 0.015M tetraborate/0.045M phosphate (pH 7.3) buffer at 22 kV. Calibration linearities for water samples in the low parts-permillion range were good (correlation coefficient > 0.99) for all solutes except p-chlorophenol. Average precision was 17% relative standard deviation. Typical detection limits were in the 200 μg/L range. Recoveries of chlorinated phenols from synthetic soil samples with methanol were quantitative.
Improvements in Amperometric Detection of Sulfite in Food Matrixes
Authors: Wygant Michele B , Statler John A , Henshall Alan
Published: February 2020

Sulfite is added to foods as an antimicrobial, antibrowning agent, or antioxidant. It also can occur naturally, and is often used in the production of beer and wine. For years the standard methodology for determination of sulfite in foods has been the Monier–Williams method, which is a combination of acid distillation and titration. Recently, AOAC adopted a chromatographic method based on a method developed by Kim and Kim for the determination of sulfite. The method combines ion exclusion chromatography with direct-current (DC) amperometric detection to provide more convenient and accurate quantitation of sulfite. However, fouling of the platinum working electrode results in a rapid decrease in method sensitivity. As a result, standards must be injected before and after every sample, and the electrode must be polished frequently to maintain adequate detection limits. Pulsed amperometric detection overcomes electrode fouling problems by repeatedly and continuously applying cleaning potentials to the working electrode. Using this technique, a reproducible electrode surface can be maintained, and injection-to-injection repeatability is greatly improved. A comparison of method performance for both DC and pulsed amperometric detection is presented. Also investigated was the stability of sulfite samples at varying pH, and in the presence or absence of a preservative.
Liquid Chromatographic Determination of Major Secondary Metabolites Produced by Aspergillus Species from Section Flavi
Authors: Sobolev Victor S , Horn Bruce W , Dorner Joe W , Cole Richard J
Published: February 2020

A liquid chromatographic (LC) method was developed for simultaneous determination of major secondary metabolites—including cyclopiazonic acid (CPA), O-methylsterigmatocystin (OMST), and the versicolorins—produced by Aspergillus species from section Flavi (A. flavus, A. parasiticus, A. tamarii, and A. caelatus) on a liquid medium. Metabolites were extracted with chloroform and quantitated without prior cleanup by means of normal- phase ion-pair partition LC on silica gel with a mobile phase of n-heptane-2-propanol-n-butanolwater- tetrabutylammonium hydroxide (2560 + 900 + 230 + 32 + 8, v/v). Recoveries of CPA and OMST from fungal cultures spiked at 10 μg/mL were 98.90 + 3.27 and 95.92 + 5.27% (n = 5), respectively. At spike levels of 100 μg/mL, recoveries were 98.89 + 3.87 and 97.65 + 4.32% (n = 5), respectively. Limits of detection for pure standards were 0.25 μg/mL for CPA (at 280 nm) and 0.30 μg/mL for OMST (at 310 nm). UV detector responses to CPA and OMST were linear to about 0.5 and 3.5 μg/injection, respectively
Reversed-Phase Ion-Pair Liquid Chromatographic Determination of Chlorophacinone and Diphacinone in Steam- Rolled Oat Baits and Steam-Rolled Oat/Wax Baits
Authors: Primus Thomas M , Griffin Doreen L , Volz Stephanite A , Johnston John J
Published: February 2020

abstract

A reversed-phase ion-pair liquid chromatographic (LC) method was developed for analysis of steam-rolled oat (SRO) baits fortified with either chlorophacinone or diphacinone. Baits were prepared with and without paraffin wax. Chlorophacinone or diphacinone was extracted from wax-free SRO baits with 5 mM tetrabutylammonium phosphate methanolic ion-pairing solution. Wax baits were initially extracted with petroleum ether and then cleaned up by liquid extraction into methanolic ion-pairing solution containing 20% water. SRO extracts were analyzed with reversed-phase ion-pair LC. Chlorophacinone and diphacinone were quantified by UV absorption at 325 nm. Recoveries from SRO fortified with chlorophacinone at 25 and 150 μg/g were 90.7 and 90.8%, respectively, whereas for diphacinone at the same levels, recoveries were 93.5 and 92.3%, respectively. Recoveries from wax baits fortified at 25 and 75 μg/g chlorophacinone were 98.5 and 100%, respectively, whereas for diphacinone at the same levels, recoveries were 93.6 and 98.0%, respectively. Method limits of detection for chlorophacinone and diphacinone in SRO baits were estimated to be 1.0 and 0.76 μg/g, respectively. Method limits of detection for chlorophacinone and diphacinone in wax baits were estimated to be 4.2 and 2.8 μg/g, respectively.
Determination of Diarrheic Shellfish Toxins in Mussels b Microliquid Chromatography-Tandem Mass Spectrometry
Authors: Draisci Rosa , Lucentini Luca , Giannetti Luigi , Boria Pierpaolo , James Kevin J , Furey Ambrose , Gillman Marion , Kelly Séan S
Published: February 2020

abstract

A fast, sensitive, and specific procedure for determining toxins that cause diarrheic shellfish poisoning (DSP) using microliquid chromatography coupled with tandem mass spectrometry (micro-LC-MS-MS) is reported. The lipophylic polyether acidic toxins okadaic acid (OA), its isomer dinophysistoxin-2 (DTX-2), the 35-methylokadaic acid dinophysistoxin-1 (DTX-1), and the novel toxin dinophysistoxin-2B (DTX-2B; recently isolated from Irish mussels) were extracted from shellfish tissues with acetone and chromatographed by isocratic elution at 10 ixL/min with CH3CN-H20, 80 + 20 (v/v), containing 0.1% trifluoroacetic acid, through a C18 reversed-phase column (1.0 mm id). The chromatograph is coupled via an ion spray interface to an atmospheric pressure ionization source. Collision-induced-dissociation (CID) ion mass spectra of the protonated molecule, [M + H]+, at m/z 805 for OA, DTX-2, and DTX-2B and at m/z 819 for DTX-1, were obtained in MS-MS experiments to identify 2 diagnostic fragment ions for each analyte that could be used for selected-reaction-monitoring (SRM) micro-LC-MS-MS analysis. The CID spectrum of DTX-2B confirmed it to be a new OA isomer, like DTX-2. Standard curves obtained by SRM micro-LC-MS-MS were linear (r2 μ 0.9992) over the range 0.05-1.00 μg/mL (i.e., 0.10-2.00 μg toxin/g hepatopancreas), and a detection limit of 15 pg/injection was obtained for each DSP toxin. Average recoveries ranged from 95 to 101%, and coefficients of variation ranged from 1.8 to 3.4%. This novel SRM micro-LC-MS-MS method was used to confirm acidic DSP toxins in Irish and Italian toxic mussels. It offers a high degree of specificity because analyte confirmation is based on retention time, molecular weight, structural information obtained from the presence of 2 diag-nostic fragments for each analyte, and ion ratios. OA was found in both Irish (< 0.7 μg/g hepatopancreas) and Italian (<1.5 μg/g hepatopancreas) mussels. DTX-1 was found only in Italian mussels (<0.3 μg/g hepatopancreas). DTX-2 (<6.1 μg/g hepatopancreas) and DTX-2B (<0.08 μg/g hepatopancreas) were unique to Irish shellfish.
Optimization of Selenium Determination in Human Milk and Whole Blood by Flow Injection Hydride Atomic Absorption Spectrometry
Authors: Alegría Amparo , Barberá Reyes , Farré Rosaura , Ferrer Emilia , Lagarda M Jesús , Torres M Angeles
Published: February 2020

abstract

A flow injection hydride atomic absorption spectrometry (FI-HAAS) method was developed for determining selenium in human milk and whole blood after microwave digestion of the sample. The sample (2 mL human milk or 0.25 mL blood) was introduced into the microwave vessel with 1.5 mL HN03 and 0.25 mL H202 and 300 W (4 min) and 600 W (4 min) were applied. The digestion was completed by heating to 140 C (2-3 h). Se (VI) was reduced to Se (IV) with hydrochloric acid. The instrumental conditions for FI-HAAS (concentrations of reducing agent and carrier acid, flow rate of argon carrier gas, and sample volume injected) were optimized. The detection limit of the proposed method was 0.23 ng/mL (assay) or 115 pg Se (absolute) in biological samples (1.15 ng/mL milk, 10.4 ng/mL blood). The precision values were 5.0% for milk and 4.0% for blood. The accuracy was evaluated with 2 reference materials, National Institute of Standards and Technology Non-Fat Milk Powder (found: 104.3 ± 7.2 ng/g, certified: 110 ± 10 ng/g) and Whole Blood Seronorm (found: 81 ± 7.3 ng/mL, reference: 83 ± 4 ng/mL). The results show the suitability of the method for selenium determination in human milk and whole blood. The method was applied to whole blood samples obtained from pregnant women and to human milk.
Ivermectin Quantitation with an Abamectin Internal Standard
Authors: Reising Kyle P
Published: February 2020

abstract

The potent antiparasitic ivermectin is detected at low concentrations (ng/g) in liver and muscle tissue by liquid chromatography after conversion to a fluorescent derivative with 1-methylimidazole and trifluoroacetic anhydride. This acetylation reaction can be compromised by residual water that eads to decreased yields. Yields of derivatives of ivermectin and abamectin, a related avermectin, are identical under all circumstances tested. Use of abamectin as an internal standard eliminates derivative yield as a source of analytical variation.
Determination of 4-Hexylresorcinol in Crab Meat
Authors: Smallwood Anthony W , Ranieri Tracy L , Satzger R Duane
Published: February 2020

abstract

A method is described for determining 4-hexylresorcinol in crab meat. 4-Hexylresorcinol is used to prevent melanosis in shrimp, and the same use has been proposed for crab meat. Because 4-hexylresorcinol may be added illegally to crab meat as a preservative, consumer protection requires that residues of the compound be monitored in crab meat. 4-Hexylresorcinol is extracted from crab meat with acetonitrile. After dilution with water, the extract is passed through a C18 solid-phase extraction column and 4-hexylresorcinol is eluted from the column with ethanol. The compound is determined by reversed-phase liquid chromatography with diode array detection at 206 nm. Limit of quantitation is 1.0 μg/g. Mean recovery in the range 1-20 μg/g is 89%, with a relative standard deviation of 6.3.